netdev - [PATCH v2] Generate netlink notification when default IPv6 route preference changes

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Date:   Thu, 10 Feb 2022 14:09:35 -0800
From:   Kalash Nainwal <kalash@...sta.com>
To:     netdev@...r.kernel.org
Cc:     fruggeri@...sta.com, kalash@...sta.com, dsahern@...il.com,
        "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH v2] Generate netlink notification when default IPv6 route preference changes

 Generate RTM_NEWROUTE netlink notification when the route preference
 changes on an existing kernel generated default route in response to
 RA messages. Currently netlink notifications are generated only when
 this route is added or deleted but not when the route preference
 changes, which can cause userspace routing application state to go
 out of sync with kernel.

Signed-off-by: Kalash Nainwal <kalash@...sta.com>
---
 net/ipv6/ndisc.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index f03b597e4121..1c06d0cd02f7 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1337,8 +1337,12 @@ static void ndisc_router_discovery(struct sk_buff *skb)
 			return;
 		}
 		neigh->flags |= NTF_ROUTER;
-	} else if (rt) {
+	} else if (rt && IPV6_EXTRACT_PREF(rt->fib6_flags) != pref) {
+		struct nl_info nlinfo = {
+			.nl_net = net,
+		};
 		rt->fib6_flags = (rt->fib6_flags & ~RTF_PREF_MASK) | RTF_PREF(pref);
+		inet6_rt_notify(RTM_NEWROUTE, rt, &nlinfo, NLM_F_REPLACE);
 	}
 
 	if (rt)
-- 
2.30.1 (Apple Git-130)