PERFORCE change 175592 for review

[Andre Oppermann]

http://p4web.freebsd.org/chv.cgi?CH=175592

Change 175592 by andre at andre_t61 on 2010/03/11 17:14:33

	Update and improve some comments.
	Add error handling skeleton to tcp_retransmit().

Affected files ...

.. //depot/projects/tcp_new/netinet/tcp_output.c#16 edit

Differences ...

==== //depot/projects/tcp_new/netinet/tcp_output.c#16 (text+ko) ====

@@ -216,6 +216,7 @@
 
 	/*
 	 * Conservative approximation of data still travelling in the network.
+	 * XXXAO: Alternative version w/o SACK.
 	 */
 	inflight = duna - tp->snd_sacked;
 
@@ -230,7 +231,7 @@
 	rwin = tcp_rcv_wnd(tp, so);
 
 	/*
-	 * Act based on the phase we are in.
+	 * Act based on the send phase we are in.
 	 */
 	switch (tp->t_phase) {
 	case TP_IDLE:
@@ -411,7 +412,7 @@
 			goto send;
 
 		/*
-		 * Always send if NODELAY is enabled.  This gives at least
+		 * Always send if NODELAY is enabled.  This causes at least
 		 * one segment per application write no matter how small
 		 * the amount of data.
 		 */
@@ -555,6 +556,8 @@
 	/*
 	 * NB: len > 0 means we sent this much data w/o error.
 	 * error == 0 means we sent everything w/o error.
+	 * NB: The difference between the three cases is subtle
+	 * but important.
 	 *
 	 * XXXAO: Avoid unconditional writes to the tcpcb.
 	 */
@@ -783,15 +786,10 @@
 	 * Do not retransmit too many times.
 	 * Limit the amount of data that is inflight.
 	 * Retransmit only the stuff that was not SACK'ed.
-	 */
-	/*
-	 * The moment we receive a duplicate ACK everything freezes.
-	 * No more new data is sent except for those allowed by limited
-	 * transmit.
+	 *
 	 * The fast recovery algorithms start their work by the third
 	 * duplicate ACK.
-	 */
-	/*
+	 *
 	 * We have the following mechanisms:
 	 *  1. Fast recovery: After we get three duplicate ACKs RFC2581
 	 *  2. NewReno RFC3782
@@ -868,6 +866,54 @@
 
 	} while (error == 0);
 
+	if (rlen > 0) {
+	}
+
+	if (error == 0) {
+	}
+
+	if (rlen > 0 || error == 0) {
+		/*
+		 * Update last send timestamp.
+		 */
+		if ((tp->t_flags & TF_TIMESTAMP) && tp->snd_tslast != to->to_tsval)
+			tp->snd_tslast = to->to_tsval;
+
+		/*
+		 * Last ACK we sent.
+		 */
+		if (tp->snd_lastack != th->th_ack)
+			tp->snd_lastack = th->th_ack;
+	}
+
+	if (rlen > 0 && error == 0) {
+	}
+
+	switch (error) {
+	case EPERM:
+	case EACCES:
+		break;
+	case ENOBUFS:
+	case ENOMEM:
+		break;
+	case EMSGSIZE:
+		break;
+	case ENETDOWN:
+	case ENETUNREACH:
+	case EHOSTDOWN:
+	case EHOSTUNREACH:
+		break;
+	case 0:
+		/*
+		 * No error.
+		 */
+		break;
+
+	default:
+		KASSERT(0 == 1,
+		    ("%s: unkown error %i", __func__, error));
+	}
+
 	return (error);
 }
 
@@ -1256,8 +1302,9 @@
 	/*
 	 * Report shrunk socket buffers.
 	 */
-	if (delta < 0)
+	if (delta < 0) {
 		/*tcp_log("our receive socket buffer was shrunk")*/;
+	}
 
 	/*
 	 * Our current open receive window to be advertized is
@@ -1288,7 +1335,7 @@
 
 	/*
 	 * Compute options for segment.
-	 * We only have to care about SYN and established connection
+	 * We only have to care about SYN-SENT and established connection
 	 * segments.  Options for SYN-ACK segments are handled in TCP
 	 * syncache. Before ESTABLISHED, force sending of initial options
 	 * unless TCP set not to do any options.