net/dccp/input.c - kernel/msm-4.9 - Gitiles

 /*
  *  net/dccp/input.c
  *
  *  An implementation of the DCCP protocol
  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  *
  *	This program is free software; you can redistribute it and/or
  *	modify it under the terms of the GNU General Public License
  *	as published by the Free Software Foundation; either version
  *	2 of the License, or (at your option) any later version.
  */

 #include <linux/dccp.h>
 #include <linux/skbuff.h>

 #include <net/sock.h>

 #include "ackvec.h"
 #include "ccid.h"
 #include "dccp.h"

 /* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
 int sysctl_dccp_sync_ratelimit	__read_mostly = HZ / 8;

 static void dccp_enqueue_skb(struct sock *sk, struct sk_buff *skb)
 {
 	__skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
 	__skb_queue_tail(&sk->sk_receive_queue, skb);
 	skb_set_owner_r(skb, sk);
 	sk->sk_data_ready(sk, 0);
 }

 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
 {
 	/*
 	 * On receiving Close/CloseReq, both RD/WR shutdown are performed.
 	 * RFC 4340, 8.3 says that we MAY send further Data/DataAcks after
 	 * receiving the closing segment, but there is no guarantee that such
 	 * data will be processed at all.
 	 */
 	sk->sk_shutdown = SHUTDOWN_MASK;
 	sock_set_flag(sk, SOCK_DONE);
 	dccp_enqueue_skb(sk, skb);
 }

 static int dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
 {
 	int queued = 0;

 	switch (sk->sk_state) {
 	/*
 	 * We ignore Close when received in one of the following states:
 	 *  - CLOSED		(may be a late or duplicate packet)
 	 *  - PASSIVE_CLOSEREQ	(the peer has sent a CloseReq earlier)
 	 *  - RESPOND		(already handled by dccp_check_req)
 	 */
 	case DCCP_CLOSING:
 		/*
 		 * Simultaneous-close: receiving a Close after sending one. This
 		 * can happen if both client and server perform active-close and
 		 * will result in an endless ping-pong of crossing and retrans-
 		 * mitted Close packets, which only terminates when one of the
 		 * nodes times out (min. 64 seconds). Quicker convergence can be
 		 * achieved when one of the nodes acts as tie-breaker.
 		 * This is ok as both ends are done with data transfer and each
 		 * end is just waiting for the other to acknowledge termination.
 		 */
 		if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT)
 			break;
 		/* fall through */
 	case DCCP_REQUESTING:
 	case DCCP_ACTIVE_CLOSEREQ:
 		dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
 		dccp_done(sk);
 		break;
 	case DCCP_OPEN:
 	case DCCP_PARTOPEN:
 		/* Give waiting application a chance to read pending data */
 		queued = 1;
 		dccp_fin(sk, skb);
 		dccp_set_state(sk, DCCP_PASSIVE_CLOSE);
 		/* fall through */
 	case DCCP_PASSIVE_CLOSE:
 		/*
 		 * Retransmitted Close: we have already enqueued the first one.
 		 */
 		sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
 	}
 	return queued;
 }

 static int dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
 {
 	int queued = 0;

 	/*
 	 *   Step 7: Check for unexpected packet types
 	 *      If (S.is_server and P.type == CloseReq)
 	 *	  Send Sync packet acknowledging P.seqno
 	 *	  Drop packet and return
 	 */
 	if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
 		dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 		return queued;
 	}

 	/* Step 13: process relevant Client states < CLOSEREQ */
 	switch (sk->sk_state) {
 	case DCCP_REQUESTING:
 		dccp_send_close(sk, 0);
 		dccp_set_state(sk, DCCP_CLOSING);
 		break;
 	case DCCP_OPEN:
 	case DCCP_PARTOPEN:
 		/* Give waiting application a chance to read pending data */
 		queued = 1;
 		dccp_fin(sk, skb);
 		dccp_set_state(sk, DCCP_PASSIVE_CLOSEREQ);
 		/* fall through */
 	case DCCP_PASSIVE_CLOSEREQ:
 		sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
 	}
 	return queued;
 }

 static u8 dccp_reset_code_convert(const u8 code)
 {
 	const u8 error_code[] = {
 	[DCCP_RESET_CODE_CLOSED]	     = 0,	/* normal termination */
 	[DCCP_RESET_CODE_UNSPECIFIED]	     = 0,	/* nothing known */
 	[DCCP_RESET_CODE_ABORTED]	     = ECONNRESET,

 	[DCCP_RESET_CODE_NO_CONNECTION]	     = ECONNREFUSED,
 	[DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
 	[DCCP_RESET_CODE_TOO_BUSY]	     = EUSERS,
 	[DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,

 	[DCCP_RESET_CODE_PACKET_ERROR]	     = ENOMSG,
 	[DCCP_RESET_CODE_BAD_INIT_COOKIE]    = EBADR,
 	[DCCP_RESET_CODE_BAD_SERVICE_CODE]   = EBADRQC,
 	[DCCP_RESET_CODE_OPTION_ERROR]	     = EILSEQ,
 	[DCCP_RESET_CODE_MANDATORY_ERROR]    = EOPNOTSUPP,
 	};

 	return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
 }

 static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
 {
 	u8 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);

 	sk->sk_err = err;

 	/* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
 	dccp_fin(sk, skb);

 	if (err && !sock_flag(sk, SOCK_DEAD))
 		sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR);
 	dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 }

 static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct dccp_sock *dp = dccp_sk(sk);

 	if (dp->dccps_hc_rx_ackvec != NULL)
 		dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
 					    DCCP_SKB_CB(skb)->dccpd_ack_seq);
 }

 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
 {
 	const struct dccp_sock *dp = dccp_sk(sk);

 	/* Don't deliver to RX CCID when node has shut down read end. */
 	if (!(sk->sk_shutdown & RCV_SHUTDOWN))
 		ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 	/*
 	 * Until the TX queue has been drained, we can not honour SHUT_WR, since
 	 * we need received feedback as input to adjust congestion control.
 	 */
 	if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
 		ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 }

 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
 {
 	const struct dccp_hdr *dh = dccp_hdr(skb);
 	struct dccp_sock *dp = dccp_sk(sk);
 	u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
 			ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;

 	/*
 	 *   Step 5: Prepare sequence numbers for Sync
 	 *     If P.type == Sync or P.type == SyncAck,
 	 *	  If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
 	 *	     / * P is valid, so update sequence number variables
 	 *		 accordingly.  After this update, P will pass the tests
 	 *		 in Step 6.  A SyncAck is generated if necessary in
 	 *		 Step 15 * /
 	 *	     Update S.GSR, S.SWL, S.SWH
 	 *	  Otherwise,
 	 *	     Drop packet and return
 	 */
 	if (dh->dccph_type == DCCP_PKT_SYNC ||
 	    dh->dccph_type == DCCP_PKT_SYNCACK) {
 		if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
 		    dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
 			dccp_update_gsr(sk, seqno);
 		else
 			return -1;
 	}

 	/*
 	 *   Step 6: Check sequence numbers
 	 *      Let LSWL = S.SWL and LAWL = S.AWL
 	 *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 	 *	  LSWL := S.GSR + 1, LAWL := S.GAR
 	 *      If LSWL <= P.seqno <= S.SWH
 	 *	     and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 	 *	  Update S.GSR, S.SWL, S.SWH
 	 *	  If P.type != Sync,
 	 *	     Update S.GAR
 	 */
 	lswl = dp->dccps_swl;
 	lawl = dp->dccps_awl;

 	if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 	    dh->dccph_type == DCCP_PKT_CLOSE ||
 	    dh->dccph_type == DCCP_PKT_RESET) {
 		lswl = ADD48(dp->dccps_gsr, 1);
 		lawl = dp->dccps_gar;
 	}

 	if (between48(seqno, lswl, dp->dccps_swh) &&
 	    (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
 	     between48(ackno, lawl, dp->dccps_awh))) {
 		dccp_update_gsr(sk, seqno);

 		if (dh->dccph_type != DCCP_PKT_SYNC &&
 		    (ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
 			dp->dccps_gar = ackno;
 	} else {
 		unsigned long now = jiffies;
 		/*
 		 *   Step 6: Check sequence numbers
 		 *      Otherwise,
 		 *         If P.type == Reset,
 		 *            Send Sync packet acknowledging S.GSR
 		 *         Otherwise,
 		 *            Send Sync packet acknowledging P.seqno
 		 *      Drop packet and return
 		 *
 		 *   These Syncs are rate-limited as per RFC 4340, 7.5.4:
 		 *   at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
 		 */
 		if (time_before(now, (dp->dccps_rate_last +
 				      sysctl_dccp_sync_ratelimit)))
 			return 0;

 		DCCP_WARN("DCCP: Step 6 failed for %s packet, "
 			  "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 			  "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 			  "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
 			  (unsigned long long) lswl, (unsigned long long) seqno,
 			  (unsigned long long) dp->dccps_swh,
 			  (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
 							      : "exists",
 			  (unsigned long long) lawl, (unsigned long long) ackno,
 			  (unsigned long long) dp->dccps_awh);

 		dp->dccps_rate_last = now;

 		if (dh->dccph_type == DCCP_PKT_RESET)
 			seqno = dp->dccps_gsr;
 		dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
 		return -1;
 	}

 	return 0;
 }

 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 				  const struct dccp_hdr *dh, const unsigned len)
 {
 	struct dccp_sock *dp = dccp_sk(sk);

 	switch (dccp_hdr(skb)->dccph_type) {
 	case DCCP_PKT_DATAACK:
 	case DCCP_PKT_DATA:
 		/*
 		 * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
 		 * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
 		 * - sk_receive_queue is full, use Code 2, "Receive Buffer"
 		 */
 		dccp_enqueue_skb(sk, skb);
 		return 0;
 	case DCCP_PKT_ACK:
 		goto discard;
 	case DCCP_PKT_RESET:
 		/*
 		 *  Step 9: Process Reset
 		 *	If P.type == Reset,
 		 *		Tear down connection
 		 *		S.state := TIMEWAIT
 		 *		Set TIMEWAIT timer
 		 *		Drop packet and return
 		 */
 		dccp_rcv_reset(sk, skb);
 		return 0;
 	case DCCP_PKT_CLOSEREQ:
 		if (dccp_rcv_closereq(sk, skb))
 			return 0;
 		goto discard;
 	case DCCP_PKT_CLOSE:
 		if (dccp_rcv_close(sk, skb))
 			return 0;
 		goto discard;
 	case DCCP_PKT_REQUEST:
 		/* Step 7
 		 *   or (S.is_server and P.type == Response)
 		 *   or (S.is_client and P.type == Request)
 		 *   or (S.state >= OPEN and P.type == Request
 		 *	and P.seqno >= S.OSR)
 		 *    or (S.state >= OPEN and P.type == Response
 		 *	and P.seqno >= S.OSR)
 		 *    or (S.state == RESPOND and P.type == Data),
 		 *  Send Sync packet acknowledging P.seqno
 		 *  Drop packet and return
 		 */
 		if (dp->dccps_role != DCCP_ROLE_LISTEN)
 			goto send_sync;
 		goto check_seq;
 	case DCCP_PKT_RESPONSE:
 		if (dp->dccps_role != DCCP_ROLE_CLIENT)
 			goto send_sync;
 check_seq:
 		if (dccp_delta_seqno(dp->dccps_osr,
 				     DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
 send_sync:
 			dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 				       DCCP_PKT_SYNC);
 		}
 		break;
 	case DCCP_PKT_SYNC:
 		dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 			       DCCP_PKT_SYNCACK);
 		/*
 		 * From RFC 4340, sec. 5.7
 		 *
 		 * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 		 * MAY have non-zero-length application data areas, whose
 		 * contents receivers MUST ignore.
 		 */
 		goto discard;
 	}

 	DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 discard:
 	__kfree_skb(skb);
 	return 0;
 }

 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 			 const struct dccp_hdr *dh, const unsigned len)
 {
 	struct dccp_sock *dp = dccp_sk(sk);

 	if (dccp_check_seqno(sk, skb))
 		goto discard;

 	if (dccp_parse_options(sk, NULL, skb))
 		return 1;

 	if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 		dccp_event_ack_recv(sk, skb);

 	if (dp->dccps_hc_rx_ackvec != NULL &&
 	    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 			    DCCP_SKB_CB(skb)->dccpd_seq, DCCPAV_RECEIVED))
 		goto discard;
 	dccp_deliver_input_to_ccids(sk, skb);

 	return __dccp_rcv_established(sk, skb, dh, len);
 discard:
 	__kfree_skb(skb);
 	return 0;
 }

 EXPORT_SYMBOL_GPL(dccp_rcv_established);

 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 					       struct sk_buff *skb,
 					       const struct dccp_hdr *dh,
 					       const unsigned len)
 {
 	/*
 	 *  Step 4: Prepare sequence numbers in REQUEST
 	 *     If S.state == REQUEST,
 	 *	  If (P.type == Response or P.type == Reset)
 	 *		and S.AWL <= P.ackno <= S.AWH,
 	 *	     / * Set sequence number variables corresponding to the
 	 *		other endpoint, so P will pass the tests in Step 6 * /
 	 *	     Set S.GSR, S.ISR, S.SWL, S.SWH
 	 *	     / * Response processing continues in Step 10; Reset
 	 *		processing continues in Step 9 * /
 	*/
 	if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 		const struct inet_connection_sock *icsk = inet_csk(sk);
 		struct dccp_sock *dp = dccp_sk(sk);
 		long tstamp = dccp_timestamp();

 		if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 			       dp->dccps_awl, dp->dccps_awh)) {
 			dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 				      "P.ackno=%llu, S.AWH=%llu \n",
 				      (unsigned long long)dp->dccps_awl,
 			   (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 				      (unsigned long long)dp->dccps_awh);
 			goto out_invalid_packet;
 		}

 		/*
 		 * If option processing (Step 8) failed, return 1 here so that
 		 * dccp_v4_do_rcv() sends a Reset. The Reset code depends on
 		 * the option type and is set in dccp_parse_options().
 		 */
 		if (dccp_parse_options(sk, NULL, skb))
 			return 1;

 		/* Obtain usec RTT sample from SYN exchange (used by CCID 3) */
 		if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
 			dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
 			    dp->dccps_options_received.dccpor_timestamp_echo));

 		/* Stop the REQUEST timer */
 		inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 		WARN_ON(sk->sk_send_head == NULL);
 		kfree_skb(sk->sk_send_head);
 		sk->sk_send_head = NULL;

 		/*
 		 * Set ISR, GSR from packet. ISS was set in dccp_v{4,6}_connect
 		 * and GSS in dccp_transmit_skb(). Setting AWL/AWH and SWL/SWH
 		 * is done as part of activating the feature values below, since
 		 * these settings depend on the local/remote Sequence Window
 		 * features, which were undefined or not confirmed until now.
 		 */
 		dp->dccps_gsr = dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;

 		dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);

 		/*
 		 *    Step 10: Process REQUEST state (second part)
 		 *       If S.state == REQUEST,
 		 *	  / * If we get here, P is a valid Response from the
 		 *	      server (see Step 4), and we should move to
 		 *	      PARTOPEN state. PARTOPEN means send an Ack,
 		 *	      don't send Data packets, retransmit Acks
 		 *	      periodically, and always include any Init Cookie
 		 *	      from the Response * /
 		 *	  S.state := PARTOPEN
 		 *	  Set PARTOPEN timer
 		 *	  Continue with S.state == PARTOPEN
 		 *	  / * Step 12 will send the Ack completing the
 		 *	      three-way handshake * /
 		 */
 		dccp_set_state(sk, DCCP_PARTOPEN);

 		/*
 		 * If feature negotiation was successful, activate features now;
 		 * an activation failure means that this host could not activate
 		 * one ore more features (e.g. insufficient memory), which would
 		 * leave at least one feature in an undefined state.
 		 */
 		if (dccp_feat_activate_values(sk, &dp->dccps_featneg))
 			goto unable_to_proceed;

 		/* Make sure socket is routed, for correct metrics. */
 		icsk->icsk_af_ops->rebuild_header(sk);

 		if (!sock_flag(sk, SOCK_DEAD)) {
 			sk->sk_state_change(sk);
 			sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 		}

 		if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 		    icsk->icsk_accept_queue.rskq_defer_accept) {
 			/* Save one ACK. Data will be ready after
 			 * several ticks, if write_pending is set.
 			 *
 			 * It may be deleted, but with this feature tcpdumps
 			 * look so _wonderfully_ clever, that I was not able
 			 * to stand against the temptation 8)     --ANK
 			 */
 			/*
 			 * OK, in DCCP we can as well do a similar trick, its
 			 * even in the draft, but there is no need for us to
 			 * schedule an ack here, as dccp_sendmsg does this for
 			 * us, also stated in the draft. -acme
 			 */
 			__kfree_skb(skb);
 			return 0;
 		}
 		dccp_send_ack(sk);
 		return -1;
 	}

 out_invalid_packet:
 	/* dccp_v4_do_rcv will send a reset */
 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 	return 1;

 unable_to_proceed:
 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_ABORTED;
 	/*
 	 * We mark this socket as no longer usable, so that the loop in
 	 * dccp_sendmsg() terminates and the application gets notified.
 	 */
 	dccp_set_state(sk, DCCP_CLOSED);
 	sk->sk_err = ECOMM;
 	return 1;
 }

 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 						   struct sk_buff *skb,
 						   const struct dccp_hdr *dh,
 						   const unsigned len)
 {
 	int queued = 0;

 	switch (dh->dccph_type) {
 	case DCCP_PKT_RESET:
 		inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 		break;
 	case DCCP_PKT_DATA:
 		if (sk->sk_state == DCCP_RESPOND)
 			break;
 	case DCCP_PKT_DATAACK:
 	case DCCP_PKT_ACK:
 		/*
 		 * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 		 * here but only if we haven't used the DELACK timer for
 		 * something else, like sending a delayed ack for a TIMESTAMP
 		 * echo, etc, for now were not clearing it, sending an extra
 		 * ACK when there is nothing else to do in DELACK is not a big
 		 * deal after all.
 		 */

 		/* Stop the PARTOPEN timer */
 		if (sk->sk_state == DCCP_PARTOPEN)
 			inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);

 		dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 		dccp_set_state(sk, DCCP_OPEN);

 		if (dh->dccph_type == DCCP_PKT_DATAACK ||
 		    dh->dccph_type == DCCP_PKT_DATA) {
 			__dccp_rcv_established(sk, skb, dh, len);
 			queued = 1; /* packet was queued
 				       (by __dccp_rcv_established) */
 		}
 		break;
 	}

 	return queued;
 }

 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 			   struct dccp_hdr *dh, unsigned len)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 	const int old_state = sk->sk_state;
 	int queued = 0;

 	/*
 	 *  Step 3: Process LISTEN state
 	 *
 	 *     If S.state == LISTEN,
 	 *	 If P.type == Request or P contains a valid Init Cookie option,
 	 *	      (* Must scan the packet's options to check for Init
 	 *		 Cookies.  Only Init Cookies are processed here,
 	 *		 however; other options are processed in Step 8.  This
 	 *		 scan need only be performed if the endpoint uses Init
 	 *		 Cookies *)
 	 *	      (* Generate a new socket and switch to that socket *)
 	 *	      Set S := new socket for this port pair
 	 *	      S.state = RESPOND
 	 *	      Choose S.ISS (initial seqno) or set from Init Cookies
 	 *	      Initialize S.GAR := S.ISS
 	 *	      Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
 	 *	      Cookies Continue with S.state == RESPOND
 	 *	      (* A Response packet will be generated in Step 11 *)
 	 *	 Otherwise,
 	 *	      Generate Reset(No Connection) unless P.type == Reset
 	 *	      Drop packet and return
 	 */
 	if (sk->sk_state == DCCP_LISTEN) {
 		if (dh->dccph_type == DCCP_PKT_REQUEST) {
 			if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 								    skb) < 0)
 				return 1;
 			goto discard;
 		}
 		if (dh->dccph_type == DCCP_PKT_RESET)
 			goto discard;

 		/* Caller (dccp_v4_do_rcv) will send Reset */
 		dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 		return 1;
 	}

 	if (sk->sk_state != DCCP_REQUESTING && sk->sk_state != DCCP_RESPOND) {
 		if (dccp_check_seqno(sk, skb))
 			goto discard;

 		/*
 		 * Step 8: Process options and mark acknowledgeable
 		 */
 		if (dccp_parse_options(sk, NULL, skb))
 			return 1;

 		if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 			dccp_event_ack_recv(sk, skb);

 		if (dp->dccps_hc_rx_ackvec != NULL &&
 		    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 				    DCCP_SKB_CB(skb)->dccpd_seq, DCCPAV_RECEIVED))
 			goto discard;

 		dccp_deliver_input_to_ccids(sk, skb);
 	}

 	/*
 	 *  Step 9: Process Reset
 	 *	If P.type == Reset,
 	 *		Tear down connection
 	 *		S.state := TIMEWAIT
 	 *		Set TIMEWAIT timer
 	 *		Drop packet and return
 	*/
 	if (dh->dccph_type == DCCP_PKT_RESET) {
 		dccp_rcv_reset(sk, skb);
 		return 0;
 		/*
 		 *   Step 7: Check for unexpected packet types
 		 *      If (S.is_server and P.type == Response)
 		 *	    or (S.is_client and P.type == Request)
 		 *	    or (S.state == RESPOND and P.type == Data),
 		 *	  Send Sync packet acknowledging P.seqno
 		 *	  Drop packet and return
 		 */
 	} else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 		    dh->dccph_type == DCCP_PKT_RESPONSE) ||
 		    (dp->dccps_role == DCCP_ROLE_CLIENT &&
 		     dh->dccph_type == DCCP_PKT_REQUEST) ||
 		    (sk->sk_state == DCCP_RESPOND &&
 		     dh->dccph_type == DCCP_PKT_DATA)) {
 		dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 		goto discard;
 	} else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 		if (dccp_rcv_closereq(sk, skb))
 			return 0;
 		goto discard;
 	} else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 		if (dccp_rcv_close(sk, skb))
 			return 0;
 		goto discard;
 	}

 	switch (sk->sk_state) {
 	case DCCP_CLOSED:
 		dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 		return 1;

 	case DCCP_REQUESTING:
 		queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 		if (queued >= 0)
 			return queued;

 		__kfree_skb(skb);
 		return 0;

 	case DCCP_RESPOND:
 	case DCCP_PARTOPEN:
 		queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 								 dh, len);
 		break;
 	}

 	if (dh->dccph_type == DCCP_PKT_ACK ||
 	    dh->dccph_type == DCCP_PKT_DATAACK) {
 		switch (old_state) {
 		case DCCP_PARTOPEN:
 			sk->sk_state_change(sk);
 			sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 			break;
 		}
 	} else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 		dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 		goto discard;
 	}

 	if (!queued) {
 discard:
 		__kfree_skb(skb);
 	}
 	return 0;
 }

 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);

 /**
  *  dccp_sample_rtt  -  Validate and finalise computation of RTT sample
  *  @delta:	number of microseconds between packet and acknowledgment
  *  The routine is kept generic to work in different contexts. It should be
  *  called immediately when the ACK used for the RTT sample arrives.
  */
 u32 dccp_sample_rtt(struct sock *sk, long delta)
 {
 	/* dccpor_elapsed_time is either zeroed out or set and > 0 */
 	delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;

 	if (unlikely(delta <= 0)) {
 		DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
 		return DCCP_SANE_RTT_MIN;
 	}
 	if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
 		DCCP_WARN("RTT sample %ld too large, using max\n", delta);
 		return DCCP_SANE_RTT_MAX;
 	}

 	return delta;
 }

 EXPORT_SYMBOL_GPL(dccp_sample_rtt);
	/*
	* net/dccp/input.c
	*
	* An implementation of the DCCP protocol
	* Arnaldo Carvalho de Melo <acme@conectiva.com.br>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*/

	#include <linux/dccp.h>
	#include <linux/skbuff.h>

	#include <net/sock.h>

	#include "ackvec.h"
	#include "ccid.h"
	#include "dccp.h"

	/* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
	int sysctl_dccp_sync_ratelimit __read_mostly = HZ / 8;

	static void dccp_enqueue_skb(struct sock sk, struct sk_buff skb)
	{
	__skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
	__skb_queue_tail(&sk->sk_receive_queue, skb);
	skb_set_owner_r(skb, sk);
	sk->sk_data_ready(sk, 0);
	}

	static void dccp_fin(struct sock sk, struct sk_buff skb)
	{
	/*
	* On receiving Close/CloseReq, both RD/WR shutdown are performed.
	* RFC 4340, 8.3 says that we MAY send further Data/DataAcks after
	* receiving the closing segment, but there is no guarantee that such
	* data will be processed at all.
	*/
	sk->sk_shutdown = SHUTDOWN_MASK;
	sock_set_flag(sk, SOCK_DONE);
	dccp_enqueue_skb(sk, skb);
	}

	static int dccp_rcv_close(struct sock sk, struct sk_buff skb)
	{
	int queued = 0;

	switch (sk->sk_state) {
	/*
	* We ignore Close when received in one of the following states:
	* - CLOSED (may be a late or duplicate packet)
	* - PASSIVE_CLOSEREQ (the peer has sent a CloseReq earlier)
	* - RESPOND (already handled by dccp_check_req)
	*/
	case DCCP_CLOSING:
	/*
	* Simultaneous-close: receiving a Close after sending one. This
	* can happen if both client and server perform active-close and
	* will result in an endless ping-pong of crossing and retrans-
	* mitted Close packets, which only terminates when one of the
	* nodes times out (min. 64 seconds). Quicker convergence can be
	* achieved when one of the nodes acts as tie-breaker.
	* This is ok as both ends are done with data transfer and each
	* end is just waiting for the other to acknowledge termination.
	*/
	if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT)
	break;
	/* fall through */
	case DCCP_REQUESTING:
	case DCCP_ACTIVE_CLOSEREQ:
	dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
	dccp_done(sk);
	break;
	case DCCP_OPEN:
	case DCCP_PARTOPEN:
	/* Give waiting application a chance to read pending data */
	queued = 1;
	dccp_fin(sk, skb);
	dccp_set_state(sk, DCCP_PASSIVE_CLOSE);
	/* fall through */
	case DCCP_PASSIVE_CLOSE:
	/*
	* Retransmitted Close: we have already enqueued the first one.
	*/
	sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
	}
	return queued;
	}

	static int dccp_rcv_closereq(struct sock sk, struct sk_buff skb)
	{
	int queued = 0;

	/*
	* Step 7: Check for unexpected packet types
	* If (S.is_server and P.type == CloseReq)
	* Send Sync packet acknowledging P.seqno
	* Drop packet and return
	*/
	if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
	dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
	return queued;
	}

	/* Step 13: process relevant Client states < CLOSEREQ */
	switch (sk->sk_state) {
	case DCCP_REQUESTING:
	dccp_send_close(sk, 0);
	dccp_set_state(sk, DCCP_CLOSING);
	break;
	case DCCP_OPEN:
	case DCCP_PARTOPEN:
	/* Give waiting application a chance to read pending data */
	queued = 1;
	dccp_fin(sk, skb);
	dccp_set_state(sk, DCCP_PASSIVE_CLOSEREQ);
	/* fall through */
	case DCCP_PASSIVE_CLOSEREQ:
	sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
	}
	return queued;
	}

	static u8 dccp_reset_code_convert(const u8 code)
	{
	const u8 error_code[] = {
	[DCCP_RESET_CODE_CLOSED] = 0, /* normal termination */
	[DCCP_RESET_CODE_UNSPECIFIED] = 0, /* nothing known */
	[DCCP_RESET_CODE_ABORTED] = ECONNRESET,

	[DCCP_RESET_CODE_NO_CONNECTION] = ECONNREFUSED,
	[DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
	[DCCP_RESET_CODE_TOO_BUSY] = EUSERS,
	[DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,

	[DCCP_RESET_CODE_PACKET_ERROR] = ENOMSG,
	[DCCP_RESET_CODE_BAD_INIT_COOKIE] = EBADR,
	[DCCP_RESET_CODE_BAD_SERVICE_CODE] = EBADRQC,
	[DCCP_RESET_CODE_OPTION_ERROR] = EILSEQ,
	[DCCP_RESET_CODE_MANDATORY_ERROR] = EOPNOTSUPP,
	};

	return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
	}

	static void dccp_rcv_reset(struct sock sk, struct sk_buff skb)
	{
	u8 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);

	sk->sk_err = err;

	/* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
	dccp_fin(sk, skb);

	if (err && !sock_flag(sk, SOCK_DEAD))
	sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR);
	dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
	}

	static void dccp_event_ack_recv(struct sock sk, struct sk_buff skb)
	{
	struct dccp_sock *dp = dccp_sk(sk);

	if (dp->dccps_hc_rx_ackvec != NULL)
	dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
	DCCP_SKB_CB(skb)->dccpd_ack_seq);
	}

	static void dccp_deliver_input_to_ccids(struct sock sk, struct sk_buff skb)
	{
	const struct dccp_sock *dp = dccp_sk(sk);

	/* Don't deliver to RX CCID when node has shut down read end. */
	if (!(sk->sk_shutdown & RCV_SHUTDOWN))
	ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
	/*
	* Until the TX queue has been drained, we can not honour SHUT_WR, since
	* we need received feedback as input to adjust congestion control.
	*/
	if (sk->sk_write_queue.qlen > 0 \|\| !(sk->sk_shutdown & SEND_SHUTDOWN))
	ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
	}

	static int dccp_check_seqno(struct sock sk, struct sk_buff skb)
	{
	const struct dccp_hdr *dh = dccp_hdr(skb);
	struct dccp_sock *dp = dccp_sk(sk);
	u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
	ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;

	/*
	* Step 5: Prepare sequence numbers for Sync
	* If P.type == Sync or P.type == SyncAck,
	* If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
	* / * P is valid, so update sequence number variables
	* accordingly. After this update, P will pass the tests
	* in Step 6. A SyncAck is generated if necessary in
	* Step 15 * /
	* Update S.GSR, S.SWL, S.SWH
	* Otherwise,
	* Drop packet and return
	*/
	if (dh->dccph_type == DCCP_PKT_SYNC \|\|
	dh->dccph_type == DCCP_PKT_SYNCACK) {
	if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
	dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
	dccp_update_gsr(sk, seqno);
	else
	return -1;
	}

	/*
	* Step 6: Check sequence numbers
	* Let LSWL = S.SWL and LAWL = S.AWL
	* If P.type == CloseReq or P.type == Close or P.type == Reset,
	* LSWL := S.GSR + 1, LAWL := S.GAR
	* If LSWL <= P.seqno <= S.SWH
	* and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
	* Update S.GSR, S.SWL, S.SWH
	* If P.type != Sync,
	* Update S.GAR
	*/
	lswl = dp->dccps_swl;
	lawl = dp->dccps_awl;

	if (dh->dccph_type == DCCP_PKT_CLOSEREQ \|\|
	dh->dccph_type == DCCP_PKT_CLOSE \|\|
	dh->dccph_type == DCCP_PKT_RESET) {
	lswl = ADD48(dp->dccps_gsr, 1);
	lawl = dp->dccps_gar;
	}

	if (between48(seqno, lswl, dp->dccps_swh) &&
	(ackno == DCCP_PKT_WITHOUT_ACK_SEQ \|\|
	between48(ackno, lawl, dp->dccps_awh))) {
	dccp_update_gsr(sk, seqno);

	if (dh->dccph_type != DCCP_PKT_SYNC &&
	(ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
	dp->dccps_gar = ackno;
	} else {
	unsigned long now = jiffies;
	/*
	* Step 6: Check sequence numbers
	* Otherwise,
	* If P.type == Reset,
	* Send Sync packet acknowledging S.GSR
	* Otherwise,
	* Send Sync packet acknowledging P.seqno
	* Drop packet and return
	*
	* These Syncs are rate-limited as per RFC 4340, 7.5.4:
	* at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
	*/
	if (time_before(now, (dp->dccps_rate_last +
	sysctl_dccp_sync_ratelimit)))
	return 0;

	DCCP_WARN("DCCP: Step 6 failed for %s packet, "
	"(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
	"(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
	"sending SYNC...\n", dccp_packet_name(dh->dccph_type),
	(unsigned long long) lswl, (unsigned long long) seqno,
	(unsigned long long) dp->dccps_swh,
	(ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
	: "exists",
	(unsigned long long) lawl, (unsigned long long) ackno,
	(unsigned long long) dp->dccps_awh);

	dp->dccps_rate_last = now;

	if (dh->dccph_type == DCCP_PKT_RESET)
	seqno = dp->dccps_gsr;
	dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
	return -1;
	}

	return 0;
	}

	static int __dccp_rcv_established(struct sock sk, struct sk_buff skb,
	const struct dccp_hdr *dh, const unsigned len)
	{
	struct dccp_sock *dp = dccp_sk(sk);

	switch (dccp_hdr(skb)->dccph_type) {
	case DCCP_PKT_DATAACK:
	case DCCP_PKT_DATA:
	/*
	* FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
	* - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
	* - sk_receive_queue is full, use Code 2, "Receive Buffer"
	*/
	dccp_enqueue_skb(sk, skb);
	return 0;
	case DCCP_PKT_ACK:
	goto discard;
	case DCCP_PKT_RESET:
	/*
	* Step 9: Process Reset
	* If P.type == Reset,
	* Tear down connection
	* S.state := TIMEWAIT
	* Set TIMEWAIT timer
	* Drop packet and return
	*/
	dccp_rcv_reset(sk, skb);
	return 0;
	case DCCP_PKT_CLOSEREQ:
	if (dccp_rcv_closereq(sk, skb))
	return 0;
	goto discard;
	case DCCP_PKT_CLOSE:
	if (dccp_rcv_close(sk, skb))
	return 0;
	goto discard;
	case DCCP_PKT_REQUEST:
	/* Step 7
	* or (S.is_server and P.type == Response)
	* or (S.is_client and P.type == Request)
	* or (S.state >= OPEN and P.type == Request
	* and P.seqno >= S.OSR)
	* or (S.state >= OPEN and P.type == Response
	* and P.seqno >= S.OSR)
	* or (S.state == RESPOND and P.type == Data),
	* Send Sync packet acknowledging P.seqno
	* Drop packet and return
	*/
	if (dp->dccps_role != DCCP_ROLE_LISTEN)
	goto send_sync;
	goto check_seq;
	case DCCP_PKT_RESPONSE:
	if (dp->dccps_role != DCCP_ROLE_CLIENT)
	goto send_sync;
	check_seq:
	if (dccp_delta_seqno(dp->dccps_osr,
	DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
	send_sync:
	dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
	DCCP_PKT_SYNC);
	}
	break;
	case DCCP_PKT_SYNC:
	dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
	DCCP_PKT_SYNCACK);
	/*
	* From RFC 4340, sec. 5.7
	*
	* As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
	* MAY have non-zero-length application data areas, whose
	* contents receivers MUST ignore.
	*/
	goto discard;
	}

	DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
	discard:
	__kfree_skb(skb);
	return 0;
	}

	int dccp_rcv_established(struct sock sk, struct sk_buff skb,
	const struct dccp_hdr *dh, const unsigned len)
	{
	struct dccp_sock *dp = dccp_sk(sk);

	if (dccp_check_seqno(sk, skb))
	goto discard;

	if (dccp_parse_options(sk, NULL, skb))
	return 1;

	if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
	dccp_event_ack_recv(sk, skb);

	if (dp->dccps_hc_rx_ackvec != NULL &&
	dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
	DCCP_SKB_CB(skb)->dccpd_seq, DCCPAV_RECEIVED))
	goto discard;
	dccp_deliver_input_to_ccids(sk, skb);

	return __dccp_rcv_established(sk, skb, dh, len);
	discard:
	__kfree_skb(skb);
	return 0;
	}

	EXPORT_SYMBOL_GPL(dccp_rcv_established);

	static int dccp_rcv_request_sent_state_process(struct sock *sk,
	struct sk_buff *skb,
	const struct dccp_hdr *dh,
	const unsigned len)
	{
	/*
	* Step 4: Prepare sequence numbers in REQUEST
	* If S.state == REQUEST,
	* If (P.type == Response or P.type == Reset)
	* and S.AWL <= P.ackno <= S.AWH,
	* / * Set sequence number variables corresponding to the
	* other endpoint, so P will pass the tests in Step 6 * /
	* Set S.GSR, S.ISR, S.SWL, S.SWH
	* / * Response processing continues in Step 10; Reset
	* processing continues in Step 9 * /
	*/
	if (dh->dccph_type == DCCP_PKT_RESPONSE) {
	const struct inet_connection_sock *icsk = inet_csk(sk);
	struct dccp_sock *dp = dccp_sk(sk);
	long tstamp = dccp_timestamp();

	if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
	dp->dccps_awl, dp->dccps_awh)) {
	dccp_pr_debug("invalid ackno: S.AWL=%llu, "
	"P.ackno=%llu, S.AWH=%llu \n",
	(unsigned long long)dp->dccps_awl,
	(unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
	(unsigned long long)dp->dccps_awh);
	goto out_invalid_packet;
	}

	/*
	* If option processing (Step 8) failed, return 1 here so that
	* dccp_v4_do_rcv() sends a Reset. The Reset code depends on
	* the option type and is set in dccp_parse_options().
	*/
	if (dccp_parse_options(sk, NULL, skb))
	return 1;

	/* Obtain usec RTT sample from SYN exchange (used by CCID 3) */
	if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
	dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
	dp->dccps_options_received.dccpor_timestamp_echo));

	/* Stop the REQUEST timer */
	inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
	WARN_ON(sk->sk_send_head == NULL);
	kfree_skb(sk->sk_send_head);
	sk->sk_send_head = NULL;

	/*
	* Set ISR, GSR from packet. ISS was set in dccp_v{4,6}_connect
	* and GSS in dccp_transmit_skb(). Setting AWL/AWH and SWL/SWH
	* is done as part of activating the feature values below, since
	* these settings depend on the local/remote Sequence Window
	* features, which were undefined or not confirmed until now.
	*/
	dp->dccps_gsr = dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;

	dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);

	/*
	* Step 10: Process REQUEST state (second part)
	* If S.state == REQUEST,
	* / * If we get here, P is a valid Response from the
	* server (see Step 4), and we should move to
	* PARTOPEN state. PARTOPEN means send an Ack,
	* don't send Data packets, retransmit Acks
	* periodically, and always include any Init Cookie
	* from the Response * /
	* S.state := PARTOPEN
	* Set PARTOPEN timer
	* Continue with S.state == PARTOPEN
	* / * Step 12 will send the Ack completing the
	* three-way handshake * /
	*/
	dccp_set_state(sk, DCCP_PARTOPEN);

	/*
	* If feature negotiation was successful, activate features now;
	* an activation failure means that this host could not activate
	* one ore more features (e.g. insufficient memory), which would
	* leave at least one feature in an undefined state.
	*/
	if (dccp_feat_activate_values(sk, &dp->dccps_featneg))
	goto unable_to_proceed;

	/* Make sure socket is routed, for correct metrics. */
	icsk->icsk_af_ops->rebuild_header(sk);

	if (!sock_flag(sk, SOCK_DEAD)) {
	sk->sk_state_change(sk);
	sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
	}

	if (sk->sk_write_pending \|\| icsk->icsk_ack.pingpong \|\|
	icsk->icsk_accept_queue.rskq_defer_accept) {
	/* Save one ACK. Data will be ready after
	* several ticks, if write_pending is set.
	*
	* It may be deleted, but with this feature tcpdumps
	* look so _wonderfully_ clever, that I was not able
	* to stand against the temptation 8) --ANK
	*/
	/*
	* OK, in DCCP we can as well do a similar trick, its
	* even in the draft, but there is no need for us to
	* schedule an ack here, as dccp_sendmsg does this for
	* us, also stated in the draft. -acme
	*/
	__kfree_skb(skb);
	return 0;
	}
	dccp_send_ack(sk);
	return -1;
	}

	out_invalid_packet:
	/* dccp_v4_do_rcv will send a reset */
	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
	return 1;

	unable_to_proceed:
	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_ABORTED;
	/*
	* We mark this socket as no longer usable, so that the loop in
	* dccp_sendmsg() terminates and the application gets notified.
	*/
	dccp_set_state(sk, DCCP_CLOSED);
	sk->sk_err = ECOMM;
	return 1;
	}

	static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
	struct sk_buff *skb,
	const struct dccp_hdr *dh,
	const unsigned len)
	{
	int queued = 0;

	switch (dh->dccph_type) {
	case DCCP_PKT_RESET:
	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
	break;
	case DCCP_PKT_DATA:
	if (sk->sk_state == DCCP_RESPOND)
	break;
	case DCCP_PKT_DATAACK:
	case DCCP_PKT_ACK:
	/*
	* FIXME: we should be reseting the PARTOPEN (DELACK) timer
	* here but only if we haven't used the DELACK timer for
	* something else, like sending a delayed ack for a TIMESTAMP
	* echo, etc, for now were not clearing it, sending an extra
	* ACK when there is nothing else to do in DELACK is not a big
	* deal after all.
	*/

	/* Stop the PARTOPEN timer */
	if (sk->sk_state == DCCP_PARTOPEN)
	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);

	dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
	dccp_set_state(sk, DCCP_OPEN);

	if (dh->dccph_type == DCCP_PKT_DATAACK \|\|
	dh->dccph_type == DCCP_PKT_DATA) {
	__dccp_rcv_established(sk, skb, dh, len);
	queued = 1; /* packet was queued
	(by __dccp_rcv_established) */
	}
	break;
	}

	return queued;
	}

	int dccp_rcv_state_process(struct sock sk, struct sk_buff skb,
	struct dccp_hdr *dh, unsigned len)
	{
	struct dccp_sock *dp = dccp_sk(sk);
	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
	const int old_state = sk->sk_state;
	int queued = 0;

	/*
	* Step 3: Process LISTEN state
	*
	* If S.state == LISTEN,
	* If P.type == Request or P contains a valid Init Cookie option,
	* (* Must scan the packet's options to check for Init
	* Cookies. Only Init Cookies are processed here,
	* however; other options are processed in Step 8. This
	* scan need only be performed if the endpoint uses Init
	* Cookies *)
	* (* Generate a new socket and switch to that socket *)
	* Set S := new socket for this port pair
	* S.state = RESPOND
	* Choose S.ISS (initial seqno) or set from Init Cookies
	* Initialize S.GAR := S.ISS
	* Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
	* Cookies Continue with S.state == RESPOND
	* (* A Response packet will be generated in Step 11 *)
	* Otherwise,
	* Generate Reset(No Connection) unless P.type == Reset
	* Drop packet and return
	*/
	if (sk->sk_state == DCCP_LISTEN) {
	if (dh->dccph_type == DCCP_PKT_REQUEST) {
	if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
	skb) < 0)
	return 1;
	goto discard;
	}
	if (dh->dccph_type == DCCP_PKT_RESET)
	goto discard;

	/* Caller (dccp_v4_do_rcv) will send Reset */
	dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
	return 1;
	}

	if (sk->sk_state != DCCP_REQUESTING && sk->sk_state != DCCP_RESPOND) {
	if (dccp_check_seqno(sk, skb))
	goto discard;

	/*
	* Step 8: Process options and mark acknowledgeable
	*/
	if (dccp_parse_options(sk, NULL, skb))
	return 1;

	if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
	dccp_event_ack_recv(sk, skb);

	if (dp->dccps_hc_rx_ackvec != NULL &&
	dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
	DCCP_SKB_CB(skb)->dccpd_seq, DCCPAV_RECEIVED))
	goto discard;

	dccp_deliver_input_to_ccids(sk, skb);
	}

	/*
	* Step 9: Process Reset
	* If P.type == Reset,
	* Tear down connection
	* S.state := TIMEWAIT
	* Set TIMEWAIT timer
	* Drop packet and return
	*/
	if (dh->dccph_type == DCCP_PKT_RESET) {
	dccp_rcv_reset(sk, skb);
	return 0;
	/*
	* Step 7: Check for unexpected packet types
	* If (S.is_server and P.type == Response)
	* or (S.is_client and P.type == Request)
	* or (S.state == RESPOND and P.type == Data),
	* Send Sync packet acknowledging P.seqno
	* Drop packet and return
	*/
	} else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
	dh->dccph_type == DCCP_PKT_RESPONSE) \|\|
	(dp->dccps_role == DCCP_ROLE_CLIENT &&
	dh->dccph_type == DCCP_PKT_REQUEST) \|\|
	(sk->sk_state == DCCP_RESPOND &&
	dh->dccph_type == DCCP_PKT_DATA)) {
	dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
	goto discard;
	} else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
	if (dccp_rcv_closereq(sk, skb))
	return 0;
	goto discard;
	} else if (dh->dccph_type == DCCP_PKT_CLOSE) {
	if (dccp_rcv_close(sk, skb))
	return 0;
	goto discard;
	}

	switch (sk->sk_state) {
	case DCCP_CLOSED:
	dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
	return 1;

	case DCCP_REQUESTING:
	queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
	if (queued >= 0)
	return queued;

	__kfree_skb(skb);
	return 0;

	case DCCP_RESPOND:
	case DCCP_PARTOPEN:
	queued = dccp_rcv_respond_partopen_state_process(sk, skb,
	dh, len);
	break;
	}

	if (dh->dccph_type == DCCP_PKT_ACK \|\|
	dh->dccph_type == DCCP_PKT_DATAACK) {
	switch (old_state) {
	case DCCP_PARTOPEN:
	sk->sk_state_change(sk);
	sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
	break;
	}
	} else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
	dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
	goto discard;
	}

	if (!queued) {
	discard:
	__kfree_skb(skb);
	}
	return 0;
	}

	EXPORT_SYMBOL_GPL(dccp_rcv_state_process);

	/**
	* dccp_sample_rtt - Validate and finalise computation of RTT sample
	* @delta: number of microseconds between packet and acknowledgment
	* The routine is kept generic to work in different contexts. It should be
	* called immediately when the ACK used for the RTT sample arrives.
	*/
	u32 dccp_sample_rtt(struct sock *sk, long delta)
	{
	/* dccpor_elapsed_time is either zeroed out or set and > 0 */
	delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;

	if (unlikely(delta <= 0)) {
	DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
	return DCCP_SANE_RTT_MIN;
	}
	if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
	DCCP_WARN("RTT sample %ld too large, using max\n", delta);
	return DCCP_SANE_RTT_MAX;
	}

	return delta;
	}

	EXPORT_SYMBOL_GPL(dccp_sample_rtt);