Re: [PATCH] udp: Split activity timeouts for UDP flows

[Stefano Brivio <sbrivio@redhat.com>]

On Sat, 14 Feb 2026 15:20:26 +0800
Yumei Huang <yuhuang@redhat.com> wrote:

> On Fri, Feb 13, 2026 at 6:17 PM Stefano Brivio <sbrivio@redhat.com> wrote:
> >
> > On Fri, 13 Feb 2026 18:04:59 +0800
> > Yumei Huang <yuhuang@redhat.com> wrote:
> >  
> > > On Fri, Feb 13, 2026 at 6:00 PM Stefano Brivio <sbrivio@redhat.com> wrote:  
> > > >
> > > > On Fri, 13 Feb 2026 17:54:56 +0800
> > > > Yumei Huang <yuhuang@redhat.com> wrote:
> > > >  
> > > > > On Fri, Feb 13, 2026 at 5:13 PM Stefano Brivio <sbrivio@redhat.com> wrote:  
> > > > > >
> > > > > > On Fri, 13 Feb 2026 15:49:41 +0800
> > > > > > Yumei Huang <yuhuang@redhat.com> wrote:
> > > > > >  
> > > > > > > But in my test, udp_flow_from_sock() is only called for
> > > > > > > the first datagram, so the if condition after flow_lookup_sa() always
> > > > > > > returns false, and a new UDP flow is created.  
> > > > > >
> > > > > > Ah, right! See below.
> > > > > >  
> > > > > > > Tried either spliced /
> > > > > > > non-spliced, pasta / passt case, no exceptions observed.  I was wondering
> > > > > > > if there is a scenario I'm not aware of.  
> > > > > >
> > > > > > Yes, I think it's just for one corner case David described in the "Flow
> > > > > > sockets" section of the "Theory of Operation" documentation in udp.c:  
> 
> [...]
>
> Just have another look, instead of this case, I feel it's more like
> the one described in
> https://passt.top/passt/commit/udp_flow.c?id=9725e79888374a4e4060a2d798f3407c0006cc8a,
> which is packets arriving between bind() and connect(), and
> udp_sock_fwd() / udp_flow_from_sock() is called again to forward the
> packets. In this case, we should count the activity. The timestamp
> might not be so accurate, but should be very close. So I'm keeping it.

Hmm, I guess you're right, and actually that path shouldn't be called
for listening sockets. In any case, if you update the packet count
whenever the timestamp is updated, as you did on v3, that should be
correct. Running tests there in a bit.

-- 
Stefano