terça-feira, 13 de dezembro de 2016

ubuntu -avaliar redirect

Hello,

We have changed nothing in our network infrastructure but only upgraded from Linux kernel 2.6.36.2 to 3.0.3. Here is the problem we are experiencing: ICMP redirected routes are cached forever, and they can be cleared only by a reboot.
Here is an example:

root@machine5:~# ip route get 1.1.1.1
1.1.1.1 via 9.0.0.1 dev eth0  src 5.5.5.5
    cache   ipid 0xfb5d rtt 1475ms rttvar 450ms cwnd 10

root@machine5:~# ip route list cache match 1.1.1.1
1.1.1.1 tos lowdelay via 9.0.0.1 dev eth0  src 5.5.5.5
    cache   ipid 0xfb5d rtt 1475ms rttvar 450ms cwnd 10
1.1.1.1 via 9.0.0.1 dev eth0  src 5.5.5.5
    cache   ipid 0xfb5d rtt 1475ms rttvar 450ms cwnd 10
...(two more entries, all go via 9.0.0.1)...

1.1.1.1 is the test destination address
5.5.5.5 is the source IP address of "machine5" via dev eth0, the only interface besides "lo" 9.0.0.1 is the incorrect gateway which we were redirected to; we want to change the route to 9.0.0.8
I found no way to clear this route. What I tried:

root@machine5:~# ip route flush cache ### CACHE FLUSH ###
root@machine5:~# ip route list cache match 1.1.1.1 # empty

root@machine5:~# ip route flush cache ### CACHE FLUSH ###
root@machine5:~# echo 1 > /proc/sys/net/ipv4/route/flush
root@machine5:~# ip route list cache match 1.1.1.1 # empty

root@machine5:~# ip route get 1.1.1.1 # magically re-inserts the route, tcpdump sees NO ICMP traffic
1.1.1.1 via 9.0.0.1 dev eth0  src 5.5.5.5
    cache   ipid 0xfb5d rtt 1475ms rttvar 450ms cwnd 10

I also tried to force a scheduled route flush:

root@machine5:~# echo 1 > /proc/sys/net/ipv4/route/gc_timeout
root@machine5:~# echo 1 > /proc/sys/net/ipv4/route/gc_interval

A reboot fixed it all.

Reações:

0 comentários: