Date: Mon, 29 Jun 2015 21:23:55 +0000 (UTC) From: Hiren Panchasara <hiren@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r284941 - head/sys/netinet Message-ID: <201506292123.t5TLNter074580@svn.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: hiren Date: Mon Jun 29 21:23:54 2015 New Revision: 284941 URL: https://svnweb.freebsd.org/changeset/base/284941 Log: 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 Differential Revision: D2946 Submitted by: jlott at averesystems dot com Reviewed by: jhb, jch, gnn, hiren Tested by: jlott at averesystems dot com, jch MFC after: 2 weeks Modified: head/sys/netinet/tcp_output.c Modified: head/sys/netinet/tcp_output.c ============================================================================== --- head/sys/netinet/tcp_output.c Mon Jun 29 19:09:16 2015 (r284940) +++ head/sys/netinet/tcp_output.c Mon Jun 29 21:23:54 2015 (r284941) @@ -1394,6 +1394,30 @@ timer: tp->t_rxtshift = 0; } tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); + } else if (len == 0 && sbavail(&so->so_snd) && + !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 { /*
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201506292123.t5TLNter074580>