[DCCP]: Implement the CLOSING timer

So that we retransmit CLOSE/CLOSEREQ packets till they elicit an
answer or we hit a timeout.

Most of the machinery uses TCP approaches, this code has to be
polished & audited, but this is better than we had before.

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

net/dccp/dccp.h

@@ -255,7 +255,7 @@ extern int	   dccp_v4_checksum(const struct sk_buff *skb,
 
 extern int	   dccp_v4_send_reset(struct sock *sk,
 				      enum dccp_reset_codes code);
-extern void	   dccp_send_close(struct sock *sk);
+extern void	   dccp_send_close(struct sock *sk, const int active);
 
 struct dccp_skb_cb {
 	__u8 dccpd_type;

net/dccp/input.c

@@ -31,14 +31,9 @@ static void dccp_fin(struct sock *sk, struct sk_buff *skb)
 
 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;
-	}
+	dccp_v4_send_reset(sk, DCCP_RESET_CODE_CLOSED);
+	dccp_fin(sk, skb);
+	dccp_set_state(sk, DCCP_CLOSED);
 }
 
 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
@@ -54,13 +49,8 @@ static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
 		return;
 	}
 
-	switch (sk->sk_state) {
-	case DCCP_PARTOPEN:
-	case DCCP_OPEN:
-		dccp_set_state(sk, DCCP_CLOSING);
-		dccp_send_close(sk);
-		break;
-	}
+	dccp_set_state(sk, DCCP_CLOSING);
+	dccp_send_close(sk, 0);
 }
 
 static inline void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
@@ -562,6 +552,12 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 		dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 			       DCCP_PKT_SYNC);
 		goto discard;
+	} else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
+		dccp_rcv_closereq(sk, skb);
+		goto discard;
+	} else if (dh->dccph_type == DCCP_PKT_CLOSE) {
+		dccp_rcv_close(sk, skb);
+		return 0;
 	}
 
 	switch (sk->sk_state) {

net/dccp/output.c

@@ -96,8 +96,7 @@ int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
 		dh->dccph_checksum = dccp_v4_checksum(skb, inet->saddr,
 						      inet->daddr);
 
-		if (dcb->dccpd_type == DCCP_PKT_ACK ||
-		    dcb->dccpd_type == DCCP_PKT_DATAACK)
+		if (set_ack)
 			dccp_event_ack_sent(sk);
 
 		DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
@@ -429,18 +428,15 @@ void dccp_send_sync(struct sock *sk, const u64 seq,
  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
  * any circumstances.
  */
-void dccp_send_close(struct sock *sk)
+void dccp_send_close(struct sock *sk, const int active)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct sk_buff *skb;
+	const unsigned int prio = active ? GFP_KERNEL : GFP_ATOMIC;
 
-	/* 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();
-	}
+	skb = alloc_skb(sk->sk_prot->max_header, prio);
+	if (skb == NULL)
+		return;
 
 	/* Reserve space for headers and prepare control bits. */
 	skb_reserve(skb, sk->sk_prot->max_header);
@@ -449,7 +445,12 @@ void dccp_send_close(struct sock *sk)
 					DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
 
 	skb_set_owner_w(skb, sk);
-	dccp_transmit_skb(sk, skb);
+	if (active) {
+		BUG_TRAP(sk->sk_send_head == NULL);
+		sk->sk_send_head = skb;
+		dccp_transmit_skb(sk, skb_clone(skb, prio));
+	} else
+		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);

net/dccp/proto.c

@@ -402,12 +402,15 @@ void dccp_close(struct sock *sk, long timeout)
 		/* Check zero linger _after_ checking for unread data. */
 		sk->sk_prot->disconnect(sk, 0);
 	} else if (dccp_close_state(sk)) {
-		dccp_send_close(sk);
+		dccp_send_close(sk, 1);
 	}
 
 	sk_stream_wait_close(sk, timeout);
 
 adjudge_to_death:
+	/*
+	 * It is the last release_sock in its life. It will remove backlog.
+	 */
 	release_sock(sk);
 	/*
 	 * Now socket is owned by kernel and we acquire BH lock
@@ -419,11 +422,26 @@ adjudge_to_death:
 
 	sock_hold(sk);
 	sock_orphan(sk);
-						
-	if (sk->sk_state != DCCP_CLOSED)
+
+	/*
+	 * The last release_sock may have processed the CLOSE or RESET
+	 * packet moving sock to CLOSED state, if not we have to fire
+	 * the CLOSE/CLOSEREQ retransmission timer, see "8.3. Termination"
+	 * in draft-ietf-dccp-spec-11. -acme
+	 */
+	if (sk->sk_state == DCCP_CLOSING) {
+		/* FIXME: should start at 2 * RTT */
+		/* Timer for repeating the CLOSE/CLOSEREQ until an answer. */
+		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+					  inet_csk(sk)->icsk_rto,
+					  DCCP_RTO_MAX);
+#if 0
+		/* Yeah, we should use sk->sk_prot->orphan_count, etc */
 		dccp_set_state(sk, DCCP_CLOSED);
+#endif
+	}
 
-	atomic_inc(&dccp_orphan_count);
+	atomic_inc(sk->sk_prot->orphan_count);
 	if (sk->sk_state == DCCP_CLOSED)
 		inet_csk_destroy_sock(sk);