Date: Mon, 10 Sep 2012 11:43:29 +0000 (UTC) From: Gleb Smirnoff <glebius@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: r240307 - stable/9/sys/netinet Message-ID: <201209101143.q8ABhTVY047020@svn.freebsd.org>
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Author: glebius Date: Mon Sep 10 11:43:28 2012 New Revision: 240307 URL: http://svn.freebsd.org/changeset/base/240307 Log: Merge r238516 from head: If ip_output() returns EMSGSIZE to tcp_output(), then the latter calls tcp_mtudisc(), which in its turn may call tcp_output(). Under certain conditions (must admit they are very special) an infinite recursion can happen. To avoid recursion we can pass struct route to ip_output() and obtain correct mtu. This allows us not to use tcp_mtudisc() but call tcp_mss_update() directly. PR: kern/155585 Submitted by: zont Modified: stable/9/sys/netinet/tcp_output.c Directory Properties: stable/9/sys/ (props changed) Modified: stable/9/sys/netinet/tcp_output.c ============================================================================== --- stable/9/sys/netinet/tcp_output.c Mon Sep 10 11:38:55 2012 (r240306) +++ stable/9/sys/netinet/tcp_output.c Mon Sep 10 11:43:28 2012 (r240307) @@ -182,7 +182,7 @@ tcp_output(struct tcpcb *tp) int idle, sendalot; int sack_rxmit, sack_bytes_rxmt; struct sackhole *p; - int tso; + int tso, mtu; struct tcpopt to; #if 0 int maxburst = TCP_MAXBURST; @@ -223,6 +223,7 @@ again: tcp_sack_adjust(tp); sendalot = 0; tso = 0; + mtu = 0; off = tp->snd_nxt - tp->snd_una; sendwin = min(tp->snd_wnd, tp->snd_cwnd); @@ -1206,6 +1207,9 @@ timer: */ #ifdef INET6 if (isipv6) { + struct route_in6 ro; + + bzero(&ro, sizeof(ro)); /* * we separately set hoplimit for every segment, since the * user might want to change the value via setsockopt. @@ -1215,10 +1219,13 @@ timer: ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); /* TODO: IPv6 IP6TOS_ECT bit on */ - error = ip6_output(m, - tp->t_inpcb->in6p_outputopts, NULL, - ((so->so_options & SO_DONTROUTE) ? - IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); + error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, + ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), + NULL, NULL, tp->t_inpcb); + + if (error == EMSGSIZE && ro.ro_rt != NULL) + mtu = ro.ro_rt->rt_rmx.rmx_mtu; + RO_RTFREE(&ro); } #endif /* INET6 */ #if defined(INET) && defined(INET6) @@ -1226,6 +1233,9 @@ timer: #endif #ifdef INET { + struct route ro; + + bzero(&ro, sizeof(ro)); ip->ip_len = m->m_pkthdr.len; #ifdef INET6 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) @@ -1242,9 +1252,13 @@ timer: if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) ip->ip_off |= IP_DF; - error = ip_output(m, tp->t_inpcb->inp_options, NULL, + error = ip_output(m, tp->t_inpcb->inp_options, &ro, ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, tp->t_inpcb); + + if (error == EMSGSIZE && ro.ro_rt != NULL) + mtu = ro.ro_rt->rt_rmx.rmx_mtu; + RO_RTFREE(&ro); } #endif /* INET */ if (error) { @@ -1291,21 +1305,18 @@ out: * For some reason the interface we used initially * to send segments changed to another or lowered * its MTU. - * - * tcp_mtudisc() will find out the new MTU and as - * its last action, initiate retransmission, so it - * is important to not do so here. - * * If TSO was active we either got an interface * without TSO capabilits or TSO was turned off. - * Disable it for this connection as too and - * immediatly retry with MSS sized segments generated - * by this function. + * If we obtained mtu from ip_output() then update + * it and try again. */ if (tso) tp->t_flags &= ~TF_TSO; - tcp_mtudisc(tp->t_inpcb, -1); - return (0); + if (mtu != 0) { + tcp_mss_update(tp, -1, mtu, NULL, NULL); + goto again; + } + return (error); case EHOSTDOWN: case EHOSTUNREACH: case ENETDOWN:
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