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authorEric Dumazet <edumazet@google.com>2019-04-16 10:55:20 -0700
committerDavid S. Miller <davem@davemloft.net>2019-04-16 21:47:39 -0700
commit50ce163a72d817a99e8974222dcf2886d5deb1ae (patch)
treed23ffa9fbfcba49b44e070227d300534ab97f3ab
parent1e1caa9735f90b5452fc48685c23552e56aa1920 (diff)
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>
-rw-r--r--net/ipv4/tcp_input.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 5def3c48870e..731d3045b50a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -402,11 +402,12 @@ static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
{
struct tcp_sock *tp = tcp_sk(sk);
+ int room;
+
+ room = min_t(int, tp->window_clamp, tcp_space(sk)) - tp->rcv_ssthresh;
/* Check #1 */
- if (tp->rcv_ssthresh < tp->window_clamp &&
- (int)tp->rcv_ssthresh < tcp_space(sk) &&
- !tcp_under_memory_pressure(sk)) {
+ if (room > 0 && !tcp_under_memory_pressure(sk)) {
int incr;
/* Check #2. Increase window, if skb with such overhead
@@ -419,8 +420,7 @@ static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
if (incr) {
incr = max_t(int, incr, 2 * skb->len);
- tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr,
- tp->window_clamp);
+ tp->rcv_ssthresh += min(room, incr);
inet_csk(sk)->icsk_ack.quick |= 1;
}
}