[DCCP]: Introduce dccp_wait_for_ccid and use it in dccp_write_xmit

This is not quite what I think we should have long term but improves
performance for now, so lets use it till we get CCID3 working well,
then we can think about using sk_write_queue, perhaps using some ideas
from Juwen Lai's old stack for 2.4.20.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dccp/ccids/ccid3.c

@@ -985,7 +985,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk,
 		ccid3_pr_debug("send_packet delay=%ld\n", delay);
 		delay /= -1000;
 		/* divide by -1000 is to convert to ms and get sign right */
-		rc = delay > 0 ? -EAGAIN : 0;
+		rc = delay > 0 ? delay : 0;
 		break;
 	default:
 		printk(KERN_CRIT "%s: %s, sk=%p, Illegal state (%d)!\n",

net/dccp/dccp.h

@@ -126,8 +126,7 @@ extern void dccp_send_delayed_ack(struct sock *sk);
 extern void dccp_send_sync(struct sock *sk, const u64 seq,
 			   const enum dccp_pkt_type pkt_type);
 
-extern int dccp_write_xmit(struct sock *sk, struct sk_buff *skb,
-			   const int len);
+extern int dccp_write_xmit(struct sock *sk, struct sk_buff *skb, long *timeo);
 
 extern void dccp_init_xmit_timers(struct sock *sk);
 static inline void dccp_clear_xmit_timers(struct sock *sk)

net/dccp/output.c

@@ -150,14 +150,71 @@ unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 	return mss_now;
 }
 
-int dccp_write_xmit(struct sock *sk, struct sk_buff *skb, const int len)
+/**
+ * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
+ * @sk: socket to wait for
+ * @timeo: for how long
+ */
+static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb,
+			      long *timeo)
+{
+	struct dccp_sock *dp = dccp_sk(sk);
+	DEFINE_WAIT(wait);
+	long delay;
+	int rc;
+
+	while (1) {
+		prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
+
+		if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
+			goto do_error;
+		if (!*timeo)
+			goto do_nonblock;
+		if (signal_pending(current))
+			goto do_interrupted;
+
+		rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
+					    skb->len);
+		if (rc <= 0)
+			break;
+		delay = msecs_to_jiffies(rc);
+		if (delay > *timeo || delay < 0)
+			goto do_nonblock;
+
+		sk->sk_write_pending++;
+		release_sock(sk);
+		*timeo -= schedule_timeout(delay);
+		lock_sock(sk);
+		sk->sk_write_pending--;
+	}
+out:
+	finish_wait(sk->sk_sleep, &wait);
+	return rc;
+
+do_error:
+	rc = -EPIPE;
+	goto out;
+do_nonblock:
+	rc = -EAGAIN;
+	goto out;
+do_interrupted:
+	rc = sock_intr_errno(*timeo);
+	goto out;
+}
+
+int dccp_write_xmit(struct sock *sk, struct sk_buff *skb, long *timeo)
 {
 	const struct dccp_sock *dp = dccp_sk(sk);
-	int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb, len);
+	int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
+					 skb->len);
+
+	if (err > 0)
+		err = dccp_wait_for_ccid(sk, skb, timeo);
 
 	if (err == 0) {
 		const struct dccp_ackpkts *ap = dp->dccps_hc_rx_ackpkts;
 		struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
+		const int len = skb->len;
 
 		if (sk->sk_state == DCCP_PARTOPEN) {
 			/* See 8.1.5.  Handshake Completion */

net/dccp/proto.c

@@ -261,7 +261,7 @@ int dccp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	if (rc != 0)
 		goto out_discard;
 
-	rc = dccp_write_xmit(sk, skb, len);
+	rc = dccp_write_xmit(sk, skb, &timeo);
 	/*
 	 * XXX we don't use sk_write_queue, so just discard the packet.
 	 *     Current plan however is to _use_ sk_write_queue with