Hi, On Mon, Dec 07, 2015, Marcel Holtmann wrote: > > 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. > > --- > > net/bluetooth/bnep/core.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c > > index 1641367..8e02289 100644 > > --- a/net/bluetooth/bnep/core.c > > +++ b/net/bluetooth/bnep/core.c > > @@ -608,8 +608,12 @@ int bnep_add_connection(struct bnep_connadd_req *req, struct socket *sock) > > s->msg.msg_flags = MSG_NOSIGNAL; > > > > #ifdef CONFIG_BT_BNEP_MC_FILTER > > - /* Set default mc filter */ > > - set_bit(bnep_mc_hash(dev->broadcast), (ulong *) &s->mc_filter); > > + /* > > + * Set default mc filter to not filter out any mc addresses > > + * as defined in the BNEP specification (revision 0.95a) > > + * http://grouper.ieee.org/groups/802/15/Bluetooth/BNEP.pdf > > + */ > > + s->mc_filter = ~0LL; > > #endif > > > > Applying: Do not filter multicast addresses by default > /data/kernel/maintainer-bluetooth-next/.git/rebase-apply/patch:15: trailing whitespace. > /* > fatal: 1 line adds whitespace errors. > Patch failed at 0001 Do not filter multicast addresses by default > > And please prefix the subject line with Bluetooth: There's also a missing Signed-off-by and the lines should be wrapped at some 74 characters (right now it's basically a single line per paragraph). Johan -- 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
