29.12.2015 14:58, Sowmini Varadhan пишет:

On (12/29/15 13:54), Stas Sergeev wrote:

quoted

ip route get 91.189.89.238
91.189.89.238 via 192.168.0.1 dev eth0  src 192.168.10.202
    cache <redirected>

         :

quoted

Now, 192.168.0.1 is also a valid gateway, but it is outside
of the network mask for the eth0 interface:

         :

quoted

So my question is: why does linux allow an invalid redirect
entries? Is it a problem with my setup, or some kernel bug,
or some router setup problem? Where should I look into, to
nail this down?

Seems like the problem is in the router that is sending
the bad redirect. You would have to check into the configuration
and/or implementation of the router- it should not be sending
back a redirect in the above case (different netmasks) even
if the ingress and egress physical interfaces are the same.

Router on 192.168.8.1 is just a PC with ubuntu, w/o any special
software. I'd be very surprised if it does so. As I understand,
linux would accept such ICMP redirect only from the router, or
could someone else also send them?

But what worries me more, is the question:
Should the linux kernel really silently accept those, breaking
the routing in a completely unexpected ways? Isn't it a bug?
The sanity check against netmask looks trivial, so why it is not there?