OVPN_NONCE_WIRE_SIZE
__skb_push(skb, OVPN_NONCE_WIRE_SIZE);
memcpy(skb->data, iv, OVPN_NONCE_WIRE_SIZE);
memcpy(iv, skb->data + OVPN_OPCODE_SIZE, OVPN_NONCE_WIRE_SIZE);
memcpy(iv + OVPN_NONCE_WIRE_SIZE, ks->nonce_tail_recv,
#define OVPN_AAD_SIZE (OVPN_OPCODE_SIZE + OVPN_NONCE_WIRE_SIZE)
#define OVPN_HEAD_ROOM (OVPN_OPCODE_SIZE + OVPN_NONCE_WIRE_SIZE + \