Date: Wed, 22 Jul 2015 15:05:46 +0000 (UTC) From: Hiren Panchasara <hiren@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: svn commit: r285793 - stable/10/sys/netinet Message-ID: <201507221505.t6MF5kIG092911@repo.freebsd.org>
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Author: hiren Date: Wed Jul 22 15:05:45 2015 New Revision: 285793 URL: https://svnweb.freebsd.org/changeset/base/285793 Log: MFC r284941: Avoid a situation where we do not set persist timer after a zero window condition. If you send a 0-length packet, but there is data is the socket buffer, and neither the rexmt or persist timer is already set, then activate the persist timer. PR: 192599 Approved by: re (delphij) Modified: stable/10/sys/netinet/tcp_output.c Directory Properties: stable/10/ (props changed) Modified: stable/10/sys/netinet/tcp_output.c ============================================================================== --- stable/10/sys/netinet/tcp_output.c Wed Jul 22 11:30:37 2015 (r285792) +++ stable/10/sys/netinet/tcp_output.c Wed Jul 22 15:05:45 2015 (r285793) @@ -1397,6 +1397,30 @@ timer: tp->t_rxtshift = 0; } tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); + } else if (len == 0 && so->so_snd.sb_cc && + !tcp_timer_active(tp, TT_REXMT) && + !tcp_timer_active(tp, TT_PERSIST)) { + /* + * Avoid a situation where we do not set persist timer + * after a zero window condition. For example: + * 1) A -> B: packet with enough data to fill the window + * 2) B -> A: ACK for #1 + new data (0 window + * advertisement) + * 3) A -> B: ACK for #2, 0 len packet + * + * In this case, A will not activate the persist timer, + * because it chose to send a packet. Unless tcp_output + * is called for some other reason (delayed ack timer, + * another input packet from B, socket syscall), A will + * not send zero window probes. + * + * So, if you send a 0-length packet, but there is data + * in the socket buffer, and neither the rexmt or + * persist timer is already set, then activate the + * persist timer. + */ + tp->t_rxtshift = 0; + tcp_setpersist(tp); } } else { /*
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