[Bluetooth] Fix resetting to default filters

The problem is that after a successful connection between the Windows
Bluetooth stack and the Linux Bluez stack, no packets from the device
ever reach the PC running Windows XP Service Pack 2. That is, a ping
from the PC never receives a response, and a ping from BlueZ never
reaches the PC. Linux packet statistics show that the PC packets are
received, but all return traffic seems to be routed over the loopback
interface.

Immediately after creating the BNEP connection with BlueZ, the Windows
Bluetooth stack sends a BNEP_FILTER_NET_TYPE_SET_MSG with an effective
length of zero. BlueZ interprets this message to mean that no filter
ranges should be allowed. The code zeros the first entry in the filter
list, which is than interpreted as meaning that no ranges of acceptable
packets are available. This interpretation is wrong and leads to all
packets being rejected by BNEP.

The Bluetooth BNEP specification clearly states the following:

The length (in octets) of this message is 4+4*N, where N is the number
of disjoint ranges of Networking protocol types that form the complete
set. Note that N=0 (empty set) denotes a reset to default filters (if
any) supported by the remote device.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/bnep/core.c

@@ -61,7 +61,7 @@
 #define BT_DBG(D...)
 #endif
 
-#define VERSION "1.0"
+#define VERSION "1.2"
 
 static LIST_HEAD(bnep_session_list);
 static DECLARE_RWSEM(bnep_session_sem);
@@ -115,6 +115,21 @@ static int bnep_send_rsp(struct bnep_session *s, u8 ctrl, u16 resp)
 	return bnep_send(s, &rsp, sizeof(rsp));
 }
 
+#ifdef CONFIG_BT_BNEP_PROTO_FILTER
+static inline void bnep_set_default_proto_filter(struct bnep_session *s)
+{
+	/* (IPv4, ARP)  */
+	s->proto_filter[0].start = htons(0x0800);
+	s->proto_filter[0].end   = htons(0x0806);
+	/* (RARP, AppleTalk) */
+	s->proto_filter[1].start = htons(0x8035);
+	s->proto_filter[1].end   = htons(0x80F3);
+	/* (IPX, IPv6) */
+	s->proto_filter[2].start = htons(0x8137);
+	s->proto_filter[2].end   = htons(0x86DD);
+}
+#endif
+
 static int bnep_ctrl_set_netfilter(struct bnep_session *s, u16 *data, int len)
 {
 	int n;
@@ -143,9 +158,13 @@ static int bnep_ctrl_set_netfilter(struct bnep_session *s, u16 *data, int len)
 			BT_DBG("proto filter start %d end %d",
 				f[i].start, f[i].end);
 		}
+
 		if (i < BNEP_MAX_PROTO_FILTERS)
 			memset(f + i, 0, sizeof(*f));
 
+		if (n == 0)
+			bnep_set_default_proto_filter(s);
+
 		bnep_send_rsp(s, BNEP_FILTER_NET_TYPE_RSP, BNEP_SUCCESS);
 	} else {
 		bnep_send_rsp(s, BNEP_FILTER_NET_TYPE_RSP, BNEP_FILTER_LIMIT_REACHED);
@@ -553,16 +572,7 @@ int bnep_add_connection(struct bnep_connadd_req *req, struct socket *sock)
 
 #ifdef CONFIG_BT_BNEP_PROTO_FILTER
 	/* Set default protocol filter */
-
-	/* (IPv4, ARP)  */
-	s->proto_filter[0].start = htons(0x0800);
-	s->proto_filter[0].end   = htons(0x0806);
-	/* (RARP, AppleTalk) */
-	s->proto_filter[1].start = htons(0x8035);
-	s->proto_filter[1].end   = htons(0x80F3);
-	/* (IPX, IPv6) */
-	s->proto_filter[2].start = htons(0x8137);
-	s->proto_filter[2].end   = htons(0x86DD);
+	bnep_set_default_proto_filter(s);
 #endif
 
 	err = register_netdev(dev);