Re: BPF into the HARP stack

on Thu, 22 Aug 2002 00:58:10 +0200, Vincent Jardin <[email protected]> said:

> I am wondering where the best place could be to add a bpf_[m]tap support into 
> the HARP stack.
>
> For example, I think that the incoming mbufs could be tapped into atm_subr.c:
>   atm_intr()
>
> About's the outgoing mbufs, I think that they could be tapped into atm_if.c:
>   atm_ifoutput().
>
> However, which DLT_XXX should I use ? I do not think that DLT_ATM_RFC1483, 
> nor DLT_ATM_CLIP are the right one because it is not useful for the ILMI, 
> ARP, ... cells.
>
> Moreover, which header shoud be appended in order to be compatible with 
> tcpdump and ethereal ?

In my Nicstar driver, I put the hooks into the device driver, right
after transmission, and as it recieved a new packet. In this way we
are not HARP specific.

I added a pseudo-header consisting of the following 5 octects:

 DIRECTION    VPI    VCI      GFC    Payload Type    Cell Loss Priority
   8bits      8bits 16 bits  4 bits    3 bits        1 bit
 0x80 = transmit
 0x00 = recieve

New pcap rules have to be added to use the ATM packets with tcpdump and
family.

when I supplied the DMA address for the first buffer of the PDU, I 
left 8 octects, so I knew I had room to add the pseudo-header without
needing a m_pullup().

--mark tinguely.

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