[src/netbsd-1-6]: src/sys/netinet Pullup rev 1.107 (requested by itojun in ti...

[jmc <jmc%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d0f41f725c77
branches:  netbsd-1-6
changeset: 531071:d0f41f725c77
user:      jmc <jmc%NetBSD.org@localhost>
date:      Sat Feb 07 20:06:58 2004 +0000

description:
Pullup rev 1.107 (requested by itojun in ticket #1605)

Deal with IPv6 path MTU < 1280 (RFC2460 section 5 last paragraph)
Check if there really is room for TCP data.

diffstat:

 sys/netinet/tcp_output.c |  33 +++++++++++++++++++++++++++------
 1 files changed, 27 insertions(+), 6 deletions(-)

diffs (83 lines):

diff -r 0ec7342fa27d -r d0f41f725c77 sys/netinet/tcp_output.c
--- a/sys/netinet/tcp_output.c  Sat Feb 07 20:06:04 2004 +0000
+++ b/sys/netinet/tcp_output.c  Sat Feb 07 20:06:58 2004 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tcp_output.c,v 1.79.4.4 2003/09/05 13:42:39 tron Exp $ */
+/*     $NetBSD: tcp_output.c,v 1.79.4.5 2004/02/07 20:06:58 jmc Exp $  */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -142,7 +142,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tcp_output.c,v 1.79.4.4 2003/09/05 13:42:39 tron Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tcp_output.c,v 1.79.4.5 2004/02/07 20:06:58 jmc Exp $");
 
 #include "opt_inet.h"
 #include "opt_ipsec.h"
@@ -219,7 +219,7 @@
 #ifndef GPROF
 __inline
 #endif
-void
+int
 tcp_segsize(struct tcpcb *tp, int *txsegsizep, int *rxsegsizep)
 {
 #ifdef INET
@@ -276,9 +276,23 @@
        ifp = rt->rt_ifp;
 
        size = tcp_mssdflt;
-       if (tp->t_mtudisc && rt->rt_rmx.rmx_mtu != 0)
+       if (tp->t_mtudisc && rt->rt_rmx.rmx_mtu != 0) {
+#ifdef INET6
+               if (in6p && rt->rt_rmx.rmx_mtu < IPV6_MMTU) {
+                       /*
+                        * RFC2460 section 5, last paragraph: if path MTU is
+                        * smaller than 1280, use 1280 as packet size and
+                        * attach fragment header.
+                        */
+                       size = IPV6_MMTU - iphlen - sizeof(struct ip6_frag) -
+                           sizeof(struct tcphdr);
+               } else
+                       size = rt->rt_rmx.rmx_mtu - iphlen -
+                           sizeof(struct tcphdr);
+#else
                size = rt->rt_rmx.rmx_mtu - iphlen - sizeof(struct tcphdr);
-       else if (ifp->if_flags & IFF_LOOPBACK)
+#endif
+       } else if (ifp->if_flags & IFF_LOOPBACK)
                size = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
 #ifdef INET
        else if (inp && tp->t_mtudisc)
@@ -344,6 +358,10 @@
 #endif
        size -= optlen;
 
+       /* there may not be any room for data if mtu is too small */
+       if (size < 0)
+               return (EMSGSIZE);
+
        /*
         * *rxsegsizep holds *estimated* inbound segment size (estimation
         * assumes that path MTU is the same for both ways).  this is only
@@ -381,6 +399,8 @@
                }
                tp->t_segsz = *txsegsizep;
        }
+
+       return (0);
 }
 
 static
@@ -520,7 +540,8 @@
                return EAFNOSUPPORT;
        }
 
-       tcp_segsize(tp, &txsegsize, &rxsegsize);
+       if (tcp_segsize(tp, &txsegsize, &rxsegsize))
+               return EMSGSIZE;
 
        idle = (tp->snd_max == tp->snd_una);