[PATCH net-next v2 0/7] ipv4,ipv6: convert the getsockopt switches to sockopt_t

This series continues the migration to sockopt_t, as described in [1].
do_ip_getsockopt() and do_ipv6_getsockopt() are the last two switches
still taking a sockptr_t pair, and everything they forward to now takes
a sockopt_t, so convert them both.

Patch 1 settles what a negative optlen means on SOL_IPV6 before the
conversion makes it matter. do_ip_getsockopt() rejects it, but
do_ipv6_getsockopt() never has, and the int options answer it as 4.
Treat it as 4, as David Laight suggested, instead of failing callers
that rely on it.

Patch 2 fixes a latent bug in sockopt_expand_out() [2] itself: it caps
the expansion at INT_MAX, but iov_iter_revert() refuses to unroll past
the smaller MAX_RW_COUNT.

MCAST_MSFILTER has to move before the switches above it. It is the last
option with the quirk sockopt_expand_out() was added for [2]: optlen only
covers the fixed part, and the real reply size comes from the gf_numsrc
field inside it. Patches 3 and 4 convert it on both families, and store
the reply length only after the final copy succeeds, so a copy failure
can't report a changed optlen.

Patches 5 and 6 convert the switches themselves. Each wrapper keeps its
__user prototype and builds the sockopt_t, so the proto layer is
untouched. ipv6_getsockopt() cannot use sockopt_init_user(), which
rejects a negative optlen, so patch 6 moves the clamp of patch 1 up
there and builds the sockopt_t after it.

Patch 7 grows the selftest with an ip and an ipv6 fixture, pinning the
returned length, errno and reply bytes.

The temporary sockptr_t-to-sockopt_t glue can go away once the higher
level callers take sockopt_t too. For now, the series keeps the proto
callbacks unchanged and converts only the leaf helpers.

Link: https://lore.kernel.org/all/20260401-getsockopt-v2-0-611df6771aff@debian.org/ (local) [1]
Link: https://lore.kernel.org/all/20260914-getsockopt_phase6-v2-0-e48befc9602e@debian.org/ (local) [2]

To: David Ahern <dsahern@kernel.org>
To: Ido Schimmel <idosch@nvidia.com>
To: David S. Miller <davem@davemloft.net>
To: Eric Dumazet <redacted>
To: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
To: Simon Horman <horms@kernel.org>
To: Alexei Starovoitov <ast@kernel.org>
To: Daniel Borkmann <daniel@iogearbox.net>
To: Andrii Nakryiko <andrii@kernel.org>
To: Eduard Zingerman <eddyz87@gmail.com>
To: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: Martin KaFai Lau <martin.lau@linux.dev>
To: Song Liu <song@kernel.org>
To: Yonghong Song <yonghong.song@linux.dev>
To: Jiri Olsa <jolsa@kernel.org>
To: Emil Tsalapatis <emil@etsalapatis.com>
To: Ihor Solodrai <ihor.solodrai@linux.dev>
To: John Fastabend <john.fastabend@gmail.com>
To: Stanislav Fomichev <sdf@fomichev.me>
To: Shuah Khan <shuah@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: bpf@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
To: Stanislav Fomichev <sdf@fomichev.me>
Cc: david.laight.linux@gmail.com

Signed-off-by: Breno Leitao <leitao@debian.org>
---
Changes in v2:
- Treat a negative optlen as 4 instead of rejecting it with
  -EINVAL as v1 did, per David Laight and Stanislav Fomichev. 
- Fix sashiko findings
- Link to v1: https://patch.msgid.link/20260925-sockopt_expand_out_v2-v1-0-c3ef2e3bb5c0@debian.org (local)

---
Breno Leitao (7):
      ipv6: treat a negative optlen as 4 in do_ipv6_getsockopt()
      net: cap sockopt_expand_out() at MAX_RW_COUNT
      ipv6: mcast: convert ip6_mc_msfget() to sockopt_t
      ipv4: igmp: convert ip_mc_gsfget() to sockopt_t
      ipv4: convert do_ip_getsockopt() to sockopt_t
      ipv6: convert do_ipv6_getsockopt() to sockopt_t
      selftests: net: getsockopt_iter: cover ip and ipv6

 include/linux/igmp.h                          |   2 +-
 include/linux/mroute.h                        |   4 +-
 include/linux/mroute6.h                       |   5 +-
 include/linux/net.h                           |  27 +-
 include/net/ip.h                              |   3 +-
 include/net/ipv6.h                            |   4 +-
 net/core/filter.c                             |  36 ++-
 net/ipv4/igmp.c                               |  23 +-
 net/ipv4/ip_sockglue.c                        | 118 ++++-----
 net/ipv4/ipmr.c                               |  11 +-
 net/ipv6/ip6mr.c                              |  13 +-
 net/ipv6/ipv6_sockglue.c                      | 117 +++++----
 net/ipv6/mcast.c                              |  19 +-
 tools/testing/selftests/net/getsockopt_iter.c | 359 ++++++++++++++++++++++++++
 14 files changed, 577 insertions(+), 164 deletions(-)
---
base-commit: aac26bee2287c88af5be5a5ff96d783b19a28790
change-id: 20260924-sockopt_expand_out_v2-ee4bc7ba4cea

Best regards,
--  
Breno Leitao [off-list ref]