This an attempt to fix the data transfer stall reported by Geliang and Gang more carefully enforcing memory constraints at the MPTCP level. Patch 1/9 moves the bound check before entering the TCP socket. Patch 2, 3 and 4 are cleanups/refactors finalized to safely re-using TCP helpers on MPTCP skbs. Patch 5 makes TCP pruning related helpers available to MPTCP and patch 6 makes use of them. Patch 7 addresses an edge scenario that could still lead to transfer stall under memory pressure. Finally patch 8 and 9 improve the MPTCP-level retransmission schema to make recovery from memory pressure significanly faster. Note that the diffstat is biases by the quite large patch 4/9, which contains mechanical transformation of existing code; "real" changes are noticiable smaller. Tested successfully vs the test cases proposed by Geliang and Gang. --- RFC -> v1: - dropped old patch 4 & 5 - addressed AI reported comments - added retrans refactor. Paolo Abeni (9): mptcp: move checks vs rcvbuf size earlier in the RX path mptcp: drop the mptcp_ooo_try_coalesce() helper mptcp: remove CB offset field mptcp: sync mptcp skb cb layout with tcp one tcp: expose the tcp_collapse_ofo_queue() helper to mptcp usage, too mptcp: implemented OoO queue pruning mptcp: track prune recovery status mptcp: move the retrans loop to a separate helper mptcp: let the retrans scheduler do its job. include/net/tcp.h | 8 ++ net/ipv4/tcp_input.c | 55 +++++--- net/mptcp/fastopen.c | 1 - net/mptcp/mib.c | 3 + net/mptcp/mib.h | 3 + net/mptcp/options.c | 55 +++++++- net/mptcp/protocol.c | 328 ++++++++++++++++++++++++++++--------------- net/mptcp/protocol.h | 11 +- net/mptcp/subflow.c | 2 + 9 files changed, 323 insertions(+), 143 deletions(-) -- 2.53.0 Currently the enforcement of the rcvbuf constraint is implemented when moving the skbs into the msk receive or OoO queue. Under significant memory pressure the above can cause permanent data transfer stalls. Move the checks early on, before landing even in the subflow queues. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- RFC -> v1: - limit vs actual buffer size - use CB info instead of skb->len Note that: - this needs the follow-up patches to really fix the stall - the memory comparison is intentionally very rough, as the msk socket lock is not currently held where the condition is now enforced. This should require some refinement, shared as-is to avoid more latency on my side --- net/mptcp/options.c | 18 ++++++++++++++++-- net/mptcp/protocol.c | 10 ++-------- 2 files changed, 18 insertions(+), 10 deletions(-) diff --git a/net/mptcp/options.c b/net/mptcp/options.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -XXX,XX +XXX,XX @@ static bool add_addr_hmac_valid(struct mptcp_sock *msk, return hmac == mp_opt->ahmac; } -/* Return false in case of error (or subflow has been reset), - * else return true. +static bool mptcp_over_limit(const struct sock *sk, struct sk_buff *skb) +{ + if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) + return false; + + return sk_rmem_alloc_get(sk) > READ_ONCE(sk->sk_rcvbuf); +} + +/* Return false when the caller must drop the packet, i.e. in case of error, + * subflow has been reset, or over memory limits. */ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) { @@ -XXX,XX +XXX,XX @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) __mptcp_data_acked(subflow->conn); mptcp_data_unlock(subflow->conn); + + if (mptcp_over_limit(subflow->conn, skb)) + return false; return true; } @@ -XXX,XX +XXX,XX @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) return true; } + if (mptcp_over_limit(subflow->conn, skb)) + return false; + mpext = skb_ext_add(skb, SKB_EXT_MPTCP); if (!mpext) return false; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk, mptcp_init_skb(ssk, skb, offset, len); - if (own_msk && sk_rmem_alloc_get(sk) < sk->sk_rcvbuf) { + if (own_msk) { mptcp_subflow_lend_fwdmem(subflow, skb); ret |= __mptcp_move_skb(sk, skb); } else { @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skbs(struct sock *sk, struct list_head *skbs, u32 *delt *delta = 0; while (1) { - /* If the msk recvbuf is full stop, don't drop */ - if (sk_rmem_alloc_get(sk) > sk->sk_rcvbuf) - break; - prefetch(skb->next); list_del(&skb->list); *delta += skb->truesize; @@ -XXX,XX +XXX,XX @@ static bool mptcp_can_spool_backlog(struct sock *sk, struct list_head *skbs) DEBUG_NET_WARN_ON_ONCE(msk->backlog_unaccounted && sk->sk_socket && mem_cgroup_from_sk(sk)); - /* Don't spool the backlog if the rcvbuf is full. */ - if (list_empty(&msk->backlog_list) || - sk_rmem_alloc_get(sk) > sk->sk_rcvbuf) + if (list_empty(&msk->backlog_list)) return false; INIT_LIST_HEAD(skbs); -- 2.53.0 It's used to save an additional comparison for in-order skbs, but is also a barrier to remove CB offset. Remove the helper, let __mptcp_try_coalesce() always perform the sequence check and remove duplicate checks from the callers. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/protocol.c | 21 ++++++--------------- 1 file changed, 6 insertions(+), 15 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, { int limit = READ_ONCE(sk->sk_rcvbuf); - if (unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || + if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq || + unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (limit >> 3)) || !skb_try_coalesce(to, from, fragstolen, delta)) @@ -XXX,XX +XXX,XX @@ static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, return true; } -static bool mptcp_ooo_try_coalesce(struct mptcp_sock *msk, struct sk_buff *to, - struct sk_buff *from) -{ - if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq) - return false; - - return mptcp_try_coalesce((struct sock *)msk, to, from); -} - /* "inspired" by tcp_rcvbuf_grow(), main difference: * - mptcp does not maintain a msk-level window clamp * - returns true when the receive buffer is actually updated @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) /* with 2 subflows, adding at end of ooo queue is quite likely * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup. */ - if (mptcp_ooo_try_coalesce(msk, msk->ooo_last_skb, skb)) { + if (mptcp_try_coalesce(sk, msk->ooo_last_skb, skb)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL); return; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); goto merge_right; } - } else if (mptcp_ooo_try_coalesce(msk, skb1, skb)) { + } else if (mptcp_try_coalesce(sk, skb1, skb)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE); return; } @@ -XXX,XX +XXX,XX @@ static void __mptcp_add_backlog(struct sock *sk, if (!list_empty(&msk->backlog_list)) tail = list_last_entry(&msk->backlog_list, struct sk_buff, list); - if (tail && MPTCP_SKB_CB(skb)->map_seq == MPTCP_SKB_CB(tail)->end_seq && - ssk == tail->sk && + if (tail && ssk == tail->sk && __mptcp_try_coalesce(sk, tail, skb, &fragstolen, &delta)) { skb->truesize -= delta; kfree_skb_partial(skb, fragstolen); @@ -XXX,XX +XXX,XX @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) end_seq = MPTCP_SKB_CB(skb)->end_seq; tail = skb_peek_tail(&sk->sk_receive_queue); - if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) { + if (!tail || !mptcp_try_coalesce(sk, tail, skb)) { int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq; /* skip overlapping data, if any */ -- 2.53.0 Instead, to track the bytes already consumed inside each skb, use a msk-level new field, tracking the amount of bytes already copied to user-space, alike what TCP is already doing. This simplify a bit the code and will make possible the next patch. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- Note: this has the potential to break almost everything. On the flip side the CB->offset vs copied_seq difference from TCP is quite confusing and removing it will be for the good. Also this explicitly relays on "mptcp: do not drop partial packets" to avoid dropping partially consumed packets --- net/mptcp/fastopen.c | 1 - net/mptcp/protocol.c | 30 +++++++++++------------------- net/mptcp/protocol.h | 2 +- net/mptcp/subflow.c | 1 + 4 files changed, 13 insertions(+), 21 deletions(-) diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/fastopen.c +++ b/net/mptcp/fastopen.c @@ -XXX,XX +XXX,XX @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subf /* Only the sequence delta is relevant */ MPTCP_SKB_CB(skb)->map_seq = -skb->len; MPTCP_SKB_CB(skb)->end_seq = 0; - MPTCP_SKB_CB(skb)->offset = 0; MPTCP_SKB_CB(skb)->has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; MPTCP_SKB_CB(skb)->cant_coalesce = 1; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq || unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || - MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (limit >> 3)) || !skb_try_coalesce(to, from, fragstolen, delta)) return false; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) skb_set_owner_r(skb, sk); } -static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset, - int copy_len) +static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); bool has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; @@ -XXX,XX +XXX,XX @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset, * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq * value */ - MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow); - MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len; - MPTCP_SKB_CB(skb)->offset = offset; + MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow) - offset; + MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + skb->len; MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp; MPTCP_SKB_CB(skb)->cant_coalesce = 0; @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk, if (offset < skb->len) { size_t len = skb->len - offset; - mptcp_init_skb(ssk, skb, offset, len); + mptcp_init_skb(ssk, skb, offset); if (own_msk) { mptcp_subflow_lend_fwdmem(subflow, skb); @@ -XXX,XX +XXX,XX @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d\n", MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq, delta); - MPTCP_SKB_CB(skb)->offset += delta; - MPTCP_SKB_CB(skb)->map_seq += delta; __skb_queue_tail(&sk->sk_receive_queue, skb); } msk->bytes_received += end_seq - msk->ack_seq; @@ -XXX,XX +XXX,XX @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, int copied = 0; skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp) { - u32 delta, offset = MPTCP_SKB_CB(skb)->offset; + u32 delta, offset = msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq; u32 data_len = skb->len - offset; u32 count; int err; @@ -XXX,XX +XXX,XX @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, if (!(flags & MSG_PEEK)) { msk->bytes_consumed += count; - if (count < data_len) { - MPTCP_SKB_CB(skb)->offset += count; - MPTCP_SKB_CB(skb)->map_seq += count; + msk->copied_seq += count; + if (count < data_len) break; - } mptcp_eat_recv_skb(sk, skb); } else { @@ -XXX,XX +XXX,XX @@ static int mptcp_disconnect(struct sock *sk, int flags) /* for fallback's sake */ WRITE_ONCE(msk->ack_seq, 0); + WRITE_ONCE(msk->copied_seq, 0); WRITE_ONCE(sk->sk_shutdown, 0); sk_error_report(sk); @@ -XXX,XX +XXX,XX @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk, u32 *off) mptcp_move_skbs(sk); while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) { - offset = MPTCP_SKB_CB(skb)->offset; + offset = msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq; if (offset < skb->len) { *off = offset; return skb; @@ -XXX,XX +XXX,XX @@ static int __mptcp_read_sock(struct sock *sk, read_descriptor_t *desc, copied += count; msk->bytes_consumed += count; - if (count < data_len) { - MPTCP_SKB_CB(skb)->offset += count; - MPTCP_SKB_CB(skb)->map_seq += count; + msk->copied_seq += count; + if (count < data_len) break; - } mptcp_eat_recv_skb(sk, skb); } diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ struct mptcp_skb_cb { u64 map_seq; u64 end_seq; - u32 offset; u8 has_rxtstamp; u8 cant_coalesce; }; @@ -XXX,XX +XXX,XX @@ struct mptcp_sock { u64 bytes_sent; u64 snd_nxt; u64 bytes_received; + u64 copied_seq; u64 ack_seq; atomic64_t rcv_wnd_sent; u64 rcv_data_fin_seq; diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -XXX,XX +XXX,XX @@ static void subflow_set_remote_key(struct mptcp_sock *msk, WRITE_ONCE(msk->remote_key, subflow->remote_key); WRITE_ONCE(msk->ack_seq, subflow->iasn); + WRITE_ONCE(msk->copied_seq, subflow->iasn); WRITE_ONCE(msk->can_ack, true); atomic64_set(&msk->rcv_wnd_sent, subflow->iasn); } -- 2.53.0 The MPTCP protocol uses a significantly different CB layout WRT TCP, as it includes different information and use 64 bits for the sequence numbers. As the msk-level rcvbuf buffer size is limited by the core socket code the INT_MAX, we can safely use 32 bits for MPTCP-level sequence number. This allow updating the MPTCP CB layout so that fields with a corresponding TCP-level data use the same area inside the CB itself. Add build time check the unsure the latter invariant. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- rfc -> v1: - keep `ack_seq` up2date --- net/mptcp/protocol.c | 81 ++++++++++++++++++++++++++------------------ net/mptcp/protocol.h | 6 ++-- 2 files changed, 52 insertions(+), 35 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ #include "protocol.h" #include "mib.h" -static unsigned int mptcp_inq_hint(const struct sock *sk); +static int mptcp_inq_hint(const struct sock *sk); #define CREATE_TRACE_POINTS #include <trace/events/mptcp.h> @@ -XXX,XX +XXX,XX @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, !skb_try_coalesce(to, from, fragstolen, delta)) return false; - pr_debug("colesced seq %llx into %llx new len %d new end seq %llx\n", + pr_debug("colesced seq %x into %x new len %d new end seq %x\n", MPTCP_SKB_CB(from)->map_seq, MPTCP_SKB_CB(to)->map_seq, to->len, MPTCP_SKB_CB(from)->end_seq); MPTCP_SKB_CB(to)->end_seq = MPTCP_SKB_CB(from)->end_seq; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) { struct sock *sk = (struct sock *)msk; struct rb_node **p, *parent; - u64 seq, end_seq, max_seq; + u32 seq, end_seq, max_seq; struct sk_buff *skb1; seq = MPTCP_SKB_CB(skb)->map_seq; end_seq = MPTCP_SKB_CB(skb)->end_seq; max_seq = atomic64_read(&msk->rcv_wnd_sent); - pr_debug("msk=%p seq=%llx limit=%llx empty=%d\n", msk, seq, max_seq, + pr_debug("msk=%p seq=%x limit=%x empty=%d\n", msk, seq, max_seq, RB_EMPTY_ROOT(&msk->out_of_order_queue)); - if (after64(end_seq, max_seq)) { + if (after(end_seq, max_seq)) { /* out of window */ mptcp_drop(sk, skb); - pr_debug("oow by %lld, rcv_wnd_sent %llu\n", - (unsigned long long)end_seq - (unsigned long)max_seq, + pr_debug("oow by %d, rcv_wnd_sent %llu\n", + end_seq - max_seq, (unsigned long long)atomic64_read(&msk->rcv_wnd_sent)); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_NODSSWINDOW); return; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) } /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */ - if (!before64(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) { + if (!before(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL); parent = &msk->ooo_last_skb->rbnode; p = &parent->rb_right; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) while (*p) { parent = *p; skb1 = rb_to_skb(parent); - if (before64(seq, MPTCP_SKB_CB(skb1)->map_seq)) { + if (before(seq, MPTCP_SKB_CB(skb1)->map_seq)) { p = &parent->rb_left; continue; } - if (before64(seq, MPTCP_SKB_CB(skb1)->end_seq)) { - if (!after64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) { + if (before(seq, MPTCP_SKB_CB(skb1)->end_seq)) { + if (!after(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) { /* All the bits are present. Drop. */ mptcp_drop(sk, skb); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); return; } - if (after64(seq, MPTCP_SKB_CB(skb1)->map_seq)) { + if (after(seq, MPTCP_SKB_CB(skb1)->map_seq)) { /* partial overlap: * | skb | * | skb1 | @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) merge_right: /* Remove other segments covered by skb. */ while ((skb1 = skb_rb_next(skb)) != NULL) { - if (before64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) + if (before(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) break; rb_erase(&skb1->rbnode, &msk->out_of_order_queue); mptcp_drop(sk, skb1); @@ -XXX,XX +XXX,XX @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset) /* the skb map_seq accounts for the skb offset: * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq - * value + * value; note that seq numbers are truncated to 32bits */ MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow) - offset; MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + skb->len; + MPTCP_SKB_CB(skb)->flags = 0; MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp; MPTCP_SKB_CB(skb)->cant_coalesce = 0; @@ -XXX,XX +XXX,XX @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset) static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) { - u64 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; + u32 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; struct mptcp_sock *msk = mptcp_sk(sk); + u32 ack_seq = msk->ack_seq; struct sk_buff *tail; mptcp_borrow_fwdmem(sk, skb); - if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) { + if (MPTCP_SKB_CB(skb)->map_seq == ack_seq) { /* in sequence */ msk->bytes_received += copy_len; WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len); @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) skb_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); return true; - } else if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) { + } else if (after(MPTCP_SKB_CB(skb)->map_seq, ack_seq)) { mptcp_data_queue_ofo(msk, skb); return false; } @@ -XXX,XX +XXX,XX @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) { struct sock *sk = (struct sock *)msk; struct sk_buff *skb, *tail; + u32 seq_delta, ack_seq; bool moved = false; struct rb_node *p; - u64 end_seq; p = rb_first(&msk->out_of_order_queue); pr_debug("msk=%p empty=%d\n", msk, RB_EMPTY_ROOT(&msk->out_of_order_queue)); while (p) { + ack_seq = msk->ack_seq; skb = rb_to_skb(p); - if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) + if (after(MPTCP_SKB_CB(skb)->map_seq, ack_seq)) break; p = rb_next(p); rb_erase(&skb->rbnode, &msk->out_of_order_queue); - if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq, - msk->ack_seq))) { + if (unlikely(!after(MPTCP_SKB_CB(skb)->end_seq, ack_seq))) { mptcp_drop(sk, skb); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); continue; } - end_seq = MPTCP_SKB_CB(skb)->end_seq; + seq_delta = MPTCP_SKB_CB(skb)->end_seq - ack_seq; tail = skb_peek_tail(&sk->sk_receive_queue); if (!tail || !mptcp_try_coalesce(sk, tail, skb)) { - int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq; + int delta = ack_seq - MPTCP_SKB_CB(skb)->map_seq; /* skip overlapping data, if any */ - pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d\n", - MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq, + pr_debug("uncoalesced seq=%x ack seq=%x delta=%d\n", + MPTCP_SKB_CB(skb)->map_seq, ack_seq, delta); __skb_queue_tail(&sk->sk_receive_queue, skb); } - msk->bytes_received += end_seq - msk->ack_seq; - WRITE_ONCE(msk->ack_seq, end_seq); + msk->bytes_received += seq_delta; + WRITE_ONCE(msk->ack_seq, msk->ack_seq + seq_delta); moved = true; } return moved; @@ -XXX,XX +XXX,XX @@ static bool mptcp_move_skbs(struct sock *sk) return enqueued; } -static unsigned int mptcp_inq_hint(const struct sock *sk) +static int mptcp_inq_hint(const struct sock *sk) { const struct mptcp_sock *msk = mptcp_sk(sk); const struct sk_buff *skb; skb = skb_peek(&sk->sk_receive_queue); if (skb) { - u64 hint_val = READ_ONCE(msk->ack_seq) - MPTCP_SKB_CB(skb)->map_seq; + int hint_val = (u32)READ_ONCE(msk->ack_seq) - + MPTCP_SKB_CB(skb)->map_seq; - if (hint_val >= INT_MAX) - return INT_MAX; + if (hint_val < 0) + return -hint_val; - return (unsigned int)hint_val; + return hint_val; } if (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN)) @@ -XXX,XX +XXX,XX @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, tcp_recv_timestamp(msg, sk, &tss); if (cmsg_flags & MPTCP_CMSG_INQ) { - unsigned int inq = mptcp_inq_hint(sk); + int inq = mptcp_inq_hint(sk); put_cmsg(msg, SOL_TCP, TCP_CM_INQ, sizeof(inq), &inq); } @@ -XXX,XX +XXX,XX @@ static int mptcp_napi_poll(struct napi_struct *napi, int budget) return work_done; } +#define CHK_CB_FIELD(mptcp_field, tcp_field) \ + ({ \ + BUILD_BUG_ON(offsetof(struct mptcp_skb_cb, mptcp_field) != \ + offsetof(struct tcp_skb_cb, tcp_field)); \ + BUILD_BUG_ON(offsetofend(struct mptcp_skb_cb, mptcp_field) != \ + offsetofend(struct tcp_skb_cb, tcp_field)); \ + }) + void __init mptcp_proto_init(void) { struct mptcp_delegated_action *delegated; int cpu; + CHK_CB_FIELD(map_seq, seq); + CHK_CB_FIELD(end_seq, end_seq); + CHK_CB_FIELD(flags, tcp_flags); + mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo; if (percpu_counter_init(&mptcp_sockets_allocated, 0, GFP_KERNEL)) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ #define MPTCP_SYNC_SNDBUF 7 struct mptcp_skb_cb { - u64 map_seq; - u64 end_seq; + u32 map_seq; + u32 end_seq; + u32 unused; + u16 flags; u8 has_rxtstamp; u8 cant_coalesce; }; -- 2.53.0 The end goal is to avoid duplicating the quite untrivial strategy at MPTCP level. After the previous patch, the mentioned helpers could process skbs standing in MPTCP-level queues without any CB-related adaptation. The only additional adjustment needed is explicitly providing the OoO queue reference, to cope with different sk layout. Additionally rename the helper to clearly document its hybrid nature and let it return the number of collapsed skbs, to allow proper accounting from the future MPTCP caller. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- rfc -> v1: - fix arg typo Note: - this will need a significant amount of testing at the TCP level and explicit approval from Eric, which I can't guess if we can hope. --- include/net/tcp.h | 8 +++++++ net/ipv4/tcp_input.c | 55 ++++++++++++++++++++++++++++---------------- 2 files changed, 43 insertions(+), 20 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index XXXXXXX..XXXXXXX 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -XXX,XX +XXX,XX @@ extern void tcp_openreq_init_rwin(struct request_sock *req, void tcp_enter_memory_pressure(struct sock *sk); void tcp_leave_memory_pressure(struct sock *sk); +unsigned int xtcp_collapse(struct sock *sk, struct sk_buff_head *list, + struct rb_root *root, struct sk_buff *head, + struct sk_buff *tail, u32 start, u32 end, + u8 scaling_ratio); +unsigned int xtcp_collapse_ofo_queue(struct sock *sk, + struct rb_root *out_of_order_queue, + struct sk_buff **ooo_last_skb, + u8 scaling_ratio); static inline int keepalive_intvl_when(const struct tcp_sock *tp) { diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index XXXXXXX..XXXXXXX 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -XXX,XX +XXX,XX @@ static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, /* Collapse contiguous sequence of skbs head..tail with * sequence numbers start..end. * + * sk can be either a TCP or an MPTCP socket. + * * If tail is NULL, this means until the end of the queue. * * Segments with FIN/SYN are not collapsed (only because this * simplifies code) + * + * Returns the number of collapsed skbs. */ -static void -tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, - struct sk_buff *head, struct sk_buff *tail, u32 start, u32 end) +unsigned int +xtcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, + struct sk_buff *head, struct sk_buff *tail, u32 start, u32 end, + u8 scaling_ratio) { struct sk_buff *skb = head, *n; + unsigned int collapsed = 0; struct sk_buff_head tmp; bool end_of_skbs; @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, /* No new bits? It is possible on ofo queue. */ if (!before(start, TCP_SKB_CB(skb)->end_seq)) { + collapsed++; skb = tcp_collapse_one(sk, skb, list, root); if (!skb) break; @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, * overlaps to the next one and mptcp allow collapsing. */ if (!(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) && - (tcp_win_from_space(sk, skb->truesize) > skb->len || + (__tcp_win_from_space(scaling_ratio, skb->truesize) > skb->len || before(TCP_SKB_CB(skb)->seq, start))) { end_of_skbs = false; break; @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, if (end_of_skbs || (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) || !skb_frags_readable(skb)) - return; + return collapsed; __skb_queue_head_init(&tmp); @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, start += size; } if (!before(start, TCP_SKB_CB(skb)->end_seq)) { + collapsed++; skb = tcp_collapse_one(sk, skb, list, root); if (!skb || skb == tail || @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, end: skb_queue_walk_safe(&tmp, skb, n) tcp_rbtree_insert(root, skb); + return collapsed; } /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs - * and tcp_collapse() them until all the queue is collapsed. + * and xtcp_collapse() them until all the queue is collapsed. */ -static void tcp_collapse_ofo_queue(struct sock *sk) +unsigned int xtcp_collapse_ofo_queue(struct sock *sk, + struct rb_root *ooo_queue, + struct sk_buff **ooo_last_skb, + u8 scaling_ratio) { - struct tcp_sock *tp = tcp_sk(sk); - u32 range_truesize, sum_tiny = 0; + u32 range_truesize, sum_tiny = 0, collapsed = 0; struct sk_buff *skb, *head; u32 start, end; - skb = skb_rb_first(&tp->out_of_order_queue); + skb = skb_rb_first(ooo_queue); new_range: if (!skb) { - tp->ooo_last_skb = skb_rb_last(&tp->out_of_order_queue); - return; + *ooo_last_skb = skb_rb_last(ooo_queue); + return collapsed; } start = TCP_SKB_CB(skb)->seq; end = TCP_SKB_CB(skb)->end_seq; @@ -XXX,XX +XXX,XX @@ static void tcp_collapse_ofo_queue(struct sock *sk) /* Do not attempt collapsing tiny skbs */ if (range_truesize != head->truesize || end - start >= SKB_WITH_OVERHEAD(PAGE_SIZE)) { - tcp_collapse(sk, NULL, &tp->out_of_order_queue, - head, skb, start, end); + collapsed += xtcp_collapse(sk, NULL, ooo_queue, + head, skb, start, end, + scaling_ratio); } else { sum_tiny += range_truesize; if (sum_tiny > sk->sk_rcvbuf >> 3) - return; + return collapsed; } goto new_range; } @@ -XXX,XX +XXX,XX @@ static void tcp_collapse_ofo_queue(struct sock *sk) if (after(TCP_SKB_CB(skb)->end_seq, end)) end = TCP_SKB_CB(skb)->end_seq; } + return collapsed; } /* @@ -XXX,XX +XXX,XX @@ static int tcp_prune_queue(struct sock *sk, const struct sk_buff *in_skb) if (tcp_can_ingest(sk, in_skb)) return 0; - tcp_collapse_ofo_queue(sk); + xtcp_collapse_ofo_queue(sk, &tp->out_of_order_queue, + &tp->ooo_last_skb, tp->scaling_ratio); if (!skb_queue_empty(&sk->sk_receive_queue)) - tcp_collapse(sk, &sk->sk_receive_queue, NULL, - skb_peek(&sk->sk_receive_queue), - NULL, - tp->copied_seq, tp->rcv_nxt); + xtcp_collapse(sk, &sk->sk_receive_queue, NULL, + skb_peek(&sk->sk_receive_queue), + NULL, + tp->copied_seq, tp->rcv_nxt, + tp->scaling_ratio); if (tcp_can_ingest(sk, in_skb)) return 0; -- 2.53.0 Leverage the hybrid helper to implement the receive queue and OoO queue collapsing at ingress time when reaching memory bounds. If the msk is owned by the user-space at incoming skb time, perform the pruning in the release_cb. The prune check is additionally performed when the skb reaches the msk-level queues. Pruning is not needed for fallback socket, as their MPTCP-level OoO queue must always be empty: remove the ingress check for such scenario and relay on the TCP-level one.. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- RFC -> v1: - use data_seq only when available - avoid ack_seq lockless access - drop limit on fallback - collapse rcvqueue, too - drop only when pruning is not possible and over rcvbuf * 2 Notes: - Similarly to path 'mptcp: move checks vs rcvbuf size earlier in the RX path', some cleanup/tuning in mptcp_over_limit() will be needed - Pruning in the release_cb() is likely not needed, should probably be removed (after more testing). --- net/mptcp/mib.c | 3 ++ net/mptcp/mib.h | 3 ++ net/mptcp/options.c | 40 +++++++++++++++++++++++--- net/mptcp/protocol.c | 68 ++++++++++++++++++++++++++++++++++++++++++++ net/mptcp/protocol.h | 2 ++ 5 files changed, 112 insertions(+), 4 deletions(-) diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/mib.c +++ b/net/mptcp/mib.c @@ -XXX,XX +XXX,XX @@ static const struct snmp_mib mptcp_snmp_list[] = { SNMP_MIB_ITEM("SimultConnectFallback", MPTCP_MIB_SIMULTCONNFALLBACK), SNMP_MIB_ITEM("FallbackFailed", MPTCP_MIB_FALLBACKFAILED), SNMP_MIB_ITEM("WinProbe", MPTCP_MIB_WINPROBE), + SNMP_MIB_ITEM("OfoPruned", MPTCP_MIB_OFO_PRUNED), + SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED), + SNMP_MIB_ITEM("RcvCollapsed", MPTCP_MIB_RCVCOLLAPSED), }; /* mptcp_mib_alloc - allocate percpu mib counters diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/mib.h +++ b/net/mptcp/mib.h @@ -XXX,XX +XXX,XX @@ enum linux_mptcp_mib_field { MPTCP_MIB_SIMULTCONNFALLBACK, /* Simultaneous connect */ MPTCP_MIB_FALLBACKFAILED, /* Can't fallback due to msk status */ MPTCP_MIB_WINPROBE, /* MPTCP-level zero window probe */ + MPTCP_MIB_OFO_PRUNED, /* MPTCP-level OoO queue pruned */ + MPTCP_MIB_RCVPRUNED, /* Dropped due to memory constrains */ + MPTCP_MIB_RCVCOLLAPSED, /* Collapsed due to memory pressure */ __MPTCP_MIB_MAX }; diff --git a/net/mptcp/options.c b/net/mptcp/options.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -XXX,XX +XXX,XX @@ static bool add_addr_hmac_valid(struct mptcp_sock *msk, return hmac == mp_opt->ahmac; } -static bool mptcp_over_limit(const struct sock *sk, struct sk_buff *skb) +static bool mptcp_over_limit(struct sock *sk, struct sk_buff *skb, + const struct mptcp_options_received *mp_opt) { + struct mptcp_sock *msk = mptcp_sk(sk); + bool ret; + if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) return false; - return sk_rmem_alloc_get(sk) > READ_ONCE(sk->sk_rcvbuf); + /* Allow some slack for backlog processing */ + if (sk_rmem_alloc_get(sk) < READ_ONCE(sk->sk_rcvbuf)) + return false; + + mptcp_data_lock(sk); + if (!sock_owned_by_user(sk)) { + /* When the data seqence is not (yet) available for the, + * incoming skb, allow pruning the whole OoO queue + */ + u32 seq = !mp_opt->use_map || mp_opt->mpc_map ? msk->ack_seq : + mp_opt->data_seq; + + __mptcp_check_prune(sk, seq); + ret = sk_rmem_alloc_get(sk) > READ_ONCE(sk->sk_rcvbuf); + } else { + u64 limit = ((u64)READ_ONCE(sk->sk_rcvbuf)) << 1; + + /* Pruning will take place later in the RX path, allow + * some extra slack. + */ + ret = sk_rmem_alloc_get(sk) > limit; + __set_bit(MPTCP_PRUNE, &msk->cb_flags); + } + mptcp_data_unlock(sk); + return ret; } /* Return false when the caller must drop the packet, i.e. in case of error, @@ -XXX,XX +XXX,XX @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) __mptcp_data_acked(subflow->conn); mptcp_data_unlock(subflow->conn); - if (mptcp_over_limit(subflow->conn, skb)) + /* Will use ack_seq as limit for OoO pruning; any value would do + * as OoO queue must be empty. + */ + mp_opt.use_map = 0; + if (mptcp_over_limit(subflow->conn, skb, &mp_opt)) return false; return true; } @@ -XXX,XX +XXX,XX @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) return true; } - if (mptcp_over_limit(subflow->conn, skb)) + if (mptcp_over_limit(subflow->conn, skb, &mp_opt)) return false; mpext = skb_ext_add(skb, SKB_EXT_MPTCP); diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset) skb_dst_drop(skb); } +/* "Inspired" from the TCP version */ +static void mptcp_prune_ofo_queue(struct sock *sk, u32 seq) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + struct rb_node *node, *prev; + bool pruned = false; + + if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) + return; + + node = &msk->ooo_last_skb->rbnode; + + do { + struct sk_buff *skb = rb_to_skb(node); + + /* If incoming skb would land last in ofo queue, stop pruning. */ + if (after(seq, MPTCP_SKB_CB(skb)->map_seq)) + break; + + pruned = true; + prev = rb_prev(node); + rb_erase(node, &msk->out_of_order_queue); + mptcp_drop(sk, skb); + msk->ooo_last_skb = rb_to_skb(prev); + if (atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf) + break; + + node = prev; + } while (node); + + if (pruned) + NET_INC_STATS(sock_net(sk), MPTCP_MIB_OFO_PRUNED); +} + +bool __mptcp_check_prune(struct sock *sk, u32 seq) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + unsigned int dropped; + + if (likely(atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf)) + return false; + + dropped = xtcp_collapse_ofo_queue(sk, &msk->out_of_order_queue, + &msk->ooo_last_skb, msk->scaling_ratio); + if (!skb_queue_empty(&sk->sk_receive_queue)) + dropped += xtcp_collapse(sk, &sk->sk_receive_queue, NULL, + skb_peek(&sk->sk_receive_queue), + NULL, + msk->copied_seq, msk->ack_seq, + msk->scaling_ratio); + + if (dropped) + MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RCVCOLLAPSED, dropped); + if (likely(atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf)) + return false; + + mptcp_prune_ofo_queue(sk, seq); + return atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf; +} + static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) { u32 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) mptcp_borrow_fwdmem(sk, skb); + if (__mptcp_check_prune(sk, MPTCP_SKB_CB(skb)->map_seq)) { + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED); + mptcp_drop(sk, skb); + return false; + } + if (MPTCP_SKB_CB(skb)->map_seq == ack_seq) { /* in sequence */ msk->bytes_received += copy_len; @@ -XXX,XX +XXX,XX @@ static void mptcp_release_cb(struct sock *sk) __mptcp_error_report(sk); if (__test_and_clear_bit(MPTCP_SYNC_SNDBUF, &msk->cb_flags)) __mptcp_sync_sndbuf(sk); + if (__test_and_clear_bit(MPTCP_PRUNE, &msk->cb_flags)) + __mptcp_check_prune(sk, msk->ack_seq - 1); } } diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ #define MPTCP_FLUSH_JOIN_LIST 5 #define MPTCP_SYNC_STATE 6 #define MPTCP_SYNC_SNDBUF 7 +#define MPTCP_PRUNE 8 struct mptcp_skb_cb { u32 map_seq; @@ -XXX,XX +XXX,XX @@ bool __mptcp_close(struct sock *sk, long timeout); void mptcp_cancel_work(struct sock *sk); void __mptcp_unaccepted_force_close(struct sock *sk); void mptcp_set_state(struct sock *sk, int state); +bool __mptcp_check_prune(struct sock *sk, u32 seq); bool mptcp_addresses_equal(const struct mptcp_addr_info *a, const struct mptcp_addr_info *b, bool use_port); -- 2.53.0 After dropping any data already acked at the TCP level, the MPTCP must avoid inducing TCP-level retransmission until the pruned data has been successfully acked at MPTCP level. Otherwise the subflows could keep retransmitting skbs carring OoO MPTCP data, preventing reinjections and stalling completely the data transfer. Explicitly keep track of the highest pruned MPTCP-level seq number and stop dropping at TCP level until such sequence has been acked. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/options.c | 7 ++++++- net/mptcp/protocol.c | 14 +++++++++++++- net/mptcp/protocol.h | 1 + net/mptcp/subflow.c | 1 + 4 files changed, 21 insertions(+), 2 deletions(-) diff --git a/net/mptcp/options.c b/net/mptcp/options.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -XXX,XX +XXX,XX @@ static bool mptcp_over_limit(struct sock *sk, struct sk_buff *skb, __set_bit(MPTCP_PRUNE, &msk->cb_flags); } mptcp_data_unlock(sk); - return ret; + + /* After pruning any packets ensure that MPTCP-driven drops do not + * cause TCP-level retransmission + */ + return ret && + !before(READ_ONCE(msk->ack_seq), READ_ONCE(msk->pruned_seq)); } /* Return false when the caller must drop the packet, i.e. in case of error, diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static void mptcp_prune_ofo_queue(struct sock *sk, u32 seq) struct mptcp_sock *msk = mptcp_sk(sk); struct rb_node *node, *prev; bool pruned = false; + u32 pruned_seq; if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) return; node = &msk->ooo_last_skb->rbnode; + pruned_seq = msk->pruned_seq; do { struct sk_buff *skb = rb_to_skb(node); @@ -XXX,XX +XXX,XX @@ static void mptcp_prune_ofo_queue(struct sock *sk, u32 seq) pruned = true; prev = rb_prev(node); rb_erase(node, &msk->out_of_order_queue); + if (after(MPTCP_SKB_CB(skb)->end_seq, pruned_seq)) + pruned_seq = MPTCP_SKB_CB(skb)->end_seq; mptcp_drop(sk, skb); msk->ooo_last_skb = rb_to_skb(prev); + if (atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf) break; node = prev; } while (node); - if (pruned) + if (pruned) { + WRITE_ONCE(msk->pruned_seq, pruned_seq); NET_INC_STATS(sock_net(sk), MPTCP_MIB_OFO_PRUNED); + } } bool __mptcp_check_prune(struct sock *sk, u32 seq) @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) mptcp_borrow_fwdmem(sk, skb); if (__mptcp_check_prune(sk, MPTCP_SKB_CB(skb)->map_seq)) { + if (after(MPTCP_SKB_CB(skb)->end_seq, msk->pruned_seq)) + WRITE_ONCE(msk->pruned_seq, MPTCP_SKB_CB(skb)->end_seq); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED); mptcp_drop(sk, skb); return false; @@ -XXX,XX +XXX,XX @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) WRITE_ONCE(msk->ack_seq, msk->ack_seq + seq_delta); moved = true; } + if (after(msk->ack_seq, msk->pruned_seq)) + WRITE_ONCE(msk->pruned_seq, (u32)msk->ack_seq); return moved; } @@ -XXX,XX +XXX,XX @@ static int mptcp_disconnect(struct sock *sk, int flags) /* for fallback's sake */ WRITE_ONCE(msk->ack_seq, 0); WRITE_ONCE(msk->copied_seq, 0); + WRITE_ONCE(msk->pruned_seq, 0); WRITE_ONCE(sk->sk_shutdown, 0); sk_error_report(sk); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ struct mptcp_sock { u64 bytes_acked; u64 snd_una; u64 wnd_end; + u32 pruned_seq; /* if after ack_seq, highest seq pruned */ u32 last_data_sent; u32 last_data_recv; u32 last_ack_recv; diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -XXX,XX +XXX,XX @@ static void subflow_set_remote_key(struct mptcp_sock *msk, WRITE_ONCE(msk->remote_key, subflow->remote_key); WRITE_ONCE(msk->ack_seq, subflow->iasn); WRITE_ONCE(msk->copied_seq, subflow->iasn); + WRITE_ONCE(msk->pruned_seq, subflow->iasn); WRITE_ONCE(msk->can_ack, true); atomic64_set(&msk->rcv_wnd_sent, subflow->iasn); } -- 2.53.0 This is a cleanup in order to make the next patch simpler. No functional change intended. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/protocol.c | 74 +++++++++++++++++++++++++------------------- 1 file changed, 43 insertions(+), 31 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static void mptcp_check_fastclose(struct mptcp_sock *msk) sk_error_report(sk); } -static void __mptcp_retrans(struct sock *sk) +/* Retransmit the specified data fragment on all the selected subflows. */ +static int __mptcp_push_retrans(struct sock *sk, struct mptcp_data_frag *dfrag) { struct mptcp_sendmsg_info info = { .data_lock_held = true, }; struct mptcp_sock *msk = mptcp_sk(sk); struct mptcp_subflow_context *subflow; - struct mptcp_data_frag *dfrag; struct sock *ssk; - int ret, err; - u16 len = 0; - - mptcp_clean_una_wakeup(sk); - - /* first check ssk: need to kick "stale" logic */ - err = mptcp_sched_get_retrans(msk); - dfrag = mptcp_rtx_head(sk); - if (!dfrag) { - if (mptcp_data_fin_enabled(msk)) { - struct inet_connection_sock *icsk = inet_csk(sk); - - WRITE_ONCE(icsk->icsk_retransmits, - icsk->icsk_retransmits + 1); - mptcp_set_datafin_timeout(sk); - mptcp_send_ack(msk); - - goto reset_timer; - } - - if (!mptcp_send_head(sk)) - goto clear_scheduled; - - goto reset_timer; - } - - if (err) - goto reset_timer; + int ret, len = 0; mptcp_for_each_subflow(msk, subflow) { if (READ_ONCE(subflow->scheduled)) { @@ -XXX,XX +XXX,XX @@ static void __mptcp_retrans(struct sock *sk) !msk->allow_subflows) { spin_unlock_bh(&msk->fallback_lock); release_sock(ssk); - goto clear_scheduled; + return -1; } while (info.sent < info.limit) { @@ -XXX,XX +XXX,XX @@ static void __mptcp_retrans(struct sock *sk) release_sock(ssk); } } + return len; +} + +static void __mptcp_retrans(struct sock *sk) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + struct mptcp_subflow_context *subflow; + struct mptcp_data_frag *dfrag; + int err, len; + + mptcp_clean_una_wakeup(sk); + + /* first check ssk: need to kick "stale" logic */ + err = mptcp_sched_get_retrans(msk); + dfrag = mptcp_rtx_head(sk); + if (!dfrag) { + if (mptcp_data_fin_enabled(msk)) { + struct inet_connection_sock *icsk = inet_csk(sk); + + WRITE_ONCE(icsk->icsk_retransmits, + icsk->icsk_retransmits + 1); + mptcp_set_datafin_timeout(sk); + mptcp_send_ack(msk); + + goto reset_timer; + } + + if (!mptcp_send_head(sk)) + goto clear_scheduled; + + goto reset_timer; + } + + if (err) + goto reset_timer; + + len = __mptcp_push_retrans(sk, dfrag); + if (len < 0) + goto clear_scheduled; msk->bytes_retrans += len; dfrag->already_sent = max(dfrag->already_sent, len); -- 2.53.0 Currently the MPTCP core enforces that when MPTCP-level retrans timer fires, at most a single dfrag is retransmitted. If some corner-cases it may be necessary retransmit multiple dfrags, and the MPTCP socket will need to wait multiple retrans timeout to accomplish that. Remove the mentioned constraint, allowing to transmit multiple dfrags per retrans period, as long as the scheduler keeps selecting subflows for retransmissions and pending data is available in the rtx queue. The default scheduler will transmit a dfrag per available subflow. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/protocol.c | 84 +++++++++++++++++++++++++------------------- 1 file changed, 47 insertions(+), 37 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static void __mptcp_clean_una_wakeup(struct sock *sk) mptcp_write_space(sk); } -static void mptcp_clean_una_wakeup(struct sock *sk) -{ - mptcp_data_lock(sk); - __mptcp_clean_una_wakeup(sk); - mptcp_data_unlock(sk); -} - static void mptcp_enter_memory_pressure(struct sock *sk) { struct mptcp_subflow_context *subflow; @@ -XXX,XX +XXX,XX @@ static void mptcp_check_fastclose(struct mptcp_sock *msk) sk_error_report(sk); } -/* Retransmit the specified data fragment on all the selected subflows. */ -static int __mptcp_push_retrans(struct sock *sk, struct mptcp_data_frag *dfrag) +/* + * Retransmit the specified data fragment on all the selected subflows, + * starting from the specified sequence + */ +static int __mptcp_push_retrans(struct sock *sk, struct mptcp_data_frag *dfrag, + u64 retrans_seq) { struct mptcp_sendmsg_info info = { .data_lock_held = true, }; struct mptcp_sock *msk = mptcp_sk(sk); @@ -XXX,XX +XXX,XX @@ static int __mptcp_push_retrans(struct sock *sk, struct mptcp_data_frag *dfrag) lock_sock(ssk); /* limit retransmission to the bytes already sent on some subflows */ - info.sent = 0; + info.sent = retrans_seq - dfrag->data_seq; info.limit = READ_ONCE(msk->csum_enabled) ? dfrag->data_len : dfrag->already_sent; @@ -XXX,XX +XXX,XX @@ static void __mptcp_retrans(struct sock *sk) struct mptcp_sock *msk = mptcp_sk(sk); struct mptcp_subflow_context *subflow; struct mptcp_data_frag *dfrag; + u64 retrans_seq; int err, len; - mptcp_clean_una_wakeup(sk); - - /* first check ssk: need to kick "stale" logic */ - err = mptcp_sched_get_retrans(msk); - dfrag = mptcp_rtx_head(sk); - if (!dfrag) { - if (mptcp_data_fin_enabled(msk)) { - struct inet_connection_sock *icsk = inet_csk(sk); + mptcp_data_lock(sk); + __mptcp_clean_una_wakeup(sk); + retrans_seq = msk->snd_una; + mptcp_data_unlock(sk); - WRITE_ONCE(icsk->icsk_retransmits, - icsk->icsk_retransmits + 1); - mptcp_set_datafin_timeout(sk); - mptcp_send_ack(msk); + for (;;) { + /* first check ssk: need to kick "stale" logic */ + err = mptcp_sched_get_retrans(msk); + dfrag = mptcp_rtx_head(sk); + if (!dfrag) { + if (mptcp_data_fin_enabled(msk)) { + struct inet_connection_sock *icsk = inet_csk(sk); + + WRITE_ONCE(icsk->icsk_retransmits, + icsk->icsk_retransmits + 1); + mptcp_set_datafin_timeout(sk); + mptcp_send_ack(msk); + break; + } - goto reset_timer; + if (!mptcp_send_head(sk)) + goto clear_scheduled; + break; } - if (!mptcp_send_head(sk)) - goto clear_scheduled; - - goto reset_timer; - } - - if (err) - goto reset_timer; + if (err) + break; - len = __mptcp_push_retrans(sk, dfrag); - if (len < 0) - goto clear_scheduled; + /* Skip the data already retransmitted in this run */ + while (dfrag && !before64(retrans_seq, dfrag->data_seq + + dfrag->already_sent)) + dfrag = list_is_last(&dfrag->list, &msk->rtx_queue) ? NULL : + list_next_entry(dfrag, list); + if (!dfrag || !dfrag->already_sent) + break; - msk->bytes_retrans += len; - dfrag->already_sent = max(dfrag->already_sent, len); + len = __mptcp_push_retrans(sk, dfrag, retrans_seq); + if (len < 0) + goto clear_scheduled; + if (!len) + break; -reset_timer: + retrans_seq += len; + msk->bytes_retrans += len; + dfrag->already_sent = max(dfrag->already_sent, len); + } mptcp_check_and_set_pending(sk); if (!mptcp_rtx_timer_pending(sk)) -- 2.53.0 This an attempt to fix the data transfer stall reported by Geliang and Gang more carefully enforcing memory constraints at the MPTCP level. Patch 1/10 moves the bound check before entering the TCP socket. Patch 2, 3, 4 and 5 are cleanups/refactors finalized to safely re-using TCP helpers on MPTCP skbs. Patch 6 makes TCP pruning related helpers available to MPTCP and patch 7 makes use of them. Patch 8 addresses an edge scenario that could still lead to transfer stall under memory pressure. Finally patch 9 and 10 improve the MPTCP-level retransmission schema to make recovery from memory pressure significanly faster. Note that the diffstat is biases by the quite large patch 4/9, which contains mechanical transformation of existing code; "real" changes are noticiable smaller. Tested successfully vs the test cases proposed by Geliang and Gang and vs the selftests. --- Notes: - Sashiko apparently can't understand that mptcp_data_lock() && sk not owned by the user-space is equivalent to the sk socket lock. As a consequences marks incorrectly as racy a few accesses under the data lock to the sk_rcvbuf. - mptcp_join with "4 subflows with under pressure" may require longer than default timeout, as the transfer in such condition can be really slow. Paolo Abeni (10): mptcp: move checks vs rcvbuf size earlier in the RX path mptcp: drop the mptcp_ooo_try_coalesce() helper mptcp: drop the cant_coalesce CB field mptcp: remove CB offset field mptcp: sync mptcp skb cb layout with tcp one tcp: expose the tcp_collapse_ofo_queue() helper to mptcp usage, too mptcp: implemented OoO queue pruning mptcp: track prune recovery status mptcp: move the retrans loop to a separate helper mptcp: let the retrans scheduler do its job. include/net/tcp.h | 8 + net/ipv4/tcp_input.c | 55 +++--- net/mptcp/fastopen.c | 9 +- net/mptcp/mib.c | 3 + net/mptcp/mib.h | 3 + net/mptcp/options.c | 58 ++++++- net/mptcp/protocol.c | 403 ++++++++++++++++++++++++++++--------------- net/mptcp/protocol.h | 18 +- net/mptcp/subflow.c | 10 ++ 9 files changed, 398 insertions(+), 169 deletions(-) -- 2.53.0 Currently the enforcement of the rcvbuf constraint is implemented when moving the skbs into the msk receive or OoO queue. Under significant memory pressure the above can cause permanent data transfer stalls. Move the checks early on, before landing even in the subflow queues. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- v1 -> v2: - deal correctly with tcp fin and zero win probe RFC -> v1: - limit vs actual buffer size - use CB info instead of skb->len Note that: - this needs the follow-up patches to really fix the stall - the memory comparison is intentionally very rough, as the msk socket lock is not currently held where the condition is now enforced. This should require some refinement, shared as-is to avoid more latency on my side --- net/mptcp/options.c | 25 +++++++++++++++++++++++-- net/mptcp/protocol.c | 10 ++-------- 2 files changed, 25 insertions(+), 10 deletions(-) diff --git a/net/mptcp/options.c b/net/mptcp/options.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -XXX,XX +XXX,XX @@ static bool add_addr_hmac_valid(struct mptcp_sock *msk, return hmac == mp_opt->ahmac; } -/* Return false in case of error (or subflow has been reset), - * else return true. +static bool mptcp_over_limit(struct sock *sk, const struct sock *ssk, + const struct sk_buff *skb) +{ + if (likely(sk_rmem_alloc_get(sk) <= READ_ONCE(sk->sk_rcvbuf))) + return false; + + /* Avoid silently dropping pure acks, fin or zero win probes. */ + if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || + TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN || + !after(TCP_SKB_CB(skb)->end_seq, tcp_sk(ssk)->rcv_nxt)) + return false; + + return true; +} + +/* Return false when the caller must drop the packet, i.e. in case of error, + * subflow has been reset, or over memory limits. */ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) { @@ -XXX,XX +XXX,XX @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) __mptcp_data_acked(subflow->conn); mptcp_data_unlock(subflow->conn); + + if (mptcp_over_limit(subflow->conn, sk, skb)) + return false; return true; } @@ -XXX,XX +XXX,XX @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) return true; } + if (mptcp_over_limit(subflow->conn, sk, skb)) + return false; + mpext = skb_ext_add(skb, SKB_EXT_MPTCP); if (!mpext) return false; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk, mptcp_init_skb(ssk, skb, offset, len); - if (own_msk && sk_rmem_alloc_get(sk) < sk->sk_rcvbuf) { + if (own_msk) { mptcp_subflow_lend_fwdmem(subflow, skb); ret |= __mptcp_move_skb(sk, skb); } else { @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skbs(struct sock *sk, struct list_head *skbs, u32 *delt *delta = 0; while (1) { - /* If the msk recvbuf is full stop, don't drop */ - if (sk_rmem_alloc_get(sk) > sk->sk_rcvbuf) - break; - prefetch(skb->next); list_del(&skb->list); *delta += skb->truesize; @@ -XXX,XX +XXX,XX @@ static bool mptcp_can_spool_backlog(struct sock *sk, struct list_head *skbs) DEBUG_NET_WARN_ON_ONCE(msk->backlog_unaccounted && sk->sk_socket && mem_cgroup_from_sk(sk)); - /* Don't spool the backlog if the rcvbuf is full. */ - if (list_empty(&msk->backlog_list) || - sk_rmem_alloc_get(sk) > sk->sk_rcvbuf) + if (list_empty(&msk->backlog_list)) return false; INIT_LIST_HEAD(skbs); -- 2.53.0 It's used to save an additional comparison for in-order skbs, but is also a barrier to remove CB offset. Remove the helper, let __mptcp_try_coalesce() always perform the sequence check and remove duplicate checks from the callers. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/protocol.c | 21 ++++++--------------- 1 file changed, 6 insertions(+), 15 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, { int limit = READ_ONCE(sk->sk_rcvbuf); - if (unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || + if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq || + unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (limit >> 3)) || !skb_try_coalesce(to, from, fragstolen, delta)) @@ -XXX,XX +XXX,XX @@ static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, return true; } -static bool mptcp_ooo_try_coalesce(struct mptcp_sock *msk, struct sk_buff *to, - struct sk_buff *from) -{ - if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq) - return false; - - return mptcp_try_coalesce((struct sock *)msk, to, from); -} - /* "inspired" by tcp_rcvbuf_grow(), main difference: * - mptcp does not maintain a msk-level window clamp * - returns true when the receive buffer is actually updated @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) /* with 2 subflows, adding at end of ooo queue is quite likely * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup. */ - if (mptcp_ooo_try_coalesce(msk, msk->ooo_last_skb, skb)) { + if (mptcp_try_coalesce(sk, msk->ooo_last_skb, skb)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL); return; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); goto merge_right; } - } else if (mptcp_ooo_try_coalesce(msk, skb1, skb)) { + } else if (mptcp_try_coalesce(sk, skb1, skb)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE); return; } @@ -XXX,XX +XXX,XX @@ static void __mptcp_add_backlog(struct sock *sk, if (!list_empty(&msk->backlog_list)) tail = list_last_entry(&msk->backlog_list, struct sk_buff, list); - if (tail && MPTCP_SKB_CB(skb)->map_seq == MPTCP_SKB_CB(tail)->end_seq && - ssk == tail->sk && + if (tail && ssk == tail->sk && __mptcp_try_coalesce(sk, tail, skb, &fragstolen, &delta)) { skb->truesize -= delta; kfree_skb_partial(skb, fragstolen); @@ -XXX,XX +XXX,XX @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) end_seq = MPTCP_SKB_CB(skb)->end_seq; tail = skb_peek_tail(&sk->sk_receive_queue); - if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) { + if (!tail || !mptcp_try_coalesce(sk, tail, skb)) { int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq; /* skip overlapping data, if any */ -- 2.53.0 Such field is used to ensure in-sequence processing in case of fastopen. Instead let's perform synchronization of the fastopen skb sequence when the IASN becomes available with the 3rd ack. When the `cant_coalesce` field has been introduced, commit f03afb3aeb9d ("mptcp: drop __mptcp_fastopen_gen_msk_ackseq()") noted that updating the already queued skb for passive fastopen socket at 3rd ack time would be difficult and race prone. The main point is that such update don't need to be synchronously performed at 3rd ack time, but is sufficient to perform it before the next segment is introduced into the msk. To such extent, add an explicit test in __mptcp_move_skb(). Performance wise this trades a conditional in the fast path - in __mptcp_try_coalesce() - with a similar one in __mptcp_move_skb() and a couple more in slow paths. After this change the user-space will always observe consistent sequence numbers in the receive queue, even in the TFO dummy mapping case. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/fastopen.c | 2 +- net/mptcp/protocol.c | 28 ++++++++++++++++++++++++++-- net/mptcp/protocol.h | 4 +++- net/mptcp/subflow.c | 7 +++++++ 4 files changed, 37 insertions(+), 4 deletions(-) diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/fastopen.c +++ b/net/mptcp/fastopen.c @@ -XXX,XX +XXX,XX @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subf MPTCP_SKB_CB(skb)->end_seq = 0; MPTCP_SKB_CB(skb)->offset = 0; MPTCP_SKB_CB(skb)->has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; - MPTCP_SKB_CB(skb)->cant_coalesce = 1; mptcp_data_lock(sk); DEBUG_NET_WARN_ON_ONCE(sock_owned_by_user_nocheck(sk)); + mptcp_sk(sk)->rcvd_dummy_seq = true; mptcp_borrow_fwdmem(sk, skb); skb_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, int limit = READ_ONCE(sk->sk_rcvbuf); if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq || - unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (limit >> 3)) || !skb_try_coalesce(to, from, fragstolen, delta)) @@ -XXX,XX +XXX,XX @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset, MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len; MPTCP_SKB_CB(skb)->offset = offset; MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp; - MPTCP_SKB_CB(skb)->cant_coalesce = 0; __skb_unlink(skb, &ssk->sk_receive_queue); @@ -XXX,XX +XXX,XX @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset, skb_dst_drop(skb); } +void __mptcp_sync_rcv_sequence(struct sock *sk) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + struct sk_buff *skb; + + if (likely(!msk->rcvd_dummy_seq)) + return; + + /* User space can have already received the TFO skb. */ + msk->rcvd_dummy_seq = false; + skb = skb_peek_tail(&sk->sk_receive_queue); + if (!skb) + return; + + MPTCP_SKB_CB(skb)->map_seq = msk->ack_seq - skb->len; + MPTCP_SKB_CB(skb)->end_seq = msk->ack_seq; +} + static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) { u64 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) mptcp_borrow_fwdmem(sk, skb); + /* Be sure to sync the eventual fastopen dummy mapping before any other + * skb lands into the msk. + */ + if (unlikely(msk->rcvd_dummy_seq)) + __mptcp_sync_rcv_sequence(sk); + if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) { /* in sequence */ msk->bytes_received += copy_len; @@ -XXX,XX +XXX,XX @@ static void mptcp_release_cb(struct sock *sk) __mptcp_error_report(sk); if (__test_and_clear_bit(MPTCP_SYNC_SNDBUF, &msk->cb_flags)) __mptcp_sync_sndbuf(sk); + if (__test_and_clear_bit(MPTCP_SYNC_SEQ, &msk->cb_flags)) + __mptcp_sync_rcv_sequence(sk); } } diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ #define MPTCP_FLUSH_JOIN_LIST 5 #define MPTCP_SYNC_STATE 6 #define MPTCP_SYNC_SNDBUF 7 +#define MPTCP_SYNC_SEQ 8 struct mptcp_skb_cb { u64 map_seq; u64 end_seq; u32 offset; u8 has_rxtstamp; - u8 cant_coalesce; }; #define MPTCP_SKB_CB(__skb) ((struct mptcp_skb_cb *)&((__skb)->cb[0])) @@ -XXX,XX +XXX,XX @@ struct mptcp_sock { u32 token; unsigned long flags; unsigned long cb_flags; + bool rcvd_dummy_seq; bool recovery; /* closing subflow write queue reinjected */ bool can_ack; bool fully_established; @@ -XXX,XX +XXX,XX @@ void mptcp_event_pm_listener(const struct sock *ssk, enum mptcp_event_type event); bool mptcp_userspace_pm_active(const struct mptcp_sock *msk); +void __mptcp_sync_rcv_sequence(struct sock *sk); void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subflow, struct request_sock *req); int mptcp_pm_genl_fill_addr(struct sk_buff *msg, diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -XXX,XX +XXX,XX @@ static void subflow_set_remote_key(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow, const struct mptcp_options_received *mp_opt) { + struct sock *sk = (struct sock *)msk; + /* active MPC subflow will reach here multiple times: * at subflow_finish_connect() time and at 4th ack time */ @@ -XXX,XX +XXX,XX @@ static void subflow_set_remote_key(struct mptcp_sock *msk, WRITE_ONCE(msk->ack_seq, subflow->iasn); WRITE_ONCE(msk->can_ack, true); atomic64_set(&msk->rcv_wnd_sent, subflow->iasn); + + if (!sock_owned_by_user(sk)) + __mptcp_sync_rcv_sequence(sk); + else + __set_bit(MPTCP_SYNC_SEQ, &msk->cb_flags); } static void mptcp_propagate_state(struct sock *sk, struct sock *ssk, -- 2.53.0 Instead, use a new msk-level field to track the bytes already consumed inside each skb, carring the amount of bytes already copied to user-space, alike what TCP is already doing. `copied_seq` is always accessed under the msk socket lock, delegating the initialization to the msk release cb, when the socket is owned by the user-space at remote key reception time. This simplify a bit the __mptcp_recvmsg_mskq() and mptcp_inq_hint() code and will also make possible the next patch. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- v1 -> v2: - deal correctly with peek, as usally "inspired" from the correspondent tcp code - update mptcp_inq_hint(), too Note: this has the potential to break almost everything. On the flip side the CB->offset vs copied_seq difference from TCP is quite confusing and removing it will be for the good. Also this explicitly relays on "mptcp: do not drop partial packets" to avoid dropping partially consumed packets --- net/mptcp/fastopen.c | 5 +-- net/mptcp/protocol.c | 89 +++++++++++++++++++------------------------- net/mptcp/protocol.h | 2 +- net/mptcp/subflow.c | 6 ++- 4 files changed, 46 insertions(+), 56 deletions(-) diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/fastopen.c +++ b/net/mptcp/fastopen.c @@ -XXX,XX +XXX,XX @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subf subflow->ssn_offset += skb->len; /* Only the sequence delta is relevant */ - MPTCP_SKB_CB(skb)->map_seq = -skb->len; - MPTCP_SKB_CB(skb)->end_seq = 0; - MPTCP_SKB_CB(skb)->offset = 0; + MPTCP_SKB_CB(skb)->map_seq = 0; + MPTCP_SKB_CB(skb)->end_seq = skb->len; MPTCP_SKB_CB(skb)->has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; mptcp_data_lock(sk); diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, int limit = READ_ONCE(sk->sk_rcvbuf); if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq || - MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (limit >> 3)) || !skb_try_coalesce(to, from, fragstolen, delta)) return false; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) skb_set_owner_r(skb, sk); } -static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset, - int copy_len) +static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); bool has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; @@ -XXX,XX +XXX,XX @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset, * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq * value */ - MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow); - MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len; - MPTCP_SKB_CB(skb)->offset = offset; + MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow) - + offset; + MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + skb->len; MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp; __skb_unlink(skb, &ssk->sk_receive_queue); @@ -XXX,XX +XXX,XX @@ void __mptcp_sync_rcv_sequence(struct sock *sk) if (!skb) return; + /* The TFO segment data sits before IDSN */ + msk->copied_seq -= skb->len; MPTCP_SKB_CB(skb)->map_seq = msk->ack_seq - skb->len; MPTCP_SKB_CB(skb)->end_seq = msk->ack_seq; } @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk, if (offset < skb->len) { size_t len = skb->len - offset; - mptcp_init_skb(ssk, skb, offset, len); + mptcp_init_skb(ssk, skb, offset); if (own_msk) { mptcp_subflow_lend_fwdmem(subflow, skb); @@ -XXX,XX +XXX,XX @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d\n", MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq, delta); - MPTCP_SKB_CB(skb)->offset += delta; - MPTCP_SKB_CB(skb)->map_seq += delta; __skb_queue_tail(&sk->sk_receive_queue, skb); } msk->bytes_received += end_seq - msk->ack_seq; @@ -XXX,XX +XXX,XX @@ static void mptcp_eat_recv_skb(struct sock *sk, struct sk_buff *skb) } static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, - size_t len, int flags, int copied_total, + size_t len, int flags, u64 *seq, struct scm_timestamping_internal *tss, int *cmsg_flags, struct sk_buff **last) { struct mptcp_sock *msk = mptcp_sk(sk); struct sk_buff *skb, *tmp; - int total_data_len = 0; int copied = 0; skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp) { - u32 delta, offset = MPTCP_SKB_CB(skb)->offset; - u32 data_len = skb->len - offset; - u32 count; + u64 offset = *seq - MPTCP_SKB_CB(skb)->map_seq; + u32 count, data_len = skb->len - offset; int err; - if (flags & MSG_PEEK) { - /* skip already peeked skbs */ - if (total_data_len + data_len <= copied_total) { - total_data_len += data_len; - *last = skb; - continue; - } - - /* skip the already peeked data in the current skb */ - delta = copied_total - total_data_len; - offset += delta; - data_len -= delta; - } + /* Skip the already peeked data. */ + if (offset >= skb->len) + continue; count = min_t(size_t, len - copied, data_len); if (!(flags & MSG_TRUNC)) { @@ -XXX,XX +XXX,XX @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, } copied += count; + *seq += count; if (!(flags & MSG_PEEK)) { msk->bytes_consumed += count; - if (count < data_len) { - MPTCP_SKB_CB(skb)->offset += count; - MPTCP_SKB_CB(skb)->map_seq += count; + if (count < data_len) break; - } mptcp_eat_recv_skb(sk, skb); } else { @@ -XXX,XX +XXX,XX @@ static bool mptcp_move_skbs(struct sock *sk) static unsigned int mptcp_inq_hint(const struct sock *sk) { const struct mptcp_sock *msk = mptcp_sk(sk); - const struct sk_buff *skb; - - skb = skb_peek(&sk->sk_receive_queue); - if (skb) { - u64 hint_val = READ_ONCE(msk->ack_seq) - MPTCP_SKB_CB(skb)->map_seq; + u64 hint_val; - if (hint_val >= INT_MAX) - return INT_MAX; + hint_val = READ_ONCE(msk->ack_seq) - msk->copied_seq; + if (hint_val >= INT_MAX) + return INT_MAX; - return (unsigned int)hint_val; - } - - if (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN)) + if (!hint_val && + (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN))) return 1; - return 0; + return (unsigned int)hint_val; } static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, @@ -XXX,XX +XXX,XX @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, struct mptcp_sock *msk = mptcp_sk(sk); struct scm_timestamping_internal tss; int copied = 0, cmsg_flags = 0; + u64 peek_seq, *seq; int target; long timeo; @@ -XXX,XX +XXX,XX @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, len = min_t(size_t, len, INT_MAX); target = sock_rcvlowat(sk, flags & MSG_WAITALL, len); + seq = &msk->copied_seq; + if (flags & MSG_PEEK) { + peek_seq = msk->copied_seq; + seq = &peek_seq; + } if (unlikely(msk->recvmsg_inq)) cmsg_flags = MPTCP_CMSG_INQ; @@ -XXX,XX +XXX,XX @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int err, bytes_read; bytes_read = __mptcp_recvmsg_mskq(sk, msg, len - copied, flags, - copied, &tss, &cmsg_flags, + seq, &tss, &cmsg_flags, &last); if (unlikely(bytes_read < 0)) { if (!copied) @@ -XXX,XX +XXX,XX @@ static int mptcp_disconnect(struct sock *sk, int flags) /* for fallback's sake */ WRITE_ONCE(msk->ack_seq, 0); + msk->copied_seq = 0; WRITE_ONCE(sk->sk_shutdown, 0); sk_error_report(sk); @@ -XXX,XX +XXX,XX @@ static void mptcp_release_cb(struct sock *sk) __mptcp_error_report(sk); if (__test_and_clear_bit(MPTCP_SYNC_SNDBUF, &msk->cb_flags)) __mptcp_sync_sndbuf(sk); - if (__test_and_clear_bit(MPTCP_SYNC_SEQ, &msk->cb_flags)) + if (__test_and_clear_bit(MPTCP_SYNC_SEQ, &msk->cb_flags)) { + struct mptcp_subflow_context *subflow; + + subflow = mptcp_subflow_ctx(msk->first); + msk->copied_seq = subflow->iasn; __mptcp_sync_rcv_sequence(sk); + } } } @@ -XXX,XX +XXX,XX @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk, u32 *off) mptcp_move_skbs(sk); while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) { - offset = MPTCP_SKB_CB(skb)->offset; + offset = msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq; if (offset < skb->len) { *off = offset; return skb; @@ -XXX,XX +XXX,XX @@ static int __mptcp_read_sock(struct sock *sk, read_descriptor_t *desc, copied += count; msk->bytes_consumed += count; - if (count < data_len) { - MPTCP_SKB_CB(skb)->offset += count; - MPTCP_SKB_CB(skb)->map_seq += count; + msk->copied_seq += count; + if (count < data_len) break; - } mptcp_eat_recv_skb(sk, skb); } diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ struct mptcp_skb_cb { u64 map_seq; u64 end_seq; - u32 offset; u8 has_rxtstamp; }; @@ -XXX,XX +XXX,XX @@ struct mptcp_sock { u64 bytes_sent; u64 snd_nxt; u64 bytes_received; + u64 copied_seq; u64 ack_seq; atomic64_t rcv_wnd_sent; u64 rcv_data_fin_seq; diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -XXX,XX +XXX,XX @@ static void subflow_set_remote_key(struct mptcp_sock *msk, WRITE_ONCE(msk->can_ack, true); atomic64_set(&msk->rcv_wnd_sent, subflow->iasn); - if (!sock_owned_by_user(sk)) + if (!sock_owned_by_user(sk)) { + msk->copied_seq = subflow->iasn; __mptcp_sync_rcv_sequence(sk); - else + } else { __set_bit(MPTCP_SYNC_SEQ, &msk->cb_flags); + } } static void mptcp_propagate_state(struct sock *sk, struct sock *ssk, -- 2.53.0 The MPTCP protocol uses a significantly different CB layout WRT TCP, as it includes different information and use 64 bits for the sequence numbers. As the msk-level rcvbuf buffer size is limited by the core socket code the INT_MAX; after validating the incoming skb vs the current receive window, we can safely use 32 bits for MPTCP-level sequence number. This allow updating the MPTCP CB layout so that fields with a corresponding TCP-level data use the same area inside the CB itself. Add build time check to ensure the latter invariant. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- v1 -> v2: - use u64 for admission checks rfc -> v1: - keep `ack_seq` up2date --- net/mptcp/fastopen.c | 2 ++ net/mptcp/protocol.c | 78 ++++++++++++++++++++++++++++---------------- net/mptcp/protocol.h | 7 ++-- 3 files changed, 56 insertions(+), 31 deletions(-) diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/fastopen.c +++ b/net/mptcp/fastopen.c @@ -XXX,XX +XXX,XX @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subf subflow->ssn_offset += skb->len; /* Only the sequence delta is relevant */ + MPTCP_SKB_CB(skb)->map_seq64 = 0; MPTCP_SKB_CB(skb)->map_seq = 0; + MPTCP_SKB_CB(skb)->flags = 0; MPTCP_SKB_CB(skb)->end_seq = skb->len; MPTCP_SKB_CB(skb)->has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, !skb_try_coalesce(to, from, fragstolen, delta)) return false; - pr_debug("colesced seq %llx into %llx new len %d new end seq %llx\n", + pr_debug("colesced seq %x into %x new len %d new end seq %x\n", MPTCP_SKB_CB(from)->map_seq, MPTCP_SKB_CB(to)->map_seq, to->len, MPTCP_SKB_CB(from)->end_seq); MPTCP_SKB_CB(to)->end_seq = MPTCP_SKB_CB(from)->end_seq; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) { struct sock *sk = (struct sock *)msk; struct rb_node **p, *parent; - u64 seq, end_seq, max_seq; + u64 end_seq, max_seq; struct sk_buff *skb1; + u32 seq; seq = MPTCP_SKB_CB(skb)->map_seq; - end_seq = MPTCP_SKB_CB(skb)->end_seq; + end_seq = MPTCP_SKB_CB(skb)->map_seq64 + skb->len; max_seq = atomic64_read(&msk->rcv_wnd_sent); - pr_debug("msk=%p seq=%llx limit=%llx empty=%d\n", msk, seq, max_seq, + /* Use the full sequence space to perform the admission checks, to + * protect vs possible wrap-arounds. + */ + pr_debug("msk=%p seq=%x limit=%llx empty=%d\n", msk, seq, max_seq, RB_EMPTY_ROOT(&msk->out_of_order_queue)); if (after64(end_seq, max_seq)) { /* out of window */ @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) } /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */ - if (!before64(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) { + if (!before(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL); parent = &msk->ooo_last_skb->rbnode; p = &parent->rb_right; @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) while (*p) { parent = *p; skb1 = rb_to_skb(parent); - if (before64(seq, MPTCP_SKB_CB(skb1)->map_seq)) { + if (before(seq, MPTCP_SKB_CB(skb1)->map_seq)) { p = &parent->rb_left; continue; } - if (before64(seq, MPTCP_SKB_CB(skb1)->end_seq)) { - if (!after64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) { + if (before(seq, MPTCP_SKB_CB(skb1)->end_seq)) { + if (!after(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) { /* All the bits are present. Drop. */ mptcp_drop(sk, skb); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); return; } - if (after64(seq, MPTCP_SKB_CB(skb1)->map_seq)) { + if (after(seq, MPTCP_SKB_CB(skb1)->map_seq)) { /* partial overlap: * | skb | * | skb1 | @@ -XXX,XX +XXX,XX @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb) merge_right: /* Remove other segments covered by skb. */ while ((skb1 = skb_rb_next(skb)) != NULL) { - if (before64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) + if (before((u32)end_seq, MPTCP_SKB_CB(skb1)->end_seq)) break; rb_erase(&skb1->rbnode, &msk->out_of_order_queue); mptcp_drop(sk, skb1); @@ -XXX,XX +XXX,XX @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset) struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); bool has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; - /* the skb map_seq accounts for the skb offset: + /* The skb map_seq accounts for the skb offset: * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq - * value + * value; note that end seq number is only available in 32bits format. */ - MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow) - - offset; + MPTCP_SKB_CB(skb)->map_seq64 = mptcp_subflow_get_mapped_dsn(subflow) - + offset; + MPTCP_SKB_CB(skb)->map_seq = (u32)MPTCP_SKB_CB(skb)->map_seq64; MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + skb->len; + MPTCP_SKB_CB(skb)->flags = 0; MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp; __skb_unlink(skb, &ssk->sk_receive_queue); @@ -XXX,XX +XXX,XX @@ void __mptcp_sync_rcv_sequence(struct sock *sk) /* The TFO segment data sits before IDSN */ msk->copied_seq -= skb->len; - MPTCP_SKB_CB(skb)->map_seq = msk->ack_seq - skb->len; + MPTCP_SKB_CB(skb)->map_seq64 = msk->ack_seq - skb->len; + MPTCP_SKB_CB(skb)->map_seq = (u32)MPTCP_SKB_CB(skb)->map_seq64; MPTCP_SKB_CB(skb)->end_seq = msk->ack_seq; } static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) { - u64 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; + u32 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; struct mptcp_sock *msk = mptcp_sk(sk); struct sk_buff *tail; @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) if (unlikely(msk->rcvd_dummy_seq)) __mptcp_sync_rcv_sequence(sk); - if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) { + if (MPTCP_SKB_CB(skb)->map_seq64 == msk->ack_seq) { /* in sequence */ msk->bytes_received += copy_len; WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len); @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) skb_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); return true; - } else if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) { + } else if (after64(MPTCP_SKB_CB(skb)->map_seq64 + skb->len, + msk->ack_seq)) { mptcp_data_queue_ofo(msk, skb); return false; } @@ -XXX,XX +XXX,XX @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) { struct sock *sk = (struct sock *)msk; struct sk_buff *skb, *tail; + u32 seq_delta, ack_seq; bool moved = false; struct rb_node *p; - u64 end_seq; p = rb_first(&msk->out_of_order_queue); pr_debug("msk=%p empty=%d\n", msk, RB_EMPTY_ROOT(&msk->out_of_order_queue)); while (p) { + ack_seq = msk->ack_seq; skb = rb_to_skb(p); - if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) + if (after(MPTCP_SKB_CB(skb)->map_seq, ack_seq)) break; p = rb_next(p); rb_erase(&skb->rbnode, &msk->out_of_order_queue); - if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq, - msk->ack_seq))) { + if (unlikely(!after(MPTCP_SKB_CB(skb)->end_seq, ack_seq))) { mptcp_drop(sk, skb); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); continue; } - end_seq = MPTCP_SKB_CB(skb)->end_seq; + seq_delta = MPTCP_SKB_CB(skb)->end_seq - ack_seq; tail = skb_peek_tail(&sk->sk_receive_queue); if (!tail || !mptcp_try_coalesce(sk, tail, skb)) { - int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq; + int delta = ack_seq - MPTCP_SKB_CB(skb)->map_seq; /* skip overlapping data, if any */ - pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d\n", - MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq, + pr_debug("uncoalesced seq=%x ack seq=%x delta=%d\n", + MPTCP_SKB_CB(skb)->map_seq, ack_seq, delta); __skb_queue_tail(&sk->sk_receive_queue, skb); } - msk->bytes_received += end_seq - msk->ack_seq; - WRITE_ONCE(msk->ack_seq, end_seq); + msk->bytes_received += seq_delta; + WRITE_ONCE(msk->ack_seq, msk->ack_seq + seq_delta); moved = true; } return moved; @@ -XXX,XX +XXX,XX @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, int copied = 0; skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp) { - u64 offset = *seq - MPTCP_SKB_CB(skb)->map_seq; + u32 offset = (u32)(*seq) - MPTCP_SKB_CB(skb)->map_seq; u32 count, data_len = skb->len - offset; int err; @@ -XXX,XX +XXX,XX @@ static int mptcp_napi_poll(struct napi_struct *napi, int budget) return work_done; } +#define CHK_CB_FIELD(mptcp_field, tcp_field) \ + ({ \ + BUILD_BUG_ON(offsetof(struct mptcp_skb_cb, mptcp_field) != \ + offsetof(struct tcp_skb_cb, tcp_field)); \ + BUILD_BUG_ON(offsetofend(struct mptcp_skb_cb, mptcp_field) != \ + offsetofend(struct tcp_skb_cb, tcp_field)); \ + }) + void __init mptcp_proto_init(void) { struct mptcp_delegated_action *delegated; int cpu; + CHK_CB_FIELD(map_seq, seq); + CHK_CB_FIELD(end_seq, end_seq); + CHK_CB_FIELD(flags, tcp_flags); + mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo; if (percpu_counter_init(&mptcp_sockets_allocated, 0, GFP_KERNEL)) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ #define MPTCP_SYNC_SEQ 8 struct mptcp_skb_cb { - u64 map_seq; - u64 end_seq; + u32 map_seq; + u32 end_seq; + u32 unused; + u16 flags; u8 has_rxtstamp; + u64 map_seq64; }; #define MPTCP_SKB_CB(__skb) ((struct mptcp_skb_cb *)&((__skb)->cb[0])) -- 2.53.0 The end goal is to avoid duplicating the quite untrivial strategy at MPTCP level. After the previous patch, the mentioned helpers could process skbs standing in MPTCP-level queues without any CB-related adaptation. The only additional adjustment needed is explicitly providing the OoO queue reference, to cope with different sk layout. Additionally rename the helper to clearly document its hybrid nature and let it return the number of collapsed skbs, to allow proper accounting from the future MPTCP caller. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- rfc -> v1: - fix arg typo Note: - this will need a significant amount of testing at the TCP level and explicit approval from Eric, which I can't guess if we can hope. --- include/net/tcp.h | 8 +++++++ net/ipv4/tcp_input.c | 55 ++++++++++++++++++++++++++++---------------- 2 files changed, 43 insertions(+), 20 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index XXXXXXX..XXXXXXX 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -XXX,XX +XXX,XX @@ extern void tcp_openreq_init_rwin(struct request_sock *req, void tcp_enter_memory_pressure(struct sock *sk); void tcp_leave_memory_pressure(struct sock *sk); +unsigned int xtcp_collapse(struct sock *sk, struct sk_buff_head *list, + struct rb_root *root, struct sk_buff *head, + struct sk_buff *tail, u32 start, u32 end, + u8 scaling_ratio); +unsigned int xtcp_collapse_ofo_queue(struct sock *sk, + struct rb_root *out_of_order_queue, + struct sk_buff **ooo_last_skb, + u8 scaling_ratio); static inline int keepalive_intvl_when(const struct tcp_sock *tp) { diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index XXXXXXX..XXXXXXX 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -XXX,XX +XXX,XX @@ static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, /* Collapse contiguous sequence of skbs head..tail with * sequence numbers start..end. * + * sk can be either a TCP or an MPTCP socket. + * * If tail is NULL, this means until the end of the queue. * * Segments with FIN/SYN are not collapsed (only because this * simplifies code) + * + * Returns the number of collapsed skbs. */ -static void -tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, - struct sk_buff *head, struct sk_buff *tail, u32 start, u32 end) +unsigned int +xtcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, + struct sk_buff *head, struct sk_buff *tail, u32 start, u32 end, + u8 scaling_ratio) { struct sk_buff *skb = head, *n; + unsigned int collapsed = 0; struct sk_buff_head tmp; bool end_of_skbs; @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, /* No new bits? It is possible on ofo queue. */ if (!before(start, TCP_SKB_CB(skb)->end_seq)) { + collapsed++; skb = tcp_collapse_one(sk, skb, list, root); if (!skb) break; @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, * overlaps to the next one and mptcp allow collapsing. */ if (!(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) && - (tcp_win_from_space(sk, skb->truesize) > skb->len || + (__tcp_win_from_space(scaling_ratio, skb->truesize) > skb->len || before(TCP_SKB_CB(skb)->seq, start))) { end_of_skbs = false; break; @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, if (end_of_skbs || (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) || !skb_frags_readable(skb)) - return; + return collapsed; __skb_queue_head_init(&tmp); @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, start += size; } if (!before(start, TCP_SKB_CB(skb)->end_seq)) { + collapsed++; skb = tcp_collapse_one(sk, skb, list, root); if (!skb || skb == tail || @@ -XXX,XX +XXX,XX @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root, end: skb_queue_walk_safe(&tmp, skb, n) tcp_rbtree_insert(root, skb); + return collapsed; } /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs - * and tcp_collapse() them until all the queue is collapsed. + * and xtcp_collapse() them until all the queue is collapsed. */ -static void tcp_collapse_ofo_queue(struct sock *sk) +unsigned int xtcp_collapse_ofo_queue(struct sock *sk, + struct rb_root *ooo_queue, + struct sk_buff **ooo_last_skb, + u8 scaling_ratio) { - struct tcp_sock *tp = tcp_sk(sk); - u32 range_truesize, sum_tiny = 0; + u32 range_truesize, sum_tiny = 0, collapsed = 0; struct sk_buff *skb, *head; u32 start, end; - skb = skb_rb_first(&tp->out_of_order_queue); + skb = skb_rb_first(ooo_queue); new_range: if (!skb) { - tp->ooo_last_skb = skb_rb_last(&tp->out_of_order_queue); - return; + *ooo_last_skb = skb_rb_last(ooo_queue); + return collapsed; } start = TCP_SKB_CB(skb)->seq; end = TCP_SKB_CB(skb)->end_seq; @@ -XXX,XX +XXX,XX @@ static void tcp_collapse_ofo_queue(struct sock *sk) /* Do not attempt collapsing tiny skbs */ if (range_truesize != head->truesize || end - start >= SKB_WITH_OVERHEAD(PAGE_SIZE)) { - tcp_collapse(sk, NULL, &tp->out_of_order_queue, - head, skb, start, end); + collapsed += xtcp_collapse(sk, NULL, ooo_queue, + head, skb, start, end, + scaling_ratio); } else { sum_tiny += range_truesize; if (sum_tiny > sk->sk_rcvbuf >> 3) - return; + return collapsed; } goto new_range; } @@ -XXX,XX +XXX,XX @@ static void tcp_collapse_ofo_queue(struct sock *sk) if (after(TCP_SKB_CB(skb)->end_seq, end)) end = TCP_SKB_CB(skb)->end_seq; } + return collapsed; } /* @@ -XXX,XX +XXX,XX @@ static int tcp_prune_queue(struct sock *sk, const struct sk_buff *in_skb) if (tcp_can_ingest(sk, in_skb)) return 0; - tcp_collapse_ofo_queue(sk); + xtcp_collapse_ofo_queue(sk, &tp->out_of_order_queue, + &tp->ooo_last_skb, tp->scaling_ratio); if (!skb_queue_empty(&sk->sk_receive_queue)) - tcp_collapse(sk, &sk->sk_receive_queue, NULL, - skb_peek(&sk->sk_receive_queue), - NULL, - tp->copied_seq, tp->rcv_nxt); + xtcp_collapse(sk, &sk->sk_receive_queue, NULL, + skb_peek(&sk->sk_receive_queue), + NULL, + tp->copied_seq, tp->rcv_nxt, + tp->scaling_ratio); if (tcp_can_ingest(sk, in_skb)) return 0; -- 2.53.0 Leverage the hybrid helpers to implement the receive queue and OoO queue collapsing at ingress time when reaching memory bounds. If the msk is owned by the user-space at incoming skb time, perform the pruning in the release_cb. The prune check is additionally performed when the skb reaches the msk-level queues. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- v1 -> v2: - collapse rcv queue, too - deal with MPC map, too - drop left-over sentence in the commit message RFC -> v1: - use data_seq only when available - avoid ack_seq lockless access - drop limit on fallback - collapse rcvqueue, too - drop only when pruning is not possible and over rcvbuf * 2 Notes: - Similarly to path 'mptcp: move checks vs rcvbuf size earlier in the RX path', some cleanup/tuning in mptcp_over_limit() will be needed - Pruning in the release_cb() is likely not needed, should probably be removed (after more testing). --- net/mptcp/mib.c | 3 ++ net/mptcp/mib.h | 3 ++ net/mptcp/options.c | 36 ++++++++++++++++++++--- net/mptcp/protocol.c | 69 ++++++++++++++++++++++++++++++++++++++++++++ net/mptcp/protocol.h | 2 ++ 5 files changed, 109 insertions(+), 4 deletions(-) diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/mib.c +++ b/net/mptcp/mib.c @@ -XXX,XX +XXX,XX @@ static const struct snmp_mib mptcp_snmp_list[] = { SNMP_MIB_ITEM("SimultConnectFallback", MPTCP_MIB_SIMULTCONNFALLBACK), SNMP_MIB_ITEM("FallbackFailed", MPTCP_MIB_FALLBACKFAILED), SNMP_MIB_ITEM("WinProbe", MPTCP_MIB_WINPROBE), + SNMP_MIB_ITEM("OfoPruned", MPTCP_MIB_OFO_PRUNED), + SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED), + SNMP_MIB_ITEM("RcvCollapsed", MPTCP_MIB_RCVCOLLAPSED), }; /* mptcp_mib_alloc - allocate percpu mib counters diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/mib.h +++ b/net/mptcp/mib.h @@ -XXX,XX +XXX,XX @@ enum linux_mptcp_mib_field { MPTCP_MIB_SIMULTCONNFALLBACK, /* Simultaneous connect */ MPTCP_MIB_FALLBACKFAILED, /* Can't fallback due to msk status */ MPTCP_MIB_WINPROBE, /* MPTCP-level zero window probe */ + MPTCP_MIB_OFO_PRUNED, /* MPTCP-level OoO queue pruned */ + MPTCP_MIB_RCVPRUNED, /* Dropped due to memory constrains */ + MPTCP_MIB_RCVCOLLAPSED, /* Collapsed due to memory pressure */ __MPTCP_MIB_MAX }; diff --git a/net/mptcp/options.c b/net/mptcp/options.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -XXX,XX +XXX,XX @@ static bool add_addr_hmac_valid(struct mptcp_sock *msk, } static bool mptcp_over_limit(struct sock *sk, const struct sock *ssk, - const struct sk_buff *skb) + const struct sk_buff *skb, + const struct mptcp_options_received *mp_opt) { + struct mptcp_sock *msk = mptcp_sk(sk); + bool ret; + if (likely(sk_rmem_alloc_get(sk) <= READ_ONCE(sk->sk_rcvbuf))) return false; @@ -XXX,XX +XXX,XX @@ static bool mptcp_over_limit(struct sock *sk, const struct sock *ssk, !after(TCP_SKB_CB(skb)->end_seq, tcp_sk(ssk)->rcv_nxt)) return false; - return true; + mptcp_data_lock(sk); + if (!sock_owned_by_user(sk)) { + /* When the data sequence is not (yet) available for the + * incoming skb, allow pruning the whole OoO queue. + */ + u32 seq = !mp_opt->use_map || mp_opt->mpc_map ? msk->ack_seq : + mp_opt->data_seq; + + __mptcp_check_prune(sk, seq); + ret = sk_rmem_alloc_get(sk) > READ_ONCE(sk->sk_rcvbuf); + } else { + u64 limit = ((u64)READ_ONCE(sk->sk_rcvbuf)) << 1; + + /* Pruning will take place later in the RX path, allow + * some extra slack. + */ + ret = sk_rmem_alloc_get(sk) > limit; + __set_bit(MPTCP_PRUNE, &msk->cb_flags); + } + mptcp_data_unlock(sk); + return ret; } /* Return false when the caller must drop the packet, i.e. in case of error, @@ -XXX,XX +XXX,XX @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) __mptcp_data_acked(subflow->conn); mptcp_data_unlock(subflow->conn); - if (mptcp_over_limit(subflow->conn, sk, skb)) + /* Will use ack_seq as limit for OoO pruning; any value would do + * as OoO queue must be empty. + */ + mp_opt.use_map = 0; + if (mptcp_over_limit(subflow->conn, sk, skb, &mp_opt)) return false; return true; } @@ -XXX,XX +XXX,XX @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) return true; } - if (mptcp_over_limit(subflow->conn, sk, skb)) + if (mptcp_over_limit(subflow->conn, sk, skb, &mp_opt)) return false; mpext = skb_ext_add(skb, SKB_EXT_MPTCP); diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ void __mptcp_sync_rcv_sequence(struct sock *sk) MPTCP_SKB_CB(skb)->end_seq = msk->ack_seq; } +/* "Inspired" from the TCP version */ +static void mptcp_prune_ofo_queue(struct sock *sk, u32 seq) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + struct rb_node *node, *prev; + bool pruned = false; + + if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) + return; + + node = &msk->ooo_last_skb->rbnode; + + do { + struct sk_buff *skb = rb_to_skb(node); + + /* Stop pruning if the incoming skb would land in OoO tail. */ + if (after(seq, MPTCP_SKB_CB(skb)->map_seq)) + break; + + pruned = true; + prev = rb_prev(node); + rb_erase(node, &msk->out_of_order_queue); + mptcp_drop(sk, skb); + msk->ooo_last_skb = rb_to_skb(prev); + if (atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf) + break; + + node = prev; + } while (node); + + if (pruned) + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFO_PRUNED); +} + +bool __mptcp_check_prune(struct sock *sk, u32 seq) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + unsigned int dropped; + + if (likely(atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf)) + return false; + + dropped = xtcp_collapse_ofo_queue(sk, &msk->out_of_order_queue, + &msk->ooo_last_skb, + msk->scaling_ratio); + if (!skb_queue_empty(&sk->sk_receive_queue)) + dropped += xtcp_collapse(sk, &sk->sk_receive_queue, NULL, + skb_peek(&sk->sk_receive_queue), + NULL, + msk->copied_seq, msk->ack_seq, + msk->scaling_ratio); + + if (dropped) + MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RCVCOLLAPSED, dropped); + if (likely(atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf)) + return false; + + mptcp_prune_ofo_queue(sk, seq); + return atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf; +} + static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) { u32 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) if (unlikely(msk->rcvd_dummy_seq)) __mptcp_sync_rcv_sequence(sk); + if (__mptcp_check_prune(sk, MPTCP_SKB_CB(skb)->map_seq)) { + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED); + mptcp_drop(sk, skb); + return false; + } + if (MPTCP_SKB_CB(skb)->map_seq64 == msk->ack_seq) { /* in sequence */ msk->bytes_received += copy_len; @@ -XXX,XX +XXX,XX @@ static void mptcp_release_cb(struct sock *sk) msk->copied_seq = subflow->iasn; __mptcp_sync_rcv_sequence(sk); } + if (__test_and_clear_bit(MPTCP_PRUNE, &msk->cb_flags)) + __mptcp_check_prune(sk, msk->ack_seq - 1); } } diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ #define MPTCP_SYNC_STATE 6 #define MPTCP_SYNC_SNDBUF 7 #define MPTCP_SYNC_SEQ 8 +#define MPTCP_PRUNE 9 struct mptcp_skb_cb { u32 map_seq; @@ -XXX,XX +XXX,XX @@ bool __mptcp_close(struct sock *sk, long timeout); void mptcp_cancel_work(struct sock *sk); void __mptcp_unaccepted_force_close(struct sock *sk); void mptcp_set_state(struct sock *sk, int state); +bool __mptcp_check_prune(struct sock *sk, u32 seq); bool mptcp_addresses_equal(const struct mptcp_addr_info *a, const struct mptcp_addr_info *b, bool use_port); -- 2.53.0 After dropping any data already acked at the TCP level, the MPTCP must avoid inducing TCP-level retransmission until the pruned data has been successfully acked at MPTCP level. Otherwise the subflows could keep retransmitting skbs carring OoO MPTCP data, preventing reinjections and stalling completely the data transfer. Explicitly keep track of the highest pruned MPTCP-level seq number and stop dropping at TCP level until such sequence has been acked. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/options.c | 7 ++++++- net/mptcp/protocol.c | 14 +++++++++++++- net/mptcp/protocol.h | 3 +++ net/mptcp/subflow.c | 1 + 4 files changed, 23 insertions(+), 2 deletions(-) diff --git a/net/mptcp/options.c b/net/mptcp/options.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -XXX,XX +XXX,XX @@ static bool mptcp_over_limit(struct sock *sk, const struct sock *ssk, __set_bit(MPTCP_PRUNE, &msk->cb_flags); } mptcp_data_unlock(sk); - return ret; + + /* After pruning any packets ensure that MPTCP-driven drops do not + * cause TCP-level retransmission + */ + return ret && + !before(READ_ONCE(msk->ack_seq), READ_ONCE(msk->pruned_seq)); } /* Return false when the caller must drop the packet, i.e. in case of error, diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static void mptcp_prune_ofo_queue(struct sock *sk, u32 seq) struct mptcp_sock *msk = mptcp_sk(sk); struct rb_node *node, *prev; bool pruned = false; + u32 pruned_seq; if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) return; node = &msk->ooo_last_skb->rbnode; + pruned_seq = msk->pruned_seq; do { struct sk_buff *skb = rb_to_skb(node); @@ -XXX,XX +XXX,XX @@ static void mptcp_prune_ofo_queue(struct sock *sk, u32 seq) pruned = true; prev = rb_prev(node); rb_erase(node, &msk->out_of_order_queue); + if (after(MPTCP_SKB_CB(skb)->end_seq, pruned_seq)) + pruned_seq = MPTCP_SKB_CB(skb)->end_seq; mptcp_drop(sk, skb); msk->ooo_last_skb = rb_to_skb(prev); + if (atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf) break; node = prev; } while (node); - if (pruned) + if (pruned) { + WRITE_ONCE(msk->pruned_seq, pruned_seq); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFO_PRUNED); + } } bool __mptcp_check_prune(struct sock *sk, u32 seq) @@ -XXX,XX +XXX,XX @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) __mptcp_sync_rcv_sequence(sk); if (__mptcp_check_prune(sk, MPTCP_SKB_CB(skb)->map_seq)) { + if (after(MPTCP_SKB_CB(skb)->end_seq, msk->pruned_seq)) + WRITE_ONCE(msk->pruned_seq, MPTCP_SKB_CB(skb)->end_seq); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED); mptcp_drop(sk, skb); return false; @@ -XXX,XX +XXX,XX @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) WRITE_ONCE(msk->ack_seq, msk->ack_seq + seq_delta); moved = true; } + if (after(msk->ack_seq, msk->pruned_seq)) + WRITE_ONCE(msk->pruned_seq, (u32)msk->ack_seq); return moved; } @@ -XXX,XX +XXX,XX @@ static int mptcp_disconnect(struct sock *sk, int flags) /* for fallback's sake */ WRITE_ONCE(msk->ack_seq, 0); msk->copied_seq = 0; + WRITE_ONCE(msk->pruned_seq, 0); WRITE_ONCE(sk->sk_shutdown, 0); sk_error_report(sk); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -XXX,XX +XXX,XX @@ struct mptcp_sock { u64 bytes_acked; u64 snd_una; u64 wnd_end; + u32 pruned_seq; /* If above ack_seq, highest + * seq pruned. + */ u32 last_data_sent; u32 last_data_recv; u32 last_ack_recv; diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -XXX,XX +XXX,XX @@ static void subflow_set_remote_key(struct mptcp_sock *msk, WRITE_ONCE(msk->remote_key, subflow->remote_key); WRITE_ONCE(msk->ack_seq, subflow->iasn); + WRITE_ONCE(msk->pruned_seq, subflow->iasn); WRITE_ONCE(msk->can_ack, true); atomic64_set(&msk->rcv_wnd_sent, subflow->iasn); -- 2.53.0 This is a cleanup in order to make the next patch simpler. No functional change intended. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/protocol.c | 74 +++++++++++++++++++++++++------------------- 1 file changed, 43 insertions(+), 31 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static void mptcp_check_fastclose(struct mptcp_sock *msk) sk_error_report(sk); } -static void __mptcp_retrans(struct sock *sk) +/* Retransmit the specified data fragment on all the selected subflows. */ +static int __mptcp_push_retrans(struct sock *sk, struct mptcp_data_frag *dfrag) { struct mptcp_sendmsg_info info = { .data_lock_held = true, }; struct mptcp_sock *msk = mptcp_sk(sk); struct mptcp_subflow_context *subflow; - struct mptcp_data_frag *dfrag; struct sock *ssk; - int ret, err; - u16 len = 0; - - mptcp_clean_una_wakeup(sk); - - /* first check ssk: need to kick "stale" logic */ - err = mptcp_sched_get_retrans(msk); - dfrag = mptcp_rtx_head(sk); - if (!dfrag) { - if (mptcp_data_fin_enabled(msk)) { - struct inet_connection_sock *icsk = inet_csk(sk); - - WRITE_ONCE(icsk->icsk_retransmits, - icsk->icsk_retransmits + 1); - mptcp_set_datafin_timeout(sk); - mptcp_send_ack(msk); - - goto reset_timer; - } - - if (!mptcp_send_head(sk)) - goto clear_scheduled; - - goto reset_timer; - } - - if (err) - goto reset_timer; + int ret, len = 0; mptcp_for_each_subflow(msk, subflow) { if (READ_ONCE(subflow->scheduled)) { @@ -XXX,XX +XXX,XX @@ static void __mptcp_retrans(struct sock *sk) !msk->allow_subflows) { spin_unlock_bh(&msk->fallback_lock); release_sock(ssk); - goto clear_scheduled; + return -1; } while (info.sent < info.limit) { @@ -XXX,XX +XXX,XX @@ static void __mptcp_retrans(struct sock *sk) release_sock(ssk); } } + return len; +} + +static void __mptcp_retrans(struct sock *sk) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + struct mptcp_subflow_context *subflow; + struct mptcp_data_frag *dfrag; + int err, len; + + mptcp_clean_una_wakeup(sk); + + /* first check ssk: need to kick "stale" logic */ + err = mptcp_sched_get_retrans(msk); + dfrag = mptcp_rtx_head(sk); + if (!dfrag) { + if (mptcp_data_fin_enabled(msk)) { + struct inet_connection_sock *icsk = inet_csk(sk); + + WRITE_ONCE(icsk->icsk_retransmits, + icsk->icsk_retransmits + 1); + mptcp_set_datafin_timeout(sk); + mptcp_send_ack(msk); + + goto reset_timer; + } + + if (!mptcp_send_head(sk)) + goto clear_scheduled; + + goto reset_timer; + } + + if (err) + goto reset_timer; + + len = __mptcp_push_retrans(sk, dfrag); + if (len < 0) + goto clear_scheduled; msk->bytes_retrans += len; dfrag->already_sent = max(dfrag->already_sent, len); -- 2.53.0 Currently the MPTCP core enforces that when MPTCP-level retrans timer fires, at most a single dfrag is retransmitted. If some corner-cases it may be necessary retransmit multiple dfrags, and the MPTCP socket will need to wait multiple retrans timeout to accomplish that. Remove the mentioned constraint, allowing to transmit multiple dfrags per retrans period, as long as the scheduler keeps selecting subflows for retransmissions and pending data is available in the rtx queue. The default scheduler will transmit a dfrag per available subflow. Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- v1 -> v2: - fix retrans sequence update (sashiko) --- net/mptcp/protocol.c | 82 ++++++++++++++++++++++++++------------------ 1 file changed, 48 insertions(+), 34 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index XXXXXXX..XXXXXXX 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -XXX,XX +XXX,XX @@ static void __mptcp_clean_una_wakeup(struct sock *sk) mptcp_write_space(sk); } -static void mptcp_clean_una_wakeup(struct sock *sk) -{ - mptcp_data_lock(sk); - __mptcp_clean_una_wakeup(sk); - mptcp_data_unlock(sk); -} - static void mptcp_enter_memory_pressure(struct sock *sk) { struct mptcp_subflow_context *subflow; @@ -XXX,XX +XXX,XX @@ static void mptcp_check_fastclose(struct mptcp_sock *msk) sk_error_report(sk); } -/* Retransmit the specified data fragment on all the selected subflows. */ +/* + * Retransmit the specified data fragment on all the selected subflows, + * starting from the specified sequence + */ static int __mptcp_push_retrans(struct sock *sk, struct mptcp_data_frag *dfrag) { struct mptcp_sendmsg_info info = { .data_lock_held = true, }; @@ -XXX,XX +XXX,XX @@ static void __mptcp_retrans(struct sock *sk) struct mptcp_sock *msk = mptcp_sk(sk); struct mptcp_subflow_context *subflow; struct mptcp_data_frag *dfrag; + u64 retrans_seq; int err, len; - mptcp_clean_una_wakeup(sk); - - /* first check ssk: need to kick "stale" logic */ - err = mptcp_sched_get_retrans(msk); - dfrag = mptcp_rtx_head(sk); - if (!dfrag) { - if (mptcp_data_fin_enabled(msk)) { - struct inet_connection_sock *icsk = inet_csk(sk); + mptcp_data_lock(sk); + __mptcp_clean_una_wakeup(sk); + retrans_seq = msk->snd_una; + mptcp_data_unlock(sk); - WRITE_ONCE(icsk->icsk_retransmits, - icsk->icsk_retransmits + 1); - mptcp_set_datafin_timeout(sk); - mptcp_send_ack(msk); + for (;;) { + /* first check ssk: need to kick "stale" logic */ + err = mptcp_sched_get_retrans(msk); + dfrag = mptcp_rtx_head(sk); + if (!dfrag) { + if (mptcp_data_fin_enabled(msk)) { + struct inet_connection_sock *icsk; + + icsk = inet_csk(sk); + WRITE_ONCE(icsk->icsk_retransmits, + icsk->icsk_retransmits + 1); + mptcp_set_datafin_timeout(sk); + mptcp_send_ack(msk); + break; + } - goto reset_timer; + if (!mptcp_send_head(sk)) + goto clear_scheduled; + break; } - if (!mptcp_send_head(sk)) - goto clear_scheduled; - - goto reset_timer; - } + if (err) + break; - if (err) - goto reset_timer; + /* Skip the data already retransmitted in this run */ + while (dfrag && !before64(retrans_seq, dfrag->data_seq + + dfrag->data_len)) + dfrag = list_is_last(&dfrag->list, &msk->rtx_queue) ? + NULL : list_next_entry(dfrag, list); + if (!dfrag || !dfrag->already_sent) + break; - len = __mptcp_push_retrans(sk, dfrag); - if (len < 0) - goto clear_scheduled; + len = __mptcp_push_retrans(sk, dfrag); + if (len < 0) + goto clear_scheduled; - msk->bytes_retrans += len; - dfrag->already_sent = max(dfrag->already_sent, len); + retrans_seq += len; + msk->bytes_retrans += len; + dfrag->already_sent = max(dfrag->already_sent, len); -reset_timer: + /* Attempt the next fragment only if the current one is + * completely retransmitted + */ + if (dfrag->already_sent < dfrag->data_len) + break; + } mptcp_check_and_set_pending(sk); if (!mptcp_rtx_timer_pending(sk)) -- 2.53.0