From: Jesse Hathaway <jesse@mbuki-mvuki.org>
To: netdev@vger.kernel.org
Subject: Race condition in route lookup
Date: Wed, 9 Oct 2019 11:00:07 -0500 [thread overview]
Message-ID: <CANSNSoV1M9stB7CnUcEhsz3FHi4NV_yrBtpYsZ205+rqnvMbvA@mail.gmail.com> (raw)
We have been experiencing a route lookup race condition on our internet facing
Linux routers. I have been able to reproduce the issue, but would love more
help in isolating the cause.
Looking up a route found in the main table returns `*` rather than the directly
connected interface about once for every 10-20 million requests. From my
reading of the iproute2 source code an asterisk is indicative of the kernel
returning and interface index of 0 rather than the correct directly connected
interface.
This is reproducible with the following bash snippet on 5.4-rc2:
$ cat route-race
#!/bin/bash
# Generate 50 million individual route gets to feed as batch input to `ip`
function ip-cmds() {
route_get='route get 192.168.11.142 from 192.168.180.10 iif vlan180'
for ((i = 0; i < 50000000; i++)); do
printf '%s\n' "${route_get}"
done
}
ip-cmds | ip -d -o -batch - | grep -E 'dev \*' | uniq -c
Example output:
$ ./route-race
6 unicast 192.168.11.142 from 192.168.180.10 dev * table main
\ cache iif vlan180
These routers have multiple routing tables and are ingesting full BGP routing
tables from multiple ISPs:
$ ip route show table all | wc -l
3105543
$ ip route show table main | wc -l
54
Please let me know what other information I can provide, thanks in advance,
Jesse Hathaway
next reply other threads:[~2019-10-09 16:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 16:00 Jesse Hathaway [this message]
2019-10-10 8:31 ` Race condition in route lookup Ido Schimmel
2019-10-10 8:46 ` Ido Schimmel
2019-10-11 14:36 ` Jesse Hathaway
2019-10-11 15:42 ` Ido Schimmel
2019-10-11 16:09 ` Jesse Hathaway
2019-10-11 17:54 ` Wei Wang
2019-10-11 18:17 ` Ido Schimmel
2019-10-11 18:25 ` Ido Schimmel
2019-10-11 18:47 ` Wei Wang
2019-10-11 18:52 ` Ido Schimmel
2019-10-11 21:01 ` Jesse Hathaway
2019-10-11 21:27 ` David Ahern
2019-10-12 6:56 ` Martin Lau
2019-10-14 0:23 ` Wei Wang
2019-10-14 17:26 ` Martin Lau
2019-10-15 14:45 ` David Ahern
2019-10-15 16:42 ` Wei Wang
2019-10-16 6:35 ` Martin Lau
2019-10-15 14:29 ` Jesse Hathaway
2019-10-15 16:44 ` Wei Wang
2019-10-16 6:39 ` Martin Lau
2019-10-16 16:35 ` Wei Wang
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