On 06/09/17 03:11, Stephen Hemminger wrote: > On Wed, 6 Sep 2017 01:35:02 +0200 > Andrew Lunn <and...@lunn.ch> wrote: > >> After the very useful feedback from Nikolay, i threw away what i had, >> and started again. To recap: >> >> The linux bridge supports IGMP snooping. It will listen to IGMP >> reports on bridge ports and keep track of which groups have been >> joined on an interface. It will then forward multicast based on this >> group membership. >> >> When the bridge adds or removed groups from an interface, it uses >> switchdev to request the hardware add an mdb to a port, so the >> hardware can perform the selective forwarding between ports. >> >> What is not covered by the current bridge code, is IGMP joins/leaves >> from the host on the brX interface. These are not reported via >> switchdev so that hardware knows the local host is interested in the >> multicast frames. >> >> Luckily, the bridge does track joins/leaves on the brX interface. The >> code is obfusticated, which is why i missed it with my first attempt. >> So the first patch tries to remove this obfustication. Currently, >> there is no notifications sent when the bridge interface joins a >> group. The second patch adds them. bridge monitor then shows >> joins/leaves in the same way as for other ports of the bridge. >> >> Then starts the work passing down to the hardware that the host has >> joined/left a group. The existing switchdev mdb object cannot be used, >> since the semantics are different. The existing >> SWITCHDEV_OBJ_ID_PORT_MDB is used to indicate a specific multicast >> group should be forwarded out that port of the switch. However here we >> require the exact opposite. We want multicast frames for the group >> received on the port to the forwarded to the host. Hence add a new >> object SWITCHDEV_OBJ_ID_HOST_MDB, a multicast database entry to >> forward to the host. This new object is then propagated through the >> DSA layers. No DSA driver changes should be needed, this should just >> work... >> >> Getting the frames to the bridge as requested turned up an issue or >> three. The offload_fwd_mark is not being set by DSA, so the bridge >> floods the received frames back to the switch ports, resulting in >> duplication since the hardware has already flooded the packet. Fixing >> that turned up an issue with the meaning of >> SWITCHDEV_ATTR_ID_PORT_PARENT_ID in DSA. A DSA fabric of three >> switches needs to look to the software bridge as a single >> switch. Otherwise the offload_fwd_mark does not work, and we get >> duplication on the non-ingress switch. But each switch returned a >> different value. And they were not unique. >> >> The third and last issue will be explained in a followup email. >> >> Open questions: >> >> Is sending notifications going to break userspace? >> Is this new switchdev object O.K. for the few non-DSA switches that exist? >> Is the SWITCHDEV_ATTR_ID_PORT_PARENT_ID change acceptable? >> >> Andrew >> >> Andrew Lunn (8): >> net: bridge: Rename mglist to host_joined >> net: bridge: Send notification when host join/leaves a group >> net: bridge: Add/del switchdev object on host join/leave >> net: dsa: slave: Handle switchdev host mdb add/del >> net: dsa: switch: handle host mdb add/remove >> net: dsa: switch: Don't add CPU port to an mdb by default >> net: dsa: set offload_fwd_mark on received packets >> net: dsa: Fix SWITCHDEV_ATTR_ID_PORT_PARENT_ID >> >> include/net/switchdev.h | 1 + >> net/bridge/br_input.c | 2 +- >> net/bridge/br_mdb.c | 50 +++++++++++++++++++++++++++++--- >> net/bridge/br_multicast.c | 18 +++++++----- >> net/bridge/br_private.h | 2 +- >> net/dsa/dsa.c | 1 + >> net/dsa/dsa_priv.h | 7 +++++ >> net/dsa/port.c | 26 +++++++++++++++++ >> net/dsa/slave.c | 16 ++++++++--- >> net/dsa/switch.c | 72 >> +++++++++++++++++++++++++++++++++++++++-------- >> net/switchdev/switchdev.c | 2 ++ >> 11 files changed, 168 insertions(+), 29 deletions(-) >> > > This looks much cleaner. I don't have DSA hardware or infrastructure to look > deeper. >
+1 This version looks great!
