ipv6: Fixed source specific default route handling.

If there are only IPv6 source specific default routes present, the
host gets -ENETUNREACH on e.g. connect() because ip6_dst_lookup_tail
calls ip6_route_output first, and given source address any, it fails,
and ip6_route_get_saddr is never called.

The change is to use the ip6_route_get_saddr, even if the initial
ip6_route_output fails, and then doing ip6_route_output _again_ after
we have appropriate source address available.

Note that this is '99% fix' to the problem; a correct fix would be to
do route lookups only within addrconf.c when picking a source address,
and never call ip6_route_output before source address has been
populated.

Signed-off-by: Markus Stenberg <markus.stenberg@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 7fde1f265c90e90f16291e6c861b6e242111c25b..c21777565c58cabd7649cc48b790ff21c88498b5 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -886,22 +886,45 @@ static int ip6_dst_lookup_tail(struct sock *sk,
 #endif
        int err;
 
-       if (!*dst)
-               *dst = ip6_route_output(net, sk, fl6);
-
-       err = (*dst)->error;
-       if (err)
-               goto out_err_release;
+       /* The correct way to handle this would be to do
+        * ip6_route_get_saddr, and then ip6_route_output; however,
+        * the route-specific preferred source forces the
+        * ip6_route_output call _before_ ip6_route_get_saddr.
+        *
+        * In source specific routing (no src=any default route),
+        * ip6_route_output will fail given src=any saddr, though, so
+        * that's why we try it again later.
+        */
+       if (ipv6_addr_any(&fl6->saddr) && (!*dst || !(*dst)->error)) {
+               struct rt6_info *rt;
+               bool had_dst = *dst != NULL;
 
-       if (ipv6_addr_any(&fl6->saddr)) {
-               struct rt6_info *rt = (struct rt6_info *) *dst;
+               if (!had_dst)
+                       *dst = ip6_route_output(net, sk, fl6);
+               rt = (*dst)->error ? NULL : (struct rt6_info *)*dst;
                err = ip6_route_get_saddr(net, rt, &fl6->daddr,
                                          sk ? inet6_sk(sk)->srcprefs : 0,
                                          &fl6->saddr);
                if (err)
                        goto out_err_release;
+
+               /* If we had an erroneous initial result, pretend it
+                * never existed and let the SA-enabled version take
+                * over.
+                */
+               if (!had_dst && (*dst)->error) {
+                       dst_release(*dst);
+                       *dst = NULL;
+               }
        }
 
+       if (!*dst)
+               *dst = ip6_route_output(net, sk, fl6);
+
+       err = (*dst)->error;
+       if (err)
+               goto out_err_release;
+
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
        /*
         * Here if the dst entry we've looked up

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 5c48293ff06235e72f586007ff1e7bb568733b92..d3588885f09705278b745c43b86563c85a0d3dea 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2245,9 +2245,10 @@ int ip6_route_get_saddr(struct net *net,
                        unsigned int prefs,
                        struct in6_addr *saddr)
 {
-       struct inet6_dev *idev = ip6_dst_idev((struct dst_entry *)rt);
+       struct inet6_dev *idev =
+               rt ? ip6_dst_idev((struct dst_entry *)rt) : NULL;
        int err = 0;
-       if (rt->rt6i_prefsrc.plen)
+       if (rt && rt->rt6i_prefsrc.plen)
                *saddr = rt->rt6i_prefsrc.addr;
        else
                err = ipv6_dev_get_saddr(net, idev ? idev->dev : NULL,