Ethernet Layer communications

[Eric Norum]

The documentation for this is in the networking suplement:

3.4.2 Tapping Into an Interface
RTEMS add two new ioctls to the BSD networking code: SIOCSIFTAP and SIOCGIFTAP. These may be used to set and get a tap function. The tap function will be called for every Ethernet packet received by the interface.
These are called like other interface ioctls, such as SIOCSIFADDR. When setting the tap function with SIOCSIFTAP, set the ifr tap field of the ifreq struct to the tap function. When retrieving the tap function with SIOCGIFTAP, the current tap function will be returned in the ifr tap field. To stop tapping packets, call SIOCSIFTAP with a ifr tap field of 0.
The tap function is called like this:
int tap (struct ifnet *, struct ether_header *, struct mbuf *)
The tap function should return 1 if the packet was fully handled, in which case the caller will simply discard the mbuf. The tap function should return 0 if the packet should be passed up to the higher networking layers.
The tap function is called with the network semaphore locked. It must not make any calls on the application levels of the networking level itself. It is safe to call other non-networking RTEMS functions.


On Apr 14, 2011, at 2:21 PM, Daron Chabot wrote:

> 
> 
> On Thu, Apr 14, 2011 at 5:16 PM, Brett Swimley <brett.swimley at aedbozeman.com> wrote:
> Thanks Daron,
> 
> I had found this reference, and it appears that libpcap uses this API, so I will continue looking. I'm hoping that the RTEMS stack does support bpf.
> 
> I had a brief grep through the source tree and noted that there were only 3 NIC drivers that had the bpf_mtap( ) interface (all ported from FreeBSD!):
> 
> dchabot at dev32new--> git grep -n bpf c/src/libchip/network 
> c/src/libchip/network/i82586.c:1280:  if (sc->arpcom.ac_if.if_bpf != 0)
> c/src/libchip/network/i82586.c:1282:    bpf_mtap(sc->arpcom.ac_if.if_bpf, m);
> c/src/libchip/network/i82586.c:1378:    if (ifp->if_bpf)
> c/src/libchip/network/i82586.c:1379:      bpf_mtap(ifp->if_bpf, m0);
> c/src/libchip/network/if_dc.c:159:#include <net/bpf.h>
> c/src/libchip/network/if_dc.c:3372:             if (ifp->if_bpf)
> c/src/libchip/network/if_dc.c:3373:                     bpf_mtap(ifp, m_head);
> c/src/libchip/network/if_fxp.c:87:#include <net/bpf.h>
> c/src/libchip/network/if_fxp.c:1262:             * Pass packet to bpf if there i
> c/src/libchip/network/if_fxp.c:1264:            if (ifp->if_bpf)
> c/src/libchip/network/if_fxp.c:1265:                    bpf_mtap(ifp, mb_head);
> 
> But, on further inspection, the bpf_mtaps( ) were "#if 0"'d out of commission.
> 
> Then there's the issue of creating /dev/bpfX device nodes...
> 
> I would be surprised if someone out there doesn't have something already, perhaps created to support message passing between nodes of a distributed, multi-processing system?
> 
> I'm looking at you Till... ;-)
> 
> 
> -- dc
>  
> 
> Brett
> 
> 
> On Thu, Apr 14, 2011 at 2:30 PM, Daron Chabot <daron.chabot at gmail.com> wrote:
> Hi Brett,
> 
> I have not looked into this in much detail, but since RTEMS' network stack is ported from FreeBSD, you may be able to use the Berkley Packet Filter (bpf) API for this.
> 
> 
> 
> -- dc
> 
> 
> 
> 
> 
> _______________________________________________
> rtems-users mailing list
> rtems-users at rtems.org
> http://www.rtems.org/mailman/listinfo/rtems-users

-- 
Eric Norum
wenorum at lbl.gov

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.rtems.org/pipermail/users/attachments/20110414/7d0281ab/attachment-0001.html>