From: Paolo Abeni pabeni@redhat.com

commit 56b824eb49d6258aa0bad09a406ceac3f643cdae upstream.

Currently the skb size after coalescing is only limited by the skb layout (the skb must not carry frag_list). A single coalesced skb covering several MSS can potentially fill completely the receive buffer. In such a case, the snd win will zero until the receive buffer will be empty again, affecting tput badly.

Fixes: 8268ed4c9d19 ("mptcp: introduce and use mptcp_try_coalesce()") Cc: stable@vger.kernel.org # please delay 2 weeks after 6.13-final release Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Link: https://patch.msgid.link/20241230-net-mptcp-rbuf-fixes-v1-3-8608af434ceb@ker... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- Notes: - We asked to delay the patch. There were no conflicts. --- net/mptcp/protocol.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index f337dd3323a0..c6a11d6df516 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -133,6 +133,7 @@ static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, int delta;

if (MPTCP_SKB_CB(from)->offset || + ((to->len + from->len) > (sk->sk_rcvbuf >> 3)) || !skb_try_coalesce(to, from, &fragstolen, &delta)) return false;