Report sequence numbers relative to their initial data sequence
numbers instead of exposing the raw connection-level values.

Keep the sequence-number baselines in the MPTCP socket so diagnostic
reporting does not depend on a subflow context that may be reset.

Link: https://github.com/multipath-tcp/mptcp_net-next/issues/445
Signed-off-by: Kalpan Jani <kalpan.jani@mpiricsoftware.com>
---
Changes since v8:
- Keep local and remote IDSN baselines in the MPTCP socket, so reporting does not depend on a subflow context that may be reset.
- Normalize mptcpi_write_seq, mptcpi_snd_una, and mptcpi_rcv_nxt relative to their IDSN baselines.
- Initialize the MPTCP_INFO output structure to zero.

v8: https://lore.kernel.org/all/20261014130809.1874184-1-kalpan.jani@mpiricsoftware.com/
---
 net/mptcp/protocol.c |  4 ++++
 net/mptcp/protocol.h |  2 ++
 net/mptcp/sockopt.c  | 14 ++++++++++----
 net/mptcp/subflow.c  |  5 ++++-
 4 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b474d03620a75..fb47384ace9c6 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3178,6 +3178,8 @@ static void __mptcp_init_sock(struct sock *sk)
 	INIT_WORK(&msk->work, mptcp_worker);
 	msk->out_of_order_queue = RB_ROOT;
 	msk->first_pending = NULL;
+	WRITE_ONCE(msk->local_idsn, 0);
+	WRITE_ONCE(msk->remote_idsn, 0);
 
 	/* msk does not go through tcp_init_sock(); seed RTO bounds. */
 	icsk->icsk_rto_min =
@@ -3722,6 +3724,7 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
 
 	msk = mptcp_sk(nsk);
 	WRITE_ONCE(msk->local_key, subflow_req->local_key);
+	WRITE_ONCE(msk->local_idsn, subflow_req->idsn);
 	WRITE_ONCE(msk->token, subflow_req->token);
 	msk->in_accept_queue = 1;
 	WRITE_ONCE(msk->fully_established, false);
@@ -4160,6 +4163,7 @@ static int mptcp_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
 					     MPTCP_MIB_TOKENFALLBACKINIT);
 	}
 
+	WRITE_ONCE(msk->local_idsn, subflow->idsn);
 	WRITE_ONCE(msk->write_seq, subflow->idsn);
 	WRITE_ONCE(msk->snd_nxt, subflow->idsn);
 	WRITE_ONCE(msk->snd_una, subflow->idsn);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 06a107d4e8392..9238031f3adb0 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -286,6 +286,8 @@ struct mptcp_sock {
 						 * lockless access read
 						 */
 	u64		remote_key;		/* same as above */
+	u64		local_idsn;
+	u64		remote_idsn;
 	u64		write_seq;
 	u64		bytes_sent;
 	u64		snd_nxt;
diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index fcf6feb2a9eb5..b1e41c967157e 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -971,6 +971,7 @@ static int mptcp_getsockopt_first_sf_only(struct mptcp_sock *msk, int level, int
 void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
 {
 	struct sock *sk = (struct sock *)msk;
+	u64 local_idsn = 0, remote_idsn = 0;
 	u32 flags = 0;
 	bool slow;
 	u32 now;
@@ -1008,9 +1009,11 @@ void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
 	info->mptcpi_flags = flags;
 
 	slow = lock_sock_fast(sk);
+	local_idsn = READ_ONCE(msk->local_idsn);
+
 	info->mptcpi_csum_enabled = READ_ONCE(msk->csum_enabled);
 	info->mptcpi_token = msk->token;
-	info->mptcpi_write_seq = msk->write_seq;
+	info->mptcpi_write_seq = msk->write_seq - local_idsn;
 	info->mptcpi_retransmits = inet_csk(sk)->icsk_retransmits;
 	info->mptcpi_bytes_sent = msk->bytes_sent;
 	info->mptcpi_bytes_received = msk->bytes_received;
@@ -1023,17 +1026,20 @@ void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
 	unlock_sock_fast(sk, slow);
 
 	mptcp_data_lock(sk);
+	if (READ_ONCE(msk->can_ack))
+		remote_idsn = READ_ONCE(msk->remote_idsn);
 	info->mptcpi_last_ack_recv = jiffies_to_msecs(now - msk->last_ack_recv);
-	info->mptcpi_snd_una = msk->snd_una;
-	info->mptcpi_rcv_nxt = msk->ack_seq;
+	info->mptcpi_snd_una = msk->snd_una - local_idsn;
+	info->mptcpi_rcv_nxt = msk->ack_seq - remote_idsn;
 	info->mptcpi_bytes_acked = msk->bytes_acked;
 	mptcp_data_unlock(sk);
+
 }
 EXPORT_SYMBOL_GPL(mptcp_diag_fill_info);
 
 static int mptcp_getsockopt_info(struct mptcp_sock *msk, char __user *optval, int __user *optlen)
 {
-	struct mptcp_info m_info;
+	struct mptcp_info m_info = {};
 	int len;
 
 	if (get_user(len, optlen))
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index af81ad5e699d1..cfc703bd5dd69 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -481,7 +481,6 @@ static void subflow_set_remote_key(struct mptcp_sock *msk,
 	if (subflow->remote_key_valid)
 		return;
 
-	subflow->remote_key_valid = 1;
 	subflow->remote_key = mp_opt->sndr_key;
 	mptcp_crypto_key_sha(subflow->remote_key, NULL, &subflow->iasn);
 	subflow->iasn++;
@@ -490,9 +489,13 @@ static void subflow_set_remote_key(struct mptcp_sock *msk,
 	subflow->map_seq = subflow->iasn;
 
 	WRITE_ONCE(msk->remote_key, subflow->remote_key);
+	WRITE_ONCE(msk->remote_idsn, subflow->iasn - 1);
 	WRITE_ONCE(msk->ack_seq, subflow->iasn);
 	WRITE_ONCE(msk->can_ack, true);
 	atomic64_set(&msk->rcv_wnd_sent, subflow->iasn);
+
+	/* publish last, once iasn and the fields above are fully populated */
+	subflow->remote_key_valid = 1;
 }
 
 static void mptcp_propagate_state(struct sock *sk, struct sock *ssk,
-- 
2.43.0

Hi Kalpan,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Success! ✅
- KVM Validation: debug (except selftest_mptcp_join): Success! ✅
- KVM Validation: debug (only selftest_mptcp_join): Success! ✅
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Perf: Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/38721441830

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/1a9206c4d367
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1186354


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)