Re: [PATCH] [IPv4] Reply net unreachable ICMP message

On Thu, 6 Dec 2007 09:47:33 +0100
Jarek Poplawski [off-list ref] wrote:

On 06-12-2007 09:14, Mitsuru Chinen wrote:

quoted

On Thu, 6 Dec 2007 08:49:47 +0100
Jarek Poplawski [off-list ref] wrote:

quoted

On 06-12-2007 07:31, Mitsuru Chinen wrote:

quoted

IPv4 stack doesn't reply any ICMP destination unreachable message
with net unreachable code when IP detagrams are being discarded
because of no route could be found in the forwarding path.
Incidentally, IPv6 stack replies such ICMPv6 message in the similar
situation.

...

quoted

quoted

This patch seems to be wrong. It overrides err codes from
fib_lookup, where such decisions should be made.

fib_lookup() replies -ESRCH in this situation.
It is necessary to override the variable by the suitable error
number like the code under e_hostunreach label.

Probably I miss something, but I can't see how can you be sure it's
only -ESRCH possible here? Isn't opt->action() in fib_rules_lookup()
supposed to return this -ENETUNREACH when needed?

Oh, excuse me. I did mistake.
fib_rules_lookup() replies -ESRCH when no route is found. The case
it replies -ENETUNREACH is that user adds unreachable route.
However, if the err value is override with no check, a blackhole
or prohibit route is treated as a unreachable route.

As the patch is already applied, I will send another patch to add
a check for it.
Thank you very much for pointing out the issue!

Best Regards,
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Mitsuru Chinen [off-list ref]