Hi,
Path MTU discovery in IPv6 is slightly broken. I takes two
ICMP6_PACKET_TOO_BIG packets to create and change the dynamic route.
When the first ICMP6 packet arrives, a dynamic route gets created
in icmp6_mtudisc_clone() and icmp6_mtudisc_update() sets its MTU
value. During notify tcp_mtudisc() removes the old route from the
inp and allocates the dynamic route. As the gateway route is not
set, the MTU is reset to 0 in _rtalloc().
The second packet will not allocate a dynamic route as it already
exists. Just the MTU is updated. Then tcp_mtudisc() does not
change the route at the inp as it already the correct one. So now
PMTU discovery is successful.
This behavior was introduced in net/route.c rev 1.269 when the
gateway route allocation was moved from rt_setgateway() to _rtalloc().
So now rtrequest() can return a route without a valid gateway route.
To fix this, I call rt_setgwroute() from _rtalloc() and rt_setgateway().
As a result icmp6_mtudisc_clone() will create a route with a gateway
route and tcp_mtudisc() will not reset the MTU to 0 during rtalloc().
ok?
bluhm
Index: net/if_spppsubr.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/net/if_spppsubr.c,v
retrieving revision 1.154
diff -u -p -r1.154 if_spppsubr.c
--- net/if_spppsubr.c 14 Jun 2016 20:44:43 -0000 1.154
+++ net/if_spppsubr.c 24 Jun 2016 22:32:28 -0000
@@ -4161,7 +4161,7 @@ sppp_update_gw_walker(struct rtentry *rt
rt->rt_gateway->sa_family ||
!ISSET(rt->rt_flags, RTF_GATEWAY))
return (0); /* do not modify non-gateway routes */
- rt_setgate(rt, rt->rt_ifa->ifa_dstaddr);
+ rt_setgate(rt, rt->rt_ifa->ifa_dstaddr, ifp->if_rdomain);
}
return (0);
}
Index: net/route.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/net/route.c,v
retrieving revision 1.309
diff -u -p -r1.309 route.c
--- net/route.c 14 Jun 2016 09:48:52 -0000 1.309
+++ net/route.c 24 Jun 2016 22:37:45 -0000
@@ -154,6 +154,7 @@ struct pool rttimer_pool; /* pool for r
void rt_timer_init(void);
int rt_setaddr(struct rtentry *, struct sockaddr *);
+void rt_setgwroute(struct rtentry *, u_int);
int rtflushclone1(struct rtentry *, void *, u_int);
void rtflushclone(unsigned int, struct rtentry *);
int rt_if_remove_rtdelete(struct rtentry *, void *, u_int);
@@ -369,7 +370,7 @@ rtalloc(struct sockaddr *dst, int flags,
struct rtentry *
_rtalloc(struct sockaddr *dst, uint32_t *src, int flags, unsigned int rtableid)
{
- struct rtentry *rt, *nhrt;
+ struct rtentry *rt;
rt = rt_match(dst, src, flags, rtableid);
@@ -381,6 +382,16 @@ _rtalloc(struct sockaddr *dst, uint32_t
if (rtisvalid(rt->rt_gwroute))
return (rt);
+ rt_setgwroute(rt, rtableid);
+
+ return (rt);
+}
+
+void
+rt_setgwroute(struct rtentry *rt, u_int rtableid)
+{
+ struct rtentry *nhrt;
+
rtfree(rt->rt_gwroute);
rt->rt_gwroute = NULL;
@@ -392,10 +403,9 @@ _rtalloc(struct sockaddr *dst, uint32_t
* this behavior. But it is safe since rt_checkgate() wont
* allow us to us this route later on.
*/
- nhrt = rt_match(rt->rt_gateway, NULL, flags | RT_RESOLVE,
- rtable_l2(rtableid));
+ nhrt = rt_match(rt->rt_gateway, NULL, RT_RESOLVE, rtable_l2(rtableid));
if (nhrt == NULL)
- return (rt);
+ return;
/*
* Next hop must be reachable, this also prevents rtentry
@@ -403,13 +413,13 @@ _rtalloc(struct sockaddr *dst, uint32_t
*/
if (ISSET(nhrt->rt_flags, RTF_CLONING|RTF_GATEWAY)) {
rtfree(nhrt);
- return (rt);
+ return;
}
/* Next hop entry must be UP and on the same interface. */
if (!ISSET(nhrt->rt_flags, RTF_UP) || nhrt->rt_ifidx != rt->rt_ifidx) {
rtfree(nhrt);
- return (rt);
+ return;
}
/*
@@ -424,8 +434,6 @@ _rtalloc(struct sockaddr *dst, uint32_t
* do the magic for us.
*/
rt->rt_gwroute = nhrt;
-
- return (rt);
}
void
@@ -595,7 +603,7 @@ create:
flags |= RTF_MODIFIED;
prio = rt->rt_priority;
stat = &rtstat.rts_newgateway;
- rt_setgate(rt, gateway);
+ rt_setgate(rt, gateway, rdomain);
}
} else
error = EHOSTUNREACH;
@@ -1089,7 +1097,8 @@ rtrequest(int req, struct rt_addrinfo *i
* it to (re)order routes.
*/
if ((error = rt_setaddr(rt, ifa->ifa_addr)) ||
- (error = rt_setgate(rt, info->rti_info[RTAX_GATEWAY]))) {
+ (error = rt_setgate(rt, info->rti_info[RTAX_GATEWAY],
+ tableid))) {
ifafree(ifa);
rtfree(rt->rt_parent);
rtfree(rt->rt_gwroute);
@@ -1169,7 +1178,7 @@ rt_setaddr(struct rtentry *rt, struct so
}
int
-rt_setgate(struct rtentry *rt, struct sockaddr *gate)
+rt_setgate(struct rtentry *rt, struct sockaddr *gate, u_int rtableid)
{
int glen = ROUNDUP(gate->sa_len);
struct sockaddr *sa;
@@ -1183,8 +1192,8 @@ rt_setgate(struct rtentry *rt, struct so
}
memmove(rt->rt_gateway, gate, glen);
- rtfree(rt->rt_gwroute);
- rt->rt_gwroute = NULL;
+ if (ISSET(rt->rt_flags, RTF_GATEWAY))
+ rt_setgwroute(rt, rtableid);
return (0);
}
Index: net/route.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/net/route.h,v
retrieving revision 1.138
diff -u -p -r1.138 route.h
--- net/route.h 14 Jun 2016 09:48:52 -0000 1.138
+++ net/route.h 24 Jun 2016 22:29:45 -0000
@@ -363,7 +363,7 @@ struct sockaddr *rt_plen2mask(struct rte
void rt_sendmsg(struct rtentry *, int, u_int);
void rt_sendaddrmsg(struct rtentry *, int, struct ifaddr *);
void rt_missmsg(int, struct rt_addrinfo *, int, uint8_t, u_int, int, u_int);
-int rt_setgate(struct rtentry *, struct sockaddr *);
+int rt_setgate(struct rtentry *, struct sockaddr *, u_int);
int rt_checkgate(struct rtentry *, struct rtentry **);
void rt_setmetrics(u_long, const struct rt_metrics *, struct rt_kmetrics *);
void rt_getmetrics(const struct rt_kmetrics *, struct rt_metrics *);
Index: net/rtsock.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/net/rtsock.c,v
retrieving revision 1.192
diff -u -p -r1.192 rtsock.c
--- net/rtsock.c 14 Jun 2016 09:48:52 -0000 1.192
+++ net/rtsock.c 24 Jun 2016 22:33:04 -0000
@@ -748,7 +748,8 @@ report:
ifa = info.rti_ifa;
}
if (info.rti_info[RTAX_GATEWAY] != NULL && (error =
- rt_setgate(rt, info.rti_info[RTAX_GATEWAY])))
+ rt_setgate(rt, info.rti_info[RTAX_GATEWAY],
+ tableid)))
goto flush;
if (ifa) {
if (rt->rt_ifa != ifa) {
