[PATCH v2] net-ipv6: fix excessive RTF_ADDRCONF flag on ::1/128 local route (and others)

[Maciej Żenczykowski]

From: Maciej Żenczykowski <m...@google.com>

There is a subtle change in behaviour introduced by:
  commit c7a1ce397adacaf5d4bb2eab0a738b5f80dc3e43
  'ipv6: Change addrconf_f6i_alloc to use ip6_route_info_create'

Before that patch /proc/net/ipv6_route includes:
00000000000000000000000000000001 80 00000000000000000000000000000000 00 
00000000000000000000000000000000 00000000 00000003 00000000 80200001 lo

Afterwards /proc/net/ipv6_route includes:
00000000000000000000000000000001 80 00000000000000000000000000000000 00 
00000000000000000000000000000000 00000000 00000002 00000000 80240001 lo

ie. the above commit causes the ::1/128 local (automatic) route to be flagged 
with RTF_ADDRCONF (0x040000).

AFAICT, this is incorrect since these routes are *not* coming from RA's.

As such, this patch restores the old behaviour.

Fixes: c7a1ce397adacaf5d4bb2eab0a738b5f80dc3e43
Cc: David Ahern <dsah...@gmail.com>
Cc: Lorenzo Colitti <lore...@google.com>
Signed-off-by: Maciej Żenczykowski <m...@google.com>
---
 net/ipv6/route.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 558c6c68855f..516b2e568dae 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -4365,13 +4365,14 @@ struct fib6_info *addrconf_f6i_alloc(struct net *net,
        struct fib6_config cfg = {
                .fc_table = l3mdev_fib_table(idev->dev) ? : RT6_TABLE_LOCAL,
                .fc_ifindex = idev->dev->ifindex,
-               .fc_flags = RTF_UP | RTF_ADDRCONF | RTF_NONEXTHOP,
+               .fc_flags = RTF_UP | RTF_NONEXTHOP,
                .fc_dst = *addr,
                .fc_dst_len = 128,
                .fc_protocol = RTPROT_KERNEL,
                .fc_nlinfo.nl_net = net,
                .fc_ignore_dev_down = true,
        };
+       struct fib6_info *f6i;
 
        if (anycast) {
                cfg.fc_type = RTN_ANYCAST;
@@ -4381,7 +4382,10 @@ struct fib6_info *addrconf_f6i_alloc(struct net *net,
                cfg.fc_flags |= RTF_LOCAL;
        }
 
-       return ip6_route_info_create(&cfg, gfp_flags, NULL);
+       f6i = ip6_route_info_create(&cfg, gfp_flags, NULL);
+       if (f6i)
+               f6i->dst_nocount = true;
+       return f6i;
 }
 
 /* remove deleted ip from prefsrc entries */
-- 
2.23.0.187.g17f5b7556c-goog