[PATCH net-next v9 0/6] rtnetlink: dump link-layer multicast addresses

[Yuyang Huang <sigefriedhyy@gmail.com>]

"ip maddr show" prints link-layer, IPv4 and IPv6 entries. The IPv4 and
IPv6 ones come over netlink today, with IFA_MC_USERS for the user count.
The link-layer list, dev->mc, is only exported via /proc/net/dev_mcast,
so iproute2 and other users still parse procfs for it.

This series adds the AF_PACKET family to RTM_GETMULTICAST so that the
link-layer multicast addresses are reported the same way. Patch 4 dumps
dev->mc in the ifaddrmsg format of the IPv4 and IPv6 dumps: IFA_MULTICAST
carries the address, IFA_MC_USERS the reference count and a new
IFA_F_GLOBAL flag marks entries added explicitly, the "static" column of
/proc/net/dev_mcast. ifa_index limits the dump to one device and
IFA_TARGET_NETNSID selects another netns. Patches 2 and 3 add a
generation counter for dev->mc changes so a multi-part dump reports
NLM_F_DUMP_INTR like the IPv4 and IPv6 ones. Patches 1 and 5 update the
rt-addr spec and patch 6 adds a selftest.

AF_PACKET dumps returned -EOPNOTSUPP before, so iproute2 can keep the
procfs fallback for older kernels. The iproute2 side is ready and will
be posted once this is in.

Changes in v9:
- Change the count of a netdev_hw_addr_list through helpers only and
  rename it to _count, as its own patch
- Use the count helpers in __hw_addr_splice() too
- Note in the spec doc that the header checks are unconditional for
  AF_PACKET only

Changes in v8:
- Set the owner of every list a device has, not only dev->mc, and
  check for dev->mc in one place when bumping the counter
- Add __hw_addr_count_inc/dec/reset() so a change of list->count and
  the counter bump stay together

Changes in v7:
- Add a per netns generation counter bumped on dev->mc changes and fold
  it into cb->seq, dev_base_seq alone did not cover the dumped entries
- Sample cb->seq under the address lock of each device and again when a
  dump round ends, so the NLMSG_DONE check sees a change too

Changes in v6:
- Move the dump to net/core/dev_addr_lists.c next to the dev->mc
  helpers
- Stamp cb->seq from dev_base_seq and check dump consistency
- Let an unexpected dump error propagate instead of skipping
- Check for an address only present in the peer netns in the
  target-netnsid selftest, the peer and local ifindex can be equal
- Document the ifa-index filter and the zero header fields in the spec

Changes in v5:
- Filter the target-netnsid selftest dump by ifa-index, a new netns
  also contains the fallback tunnel devices

Changes in v4:
- Reset the resume offset when the device the dump stopped at is gone
- Use a tracked netns reference (put_net_track)
- Say ifa-family must be set in the spec doc, drop the AF_UNSPEC remark
- Close the netlink socket and guard the checks in the selftest
- Drop the Fixes tag

Changes in v3:
- Report the static bit as a new IFA_F_GLOBAL flag in IFA_FLAGS
  instead of IFA_F_PERMANENT
- Support IFA_TARGET_NETNSID and test it
- Describe global_use accurately, it is also set by dev_mc_add_excl()
- Fix the target-netnsid type in the rt-addr spec, as its own patch

Changes in v2:
- Always validate the request header, not only with strict checking
- Use a single "with" statement in the selftest (ruff)

Yuyang Huang (6):
  netlink: specs: rt-addr: fix the type of target-netnsid
  net: change netdev_hw_addr_list count through helpers
  net: add a generation counter for dev->mc changes
  net: add AF_PACKET multicast dumps
  netlink: specs: rt-addr: document AF_PACKET multicast dumps
  selftests: net: test AF_PACKET multicast dumps

 Documentation/netlink/specs/rt-addr.yaml      |  20 +-
 .../net/ethernet/cavium/octeon/octeon_mgmt.c  |   4 +-
 .../net/wireless/microchip/wilc1000/netdev.c  |   8 +-
 include/linux/netdevice.h                     |  11 +-
 include/net/net_namespace.h                   |   1 +
 include/uapi/linux/if_addr.h                  |   1 +
 net/core/dev_addr_lists.c                     | 259 +++++++++++++++++-
 net/core/dev_addr_lists_test.c                |  18 +-
 net/core/rtnetlink.c                          |   2 +
 net/mac80211/driver-ops.h                     |   2 +-
 tools/testing/selftests/net/rtnetlink.py      |  73 ++++-
 11 files changed, 364 insertions(+), 35 deletions(-)

-- 
2.43.0