Re: updates needed to print-udp.c.. (was Re: RFC 9868 on Transport Options for UDP)

[Bill Fenner <fenner () gmail com>]

On Wed, Oct 8, 2025 at 10:51 AM Guy Harris <gharris () sonic net> wrote:

> On Oct 8, 2025, at 10:33 AM, Francois via tcpdump-workers <
> tcpdump-workers () lists tcpdump org> wrote:
>
> > On 08/10/2025 18:53, Guy Harris wrote:
> >
> > > OK, so does this finally make the Length field in the UDP header serve
> a useful purpose, or was there a purpose for it *before* this that I didn't
> know about?
> > One example on network stacks: Linux, net/ipv4/udp.c and net/ipv6/udp.c:
> length checks.
>
> But if the UDP header hadn't had a length field in the first place, and
> the UDP payload always ran to the end of the (possibly-reassembled) IP
> datagram, there wouldn't be a length field to check.


RFC9868 basically had a couple of guesses as to why there is a separate
length field, but basically says the reasons are lost to time.

  Bill
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