ipv6: Avoid redoing fib6_lookup() with reachable = 0 by saving fn

This patch save the fn before doing rt6_backtrack.
Hence, without redo-ing the fib6_lookup(), saved_fn can be used
to redo rt6_select() with RT6_LOOKUP_F_REACHABLE off.

Some minor changes I think make sense to review as a single patch:
* Remove the 'out:' goto label.
* Remove the 'reachable' variable. Only use the 'strict' variable instead.

After this patch, "failing ip6_ins_rt()" should be the only case that
requires a redo of fib6_lookup().

Cc: David Miller <davem@davemloft.net>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 14 deletions

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 98c523f4a3c3..c91083156edb 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -917,31 +917,40 @@ static struct rt6_info *rt6_alloc_clone(struct rt6_info *ort,
 static struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table, int oif,
                                       struct flowi6 *fl6, int flags)
 {
-        struct fib6_node *fn;
+        struct fib6_node *fn, *saved_fn;
         struct rt6_info *rt, *nrt;
         int strict = 0;
         int attempts = 3;
         int err;
-        int reachable = net->ipv6.devconf_all->forwarding ? 0 : RT6_LOOKUP_F_REACHABLE;
 
         strict |= flags & RT6_LOOKUP_F_IFACE;
+        if (net->ipv6.devconf_all->forwarding == 0)
+                strict |= RT6_LOOKUP_F_REACHABLE;
 
 redo_fib6_lookup_lock:
         read_lock_bh(&table->tb6_lock);
 
-redo_fib6_lookup:
         fn = fib6_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
+        saved_fn = fn;
 
 redo_rt6_select:
-        rt = rt6_select(fn, oif, strict | reachable);
+        rt = rt6_select(fn, oif, strict);
         if (rt->rt6i_nsiblings)
-                rt = rt6_multipath_select(rt, fl6, oif, strict | reachable);
+                rt = rt6_multipath_select(rt, fl6, oif, strict);
         if (rt == net->ipv6.ip6_null_entry) {
                 fn = fib6_backtrack(fn, &fl6->saddr);
                 if (fn)
                         goto redo_rt6_select;
-                else
-                        goto out;
+                else if (strict & RT6_LOOKUP_F_REACHABLE) {
+                        /* also consider unreachable route */
+                        strict &= ~RT6_LOOKUP_F_REACHABLE;
+                        fn = saved_fn;
+                        goto redo_rt6_select;
+                } else {
+                        dst_hold(&rt->dst);
+                        read_unlock_bh(&table->tb6_lock);
+                        goto out2;
+                }
         }
 
         dst_hold(&rt->dst);
@@ -977,13 +986,6 @@ redo_rt6_select:
         ip6_rt_put(rt);
         goto redo_fib6_lookup_lock;
 
-out:
-        if (reachable) {
-                reachable = 0;
-                goto redo_fib6_lookup;
-        }
-        dst_hold(&rt->dst);
-        read_unlock_bh(&table->tb6_lock);
 out2:
         rt->dst.lastuse = jiffies;
         rt->dst.__use++;