Re: activities report for July 2026

[Denis Ovsienko <denis () ovsienko info>]

On Sun, 2 Aug 2026 13:48:31 -0700
Guy Harris <gharris () sonic net> wrote:

[...]

> Perhaps one could argue that it *should* be supported, but, at least
> in libpcap, we'd only be able to use it in 1) our own cBPF
> interpreter and 2) in-kernel cBPF interpreters in OS versions where
> we know it's supported, and to get it supported in them, you'd have
> to get the individual OS developers to add support.

This would be a monumental task, but the gain could be zero because:

* "ret x" would have the same effect as "txa; ret" because the value of
  A makes no difference after the return, except each "ret x" per
  filter program would save one BPF instruction, and

* libpcap always generates filter programs with one or two return
  instructions, and

* the only type of return instruction libpcap generates is "ret #k".

It would be interesting to know if any non-libpcap use cases that use
"ret" (from the A register) exist.

-- 
    Denis Ovsienko
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