Message ID | 1484832999-1849-1-git-send-email-alexey.kodanev@oracle.com |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
On Thu, 2017-01-19 at 16:36 +0300, Alexey Kodanev wrote: > Found that if we run LTP netstress test with large MSS (65K), > the first attempt from server to send data comparable to this > MSS on fastopen connection will be delayed by the probe timer. > > This also contradicts with the fact that we should bound to the half > of the window if it is large. > > Fix this flaw by correctly initializing max_window. Before that, it > could have large values that affect further calculations of 'size_goal'. > > Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path") > Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com> Acked-by: Eric Dumazet <edumazet@google.com> Thanks Alexey !
From: Alexey Kodanev <alexey.kodanev@oracle.com> Date: Thu, 19 Jan 2017 16:36:39 +0300 > Found that if we run LTP netstress test with large MSS (65K), > the first attempt from server to send data comparable to this > MSS on fastopen connection will be delayed by the probe timer. > > Here is an example: > > < S seq 0:0 win 43690 options [mss 65495 wscale 7 tfo cookie] length 32 > > S. seq 0:0 ack 1 win 43690 options [mss 65495 wscale 7] length 0 > < . ack 1 win 342 length 0 > > Inside tcp_sendmsg(), tcp_send_mss() returns max MSS in 'mss_now', > as well as in 'size_goal'. This results the segment not queued for > transmition until all the data copied from user buffer. Then, inside > __tcp_push_pending_frames(), it breaks on send window test and > continues with the check probe timer. > > Fragmentation occurs in tcp_write_wakeup()... > > +0.2 > P. seq 1:43777 ack 1 win 342 length 43776 > < . ack 43777, win 1365 length 0 > > P. seq 43777:65001 ack 1 win 342 options [...] length 21224 > ... > > This also contradicts with the fact that we should bound to the half > of the window if it is large. > > Fix this flaw by correctly initializing max_window. Before that, it > could have large values that affect further calculations of 'size_goal'. > > Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path") > Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com> Applied and queued up for -stable, thanks.
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c index f519195..dd2560c 100644 --- a/net/ipv4/tcp_fastopen.c +++ b/net/ipv4/tcp_fastopen.c @@ -205,6 +205,7 @@ void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb) * scaled. So correct it appropriately. */ tp->snd_wnd = ntohs(tcp_hdr(skb)->window); + tp->max_window = tp->snd_wnd; /* Activate the retrans timer so that SYNACK can be retransmitted. * The request socket is not added to the ehash