llcp_allocate_pdu
skb = llcp_allocate_pdu(sock, LLCP_PDU_DISC, 0);
skb = llcp_allocate_pdu(sock, LLCP_PDU_CONNECT, size);
skb = llcp_allocate_pdu(sock, LLCP_PDU_CC, size);
pdu = llcp_allocate_pdu(sock, LLCP_PDU_I,
skb = llcp_allocate_pdu(sock, LLCP_PDU_RR, LLCP_SEQUENCE_SIZE);