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When doing RFC3042 limited transmit on the first on second

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duplicate ACK make sure we actually have new data to send.
This prevents us from sending unneccessary pure ACKs.

Reported by:	Matt Miller <matt@matthewjmiller.net>
Tested by:	Matt Miller <matt@matthewjmiller.net>
MFC after:	2 weeks
This commit is contained in:
Andre Oppermann 2013-04-23 14:06:32 +00:00
parent 1d8053c5c0
commit 5628dd0893
1 changed files with 12 additions and 1 deletions
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13
sys/netinet/tcp_input.c
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@ -2564,6 +2564,7 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
u_long oldcwnd = tp->snd_cwnd;
tcp_seq oldsndmax = tp->snd_max;
u_int sent;
int avail;
KASSERT(tp->t_dupacks == 1 ||
tp->t_dupacks == 2,
@ -2585,7 +2586,17 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
*/
break;
}
(void) tcp_output(tp);
/*
* Only call tcp_output when there
* is new data available to be sent.
* Otherwise we would send pure ACKs.
*/
SOCKBUF_LOCK(&so->so_snd);
avail = so->so_snd.sb_cc -
(tp->snd_nxt - tp->snd_una);
SOCKBUF_UNLOCK(&so->so_snd);
if (avail > 0)
(void) tcp_output(tp);
sent = tp->snd_max - oldsndmax;
if (sent > tp->t_maxseg) {
KASSERT((tp->t_dupacks == 2 &&