packet: restore packet statistics tp_packets to include drops

getsockopt PACKET_STATISTICS returns tp_packets + tp_drops. Commit
ee80fbf3 ("packet: account statistics only in tpacket_stats_u")
cleaned up the getsockopt PACKET_STATISTICS code.
This also changed semantics. Historically, tp_packets included
tp_drops on return. The commit removed the line that adds tp_drops
into tp_packets.

This patch reinstates the old semantics.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/packet/af_packet.c

@@ -3259,9 +3259,11 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
 
 		if (po->tp_version == TPACKET_V3) {
 			lv = sizeof(struct tpacket_stats_v3);
+			st.stats3.tp_packets += st.stats3.tp_drops;
 			data = &st.stats3;
 		} else {
 			lv = sizeof(struct tpacket_stats);
+			st.stats1.tp_packets += st.stats1.tp_drops;
 			data = &st.stats1;
 		}