tcpdump mailing list archives
Re: TCP Header Flags
From: Francois-Xavier Le Bail <devel.fx.lebail () orange fr>
Date: Sun, 19 Feb 2023 13:34:04 +0100
On 18/02/2023 21:51, Denis Ovsienko wrote:
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.
We could keep "tcp-push" indefinitely...
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.
There is not even consistency in the tcpdump man page (PUSH and PSH): $ git grep -En '\<(PSH|PUSH)\>' tcpdump.1.in tcpdump.1.in:1322:F (FIN), P (PUSH), R (RST), U (URG), W (ECN CWR), E (ECN-Echo) or tcpdump.1.in:1389:The PUSH flag is set in the packet. tcpdump.1.in:1415:.I CWR | ECE | URG | ACK | PSH | RST | SYN | FIN tcpdump.1.in:1486:left, so the PSH bit is bit number 3, while the URG bit is number 5. _______________________________________________ tcpdump-workers mailing list -- tcpdump-workers () lists tcpdump org To unsubscribe send an email to tcpdump-workers-leave () lists tcpdump org %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s
Current thread:
- TCP Header Flags Francois-Xavier Le Bail (Feb 18)
- Re: TCP Header Flags Denis Ovsienko (Feb 18)
- Re: TCP Header Flags Francois-Xavier Le Bail (Feb 19)
- Re: TCP Header Flags Francois-Xavier Le Bail (Feb 26)
- Re: TCP Header Flags Denis Ovsienko (Feb 26)
- Re: TCP Header Flags Francois-Xavier Le Bail (Feb 26)
- Re: TCP Header Flags Denis Ovsienko (Feb 27)
- Re: TCP Header Flags Francois-Xavier Le Bail (Feb 19)
- Re: TCP Header Flags Denis Ovsienko (Feb 18)
- Re: TCP Header Flags Francois-Xavier Le Bail (Feb 26)