Hello Florian,
On 26/11/14(Wed) 06:56, Florian Riehm wrote:
> since OpenBSD 5.6 route change messages can change the interface of a route
> (rt_ifa) even if a message doesn't seem to require it because of a changed
> gateway or stuff like that.
> I would like to ask if it's a regression or if the new behavior is intended.
Since the behavior is different and it's not documented, it is a
regression, thanks for reporting it. I've just committed some new
tests in order to prevent this from happening again.
> Example: (only for testing - it doesn't represent my network topology)
> ifconfig em0 inet6 fd88::1/64
> ifconfig em1 inet6 fd99::1/64
> route add -inet6 fd88::666 fd99::1
> route get fd88::666
> interface: em1 (as expected)
> route change fd88::666 -mtu 1500
> route get fd88::666
> interface: em0 (broken - trying to ping the target results in "No route to
> host")
>
> In the example I can workaround the problem with adding a gateway while
> changing
> the mtu:
> route change fd88::666 fd99::1 -mtu 1500
>
> A comment in route_output (rtsock.c) says
> /*
> * new gateway could require new ifaddr, ifp;
> * flags may also be different; ifp may be specified
> * by ll sockaddr when protocol address is ambiguous
> */
> but their is no check for a 'new gateway'.
You're right. What's happening here is that we always call rt_geifa() in
the first place. This is a nasty function that tries to find an ifaddr
to attach a route. But if the gateway is not new or you didn't specify
any of the "-ifp" or "-ifa" argument we should not look for a different
ifaddr.
Here's a slightly different diff, could you tell me if it fixes the
regression in your case?
Index: net/rtsock.c
===================================================================
RCS file: /home/ncvs/src/sys/net/rtsock.c,v
retrieving revision 1.152
diff -u -p -r1.152 rtsock.c
--- net/rtsock.c 12 Aug 2014 13:52:08 -0000 1.152
+++ net/rtsock.c 26 Nov 2014 11:55:25 -0000
@@ -740,13 +740,6 @@ report:
break;
case RTM_CHANGE:
- /*
- * new gateway could require new ifaddr, ifp;
- * flags may also be different; ifp may be specified
- * by ll sockaddr when protocol address is ambiguous
- */
- if ((error = rt_getifa(&info, tableid)) != 0)
- goto flush;
newgate = 0;
if (info.rti_info[RTAX_GATEWAY] != NULL)
if (rt->rt_gateway == NULL ||
@@ -761,7 +754,17 @@ report:
error = EDQUOT;
goto flush;
}
- ifa = info.rti_ifa;
+ /*
+ * new gateway could require new ifaddr, ifp;
+ * flags may also be different; ifp may be specified
+ * by ll sockaddr when protocol address is ambiguous
+ */
+ if (newgate || info.rti_info[RTAX_IFP] != NULL ||
+ info.rti_info[RTAX_IFA] != NULL) {
+ if ((error = rt_getifa(&info, tableid)) != 0)
+ goto flush;
+ ifa = info.rti_ifa;
+ }
if (ifa) {
if (rt->rt_ifa != ifa) {
if (rt->rt_ifa->ifa_rtrequest)
