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.ro...@fkie.fraunhofer.de http://www.fkie.fraunhofer.de
