DTrace IP Provider [PSARC/2008/302 FastTrack timeout 05/07/2008]

[Brendan Gregg - Sun Microsystems]

On Thu, May 15, 2008 at 05:21:04PM -0700, Erik Nordmark wrote:
> Brendan Gregg - Sun Microsystems wrote:
> 
> >Ok, so you are suggesting we commit to providing "IP packet length" in the
> >TCP layer?  UDP?  SCTP?  etc?
> 
> For the IP layer. More specifically, for ipinfo_t change from:
>         uint16_t ip_plength;            /* payload length */
> to
> 	uint32_t ip_length;		/* IP packet length */
> 
> (the 16->32 change was what Darren suggested.)
> 
> When doing providers for TCP, UDP, SCTP it makes sense that they define 
> their own notion of length. But that isn't part of this case.

After speaking to Erik on the phone, we have agreed to keep ip_plength
as the payload length and to make sure the documentation describes it as
the payload length at time of tracing, and that it is an approximation.
IP packet length can be fetched in the IP provider using args[4]->ipv4_length
and args[5]->ipv6_plen + IPV6_HDR_LEN; and if this becomes a nuisance for
customers, we can later add an additional members to the IP provider in
args[4] and args[5] to make it easier.

Brendan

-- 
Brendan
[CA, USA]