tcpdump mailing list archives
Re: DLT value for IP over IB (Infiniband)
From: Guy Harris <guy () alum mit edu>
Date: Thu, 14 Jul 2011 10:20:09 -0700
On Jul 14, 2011, at 5:23 AM, Darren Reed wrote:
Some more follow up on this... Looks are deceiving - there is no RFC 4391/4392 header being prepended to the IP packet: /* * In order to transmit the datagram to correct destination, an extra * header including destination address is required. IB does not provide an * interface for sending a link layer header directly to the IB link and the * link layer header received from the IB link is missing information that * GLDv3 requires. So mac_ib plugin defines a "soft" header as below. */ (From a header file on Solaris) The above probably explains this output on Linux: # tcpdump -i ib0 -vv -e -c 5 tcpdump: WARNING: arptype 32 not supported by libpcap - falling back to cooked socket
What explains that part of the output is that libpcap doesn't have any code to map ARPHRD_INFINIBAND to any DLT_ value, because nobody's contributed any such code. Perhaps that's because there's no DLT_ value that corresponds to whatever the link-layer header looks like on ARPHRD_INFINIBAND devices on Linux; it's not because of anything specific to Solaris.
... and which ultimately means there is not likely to ever be a real link layer header presented for outbound packets. For inbound, it would seem that it is implementation dependent.
If "implementation-dependent" means "it's different on Solaris and Linux", the solution is simple - different LINKTYPE_ values for Solaris and Linux; there's already precedent for LINKTYPE_ values for particular OS's flavor of link-layer headers: there are both LINKTYPE_ARCNET_BSD and LINKTYPE_ARCNET_LINUX, there's LINKTYPE_APPLE_IP_OVER_IEEE1394 for Apple's headers for IP-over-FireWire, there are a bunch of other LINKTYPE_ values with LINUX in the name, etc.- This is the tcpdump-workers list. Visit https://cod.sandelman.ca/ to unsubscribe.
Current thread:
- DLT value for IP over IB (Infiniband) Darren Reed (Jul 13)
- Re: DLT value for IP over IB (Infiniband) Darren Reed (Jul 14)
- Re: DLT value for IP over IB (Infiniband) Guy Harris (Jul 14)
- Re: DLT value for IP over IB (Infiniband) Darren Reed (Jul 14)
- Re: DLT value for IP over IB (Infiniband) Darren Reed (Jul 29)
- Re: DLT value for IP over IB (Infiniband) Guy Harris (Jul 29)
- Re: DLT value for IP over IB (Infiniband) Darren Reed (Aug 02)
- Re: DLT value for IP over IB (Infiniband) Guy Harris (Jul 14)
- Re: DLT value for IP over IB (Infiniband) Darren Reed (Jul 14)
- <Possible follow-ups>
- Re: DLT value for IP over IB (Infiniband) Darren Reed (Aug 02)