In an upcoming commit I want to store a pointer in MAC learning entries
in the bridge, instead of an integer port number. The MAC learning library
has other clients, and the others do not gracefully fit this new model, so
in fact the data will have to become a union. However, this does not fit
well with the current mac_learning API, since mac_learning_learn()
currently initializes and compares the data. It seems better to break up
the API so that only the client has to know the data's format and how to
initialize it or compare it. This commit makes this possible.
This commit doesn't change the type of the data stored in a MAC learning
entry yet.
As a side effect this commit has the benefit that clients that don't need
gratuitous ARP locking don't have to specify any policy for it at all.
Normally we filter out packets received on a bond if we have
learned the source MAC as belonging to another port to avoid packets
sent on one slave and reflected back on another. The exception to
this is gratuitous ARPs because they indicate that the host
has moved to another port. However, this can result in an additional
problem on the switch that the host moved to if the gratuitous ARP is
reflected back on a bond slave. In this case, we incorrectly relearn
the slave as the source of the MAC address. To solve this, we lock the
learning entry for 5 seconds after receiving a gratuitous ARP against
further updates caused by gratuitous ARPs on bond slaves.
Bug #2516
Reported-by: Ian Campbell <ian.campbell@citrix.com>
RSPAN does not work properly unless MAC learning for the VLAN is
disabled on all switches between the origin and monitoring point.
This allows learning to be disabled on a given VLAN so vSwitch can
acts as an intermediate switch.
Feature #2136
Given a possible 1,024 ports on a bridge the previous limit of 2,048
entries seems low.
If we want to increase this further we should introduce dynamic allocation
of table entries to avoid wasting memory in the common case.
CC: Keith Amidon <keith@nicira.com>
The vswitchd bonding code needs to iterate through the table entries to
be able to send out gratuitous learning packets when bond slaves go down.
It might be best to create an abstract interface to the MAC learning table,
but this commit does the simpler thing and exposes the data structures in
the header file.
