Re: Requesting LINKTYPE constant be defined/reserved for: IP over IB

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

On Dec 19, 2012, at 1:27 PM, Stuart Werbner <swerbner () us ibm com> wrote:

> I am requesting a new LINKTYPE_ (LINKTYPE_IB) value for IP over Infiniband
> be reserved, in order to properly support this protocol within tcpdump and
> libpcap for upcoming AIX kernel releases.

So you're using LINKTYPE_ values, rather than SNMP interface type values, as the network type in pcap files now?  Good.

If you're writing nanosecond time stamps to files, are you now using a1 b2 3c 4d rather than a1 b2 c3 d4 as the magic 
number, so that programs or libraries reading the files can determine what the time stamp resolution is?

(And speaking of AIX's libpcap/tcpdump, there's AIX support in the tcpdump.org libpcap, but it seems to be tripping 
across some bugs in AIX's BPF implementation, at least in the versions of AIX against which the people reporting the 
bugs tried it.)

> If this value is already defined, please indicate that.
>
> I have discovered that within an AIX kernel header file, DLT_IB (Data-link
> Level Type) is defined, but I believe we are still in need of a Link-Layer
> Header Type.
>
> Here are the RFCs related to IP over Infiniband:
> * RFC 3827
> * RFC 4391


In the existing link-layer header type list:

        http://www.tcpdump.org/linktypes.html

there's a LINKTYPE_IPOIB value, in which the packet data is as described in section 6 of RFC 4391, starting with the 
4-octet encapsulation header.

RFC 3827 just speaks of a snoop link-layer header type value for IP-over-IB, referring to a "work in progress" 
document; as RFC 3827 came from Sun, and as LINKTYPE_IPOIB was provided in response to a request from somebody from 
Sun^WOracle, the snoop link-layer header type probably refers to the same thing.
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