diff options
| author | Christoph Paasch <cpaasch@openai.com> | 2025-08-15 19:28:19 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-08-18 17:39:58 -0700 |
| commit | ccab044697980c6c01ab51f43f48f13b8a3e5c33 (patch) | |
| tree | dafc3d3bc4ba75583935b0ef260322cfe81c927c | |
| parent | 84967deee9d9870b15bc4c3acb50f1d401807902 (diff) | |
mptcp: drop skb if MPTCP skb extension allocation fails
When skb_ext_add(skb, SKB_EXT_MPTCP) fails in mptcp_incoming_options(),
we used to return true, letting the segment proceed through the TCP
receive path without a DSS mapping. Such segments can leave inconsistent
mapping state and trigger a mid-stream fallback to TCP, which in testing
collapsed (by artificially forcing failures in skb_ext_add) throughput
to zero.
Return false instead so the TCP input path drops the skb (see
tcp_data_queue() and step-7 processing). This is the safer choice
under memory pressure: it preserves MPTCP correctness and provides
backpressure to the sender.
Control packets remain unaffected: ACK updates and DATA_FIN handling
happen before attempting the extension allocation, and tcp_reset()
continues to ignore the return value.
With this change, MPTCP continues to work at high throughput if we
artificially inject failures into skb_ext_add.
Fixes: 6787b7e350d3 ("mptcp: avoid processing packet if a subflow reset")
Cc: stable@vger.kernel.org
Signed-off-by: Christoph Paasch <cpaasch@openai.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250815-net-mptcp-misc-fixes-6-17-rc2-v1-1-521fe9957892@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/mptcp/options.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 70c0ab0ecf90..2a8ea28442b2 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -1118,7 +1118,9 @@ static bool add_addr_hmac_valid(struct mptcp_sock *msk, return hmac == mp_opt->ahmac; } -/* Return false if a subflow has been reset, else return true */ +/* Return false in case of error (or subflow has been reset), + * else return true. + */ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); @@ -1222,7 +1224,7 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) mpext = skb_ext_add(skb, SKB_EXT_MPTCP); if (!mpext) - return true; + return false; memset(mpext, 0, sizeof(*mpext)); |