Christoph Lameter a écrit :

On Tue, 25 Aug 2009, Eric Dumazet wrote:

quoted

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The initial point was that the SNMP counters are not updated if IP_RECVERR
is not set which is clearly a bug and your and my patch addresses that.

Technically speaking, the send() syscall is in error. Frame is not sent, so
there is no drop at all. Like trying to send() from a bad user buffer, or write()
to a too big file...

Frame is submitted to the IP layer which discards it. That is the
definition of an output discard.

Last patch accounts for this *error* AFAIK, or did I missed something ?

quoted

Question is : should we just allow send() to return an error (-ENOBUF) regardless
of IP_RECVERR being set or not ? I dont think it would be so bad after all.
Most apps probably dont care, or already handle the error.

Some applications will then start to fail because so far you can send with
impunity without getting errors. AFAICT IP_RECVERR was added to preserve
that behavior. Your patch is changing basic send() semantics.

Sorry ???, I guess your machines have plenty available LOWMEM then, and kmalloc() never fail then...

man P send

      ENOBUFS
              Insufficient resources were available in the system to perform the operation.

basic send() semantics are respected.