From: Jindrich Makovicka on
Currently, the forcedeth driver reconfigures the packet filter every
time a multicast stream is (un-)subscribed. As the receiving has to be
stopped and started in this case, any multicast subscription can cause
packet loss, allowing userspace applications to disrupt incoming

With the following patch, nv_set_multicast first checks the cached
state of the packet filter, and skips the reconfiguration if the state
does not change. With the default settings, this can reduce some
useless reconfiguration attempts. When switched to promiscuous mode,
all reconfigurations are skipped with the patch, which can be used to
mitigate packet loss problems when receiving and re-subscribing many
multicasts simultaneously on a single machine.

Signed-off-by: Jindrich Makovicka <makovick(a)>

Jindrich Makovicka