Thursday, October 31, 2019

Re: minor tcpdump.8 inconsistency

Jason McIntyre <jmc@kerhand.co.uk> wrote:

> On Thu, Oct 31, 2019 at 02:15:34PM +0100, Tim Kuijsten wrote:
> > minor inconsistency
> >
> > diff --git a/tcpdump.8 b/tcpdump.8
> > index ce16951..8c2cf33 100644
> > --- a/tcpdump.8
> > +++ b/tcpdump.8
> > @@ -1257,7 +1257,7 @@ end of this connection.
> > .Ar window
> > is the number of bytes of receive buffer space available
> > at the other end of this connection.
> > -.Ar urg
> > +.Ar urgent
> > indicates there is urgent data in the packet.
> > .Ar options
> > are TCP options enclosed in angle brackets e.g.,
> >
>
> hi.
>
> have you established that it's the documentation that is wrong? i.e.
> that "urgent" is printed, and not actually "urg"?

The situation is a bit more subtle than that. Just above, the manual
page leads with this header.

The general format of a TCP protocol line is:

src > dst: flags src-os data-seqno ack window urgent options

It is saying there's a section of the line regarding the _window_, then a
section regarding _urgent_, then a section regarding _options_. In the
next paragraph it vaguely describes each of these without getting into
the specifics of the actual printed format (for instance, _window_ is
actually printed as " win %u".

The .Ar above are the "section names" of the line. I think Tim's diff is
right.

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