ieee802154/dgram: Pass source address in dgram_recvmsg

This patch lets dgram_recvmsg fill in the sockaddr struct in
msg->msg_name with the source address of the packet.
This is used by the userland functions recvmsg and recvfrom to get the
senders address.

[Stefan: Changed from old zigbee legacy tree to mainline]
Signed-off-by: Stephen Röttger <stephen.roettger@zero-entropy.de>
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ieee802154/dgram.c

@@ -291,6 +291,9 @@ static int dgram_recvmsg(struct kiocb *iocb, struct sock *sk,
 	size_t copied = 0;
 	int err = -EOPNOTSUPP;
 	struct sk_buff *skb;
+	struct sockaddr_ieee802154 *saddr;
+
+	saddr = (struct sockaddr_ieee802154 *)msg->msg_name;
 
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb)
@@ -309,6 +312,13 @@ static int dgram_recvmsg(struct kiocb *iocb, struct sock *sk,
 
 	sock_recv_ts_and_drops(msg, sk, skb);
 
+	if (saddr) {
+		saddr->family = AF_IEEE802154;
+		saddr->addr = mac_cb(skb)->sa;
+	}
+	if (addr_len)
+		*addr_len = sizeof(*saddr);
+
 	if (flags & MSG_TRUNC)
 		copied = skb->len;
 done: