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

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Date:   Mon,  2 Sep 2019 09:23:36 -0700
From:   Maciej Żenczykowski <zenczykowski@...il.com>
To:     Maciej Żenczykowski <maze@...gle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, David Ahern <dsahern@...il.com>,
        Lorenzo Colitti <lorenzo@...gle.com>
Subject: [PATCH v2] net-ipv6: fix excessive RTF_ADDRCONF flag on ::1/128 local route (and others)

From: Maciej Żenczykowski <maze@...gle.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 <dsahern@...il.com>
Cc: Lorenzo Colitti <lorenzo@...gle.com>
Signed-off-by: Maciej Żenczykowski <maze@...gle.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