From: David Gibson <david@gibson.dropbear.id.au>
To: Stefano Brivio <sbrivio@redhat.com>
Cc: passt-dev@passt.top, Jon Maloy <jmaloy@redhat.com>
Subject: Re: [PATCH v2] tcp: probe for SO_PEEK_OFF both in tcpv4 and tcp6
Date: Wed, 24 Jul 2024 13:31:49 +1000 [thread overview]
Message-ID: <ZqB1pSY4u6tZHz0K@zatzit> (raw)
In-Reply-To: <ZqBNbx6-qnowS8V-@zatzit>
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On Wed, Jul 24, 2024 at 10:40:15AM +1000, David Gibson wrote:
> On Tue, Jul 23, 2024 at 10:29:36PM +0200, Stefano Brivio wrote:
> > On Tue, 23 Jul 2024 00:09:37 +0200
> > Stefano Brivio <sbrivio@redhat.com> wrote:
> >
> > > From: Jon Maloy <jmaloy@redhat.com>
> > >
> > > Based on an original patch by Jon Maloy:
> > >
> >
> > ...so, with this, the probing issue is solved: on a 6.10 kernel,
> > SO_PEEK_OFF is not used, unless I disable IPv6 (with --ipv4-only / -4).
> >
> > However, if I disable it, for some reason, resorting to IPv4, at least
> > together with the flow table (applying just this patch to HEAD), I get
> > something that looks like one of the "old" TCP stalls. On the host:
> >
> > $ ./passt -f -t 10000 -4
> >
> > and in the guest:
> >
> > # ip link set dev eth0 up
> > # dhclient eth0
> > # iperf3 -s -p 10000
> >
> > back to the host:
> >
> > $ iperf3 -c 127.0.0.1 -p 10000
> > Connecting to host 127.0.0.1, port 10000
> > [ 5] local 127.0.0.1 port 39046 connected to 127.0.0.1 port 10000
> > [ ID] Interval Transfer Bitrate Retr Cwnd
> > [ 5] 0.00-1.00 sec 11.2 MBytes 94.3 Mbits/sec 0 5.50 MBytes
> > [ 5] 1.00-2.00 sec 0.00 Bytes 0.00 bits/sec 0 5.50 MBytes
> > [ 5] 2.00-3.00 sec 0.00 Bytes 0.00 bits/sec 0 5.50 MBytes
> >
> > ...the transfer never recovers.
>
> Bother. I've reproduced and am debugging now.
Found it. Looks like one of the cases where we need to set
SO_PEEK_OFF was lost somewhere in the refactorings :(.
> > I didn't really have time to debug this further.
> >
> > At the moment I would be inclined to temporarily revert commit
> > e63d281871ef ("tcp: leverage support of SO_PEEK_OFF socket option when
> > available"), but it's not a good idea if this happens to be hiding some
> > (unlikely?) issue with the flow table.
> >
>
--
David Gibson (he or they) | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you, not the other way
| around.
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2024-07-24 3:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-22 22:09 [PATCH v2] tcp: probe for SO_PEEK_OFF both in tcpv4 and tcp6 Stefano Brivio
2024-07-23 6:57 ` David Gibson
2024-07-23 20:29 ` Stefano Brivio
2024-07-24 0:40 ` David Gibson
2024-07-24 3:31 ` David Gibson [this message]
2024-07-24 7:29 ` Stefano Brivio
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