tcp: tcp_grow_window() needs to respect tcp_space()
authorEric Dumazet <edumazet@google.com>
Tue, 16 Apr 2019 17:55:20 +0000 (10:55 -0700)
committerDavid S. Miller <davem@davemloft.net>
Wed, 17 Apr 2019 04:47:39 +0000 (21:47 -0700)
commit50ce163a72d817a99e8974222dcf2886d5deb1ae
treed23ffa9fbfcba49b44e070227d300534ab97f3ab
parent1e1caa9735f90b5452fc48685c23552e56aa1920
tcp: tcp_grow_window() needs to respect tcp_space()

For some reason, tcp_grow_window() correctly tests if enough room
is present before attempting to increase tp->rcv_ssthresh,
but does not prevent it to grow past tcp_space()

This is causing hard to debug issues, like failing
the (__tcp_select_window(sk) >= tp->rcv_wnd) test
in __tcp_ack_snd_check(), causing ACK delays and possibly
slow flows.

Depending on tcp_rmem[2], MTU, skb->len/skb->truesize ratio,
we can see the problem happening on "netperf -t TCP_RR -- -r 2000,2000"
after about 60 round trips, when the active side no longer sends
immediate acks.

This bug predates git history.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Wei Wang <weiwan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv4/tcp_input.c