DHCP server for freebsd on IPoIB

Rodney W. Grimes freebsd-rwg at gndrsh.dnsmgr.net
Wed Feb 12 17:19:16 UTC 2020

> On 2020-02-11 22:46, Kumar, Anmol wrote:
> > Hi,
> > I am trying to make  dhcp 4.4.2b1 work on Mellanox Infiniband for IPoIB.
> > 
> >    1.  Seems like , bpf does not have support for IPoIB as family passed in zero so IPoIB driver returns error.
> >    2.  I tried using sockets for DHCP server and send is successful (returning exact number of bytes in packet) but I do not see packet in IPoIB driver.
> >    3.  Able to receive DHCP broadcast request to DHCP server code (user space)
> >    4.  Ping is working fine (statically assign IP address) and seems like issue with DHCP broadcast replies in DHCPOFFER (same code works with Linux)
> > 
> > Any help will be appreciated .
> > 
> Hi Kumar,
> IPoIB is an IP carrier.
> Doesn't dhcp require an ethernet carrier for the reception of frames via 
> BPF to work?

I was thinking about this myself, unlike ARP which is NOT an IP protocol,
dhcp IS at the IP/UDP layer.  What may be an issue is that these are IP
broadcast packets that would have to be mapped to IB multicast and that
I am unfamiliar with.

I think the problem that Kumar may of run into is that bpf doesnt hook
at the IP layer, it hooks at the "data link layer."  It might be possible
to work around this by using some netgraph plumbing and ng_bpf.

Is there support in FreeBSD for bpf at the IB link layer?

> --HPS
Rod Grimes                                                 rgrimes at freebsd.org

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