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From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Tue, 18 Feb 2025 12:24:46 +0100
Subject: [PATCH mptcp-net v2 1/2] mptcp: reset when MPTCP opts are dropped
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Message-Id: <20250218-mptcp-dss-drop-mpj-v2-1-0c6caa10ec52@kernel.org>
References: <20250218-mptcp-dss-drop-mpj-v2-0-0c6caa10ec52@kernel.org>
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To: mptcp@lists.linux.dev
Cc: Paolo Abeni <pabeni@redhat.com>,
"Matthieu Baerts (NGI0)" <matttbe@kernel.org>,
"Chester A. Unal" <chester.a.unal@xpedite-tech.com>
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Before this patch, if the checksum was not used, the subflow was only
reset if map_data_len was !=3D 0. If there were no MPTCP options or an
invalid mapping, map_data_len was not set to the data len, and then the
subflow was not reset as it should have been, leaving the MPTCP
connection in a wrong fallback mode.
This map_data_len condition has been introduced to handle the reception
of the infinite mapping. Instead, a new dedicated mapping error could
have been returned and treated as a special case. However, the commit
31bf11de146c ("mptcp: introduce MAPPING_BAD_CSUM") has been introduced
by Paolo Abeni soon after, and backported later on to stable. It better
handle the csum case, and it means the exception for valid_csum_seen in
subflow_can_fallback(), plus this one for the infinite mapping in
subflow_check_data_avail(), are no longer needed.
In other words, the code can be simplified there: a fallback should only
be done if msk->allow_infinite_fallback is set. This boolean is set to
false once MPTCP-specific operations acting on the whole MPTCP
connection vs the initial path have been done, e.g. a second path has
been created, or an MPTCP re-injection -- yes, possible even with a
single subflow. The subflow_can_fallback() helper can then be dropped,
and replaced by this single condition.
This also makes the code clearer: a fallback should only be done if it
is possible to do so.
While at it, no need to set map_data_len to 0 in get_mapping_status()
for the infinite mapping case: it will be set to skb->len just after, at
the end of subflow_check_data_avail(), and not read in between.
Fixes: f8d4bcacff3b ("mptcp: infinite mapping receiving")
Reported-by: Chester A. Unal <chester.a.unal@xpedite-tech.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/544
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Acked-by: Paolo Abeni <pabeni@redhat.com>
---
Notes:
- v2:
- Squash previous patches 1 and 2, and drop csum case from
subflow_can_fallback (Paolo).
- v2 is quite different, Chester's Tested-by tag has not been added.
---
net/mptcp/subflow.c | 15 +--------------
1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index d2caffa56bdd98f5fd9ef07fdcb3610ea186b848..5255e0cc409437ab1abb66fc855=
7d18aa4244af7 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1139,7 +1139,6 @@ static enum mapping_status get_mapping_status(struct =
sock *ssk,
if (data_len =3D=3D 0) {
pr_debug("infinite mapping received\n");
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
- subflow->map_data_len =3D 0;
return MAPPING_INVALID;
}
=20
@@ -1298,18 +1297,6 @@ static void subflow_sched_work_if_closed(struct mptc=
p_sock *msk, struct sock *ss
mptcp_schedule_work(sk);
}
=20
-static bool subflow_can_fallback(struct mptcp_subflow_context *subflow)
-{
- struct mptcp_sock *msk =3D mptcp_sk(subflow->conn);
-
- if (subflow->mp_join)
- return false;
- else if (READ_ONCE(msk->csum_enabled))
- return !subflow->valid_csum_seen;
- else
- return READ_ONCE(msk->allow_infinite_fallback);
-}
-
static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk)
{
struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk);
@@ -1405,7 +1392,7 @@ static bool subflow_check_data_avail(struct sock *ssk)
return true;
}
=20
- if (!subflow_can_fallback(subflow) && subflow->map_data_len) {
+ if (!READ_ONCE(msk->allow_infinite_fallback)) {
/* fatal protocol error, close the socket.
* subflow_error_report() will introduce the appropriate barriers
*/
--=20
2.47.1
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From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Tue, 18 Feb 2025 12:24:47 +0100
Subject: [PATCH mptcp-net v2 2/2] mptcp: safety check before fallback
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To: mptcp@lists.linux.dev
Cc: Paolo Abeni <pabeni@redhat.com>,
"Matthieu Baerts (NGI0)" <matttbe@kernel.org>
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Recently, some fallback have been initiated, while the connection was
not supposed to fallback.
Add a safety check with a warning to detect when an wrong attempt to
fallback is being done. This should help detecting any future issues
quicker.
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Acked-by: Paolo Abeni <pabeni@redhat.com>
---
Notes:
- I guess this patch could be sent to -net as well.
- We could also squash this in one of the previous commit, but because
the two are needed to avoid the warning, maybe better with a
dedicated commit?
---
net/mptcp/protocol.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index bac5c925a72f6637e33ada9869984c5902bd6a43..3d72ca1553227cb41ba8c205f42=
d1f01cc264a7e 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1198,6 +1198,8 @@ static inline void __mptcp_do_fallback(struct mptcp_s=
ock *msk)
pr_debug("TCP fallback already done (msk=3D%p)\n", msk);
return;
}
+ if (WARN_ON_ONCE(!READ_ONCE(msk->allow_infinite_fallback)))
+ return;
set_bit(MPTCP_FALLBACK_DONE, &msk->flags);
}
=20
--=20
2.47.1