Hi Daniel
On 2025-04-11 16:49, Daniel P. Berrangé wrote:
> On Fri, Apr 11, 2025 at 02:54:29PM +0100, Daniel P. Berrangé wrote:
> > On Tue, Apr 08, 2025 at 01:25:04PM +0200, Juraj Marcin wrote:
> > > From: Juraj Marcin <jmar...@redhat.com>
> > >
> > > With the default TCP stack configuration, it could be even 2 hours
> > > before the connection times out due to the other side not being
> > > reachable. However, in some cases, the application needs to be aware of
> > > a connection issue much sooner.
> > >
> > > This is the case, for example, for postcopy live migration. If there is
> > > no traffic from the migration destination guest (server-side) to the
> > > migration source guest (client-side), the destination keeps waiting for
> > > pages indefinitely and does not switch to the postcopy-paused state.
> > > This can happen, for example, if the destination QEMU instance is
> > > started with the '-S' command line option and the machine is not started
> > > yet, or if the machine is idle and produces no new page faults for
> > > not-yet-migrated pages.
> > >
> > > This patch introduces new inet socket parameters that control count,
> > > idle period, and interval of TCP keep-alive packets before the
> > > connection is considered broken. These parameters are available on
> > > systems where the respective TCP socket options are defined
> > > (TCP_KEEPCNT, TCP_KEEPIDLE, TCP_KEEPINTVL).
> > >
> > > The default value for all is 0, which means the system configuration is
> > > used.
> > >
> > > Signed-off-by: Juraj Marcin <jmar...@redhat.com>
> > > ---
> > > meson.build | 6 ++++
> > > qapi/sockets.json | 15 ++++++++
> > > util/qemu-sockets.c | 88 +++++++++++++++++++++++++++++++++++++++++++++
> > > 3 files changed, 109 insertions(+)
> > >
> > > diff --git a/meson.build b/meson.build
> > > index 41f68d3806..680f47cf42 100644
> > > --- a/meson.build
> > > +++ b/meson.build
> > > @@ -2734,6 +2734,12 @@ if linux_io_uring.found()
> > > config_host_data.set('HAVE_IO_URING_PREP_WRITEV2',
> > > cc.has_header_symbol('liburing.h',
> > > 'io_uring_prep_writev2'))
> > > endif
> > > +config_host_data.set('HAVE_TCP_KEEPCNT',
> > > + cc.has_header_symbol('netinet/tcp.h',
> > > 'TCP_KEEPCN'T))
> > > +config_host_data.set('HAVE_TCP_KEEPIDLE',
> > > + cc.has_header_symbol('netinet/tcp.h',
> > > 'TCP_KEEPIDLE'))
> > > +config_host_data.set('HAVE_TCP_KEEPINTVL',
> > > + cc.has_header_symbol('netinet/tcp.h',
> > > 'TCP_KEEPINTVL'))
> >
> > What platforms are you aware of that do NOT have these
> > settings available ? I'm wondering if we can just assume
> > they always exist.
>
> macOS appears to have these, except that 'TCP_KEEPIDLE' is under a
> differnt name 'TCP_KEEPALIVE':
>
>
> https://github.com/apple/darwin-xnu/blob/xnu-4570.1.46/bsd/man/man4/tcp.4#L172
>
> Likewise I see them available in mingw for Wndows builds, with both
> names
>
> $ grep -r TCP_KEEP /usr/i686-w64-mingw32/sys-root/mingw/include/
> /usr/i686-w64-mingw32/sys-root/mingw/include/ws2ipdef.h:#define TCP_KEEPALIVE
> 3
> /usr/i686-w64-mingw32/sys-root/mingw/include/ws2ipdef.h:#define TCP_KEEPCNT 16
> /usr/i686-w64-mingw32/sys-root/mingw/include/ws2ipdef.h:#define TCP_KEEPIDLE
> TCP_KEEPALIVE
> /usr/i686-w64-mingw32/sys-root/mingw/include/ws2ipdef.h:#define TCP_KEEPINTVL
> 17
>
> but your patch wouldn't enable it because it checks netinet/tcp.h
>
> AFAICT, the only platform that matters to QEMU that seems to miss this
> is OpenBSD
>
Yes, I couldn't find them in the OpenBSD man-pages. Other BSD variants
support all of them. I will mention it explicitly in the QAPI docs, that
OpenBSD is not supported.
I will also fix it for Windows and Darwin, and submit an updated series.
Thank you!
Best regards,
Juraj Marcin
>
> With regards,
> Daniel
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