linux-kernel - [PATCH AUTOSEL for 4.14 02/64] net: ipv6: Fixup device for anycast routes during copy

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Date:   Sat, 2 Dec 2017 15:51:13 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     David Ahern <dsahern@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 4.14 02/64] net: ipv6: Fixup device for anycast
 routes during copy

From: David Ahern <dsahern@...il.com>

[ Upstream commit 98d11291d189cb5adf49694d0ad1b971c0212697 ]

Florian reported a breakage with anycast routes due to commit
4832c30d5458 ("net: ipv6: put host and anycast routes on device with
address"). Prior to this commit anycast routes were added against the
loopback device causing repetitive route entries with no insight into
why they existed. e.g.:
  $ ip -6 ro ls  table local type anycast
  anycast 2001:db8:1:: dev lo proto kernel metric 0 pref medium
  anycast 2001:db8:2:: dev lo proto kernel metric 0 pref medium
  anycast fe80:: dev lo proto kernel metric 0 pref medium
  anycast fe80:: dev lo proto kernel metric 0 pref medium

The point of commit 4832c30d5458 is to add the routes using the device
with the address which is causing the route to be added. e.g.,:
  $ ip -6 ro ls  table local type anycast
  anycast 2001:db8:1:: dev eth1 proto kernel metric 0 pref medium
  anycast 2001:db8:2:: dev eth2 proto kernel metric 0 pref medium
  anycast fe80:: dev eth2 proto kernel metric 0 pref medium
  anycast fe80:: dev eth1 proto kernel metric 0 pref medium

For traffic to work as it did before, the dst device needs to be switched
to the loopback when the copy is created similar to local routes.

Fixes: 4832c30d5458 ("net: ipv6: put host and anycast routes on device with address")
Signed-off-by: David Ahern <dsahern@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 net/ipv6/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index a96d5b385d8f..598efa8cfe25 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -960,7 +960,7 @@ static struct net_device *ip6_rt_get_dev_rcu(struct rt6_info *rt)
 {
 	struct net_device *dev = rt->dst.dev;

-	if (rt->rt6i_flags & RTF_LOCAL) {
+	if (rt->rt6i_flags & (RTF_LOCAL | RTF_ANYCAST)) {
 		/* for copies of local routes, dst->dev needs to be the
 		 * device if it is a master device, the master device if
 		 * device is enslaved, and the loopback as the default
-- 
2.11.0