> >> You need to know the incoming hardware the packet arrived on to
> >> assign an address to the host, so I hope this is what IP_RECVIF is
> >> telling you.
> 
> IP_RECVIF gets you the if_index value for the interface in question.
> Mapping that to anything useful is up to the packet recipient.

I remember these being discussed at one of the last XNET meetings I
attanded.  I couldn't then work out how if_index numbers helped you
do anything useful :-)

The guys from sun seemed to think they were vital though.

(I recall them being defined as 'small integers' - I always fancy random
32 bit ones myself (mathematically small!))

    David