[DCCP]: Initial implementation

Development to this point was done on a subversion repository at:

http://oops.ghostprotocols.net:81/cgi-bin/viewcvs.cgi/dccp-2.6/

This repository will be kept at this site for the foreseable future,
so that interested parties can see the history of this code,
attributions, etc.

If I ever decide to take this offline I'll provide the full history at
some other suitable place.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 510 insertions, 0 deletions

diff --git a/net/dccp/input.c b/net/dccp/input.c
new file mode 100644
index 0000000..622e976
--- /dev/null
+++ b/net/dccp/input.c
@@ -0,0 +1,510 @@
+/*
+ *  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/config.h>
+#include <linux/dccp.h>
+#include <linux/skbuff.h>
+
+#include <net/sock.h>
+
+#include "ccid.h"
+#include "dccp.h"
+
+static void dccp_fin(struct sock *sk, struct sk_buff *skb)
+{
+	sk->sk_shutdown |= RCV_SHUTDOWN;
+	sock_set_flag(sk, SOCK_DONE);
+	__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_rcv_close(struct sock *sk, struct sk_buff *skb)
+{
+	switch (sk->sk_state) {
+	case DCCP_PARTOPEN:
+	case DCCP_OPEN:
+		dccp_v4_send_reset(sk, DCCP_RESET_CODE_CLOSED);
+		dccp_fin(sk, skb);
+		dccp_set_state(sk, DCCP_CLOSED);
+		break;
+	}
+}
+
+static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
+{
+	/*
+	 *   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);
+		return;
+	}
+
+	switch (sk->sk_state) {
+	case DCCP_PARTOPEN:
+	case DCCP_OPEN:
+		dccp_set_state(sk, DCCP_CLOSING);
+		dccp_send_close(sk);
+		break;
+	}
+}
+
+static inline void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
+{
+	struct dccp_sock *dp = dccp_sk(sk);
+
+	if (dp->dccps_options.dccpo_send_ack_vector)
+		dccp_ackpkts_check_rcv_ackno(dp->dccps_hc_rx_ackpkts, sk,
+					     DCCP_SKB_CB(skb)->dccpd_ack_seq);
+}
+
+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 = dp->dccps_swl;
+	u64 lawl = dp->dccps_awl;
+
+	/*
+	 *   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(DCCP_SKB_CB(skb)->dccpd_ack_seq, dp->dccps_awl, dp->dccps_awh) &&
+		    !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
+			dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
+		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
+	 *      Otherwise,
+	 *	  Send Sync packet acknowledging P.seqno
+	 *	  Drop packet and return
+	 */
+	} else if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
+		   dh->dccph_type == DCCP_PKT_CLOSE ||
+		   dh->dccph_type == DCCP_PKT_RESET) {
+		lswl = dp->dccps_gsr;
+		dccp_inc_seqno(&lswl);
+		lawl = dp->dccps_gar;
+	}
+
+	if (between48(DCCP_SKB_CB(skb)->dccpd_seq, lswl, dp->dccps_swh) &&
+	    (DCCP_SKB_CB(skb)->dccpd_ack_seq == DCCP_PKT_WITHOUT_ACK_SEQ ||
+	     between48(DCCP_SKB_CB(skb)->dccpd_ack_seq, lawl, dp->dccps_awh))) {
+		dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
+
+		if (dh->dccph_type != DCCP_PKT_SYNC &&
+		    DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
+			dp->dccps_gar = DCCP_SKB_CB(skb)->dccpd_ack_seq;
+	} else {
+		dccp_pr_debug("Step 6 failed, sending SYNC...\n");
+		dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
+		return -1;
+	}
+
+	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, skb))
+		goto discard;
+
+	if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
+		dccp_event_ack_recv(sk, skb);
+
+	/*
+	 * FIXME: check ECN to see if we should use
+	 * DCCP_ACKPKTS_STATE_ECN_MARKED
+	 */
+	if (dp->dccps_options.dccpo_send_ack_vector) {
+		struct dccp_ackpkts *ap = dp->dccps_hc_rx_ackpkts;
+
+		if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts,
+				     DCCP_SKB_CB(skb)->dccpd_seq,
+				     DCCP_ACKPKTS_STATE_RECEIVED)) {
+			LIMIT_NETDEBUG(pr_info("DCCP: acknowledgeable packets buffer full!\n"));
+			ap->dccpap_ack_seqno = DCCP_MAX_SEQNO + 1;
+			inet_csk_schedule_ack(sk);
+			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, TCP_DELACK_MIN, TCP_RTO_MAX);
+			goto discard;
+		}
+
+		/*
+		 * FIXME: this activation is probably wrong, have to study more
+		 * TCP delack machinery and how it fits into DCCP draft, but
+		 * for now it kinda "works" 8)
+		 */
+		if (!inet_csk_ack_scheduled(sk)) {
+			inet_csk_schedule_ack(sk);
+			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5 * HZ, TCP_RTO_MAX);
+		}
+	}
+
+	ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
+	ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
+
+	switch (dccp_hdr(skb)->dccph_type) {
+	case DCCP_PKT_DATAACK:
+	case DCCP_PKT_DATA:
+		/*
+		 * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED option
+		 * if it is.
+		 */
+		__skb_pull(skb, dh->dccph_doff * 4);
+		__skb_queue_tail(&sk->sk_receive_queue, skb);
+		skb_set_owner_r(skb, sk);
+		sk->sk_data_ready(sk, 0);
+		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_fin(sk, skb);
+		dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
+		return 0;
+	case DCCP_PKT_CLOSEREQ:
+		dccp_rcv_closereq(sk, skb);
+		goto discard;
+	case DCCP_PKT_CLOSE:
+		dccp_rcv_close(sk, skb);
+		return 0;
+	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 (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
+send_sync:
+			dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
+		}
+		break;
+	}
+
+	DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
+discard:
+	__kfree_skb(skb);
+	return 0;
+}
+
+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);
+
+		/* Stop the REQUEST timer */
+		inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
+		BUG_TRAP(sk->sk_send_head != NULL);
+		__kfree_skb(sk->sk_send_head);
+		sk->sk_send_head = NULL;
+
+		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",
+				      dp->dccps_awl, DCCP_SKB_CB(skb)->dccpd_ack_seq, dp->dccps_awh);
+			goto out_invalid_packet;
+		}
+
+		dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
+		dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
+
+		if (ccid_hc_rx_init(dp->dccps_hc_rx_ccid, sk) != 0 ||
+		    ccid_hc_tx_init(dp->dccps_hc_tx_ccid, sk) != 0) {
+			ccid_hc_rx_exit(dp->dccps_hc_rx_ccid, sk);
+			ccid_hc_tx_exit(dp->dccps_hc_tx_ccid, sk);
+			/* FIXME: send appropriate RESET code */
+			goto out_invalid_packet;
+		}
+
+		dccp_sync_mss(sk, dp->dccps_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. */
+		inet_sk_rebuild_header(sk);
+
+		if (!sock_flag(sk, SOCK_DEAD)) {
+			sk->sk_state_change(sk);
+			sk_wake_async(sk, 0, 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:
+	return 1; /* dccp_v4_do_rcv will send a reset, but...
+		     FIXME: the reset code should be DCCP_RESET_CODE_PACKET_ERROR  */
+}
+
+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_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) {
+			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);
+	const int old_state = sk->sk_state;
+	int queued = 0;
+
+	if (sk->sk_state != DCCP_LISTEN && 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, skb))
+			goto discard;
+
+		if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
+			dccp_event_ack_recv(sk, skb);
+
+		ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
+		ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
+
+		/*
+		 * FIXME: check ECN to see if we should use
+		 * DCCP_ACKPKTS_STATE_ECN_MARKED
+		 */
+		if (dp->dccps_options.dccpo_send_ack_vector) {
+			if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts,
+					     DCCP_SKB_CB(skb)->dccpd_seq,
+					     DCCP_ACKPKTS_STATE_RECEIVED))
+				goto discard;
+			/*
+			 * FIXME: this activation is probably wrong, have to study more
+			 * TCP delack machinery and how it fits into DCCP draft, but
+			 * for now it kinda "works" 8)
+			 */
+			if (dp->dccps_hc_rx_ackpkts->dccpap_ack_seqno == DCCP_MAX_SEQNO + 1 &&
+			    !inet_csk_ack_scheduled(sk)) {
+				inet_csk_schedule_ack(sk);
+				inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, TCP_DELACK_MIN, TCP_RTO_MAX);
+			}
+		}
+	}
+
+	/*
+	 *  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) {
+		/* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
+		dccp_fin(sk, skb);
+		dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
+		return 0;
+		/*
+		 *   Step 7: Check for unexpected packet types
+		 *      If (S.is_server and P.type == CloseReq)
+		 *	    or (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 || dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
+		    (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, DCCP_SKB_CB(skb)->dccpd_seq);
+		goto discard;
+	}
+
+	switch (sk->sk_state) {
+	case DCCP_CLOSED:
+		return 1;
+
+	case DCCP_LISTEN:
+		if (dh->dccph_type == DCCP_PKT_ACK ||
+		    dh->dccph_type == DCCP_PKT_DATAACK)
+			return 1;
+
+		if (dh->dccph_type == DCCP_PKT_RESET)
+			goto discard;
+
+		if (dh->dccph_type == DCCP_PKT_REQUEST) {
+			if (dccp_v4_conn_request(sk, skb) < 0)
+				return 1;
+
+			/* FIXME: do congestion control initialization */
+			goto discard;
+		}
+		goto discard;
+
+	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, 0, POLL_OUT);
+			break;
+		}
+	}
+
+	if (!queued) { 
+discard:
+		__kfree_skb(skb);
+	}
+	return 0;
+}