[PATCH 5.2 17/85] net-ipv6: fix excessive RTF_ADDRCONF flag on ::1/128 local route (and others)

Greg Kroah-Hartman
2019-09-18T06:30:28Z

From: "Maciej Żenczykowski" <maze@google.com>

[ Upstream commit d55a2e374a94fa34a3048c6a2be535266e506d97 ]

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: c7a1ce397ada ("ipv6: Change addrconf_f6i_alloc to use ip6_route_info_create")
Cc: David Ahern <dsahern@gmail.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/route.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3841,13 +3841,14 @@ struct fib6_info *addrconf_f6i_alloc(str
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;
@@ -3857,7 +3858,10 @@ struct fib6_info *addrconf_f6i_alloc(str
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 */