Re: RTNETLINK question: no RTM_DELROUTE for IPv4 when link broughtdown, but for IPv6?

From: Patrick McHardy
Date: Sun Jun 18 2006 - 13:50:22 EST

Arnd Hannemann wrote:
> I'm working on a script which parses "ip monitor route" output to detect
> changes of the linux kernel routing table.
> If an interface is brought down via ifconfig, I expected to see "deleted
> <route>" messages, but they are missing for IPv4.
> Is this the desired behaviour, or a bug(tm)?

Its known behaviour and is AFAIK generally not considered a bug.
I personally would also prefer more consistency, but in the end,
pure passive listening doesn't work anyway since messages can get
lost, so any reliable software needs to resync against the kernel
(and if it is interested in events synthesize them) occasionally,
and it shouldn't be any trouble to do some additional resyncing of
routes after an interface went down/disappeared. I'm currently
pushing a number of patches against libnl to Thomas, which should
be a great aid for reliable event generation in userspace.

I'm also working on a small language which allows you to do
integrate these events through logical expressions, do result
set joins based on relations, react on state transistions etc.,
which is meant for easier and more reliable network
configuration, so it would be interesting to hear what you're
trying to do.

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