Messages in this thread | | | From | Henning Rogge <> | Date | Tue, 13 Nov 2018 08:01:47 +0100 | Subject | [rtnetlink] Potential bug in Linux (rt)netlink code (repost from linux-netdev)? |
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Hi,
I am working on a self-written routing agent (https://github.com/OLSR/OONF) and am stuck on a problem with netlink that I cannot explain with an userspace error.
I am using a netlink socket for setting routes (RTM_NEWROUTE/RTM_DELROUTE), querying the kernel for the current routes in the database (via a RTM_GETROUTE dump) and for getting multicast messages for ongoing routing changes.
After a few netlink messages I get to the point where the kernel just does not responst to a RTM_NEWROUTE. No error, no answer, despite the NLM_F_ACK flag set)... but sometime when (during shutdown of the routing agent) the program sends another route command (most times a RTM_DELROUTE) I get a single netlink packet with a "successful" response for both the "missing" RTM_NEWROUTE and one for the new RTM DELROUTE sequence number.
I am testing two routing agents, each of them in a systemd-nspawn based container connected over a bridge on the host system on a current Debian Testing (kernel 4.18.0-1-amd64).
I am directly using the netlink sockets, without any other userspace library in between.
I have checked the hexdumps of a couple of netlink messages (including the ones just before the bug happens) by hand and they seem to be okay.
When I tried to add a "netlink listener" socket for futher debugging (ip link add nlmon0 type nlmon) the problem vanished until I removed the listener socket again.
Any ideas how to debug this problem? Unfortunately I have no short example program to trigger the bug... I have rarely seen the problem for years (once every couple of months), but until a few days ago I never managed to reproduce it.
I have asked on linux-netdev but got no reply expect for a question about rate-limitation.
Henning Rogge -- Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für Kommunikation, Informationsverarbeitung und Ergonomie FKIE Kommunikationssysteme (KOM) Zanderstrasse 5, 53177 Bonn, Germany Telefon +49 228 50212-469 mailto:henning.rogge@fkie.fraunhofer.de http://www.fkie.fraunhofer.de
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