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@arista.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)

On 2/10/22 2:09 PM, Kalash Nainwal wrote:
>  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@arista.com>
> ---
>  net/ipv6/ndisc.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>

Hello:

This patch was applied to netdev/net-next.git (master)
by David S. Miller <davem@davemloft.net>:

On Thu, 10 Feb 2022 14:09:35 -0800 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [v2] Generate netlink notification when default IPv6 route preference changes
    https://git.kernel.org/netdev/net-next/c/806c37ddcf28

You are awesome, thank you!
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