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| author | Lutz Donnerhacke <donner@FreeBSD.org> | 2021-02-06 10:25:04 +0000 |
|---|---|---|
| committer | Lutz Donnerhacke <donner@FreeBSD.org> | 2021-02-06 14:01:15 +0000 |
| commit | c869d905baa4e329dfd6793e7487b5985248ddb6 (patch) | |
| tree | 1b3a9d610a989df670ff8983b6bd10066f7501ba /share/man | |
| parent | 689561d4032233bc171cff30d6756c3cf3b22720 (diff) | |
| download | src-c869d905baa4e329dfd6793e7487b5985248ddb6.tar.gz src-c869d905baa4e329dfd6793e7487b5985248ddb6.zip | |
netgraph/ng_bridge: Derive forwarding mode from first attached hook
Handling of unknown MACs on an bridge with incomplete learning
capabilites (aka uplink ports) can be defined in different ways.
The classical approach is to broadcast unicast frames send to an
unknown MAC, because the unknown devices can be everywhere. This mode
is default for ng_bridge(4).
In the case of dedicated uplink ports, which prohibit learning of MAC
addresses in order to save memory and CPU cycles, the broadcast
approach is dangerous. All traffic to the uplink port is broadcasted
to every downlink port, too. In this case, it's better to restrict the
distribution of frames to unknown MAC to the uplink ports only.
In order to keep the chance small and the handling as natural as
possible, the first attached link is used to determine the behaviour
of the bridge: If it is an "uplink" port, then the bridge switch from
classical mode to restricted mode.
Reviewed By: kp
Approved by: kp (mentor)
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D28487
Diffstat (limited to 'share/man')
| -rw-r--r-- | share/man/man4/ng_bridge.4 | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/share/man/man4/ng_bridge.4 b/share/man/man4/ng_bridge.4 index 1f3831e3fb75..be128d62c938 100644 --- a/share/man/man4/ng_bridge.4 +++ b/share/man/man4/ng_bridge.4 @@ -109,6 +109,22 @@ hook of the bridge, and ignore the complexity of the outside world. Frames with unknown MACs are always sent out to .Ar uplink hooks, so no functionality is lost. +.Pp +Frames with unknown destination MAC addresses are replicated to any +available hook, unless the first connected hook is an +.Ar uplink +hook. +In this case the node assumes, that all unknown MAC addresses are +located soley on the +.Ar uplink +hooks and only those hooks will be used to send out frames with +unknown destination MACs. +If the first connected hook is an +.Ar link +hook, the node will replicate such frames to all types of hooks, +even if +.Ar uplink +hooks are connected later. .Sh CONTROL MESSAGES This node type supports the generic control messages, plus the following: |