On 21/01/17 21:01, Linus Lüssing wrote:

From: Felix Fietkau <nbd@nbd.name>

Implements an optional, per bridge port flag and feature to deliver
multicast packets to any host on the according port via unicast
individually. This is done by copying the packet per host and
changing the multicast destination MAC to a unicast one accordingly.

multicast-to-unicast works on top of the multicast snooping feature of
the bridge. Which means unicast copies are only delivered to hosts which
are interested in it and signalized this via IGMP/MLD reports
previously.

This feature is intended for interface types which have a more reliable
and/or efficient way to deliver unicast packets than broadcast ones
(e.g. wifi).

However, it should only be enabled on interfaces where no IGMPv2/MLDv1
report suppression takes place. This feature is disabled by default.

The initial patch and idea is from Felix Fietkau.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
[linus.luessing@c0d3.blue: various bug + style fixes, commit message]
Signed-off-by: Linus Lüssing <redacted>

---

This feature is used and enabled by default in OpenWRT and LEDE for AP
interfaces for more than a year now to allow both a more robust multicast
delivery and multicast at higher rates (e.g. multicast streaming).

In OpenWRT/LEDE the IGMP/MLD report suppression issue is overcome by
the network daemon enabling AP isolation and by that separating all STAs.
Delivery of STA-to-STA IP mulitcast is made possible again by
enabling and utilizing the bridge hairpin mode, which considers the
incoming port as a potential outgoing port, too.

Hairpin-mode is performed after multicast snooping, therefore leading to
only deliver reports to STAs running a multicast router.

Changes in v5:
* fix a potential pagefault in br_ip6_multicast_mld2_report():
  -> a pskb_may_pull() might reallocate skb->data, therefore perform
     the "src = eth_hdr(skb)->h_source" only afterwards
* simplify code by always adding ether source address to a port group
  and checking the per-port multicast-to-unicast flag instead of a
  per-port-group one (thanks Stephen!)

Changes in v4:
* readd "From: Felix Fietkau [...]" (missed it again in v3)

Changes in v3:
* fix an uninitialized variable bug introduced in br_multicast_flood()
  in v2, found by kbuild test bot

Changes in v2:
* netlink support (thanks Nik!)
* fixed switching between multicast_to_unicast on/off
  -> even after toggling an already existing entry would
     stale in its mode and would never be replaced
  -> new extra check in br_port_group_equal)
* reduced checks in br_multicast_flood() from two to one
  to address fast-path concerns (thanks Nik!)
* rev-christmas tree ordering (thanks Nik!)
* removed "net_bridge_port_group::unicast", using
  ::flags instead (thanks Nik!)
* BR_MULTICAST_TO_UCAST -> BR_MULTICAST_TO_UNICAST
  (BR_MULTICAST_FLAST_LEAVE has the same length anyway)
* simplified maybe_deliver_addr()
  (no return, no "prev" paramater -> was a NOP anyway)
* added "From: Felix Fietkau [...]"
* added "Signed-off-by: Felix Fietkau [...]"
---
 include/linux/if_bridge.h    |  1 +
 include/uapi/linux/if_link.h |  1 +
 net/bridge/br_forward.c      | 39 ++++++++++++++++++-
 net/bridge/br_mdb.c          |  2 +-
 net/bridge/br_multicast.c    | 90 ++++++++++++++++++++++++++++++++------------
 net/bridge/br_netlink.c      |  5 +++
 net/bridge/br_private.h      |  3 +-
 net/bridge/br_sysfs_if.c     |  2 +
 8 files changed, 114 insertions(+), 29 deletions(-)

Reviewed-by: Nikolay Aleksandrov <redacted>