text: 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/uapi/linux/if_packet.h
  +++ b/include/uapi/linux/if_packet.h
  @@ -31,6 +31,8 @@ struct sockaddr_ll {
   #define PACKET_KERNEL		7		/* To kernel space	*/
   /* Unused, PACKET_FASTROUTE and PACKET_LOOPBACK are invisible to user space */
   #define PACKET_FASTROUTE	6		/* Fastrouted frame	*/
  +#define PACKET_MASK_ANY		0xffffffff	/* mask for packet type bits */
  +
   
   /* Packet socket options */
   
  @@ -54,6 +56,7 @@ struct sockaddr_ll {
   #define PACKET_FANOUT			18
   #define PACKET_TX_HAS_OFF		19
   #define PACKET_QDISC_BYPASS		20
  +#define PACKET_RECV_TYPE		21
   
   #define PACKET_FANOUT_HASH		0
   #define PACKET_FANOUT_LB		1
  --- a/net/packet/af_packet.c
  +++ b/net/packet/af_packet.c
  @@ -1541,6 +1541,7 @@ 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
  @@ -1548,6 +1549,7 @@ 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
  @@ -1560,7 +1562,7 @@ 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)))
  @@ -1767,12 +1769,12 @@ 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;
   
  @@ -1892,12 +1894,12 @@ static int tpacket_rcv(struct sk_buff *s
   	BUILD_BUG_ON(TPACKET_ALIGN(sizeof(*h.h2)) != 32);
   	BUILD_BUG_ON(TPACKET_ALIGN(sizeof(*h.h3)) != 48);
   
  -	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;
   
  @@ -2853,6 +2855,7 @@ 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;
  @@ -3442,6 +3445,16 @@ packet_setsockopt(struct socket *sock, i
   		po->xmit = val ? packet_direct_xmit : dev_queue_xmit;
   		return 0;
   	}
  +        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 & ~BIT(PACKET_LOOPBACK);
  +                return 0;
  +        }
   	default:
   		return -ENOPROTOOPT;
   	}
  @@ -3493,6 +3506,13 @@ static int packet_getsockopt(struct sock
   	case PACKET_VNET_HDR:
   		val = po->has_vnet_hdr;
   		break;
  +	case PACKET_RECV_TYPE:
  +		if (len > sizeof(unsigned int))
  +			len = sizeof(unsigned int);
  +		val = po->pkt_type;
  +
  +		data = &val;
  +		break;
   	case PACKET_VERSION:
   		val = po->tp_version;
   		break;
  --- a/net/packet/internal.h
  +++ b/net/packet/internal.h
  @@ -117,6 +117,7 @@ struct packet_sock {
   	struct net_device __rcu	*cached_dev;
   	int			(*xmit)(struct sk_buff *skb);
   	struct packet_type	prot_hook ____cacheline_aligned_in_smp;
  +	unsigned int		pkt_type;
   };
   
   static struct packet_sock *pkt_sk(struct sock *sk)
  