Date: Fri, 5 Jul 2013 14:24:38 +0000 (UTC) From: Andre Oppermann <andre@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org Subject: svn commit: r252786 - stable/9/sys/netinet Message-ID: <201307051424.r65EOco3056662@svn.freebsd.org>
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Author: andre Date: Fri Jul 5 14:24:37 2013 New Revision: 252786 URL: http://svnweb.freebsd.org/changeset/base/252786 Log: MFC r249809: When doing RFC3042 limited transmit on the first on second 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> Modified: stable/9/sys/netinet/tcp_input.c Directory Properties: stable/9/sys/ (props changed) Modified: stable/9/sys/netinet/tcp_input.c ============================================================================== --- stable/9/sys/netinet/tcp_input.c Fri Jul 5 14:18:09 2013 (r252785) +++ stable/9/sys/netinet/tcp_input.c Fri Jul 5 14:24:37 2013 (r252786) @@ -2532,6 +2532,7 @@ tcp_do_segment(struct mbuf *m, struct tc 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, @@ -2553,7 +2554,17 @@ tcp_do_segment(struct mbuf *m, struct tc */ 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 &&
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