This patch allows the user to specify desired packet types (outgoing,
broadcast, unicast, etc.) on packet sockets via setsockopt.
This can reduce the load in situations where only a limited number
of packet types are necessary

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

--- a/include/linux/if_packet.h
+++ b/include/linux/if_packet.h
@@ -29,6 +29,8 @@ struct sockaddr_ll {
 /* These ones are invisible by user level */
 #define PACKET_LOOPBACK		5		/* MC/BRD frame looped back */
 #define PACKET_FASTROUTE	6		/* Fastrouted frame	*/
+#define PACKET_MASK_ANY		0xffffffff	/* mask for packet type bits */
+
 
 /* Packet socket options */
 
@@ -50,6 +52,7 @@ struct sockaddr_ll {
 #define PACKET_TX_TIMESTAMP		16
 #define PACKET_TIMESTAMP		17
 #define PACKET_FANOUT			18
+#define PACKET_RECV_TYPE		19
 
 #define PACKET_FANOUT_HASH		0
 #define PACKET_FANOUT_LB		1
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -296,6 +296,7 @@ struct packet_sock {
 	unsigned int		tp_loss:1;
 	unsigned int		tp_tstamp;
 	struct packet_type	prot_hook ____cacheline_aligned_in_smp;
+	unsigned int		pkt_type;
 };
 
 #define PACKET_FANOUT_MAX	256
@@ -1383,6 +1384,7 @@ static int packet_rcv_spkt(struct sk_buf
 {
 	struct sock *sk;
 	struct sockaddr_pkt *spkt;
+	struct packet_sock *po;
 
 	/*
 	 *	When we registered the protocol we saved the socket in the data
@@ -1390,6 +1392,7 @@ static int packet_rcv_spkt(struct sk_buf
 	 */
 
 	sk = pt->af_packet_priv;
+	po = pkt_sk(sk);
 
 	/*
 	 *	Yank back the headers [hope the device set this
@@ -1402,7 +1405,7 @@ static int packet_rcv_spkt(struct sk_buf
 	 *	so that this procedure is noop.
 	 */
 
-	if (skb->pkt_type == PACKET_LOOPBACK)
+	if (!(po->pkt_type & (1 << skb->pkt_type)))
 		goto out;
 
 	if (!net_eq(dev_net(dev), sock_net(sk)))
@@ -1596,12 +1599,12 @@ static int packet_rcv(struct sk_buff *sk
 	int skb_len = skb->len;
 	unsigned int snaplen, res;
 
-	if (skb->pkt_type == PACKET_LOOPBACK)
-		goto drop;
-
 	sk = pt->af_packet_priv;
 	po = pkt_sk(sk);
 
+	if (!(po->pkt_type & (1 << skb->pkt_type)))
+		goto drop;
+
 	if (!net_eq(dev_net(dev), sock_net(sk)))
 		goto drop;
 
@@ -1720,12 +1723,12 @@ static int tpacket_rcv(struct sk_buff *s
 	struct timespec ts;
 	struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
 
-	if (skb->pkt_type == PACKET_LOOPBACK)
-		goto drop;
-
 	sk = pt->af_packet_priv;
 	po = pkt_sk(sk);
 
+	if (!(po->pkt_type & (1 << skb->pkt_type)))
+		goto drop;
+
 	if (!net_eq(dev_net(dev), sock_net(sk)))
 		goto drop;
 
@@ -2595,6 +2598,7 @@ static int packet_create(struct net *net
 	spin_lock_init(&po->bind_lock);
 	mutex_init(&po->pg_vec_lock);
 	po->prot_hook.func = packet_rcv;
+	po->pkt_type = PACKET_MASK_ANY & ~(1 << PACKET_LOOPBACK);
 
 	if (sock->type == SOCK_PACKET)
 		po->prot_hook.func = packet_rcv_spkt;
@@ -3192,6 +3196,16 @@ packet_setsockopt(struct socket *sock, i
 
 		return fanout_add(sk, val & 0xffff, val >> 16);
 	}
+        case PACKET_RECV_TYPE:
+        {
+                unsigned int val;
+                if (optlen != sizeof(val))
+                        return -EINVAL;
+                if (copy_from_user(&val, optval, sizeof(val)))
+                        return -EFAULT;
+                po->pkt_type = val & ~PACKET_LOOPBACK;
+                return 0;
+        }
 	default:
 		return -ENOPROTOOPT;
 	}
@@ -3262,6 +3276,13 @@ static int packet_getsockopt(struct sock
 
 		data = &val;
 		break;
+	case PACKET_RECV_TYPE:
+		if (len > sizeof(unsigned int))
+			len = sizeof(unsigned int);
+		val = po->pkt_type;
+
+		data = &val;
+		break;
 	case PACKET_VERSION:
 		if (len > sizeof(int))
 			len = sizeof(int);
