static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
{
	struct request_sock *req;
	struct dccp_request_sock *dreq;
	struct inet_request_sock *ireq;
	struct ipv6_pinfo *np = inet6_sk(sk);
	const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);

	if (skb->protocol == htons(ETH_P_IP))
		return dccp_v4_conn_request(sk, skb);

	if (!ipv6_unicast_destination(skb))
		return 0;	/* discard, don't send a reset here */

	if (dccp_bad_service_code(sk, service)) {
		dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
		goto drop;
	}
	/*
	 * There are no SYN attacks on IPv6, yet...
	 */
	dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
	if (inet_csk_reqsk_queue_is_full(sk))
		goto drop;

	if (sk_acceptq_is_full(sk))
		goto drop;

	req = inet_reqsk_alloc(&dccp6_request_sock_ops, sk, true);
	if (req == NULL)
		goto drop;

	if (dccp_reqsk_init(req, dccp_sk(sk), skb))
		goto drop_and_free;

	dreq = dccp_rsk(req);
	if (dccp_parse_options(sk, dreq, skb))
		goto drop_and_free;

	if (security_inet_conn_request(sk, skb, req))
		goto drop_and_free;

	ireq = inet_rsk(req);
	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
	ireq->ireq_family = AF_INET6;

	if (ipv6_opt_accepted(sk, skb, IP6CB(skb)) ||
	    np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
	    np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
		atomic_inc(&skb->users);
		ireq->pktopts = skb;
	}
	ireq->ir_iif = sk->sk_bound_dev_if;

	/* So that link locals have meaning */
	if (!sk->sk_bound_dev_if &&
	    ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
		ireq->ir_iif = inet6_iif(skb);

	/*
	 * Step 3: Process LISTEN state
	 *
	 *   Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
	 *
	 * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
	 */
	dreq->dreq_isr	   = dcb->dccpd_seq;
	dreq->dreq_gsr     = dreq->dreq_isr;
	dreq->dreq_iss	   = dccp_v6_init_sequence(skb);
	dreq->dreq_gss     = dreq->dreq_iss;
	dreq->dreq_service = service;

	if (dccp_v6_send_response(sk, req))
		goto drop_and_free;

	inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
	return 0;

drop_and_free:
	reqsk_free(req);
drop:
	__DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
	return -1;
}

Unknown