Commit 972ca7a3 authored by Paolo Abeni's avatar Paolo Abeni Committed by Jakub Kicinski
Browse files

tcp: do not set a zero size receive buffer 



The nipa CI is reporting frequent failures in the mptcp_connect
self-tests.

In the failing scenarios (TCP -> MPTCP) the involved sockets are
actually plain TCP ones, as fallback for passive socket at 2whs
time cause the MPTCP listener to actually create a TCP socket.

The transfer is stuck due to the receiver buffer being zero.
With the stronger check in place, tcp_clamp_window() can be invoked
while the TCP socket has sk_rmem_alloc == 0, and the receive buffer
will be zeroed, too.

Check for the critical condition in tcp_prune_queue() and just
drop the packet without shrinking the receiver buffer.

Fixes: 1d2fbaad ("tcp: stronger sk_rcvbuf checks")
Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20c18165d3f848e1c5c1b782d88c1a5ab38b3f70.1753118029.git.pabeni@redhat.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 8839d1cc

net/ipv4/tcp_input.c

+4 −0
Original line number Diff line number Diff line
@@ -5549,6 +5549,10 @@ static int tcp_prune_queue(struct sock *sk, const struct sk_buff *in_skb) 
{

	struct tcp_sock *tp = tcp_sk(sk);



	/* Do nothing if our queues are empty. */

	if (!atomic_read(&sk->sk_rmem_alloc))

		return -1;



	NET_INC_STATS(sock_net(sk), LINUX_MIB_PRUNECALLED);



	if (!tcp_can_ingest(sk, in_skb))