Initial import of modified Linux 2.6.28 tree

Original upstream URL:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git | branch linux-2.6.28.y

1 files changed, 731 insertions, 0 deletions

diff --git a/net/dccp/input.c b/net/dccp/input.c
new file mode 100644
index 0000000..779d0ed
--- /dev/null
+++ b/net/dccp/input.c
@@ -0,0 +1,731 @@
+/*
+ *  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 (dccp_msk(sk)->dccpms_send_ack_vector)
+		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 (dccp_msk(sk)->dccpms_send_ack_vector &&
+	    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
+			    DCCP_SKB_CB(skb)->dccpd_seq,
+			    DCCP_ACKVEC_STATE_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 (dccp_parse_options(sk, NULL, skb))
+			goto out_invalid_packet;
+
+		/* 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));
+
+		if (dccp_msk(sk)->dccpms_send_ack_vector &&
+		    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
+				    DCCP_SKB_CB(skb)->dccpd_seq,
+				    DCCP_ACKVEC_STATE_RECEIVED))
+			goto out_invalid_packet; /* FIXME: change error code */
+
+		/* 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;
+
+		dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
+		dccp_update_gsr(sk, dp->dccps_isr);
+		/*
+		 * SWL and AWL are initially adjusted so that they are not less than
+		 * the initial Sequence Numbers received and sent, respectively:
+		 *	SWL := max(GSR + 1 - floor(W/4), ISR),
+		 *	AWL := max(GSS - W' + 1, ISS).
+		 * These adjustments MUST be applied only at the beginning of the
+		 * connection.
+		 *
+		 * AWL was adjusted in dccp_v4_connect -acme
+		 */
+		dccp_set_seqno(&dp->dccps_swl,
+			       max48(dp->dccps_swl, dp->dccps_isr));
+
+		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);
+
+		/* 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;
+}
+
+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;
+
+			/* FIXME: do congestion control initialization */
+			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) {
+		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 (dccp_msk(sk)->dccpms_send_ack_vector &&
+		    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
+				    DCCP_SKB_CB(skb)->dccpd_seq,
+				    DCCP_ACKVEC_STATE_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:
+		/* FIXME: do congestion control initialization */
+
+		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);