packet: fill the gap of TPACKET_ALIGNMENT with zeros

struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT.
Explicitly defining and zeroing the gap of this makes additional changes
easier.

Signed-off-by: Atzm Watanabe <atzm@stratosphere.co.jp>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/if_packet.h

@@ -133,7 +133,7 @@ struct tpacket2_hdr {
 	__u32		tp_sec;
 	__u32		tp_nsec;
 	__u16		tp_vlan_tci;
-	__u16		tp_padding;
+	__u8		tp_padding[6];
 };
 
 struct tpacket_hdr_variant1 {
@@ -154,6 +154,7 @@ struct tpacket3_hdr {
 	union {
 		struct tpacket_hdr_variant1 hv1;
 	};
+	__u8		tp_padding[12];
 };
 
 struct tpacket_bd_ts {

net/packet/af_packet.c

@@ -1929,7 +1929,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		} else {
 			h.h2->tp_vlan_tci = 0;
 		}
-		h.h2->tp_padding = 0;
+		memset(h.h2->tp_padding, 0, sizeof(h.h2->tp_padding));
 		hdrlen = sizeof(*h.h2);
 		break;
 	case TPACKET_V3:
@@ -1943,6 +1943,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		h.h3->tp_net = netoff;
 		h.h3->tp_sec  = ts.tv_sec;
 		h.h3->tp_nsec = ts.tv_nsec;
+		memset(h.h3->tp_padding, 0, sizeof(h.h3->tp_padding));
 		hdrlen = sizeof(*h.h3);
 		break;
 	default: