Re: pcap_inject() fails with rc 0 on HP-UX

[Guy Harris <guy () alum mit edu>]

On Apr 4, 2006, at 8:51 AM, Harley Stenzel wrote:

> On 4/3/06, Rick Jones <rick.jones2 () hp com> wrote:
> > I believe this is a long-standing limitation of promiscuous mode  
> > support
> > in HP-UX - only one process may have a promiscuous stream open on an
> > interface at one time.  I believe that is the case for  
> > DL_PROMISC_PHYS
> > (give me everything that reaches the NIC). I cannot recall if that  
> > would
> > be the same for the lesser "give me everything that the NIC gives the
> > host" DL_PROMISC_SAP.
>
> Using tcpdump as an example:
>
> bash-3.00# tcpdump -p -i lan2 > /dev/null &
> [1] 14650
> tcpdump: verbose output suppressed, use -v or -vv for full protocol  
> decode
> listening on lan2, link-type EN10MB (Ethernet), capture size 96 bytes
>
> bash-3.00#  tcpdump -p -i lan2 > /dev/null
> tcpdump: recv_ack: promisc_sap: UNIX error - Device busy

That's requesting DL_PROMISC_SAP mode.  Perhaps in HP-UX, only one  
process can request that mode at a time, as Rick hypothesized might  
be the case - if so, it's yet another reason for a "userland  
protocol" library that would use the underlying packet capture  
mechanism's features in the right way for a userland protocol  
implementation atop some link layer (e.g., not doing SAP promiscuity  
on those platforms with such a notion).

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