Re: [PATCH] flow: Set EPOLLFD_ID_DEFAULT on newly allocated flows, not EPOLLFD_ID_INVALID

[Stefano Brivio <sbrivio@redhat.com>]

On Mon,  8 Dec 2025 22:28:22 +0100
Stefano Brivio <sbrivio@redhat.com> wrote:

> We're somehow hitting:
> 
>   ASSERTION FAILED in flow_epollfd (flow.c:362): f->epollid < ((1 << 8) - 1)
> 
> on an inbound spliced connection, with a single forwarded port, an
> HTTP server in a Podman container, and a GET request. Reproducer at
> https://bodhi.fedoraproject.org/updates/FEDORA-2025-93b4eb64c3#comment-4473411
> 
>   printf 'FROM registry.fedoraproject.org/fedora:latest\nRUN /usr/bin/dnf install -y httpd\nEXPOSE 80\nCMD ["-D", "FOREGROUND"]\nENTRYPOINT ["/usr/sbin/httpd"]\n' > Containerfile
>   podman build -t fedora-httpd $(pwd)
>   podman run -d -p 8080:80 localhost/fedora-httpd
> 
>   curl http://localhost:8080
> 
> I guess we don't set EPOLLFD_ID_DEFAULT early enough on inbound spliced
> sockets for some reason and we get a socket event while we still have
> EPOLLFD_ID_INVALID set.
> 
> As we're not really using epoll identifiers yet, set
> EPOLLFD_ID_DEFAULT right away on newly allocated flows, while we
> figure this out.
> 
> Link: https://bodhi.fedoraproject.org/updates/FEDORA-2025-93b4eb64c3#comment-4473411
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> ---
> I just merged this, posting for awareness / review.

Ah, never mind, this makes it worse somehow:

5.6384: Flow 0 (TCP connection (spliced)): SPLICE_CONNECT
5.6384: Flow 0 (TCP connection (spliced)): ERROR on epoll_ctl(): No such file or directory

...still looking for a workaround / fix.

-- 
Stefano