Re: [PATCH 3/8] man/man7/unix.7: SIOCINQ: Document behavior for SOCK_SEQPACKET

["Günther Noack" <gnoack3000@gmail.com>]

On Sat, Oct 24, 2026 at 05:34:00AM +0000, Kuniyuki Iwashima wrote:
> On Wed, 21 Oct 2026 23:07:55 +0200, Günther Noack wrote:
> > Document the SIOCINQ behavior for SOCK_SEQPACKET,
> > which sums up the lengths of all messages in the receive queue.
> > 
> > Restructure sentence order, so that socket type differences are
> > discussed in on paragraph, and commonalities in the next.
> > 
> > For reference, the SIOCINQ lookup is implemented in
> > unix_inq_len() in linux.git net/unix/af_unix.c.
> > 
> > This function first rejects SIOCINQ for listening sockets with
> > -EINVAL, then does a case analysis for the three types of Unix Domain
> > Sockets:
> > 
> > For SOCK_STREAM, the result is:
> > 
> > 	return READ_ONCE(unix_sk(sk)->inq_len);
> > 
> > For SOCK_SEQPACKET, the result is calculated using:
> > 
> > 	skb_queue_walk(&sk->sk_receive_queue, skb)
> >         	amount += unix_skb_len(skb);
> > 
> > For SOCK_DGRAM, the result is:
> > 
> > 	skb = skb_peek(&sk->sk_receive_queue);
> > 	if (skb)
> > 		amount = skb->len;
> > 
> > Cc: Kuniyuki Iwashima <kuniyu@google.com>
> > Assisted-by: LLM
> > Signed-off-by: Günther Noack <gnoack3000@gmail.com>
> > ---
> > 
> > Notes:
> >     I double checked this all in the code, and quoted the code.  Both the
> >     commit message and commit body were substantially edited based on the
> >     initial LLM-based version.  (Nevertheless, I would have likely missed
> >     the inaccuracy if the LLM hadn't found it.)
> >     
> >     The LLM initially just slapped an additional sentence into the
> >     paragraph, but that was mixing the socket-type-specific concerns with
> >     the general description -- I split that paragraph apart so that we
> >     have one paragraph for the three socket types and one for the
> >     socket-type-independent description.
> > 
> >  man/man7/unix.7 | 20 +++++++++++++-------
> >  1 file changed, 13 insertions(+), 7 deletions(-)
> > 
> > diff --git a/man/man7/unix.7 b/man/man7/unix.7
> > index d0c1765dfd79..4c46b54206a5 100644
> > --- a/man/man7/unix.7
> > +++ b/man/man7/unix.7
> > @@ -606,6 +606,19 @@ can be:
> >  For
> >  .B SOCK_STREAM
> 
> and SOCK_SEQPACKET

OK fair.  This was explained a bit below, but maybe too close to the
implementation.  When I initially looked at this, I found it a bit
surprising that for SOCK_SEQPACKET, it returns the size of all of them
combined, but for SOCK_DGRAM only the size of the next one.

I'll conflate this as you suggested into "For SOCK_STREAM and
SOCK_SEQPACKET..." (dropping the other sentence about SOCK_SEQPACKET.)


> >  sockets, this call returns the number of unread bytes in the receive buffer.
> > +For
> > +.B SOCK_DGRAM
> > +sockets,
> > +the returned value is the same as
> > +for Internet domain datagram sockets;
> > +see
> > +.BR udp (7).
> 
> Simply say it's the length of the first datagram.
> so that we don't need to jump to udp doc.

Sounds good, it now reads:

  For SOCK_DGRAM sockets, this call returns the size of the next
  pending datagram, or 0 when no datagram is pending.

(Using the same wording as udp(7))

> > +For
> > +.B SOCK_SEQPACKET
> > +sockets,
> > +this call returns the total number of bytes
> > +in all messages queued in the receive buffer.
> > +.IP

(Dropped this part as discussed above)

–Günther