Hi Danny, > A Linux PC is connected with another device over Bluetooth PAN using a > BNEP interface. > > Whenever a packet is tried to be sent over the BNEP interface, the > function "bnep_net_xmit()" in "net/bluetooth/bnep/netdev.c" is called. > This function calls "bnep_net_mc_filter()", which checks (if the > destination address is multicast) if the address is set in a certain > multicast filter (&s->mc_filter). If it is not, then it is not sent out. > > This filter is only changed in two other functions, found in > net/bluetooth/bnep/core.c": in "bnep_ctrl_set_mc_filter()", which is > only called if a message of type "BNEP_FILTER_MULTI_ADDR_SET" is > received. Otherwise, it is set in "bnep_add_connection()", where it is > set to a default value which only adds the broadcast address to the > filter: > > set_bit(bnep_mc_hash(dev->broadcast), (ulong *) &s->mc_filter); > > To sum up, if the BNEP interface does not receive any message of type > "BNEP_FILTER_MULTI_ADDR_SET", it will not send out any messages with > multicast destination addresses except for broadcast. > > However, in the BNEP specification (page 27 in > http://grouper.ieee.org/groups/802/15/Bluetooth/BNEP.pdf), it is said > that per default, all multicast addresses should not be filtered, i.e. > the BNEP interface should be able to send packets with any multicast > destination address. > > It seems that the default case is wrong: the multicast filter should not > block almost all multicast addresses, but should not filter out any. > > This leads to the problem that e.g. Neighbor Solicitation messages sent > with Bluetooth PAN over the BNEP interface to a multicast destination > address other than broadcast are blocked and not sent out. > > Therefore, in the default case, we set the mc_filter to ~0LL to not > filter out any multicast addresses. > > Signed-off-by: Danny Schweizer <danny.schweizer@xxxxxxxxxxx> > --- > net/bluetooth/bnep/core.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) patch has been applied to bluetooth-next tree. Regards Marcel -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
