ip_output()/if_output() behaviour

[Michael Tuexen]

Dear all,

I'm investigating a problem and need to understand the behaviour
of ip_output(). Is it correct that if ip_output() returns an
non-zero error, the corresponding packet was never sent?
In the SCTP stack we assume this, but it seems that at least
the em and the igb driver might return an error from
igb_mq_start_locked(), for example, but have accepted the packet.

Before digging further, I would like to know what the intended
behaviour of ip_output() is.

Thanks in advance
Michael