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From: Ido Schimmel <>
To: Jonas Gorski <>
Cc: Network Development <>,
	David Ahern <>
Subject: Re: RTM_DELROUTE not sent anymore when deleting (last) nexthop of routes in 6.1
Date: Thu, 24 Nov 2022 14:41:31 +0200	[thread overview]
Message-ID: <Y39me56NhhPYewYK@shredder> (raw)
In-Reply-To: <>

On Thu, Nov 24, 2022 at 10:20:00AM +0100, Jonas Gorski wrote:
> Hello,
> when an IPv4 route gets removed because its nexthop was deleted, the
> kernel does not send a RTM_DELROUTE netlink notifications anymore in
> 6.1. A bisect lead me to 61b91eb33a69 ("ipv4: Handle attempt to delete
> multipath route when fib_info contains an nh reference"), and
> reverting it makes it work again.
> It can be reproduced by doing the following and listening to netlink
> (e.g. via ip monitor)
> ip a a dev veth1
> ip nexthop add id 100 via dev veth1
> ip route add nhid 100
> ip nexthop del id 100
> where the nexthop del will trigger a RTM_DELNEXTHOP message, but no
> RTM_DELROUTE, but the route is gone afterwards anyways.

I tried the reproducer and I get the same notifications in ip monitor
regardless of whether 61b91eb33a69 is reverted or not.

Looking at the code and thinking about it, I don't think we ever
generated RTM_DELROUTE notifications when IPv4 routes were flushed (to
avoid a notification storm).

Are you running an upstream kernel?


> Doing the same thing with IPv6 still works as expected
> ip a a 2001:db8:91::1/64 dev veth1
> ip nexthop add id 100 via 2001:db8:91::2 dev veth1
> ip route add 2001:db8:101::/64 nhid 100
> ip nexthop del id 100
> Here the kernel will send out both the RTM_DELNEXTHOP and the
> RTM_DELROUTE netlink messages.
> Unfortunately my net-foo is not good enough to propose a fix.
> Best regards
> Jonas

  reply	other threads:[~2022-11-24 12:42 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-24  9:20 RTM_DELROUTE not sent anymore when deleting (last) nexthop of routes in 6.1 Jonas Gorski
2022-11-24 12:41 ` Ido Schimmel [this message]
2022-11-24 14:15   ` Jonas Gorski
2022-11-24 14:40     ` Jonas Gorski
2022-11-24 14:50       ` Ido Schimmel
2022-11-24 15:20         ` Jonas Gorski
2022-11-24 16:04           ` Ido Schimmel
2022-11-24 16:58             ` Jonas Gorski
2022-11-25  3:53   ` David Ahern
2022-11-25  8:36 ` RTM_DELROUTE not sent anymore when deleting (last) nexthop of routes in 6.1 #forregzbot Thorsten Leemhuis
2022-11-27 12:08   ` Thorsten Leemhuis
2022-11-29  8:50     ` Thorsten Leemhuis

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