[PATCH v3 0/4] nvme-tcp: add IPv6 traffic class support

From: Geliang Tang <redacted>

This series adds IPv6 traffic class (tclass) support to the NVMe/TCP
fabrics stack, mirroring the existing IPv4 TOS configuration.

The current code path only handles IPv4: nvme-fabrics exposes a 'tos'
option, the host (nvme-tcp) applies IP_TOS to each queue socket, and
the target (nvmet-tcp) reflects the value received on the wire. This
leaves no way to control or observe the IPv6 traffic class for NVMe/TCP
connections, which is a real gap for deployments running over IPv6 that
need a non-default tclass.

The series also refactors the socket option configuration on both host
and target sides to use the generic do_sock_setsockopt() helper. This
change eliminates the need for protocol-specific helpers and decouples
the configuration from the underlying transport protocol, laying the
groundwork for future protocol extensions such as MPTCP.

The series is split into two logical parts: the do_sock_setsockopt
refactoring (patches 1-2) and the IPv6 traffic class support (patches
3-4), following the natural host/target layering.

This was tested with the selftests mptcp_nvme.sh [1] to pass "--tos"
on the host side and validate that the value is reflected on the wire
by the target.

[1]
https://patchwork.kernel.org/project/linux-nvme/cover/cover.1779934709.git.tanggeliang@kylinos.cn/

v3:
 - add two patches to unify socket option configuration using
   do_sock_setsockopt on both host and target sides.
 - use do_sock_setsockopt for IPV6_TCLASS rather than exporting and
   calling ip6_sock_set_tclass, as suggested by Jakub.
 - reuse the existing NVMF_OPT_TOS for IPv6 sockets instead of adding
   a new NVMF_OPT_TCLASS option, as suggested by Stanislav.

v2:
 - Export and use the ip6_sock_set_tclass() helper in both target and host
   paths, aligning with the existing ip_sock_set_tos() usage.
 - Add CONFIG_IPV6 and AF_INET6 guards to avoid build failures when IPv6
   is disabled.
 - Use rcv_flowinfo from the target socket instead of np->tclass.
 - https://patchwork.kernel.org/project/linux-nvme/cover/cover.1786171863.git.tanggeliang@kylinos.cn/

v1:
 - https://patchwork.kernel.org/project/linux-nvme/cover/cover.1785122120.git.tanggeliang@kylinos.cn/

Geliang Tang (4):
  nvmet-tcp: unify sockopt with do_sock_setsockopt
  nvme-tcp: unify sockopt with do_sock_setsockopt
  nvmet-tcp: support IPv6 traffic class
  nvme-tcp: support IPv6 traffic class

 drivers/nvme/host/tcp.c   | 68 +++++++++++++++++++++++++++++++++------
 drivers/nvme/target/tcp.c | 68 ++++++++++++++++++++++++++++++++++-----
 2 files changed, 119 insertions(+), 17 deletions(-)

-- 
2.53.0