[PATCH v4 0/7] util/qemu-sockets: Introduce inet socket options controlling TCP keep-alive

[Juraj Marcin <jmarcin@redhat.com>]

This series extends the work introduced by commit aec21d3175 ("qapi: Add
InetSocketAddress member keep-alive"). [1]

First, the series fixes an issue in qio_dns_resolver_lookup_sync_inet(),
where the InetSocketAddress structure is only partially copied. Next, it
refactors setting client socket options into a separate function and the
success and failure paths in inet_listen_saddr() in preparation for
keep-alive support on server sockets and the addition of new TCP
keep-alive options.

Then, the series extends the support for keep-alive on server sockets.

Before adding new inet address options, there are a couple of issues
with the inet address options parsing this series resolves:
- the parser contains a bug where it does not allow options with names that
  start with the name of another flag,
- the parser lacks some common function for parsing numeric values,
- the parser supports only a subset of the inet address options, namely
  the 'numeric' flag is missing.
This is resolved by the sixth patch by reworking with parser using the
QemuOpts parser. The series also includes unit tests to verify, there is
no regression in the refactored parser.

Finally, the series introduces three new InetSocketAddress options for
the control of TCP keep-alive settings. By default, the value of all new
settings is 0, which means no custom socket option value is set.

This is useful, for example, for live migration. In case there is no
traffic from the destination to the source machine during postcopy, the
destination cannot detect a failed connection due to a lack of
non-acknowledged packets and stays in the postcopy-active state until
paused by the management of the QEMU instance.

[1]: https://lore.kernel.org/all/20190725094937.32454-1-vsementsov@virtuozzo.com/

---
V4:
- refactored inet_parse() to use QemuOpts, this resolves a bug and
  allows more option types, with tests
- fixed HAVE_TCP_* macros on Windows and macOS and other suggestions by
  Daniel

V3:
https://lore.kernel.org/all/20250408112508.1638722-1-jmarcin@redhat.com/
- moved the InetSocketAddress struct copy fix and the common function
  setting socket options into a separate commit
- refactored inet_listen_saddr()

V2:
https://lore.kernel.org/all/20250319163638.456417-1-jmarcin@redhat.com/
- moved socket options setting into a common function for both server
  and client sockets (suggested by Vladimir)

V1:
https://lore.kernel.org/all/20250303143312.640909-1-jmarcin@redhat.com/

Juraj Marcin (7):
  io: Fix partial struct copy in qio_dns_resolver_lookup_sync_inet()
  util/qemu-sockets: Refactor setting client sockopts into a separate
    function
  util/qemu-sockets: Refactor success and failure paths in
    inet_listen_saddr()
  util/qemu-sockets: Add support for keep-alive flag to passive sockets
  tests/unit/test-util-sockets: Add tests for inet_parse()
  util/qemu-sockets: Refactor inet_parse() to use QemuOpts
  util/qemu-sockets: Introduce inet socket options controlling TCP
    keep-alive

 io/dns-resolver.c              |  21 +--
 meson.build                    |  30 +++
 qapi/sockets.json              |  23 ++-
 tests/unit/test-util-sockets.c | 196 ++++++++++++++++++++
 util/qemu-sockets.c            | 330 ++++++++++++++++++++-------------
 5 files changed, 458 insertions(+), 142 deletions(-)

-- 
2.49.0