Re: TCP Header Flags

[Denis Ovsienko <denis () ovsienko info>]

On Sat, 18 Feb 2023 17:06:29 +0100
Francois-Xavier Le Bail <devel.fx.lebail () orange fr> wrote:

> Hello,
>
> https://www.rfc-editor.org/rfc/rfc9293 states:
> "Control bits:
>
>     The control bits are also known as "flags". Assignment is managed
> by IANA from the "TCP Header Flags" registry [62]. The currently
> assigned control bits are CWR, ECE, URG, ACK, PSH, RST, SYN, and FIN."
>
> (All on three characters.)
>
> To be in sync with it, we could use 'tcp-psh' in addition to
> 'tcp-push' in libpcap scanner.l, and in pcap-filter.7 and tcpdump.1
> man pages.

That's an interesting point.  Adding "tcp-psh" would certainly restore
consistency with the registry on one hand.  On the other, for backward
compatibility reasons "tcp-push" would have to remain a valid alias for
who knows how many years.  I wonder if there would be any other
incurred future maintenance.

The fact tcpdump(1) prose says "PUSH" instead of "PSH" may be related
to the origin of this discrepancy.  Perhaps this is the only part that
can be fixed immediately without unwanted side effects.

-- 
    Denis Ovsienko
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