ipv6: reallocate addrconf router for ipv6 address when lo device up

commit 25fb6ca4ed9cad72f14f61629b68dc03c0d9713f
"net IPv6 : Fix broken IPv6 routing table after loopback down-up"
allocates addrconf router for ipv6 address when lo device up.
but commit a881ae1f625c599b460cc8f8a7fcb1c438f699ad
"ipv6:don't call addrconf_dst_alloc again when enable lo" breaks
this behavior.

Since the addrconf router is moved to the garbage list when
lo device down, we should release this router and rellocate
a new one for ipv6 address when lo device up.

This patch solves bug 67951 on bugzilla
https://bugzilla.kernel.org/show_bug.cgi?id=67951

change from v1:
use ip6_rt_put to repleace ip6_del_rt, thanks Hannes!
change code style, suggested by Sergei.

CC: Sabrina Dubroca <sd@queasysnail.net>
CC: Hannes Frederic Sowa <hannes@stressinduktion.org>
Reported-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 2 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 31bdedc32bdd..ad235690684c 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2657,8 +2657,18 @@ static void init_loopback(struct net_device *dev)
                         if (sp_ifa->flags & (IFA_F_DADFAILED | IFA_F_TENTATIVE))
                                 continue;
 
-                        if (sp_ifa->rt)
-                                continue;
+                        if (sp_ifa->rt) {
+                                /* This dst has been added to garbage list when
+                                 * lo device down, release this obsolete dst and
+                                 * reallocate a new router for ifa.
+                                 */
+                                if (sp_ifa->rt->dst.obsolete > 0) {
+                                        ip6_rt_put(sp_ifa->rt);
+                                        sp_ifa->rt = NULL;
+                                } else {
+                                        continue;
+                                }
+                        }
 
                         sp_rt = addrconf_dst_alloc(idev, &sp_ifa->addr, false);