kern/104851: On link routes not configured when using both IPv6 autoconfiguration and manual configuration

[Jan Melen]

>Number:         104851
>Category:       kern
>Synopsis:       On link routes not configured when using both IPv6 autoconfiguration and manual configuration
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Oct 27 05:20:17 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Jan Melen
>Release:        RELENG_6_1
>Organization:
>Environment:
FreeBSD melen.org 6.1-RELEASE FreeBSD 6.1-RELEASE #0: Mon Oct  9 11:36:12 EEST 2006     root at melen.org:/usr/src/sys/i386/compile/SMP  i386

>Description:
I have a problem with routes in 6.1 when configuring IPv6 address using both
autoconfigured addresses at the same time with statically configured
addresses from different prefixes.

If the host is not accepting router advertisements everything seems to work
fine:
# sysctl -a | grep rtad
net.inet6.ip6.accept_rtadv: 0
# ifconfig fxp0 inet6 3ffe:101::1 prefixlen 64

# netstat -rn -f inet6 | grep 3ffe:101
3ffe:101::/64                     link#1                        UC
fxp0
3ffe:101::1                       00:12:3f:71:3e:ef             UHL
lo0
#

As you can see I have two routes one for the loopback and one for the prefix
as it should GREAT!

Now if I'll set the host to accept router advertisements then the route for
the 3ffe:101:: prefix will be deleted as the first router advertisement is
received. The router advertises prefix 3ffe:14b8:400:101::/64.

# sysctl net.inet6.ip6.accept_rtadv=1
net.inet6.ip6.accept_rtadv: 0 -> 1
# rtsol -a
# netstat -rn -f inet6 | grep 3ffe:101
3ffe:101::1                       00:12:3f:71:3e:ef             UHL
lo0
#

It seems that the route is deleted because in function pfxlist_onlink_check()
there is a check that if the state has changed to DETACHED the
nd6_prefix_offlink will be called which then removes the route:
        if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0 &&
            (pr->ndpr_stateflags & NDPRF_ONLINK) != 0) {
                if ((e = nd6_prefix_offlink(pr)) != 0) {
                        nd6log((LOG_ERR,
                            "pfxlist_onlink_check: failed to "
                            "make %s/%d offlink, errno=%d\n",
                            ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                            pr->ndpr_plen, e));
                }
        }

Result is the same if I first do the autoconfiguration part and then after
I have the autoconfigured address add the manually configured address the
result is that there wont be any route for the manually configured prefix
(3ffe:101::/64).

>How-To-Repeat:
Add any prefix that is not the same as advertised prefix on the link and you will notice that the route for that prefix on link will be missing.

>Fix:

The solution is that we check if the valid lifetime for the address is infinite, then skip the reachable router check for that prefix.

--- nd6_rtr.c.orig      Mon Mar 20 18:23:08 2006
+++ nd6_rtr.c   Thu Oct 26 09:48:59 2006
@@ -1409,12 +1409,20 @@
                        if (pr->ndpr_raf_onlink == 0)
                                continue;

-                       if ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
+                       /* For some reason nd6 tries to find a active
+                       * advertising router also for prefixes that are
+                       * statically configured which shouldn't be the case
+                       */
+                       if (pr->ndpr_vltime == ND6_INFINITE_LIFETIME) {
+                               pr->ndpr_stateflags &= ~NDPRF_DETACHED;
+                       } else {
+                       if ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
                            find_pfxlist_reachable_router(pr) == NULL)
                                pr->ndpr_stateflags |= NDPRF_DETACHED;
                        if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0 &&
                            find_pfxlist_reachable_router(pr) != 0)
                                pr->ndpr_stateflags &= ~NDPRF_DETACHED;
+                       }
                }
        } else {
                /* there is no prefix that has a reachable router */

>Release-Note:
>Audit-Trail:
>Unformatted: