2 sent pkts have tag for vlan 10 & 20, one should be received on socket created on eth1.10 and another on socket for eth1.20. But it doesn't happen

Question

The packets sent with vlan tag 10 & 20 are received on both sockets. Why I am receiving 4 packets while only 2 packets were sent and also all received packets are untagged (without vlan tag)? What might be the issue?

here is the relevant code: Create: sock = socket(AF_PACKET, SOCK_RAW, htons(MY_ETHTYPE));

memset(&if_opts, 0, sizeof(if_opts));
strncpy(if_opts.ifr_name, "eth1.10", IFNAMSIZ - 1);
setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, (void *)&if_opts, sizeof(if_opts);
ioctl(sock, SIOCGIFFLAGS, &if_opts);
if_opts.ifr_flags |= IFF_PROMISC;
ioctl(sock, SIOCSIFFLAGS, &if_opts);

setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
                  "eth1.10",
                  sizeof("eth1.10"));

Recv: size = recvfrom(sock, buf, BUF_SIZE, MSG_DONTWAIT, NULL, NULL);