[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, 406 insertions, 0 deletions

diff --git a/net/dccp/output.c b/net/dccp/output.c
new file mode 100644
index 0000000..22ca291
--- /dev/null
+++ b/net/dccp/output.c
@@ -0,0 +1,406 @@
+/*
+ *  net/dccp/output.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 inline void dccp_event_ack_sent(struct sock *sk)
+{
+	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
+}
+
+/*
+ * All SKB's seen here are completely headerless. It is our
+ * job to build the DCCP header, and pass the packet down to
+ * IP so it can do the same plus pass the packet off to the
+ * device.
+ */
+int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
+{
+	if (likely(skb != NULL)) {
+		const struct inet_sock *inet = inet_sk(sk);
+		struct dccp_sock *dp = dccp_sk(sk);
+		struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
+		struct dccp_hdr *dh;
+		/* XXX For now we're using only 48 bits sequence numbers */
+		const int dccp_header_size = sizeof(*dh) +
+					     sizeof(struct dccp_hdr_ext) +
+					     dccp_packet_hdr_len(dcb->dccpd_type);
+		int err, set_ack = 1;
+		u64 ackno = dp->dccps_gsr;
+
+		/*
+		 * FIXME: study DCCP_PKT_SYNC[ACK] to see what is the right thing 
+		 * to do here...
+		 */
+		dccp_inc_seqno(&dp->dccps_gss);
+
+		dcb->dccpd_seq = dp->dccps_gss;
+		dccp_insert_options(sk, skb);
+
+		switch (dcb->dccpd_type) {
+		case DCCP_PKT_DATA:
+			set_ack = 0;
+			break;
+		case DCCP_PKT_SYNC:
+		case DCCP_PKT_SYNCACK:
+			ackno = dcb->dccpd_seq;
+			break;
+		}
+		
+		skb->h.raw = skb_push(skb, dccp_header_size);
+		dh = dccp_hdr(skb);
+		/* Data packets are not cloned as they are never retransmitted */
+		if (skb_cloned(skb))
+			skb_set_owner_w(skb, sk);
+
+		/* Build DCCP header and checksum it. */
+		memset(dh, 0, dccp_header_size);
+		dh->dccph_type	= dcb->dccpd_type;
+		dh->dccph_sport	= inet->sport;
+		dh->dccph_dport	= inet->dport;
+		dh->dccph_doff	= (dccp_header_size + dcb->dccpd_opt_len) / 4;
+		dh->dccph_ccval	= dcb->dccpd_ccval;
+		/* XXX For now we're using only 48 bits sequence numbers */
+		dh->dccph_x	= 1;
+
+		dp->dccps_awh = dp->dccps_gss;
+		dccp_hdr_set_seq(dh, dp->dccps_gss);
+		if (set_ack)
+			dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
+
+		switch (dcb->dccpd_type) {
+		case DCCP_PKT_REQUEST:
+			dccp_hdr_request(skb)->dccph_req_service = dcb->dccpd_service;
+			break;
+		case DCCP_PKT_RESET:
+			dccp_hdr_reset(skb)->dccph_reset_code = dcb->dccpd_reset_code;
+			break;
+		}
+
+		dh->dccph_checksum = dccp_v4_checksum(skb);
+
+		if (dcb->dccpd_type == DCCP_PKT_ACK ||
+		    dcb->dccpd_type == DCCP_PKT_DATAACK)
+			dccp_event_ack_sent(sk);
+
+		DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
+
+		err = ip_queue_xmit(skb, 0);
+		if (err <= 0)
+			return err;
+
+		/* NET_XMIT_CN is special. It does not guarantee,
+		 * that this packet is lost. It tells that device
+		 * is about to start to drop packets or already
+		 * drops some packets of the same priority and
+		 * invokes us to send less aggressively.
+		 */
+		return err == NET_XMIT_CN ? 0 : err;
+	}
+	return -ENOBUFS;
+}
+
+unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
+{
+	struct dccp_sock *dp = dccp_sk(sk);
+	int mss_now;
+
+	/*
+	 * FIXME: we really should be using the af_specific thing to support IPv6.
+	 * mss_now = pmtu - tp->af_specific->net_header_len - sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext);
+	 */
+	mss_now = pmtu - sizeof(struct iphdr) - sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext);
+
+	/* Now subtract optional transport overhead */
+	mss_now -= dp->dccps_ext_header_len;
+
+	/*
+	 * FIXME: this should come from the CCID infrastructure, where, say,
+	 * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
+	 * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
+	 * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
+	 * make it a multiple of 4
+	 */
+
+	mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
+
+	/* And store cached results */
+	dp->dccps_pmtu_cookie = pmtu;
+	dp->dccps_mss_cache = mss_now;
+
+	return mss_now;
+}
+
+int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
+{
+	if (inet_sk_rebuild_header(sk) != 0)
+		return -EHOSTUNREACH; /* Routing failure or similar. */
+
+	return dccp_transmit_skb(sk, (skb_cloned(skb) ?
+				      pskb_copy(skb, GFP_ATOMIC):
+				      skb_clone(skb, GFP_ATOMIC)));
+}
+
+struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
+				   struct request_sock *req)
+{
+	struct dccp_hdr *dh;
+	const int dccp_header_size = sizeof(struct dccp_hdr) +
+				     sizeof(struct dccp_hdr_ext) +
+				     sizeof(struct dccp_hdr_response);
+	struct sk_buff *skb = sock_wmalloc(sk, MAX_HEADER + DCCP_MAX_OPT_LEN +
+					       dccp_header_size, 1,
+					   GFP_ATOMIC);
+	if (skb == NULL)
+		return NULL;
+
+	/* Reserve space for headers. */
+	skb_reserve(skb, MAX_HEADER + DCCP_MAX_OPT_LEN + dccp_header_size);
+
+	skb->dst = dst_clone(dst);
+	skb->csum = 0;
+
+	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
+	DCCP_SKB_CB(skb)->dccpd_seq  = dccp_rsk(req)->dreq_iss;
+	dccp_insert_options(sk, skb);
+
+	skb->h.raw = skb_push(skb, dccp_header_size);
+
+	dh = dccp_hdr(skb);
+	memset(dh, 0, dccp_header_size);
+
+	dh->dccph_sport	= inet_sk(sk)->sport;
+	dh->dccph_dport	= inet_rsk(req)->rmt_port;
+	dh->dccph_doff	= (dccp_header_size + DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
+	dh->dccph_type	= DCCP_PKT_RESPONSE;
+	dh->dccph_x	= 1;
+	dccp_hdr_set_seq(dh, dccp_rsk(req)->dreq_iss);
+	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dccp_rsk(req)->dreq_isr);
+
+	dh->dccph_checksum = dccp_v4_checksum(skb);
+
+	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
+	return skb;
+}
+
+struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
+				const enum dccp_reset_codes code)
+				   
+{
+	struct dccp_hdr *dh;
+	struct dccp_sock *dp = dccp_sk(sk);
+	const int dccp_header_size = sizeof(struct dccp_hdr) +
+				     sizeof(struct dccp_hdr_ext) +
+				     sizeof(struct dccp_hdr_reset);
+	struct sk_buff *skb = sock_wmalloc(sk, MAX_HEADER + DCCP_MAX_OPT_LEN +
+					       dccp_header_size, 1,
+					   GFP_ATOMIC);
+	if (skb == NULL)
+		return NULL;
+
+	/* Reserve space for headers. */
+	skb_reserve(skb, MAX_HEADER + DCCP_MAX_OPT_LEN + dccp_header_size);
+
+	skb->dst = dst_clone(dst);
+	skb->csum = 0;
+
+	dccp_inc_seqno(&dp->dccps_gss);
+
+	DCCP_SKB_CB(skb)->dccpd_reset_code = code;
+	DCCP_SKB_CB(skb)->dccpd_type	   = DCCP_PKT_RESET;
+	DCCP_SKB_CB(skb)->dccpd_seq	   = dp->dccps_gss;
+	dccp_insert_options(sk, skb);
+
+	skb->h.raw = skb_push(skb, dccp_header_size);
+
+	dh = dccp_hdr(skb);
+	memset(dh, 0, dccp_header_size);
+
+	dh->dccph_sport	= inet_sk(sk)->sport;
+	dh->dccph_dport	= inet_sk(sk)->dport;
+	dh->dccph_doff	= (dccp_header_size + DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
+	dh->dccph_type	= DCCP_PKT_RESET;
+	dh->dccph_x	= 1;
+	dccp_hdr_set_seq(dh, dp->dccps_gss);
+	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);
+
+	dccp_hdr_reset(skb)->dccph_reset_code = code;
+
+	dh->dccph_checksum = dccp_v4_checksum(skb);
+
+	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
+	return skb;
+}
+
+/*
+ * Do all connect socket setups that can be done AF independent.
+ */
+static inline void dccp_connect_init(struct sock *sk)
+{
+	struct dst_entry *dst = __sk_dst_get(sk);
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	sk->sk_err = 0;
+	sock_reset_flag(sk, SOCK_DONE);
+	
+	dccp_sync_mss(sk, dst_mtu(dst));
+
+	/*
+	 * FIXME: set dp->{dccps_swh,dccps_swl}, with
+	 * something like dccp_inc_seq
+	 */
+
+	icsk->icsk_retransmits = 0;
+}
+
+int dccp_connect(struct sock *sk)
+{
+	struct sk_buff *skb;
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	dccp_connect_init(sk);
+
+	skb = alloc_skb(MAX_DCCP_HEADER + 15, sk->sk_allocation);
+	if (unlikely(skb == NULL))
+		return -ENOBUFS;
+
+	/* Reserve space for headers. */
+	skb_reserve(skb, MAX_DCCP_HEADER);
+
+	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
+	/* FIXME: set service to something meaningful, coming
+	 * from userspace*/
+	DCCP_SKB_CB(skb)->dccpd_service = 0;
+	skb->csum = 0;
+	skb_set_owner_w(skb, sk);
+
+	BUG_TRAP(sk->sk_send_head == NULL);
+	sk->sk_send_head = skb;
+	dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
+	DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
+
+	/* Timer for repeating the REQUEST until an answer. */
+	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
+	return 0;
+}
+
+void dccp_send_ack(struct sock *sk)
+{
+	/* If we have been reset, we may not send again. */
+	if (sk->sk_state != DCCP_CLOSED) {
+		struct sk_buff *skb = alloc_skb(MAX_DCCP_HEADER, GFP_ATOMIC);
+
+		if (skb == NULL) {
+			inet_csk_schedule_ack(sk);
+			inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
+			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, TCP_DELACK_MAX, TCP_RTO_MAX);
+			return;
+		}
+
+		/* Reserve space for headers */
+		skb_reserve(skb, MAX_DCCP_HEADER);
+		skb->csum = 0;
+		DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
+		skb_set_owner_w(skb, sk);
+		dccp_transmit_skb(sk, skb);
+	}
+}
+
+EXPORT_SYMBOL_GPL(dccp_send_ack);
+
+void dccp_send_delayed_ack(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	/*
+	 * FIXME: tune this timer. elapsed time fixes the skew, so no problem
+	 * with using 2s, and active senders also piggyback the ACK into a
+	 * DATAACK packet, so this is really for quiescent senders.
+	 */
+	unsigned long timeout = jiffies + 2 * HZ;
+
+	/* Use new timeout only if there wasn't a older one earlier. */
+	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
+		/* If delack timer was blocked or is about to expire,
+		 * send ACK now.
+		 *
+		 * FIXME: check the "about to expire" part
+		 */
+		if (icsk->icsk_ack.blocked) {
+			dccp_send_ack(sk);
+			return;
+		}
+
+		if (!time_before(timeout, icsk->icsk_ack.timeout))
+			timeout = icsk->icsk_ack.timeout;
+	}
+	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
+	icsk->icsk_ack.timeout = timeout;
+	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
+}
+
+void dccp_send_sync(struct sock *sk, u64 seq)
+{
+	/*
+	 * We are not putting this on the write queue, so
+	 * dccp_transmit_skb() will set the ownership to this
+	 * sock.
+	 */
+	struct sk_buff *skb = alloc_skb(MAX_DCCP_HEADER, GFP_ATOMIC);
+
+	if (skb == NULL)
+		/* FIXME: how to make sure the sync is sent? */
+		return;
+
+	/* Reserve space for headers and prepare control bits. */
+	skb_reserve(skb, MAX_DCCP_HEADER);
+	skb->csum = 0;
+	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_SYNC;
+	DCCP_SKB_CB(skb)->dccpd_seq = seq;
+
+	skb_set_owner_w(skb, sk);
+	dccp_transmit_skb(sk, skb);
+}
+
+/* Send a DCCP_PKT_CLOSE/CLOSEREQ.  The caller locks the socket for us.  This cannot be
+ * allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under any circumstances.
+ */
+void dccp_send_close(struct sock *sk)
+{
+	struct dccp_sock *dp = dccp_sk(sk);
+	struct sk_buff *skb;
+
+	/* Socket is locked, keep trying until memory is available. */
+	for (;;) {
+		skb = alloc_skb(sk->sk_prot->max_header, GFP_KERNEL);
+		if (skb != NULL)
+			break;
+		yield();
+	}
+
+	/* Reserve space for headers and prepare control bits. */
+	skb_reserve(skb, sk->sk_prot->max_header);
+	skb->csum = 0;
+	DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ? DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
+
+	skb_set_owner_w(skb, sk);
+	dccp_transmit_skb(sk, skb);
+
+	ccid_hc_rx_exit(dp->dccps_hc_rx_ccid, sk);
+	ccid_hc_tx_exit(dp->dccps_hc_tx_ccid, sk);
+}