[PATCH v2 0/3] nvme-tcp: add IPv6 traffic class support

[Geliang Tang <geliang@kernel.org>]

From: Geliang Tang <tanggeliang@kylinos.cn>

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 or
MPTCP subflows that need a non-default tclass.

The series is split into three patches following the natural
fabrics/host/target layering:

1. nvme-fabrics: add IPv6 traffic class option
   Parse the new 'tclass' option in nvmf_parse_options(), validate
   that it is in the 0-255 range, and store it in
   struct nvmf_ctrl_options. Use -1 to mean "transport default",
   matching the existing tos handling.

2. nvme-tcp: support IPv6 traffic class
   Advertise NVMF_OPT_TCLASS in the nvme_tcp transport and, when a
   tclass was provided, set IPV6_TCLASS on each queue socket. The
   existing IP_TOS path is left untouched so IPv4 behaviour is
   unchanged.

3. nvmet-tcp: support IPv6 traffic class
   On the target side, differentiate the socket family: for AF_INET
   keep the existing TOS handling, and for AF_INET6 read the traffic
   class from the incoming socket and apply it via IPV6_TCLASS.

Follow-up changes outside of this series expose the same option
through libnvme and the nvme-cli, so the new tclass can be selected
from the user-facing command line; those patches will be sent in a
separate series.

This was tested with the selftests mptcp_nvme.sh [1], extended in
"nvme: add tclass support" to pass "--tclass" on the host side and
validate that the value is reflected on the wire by the target.

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.

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

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

Geliang Tang (3):
  ipv6: extract and export ip6_sock_set_tclass helpers
  nvme-tcp: support IPv6 traffic class
  nvmet-tcp: support IPv6 traffic class

 drivers/nvme/host/fabrics.c | 18 ++++++++++++++++++
 drivers/nvme/host/fabrics.h |  3 +++
 drivers/nvme/host/tcp.c     |  8 +++++++-
 drivers/nvme/target/tcp.c   |  8 ++++++++
 include/net/ipv6.h          |  3 +++
 net/ipv6/ipv6_sockglue.c    | 31 +++++++++++++++++++++++--------
 6 files changed, 62 insertions(+), 9 deletions(-)

-- 
2.53.0