* If a new buffer had its last part in common with an existing larger buffer,

BufferQueue::Add() tried to remove a negative amount of bytes. This could
  bring a download to a complete halt (as could the other one due to the list
  link mixup).
* While the RTT computation still seems to work not that good (with a drop quote
  of 50% I would easily reach retransmit timeouts of 80 secs), TCP should now
  work a lot better on a flaky connection.
* Renamed _GetMSS() to _MaxSegmentSize().
* Minor cleanup.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22677 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/kernel/network/protocols/tcp/BufferQueue.cpp

@@ -72,7 +72,8 @@ BufferQueue::Add(net_buffer *buffer, tcp_sequence sequence)
 {
 	TRACE(("BufferQueue@%p::Add(buffer %p, size %lu, sequence %lu)\n",
 		this, buffer, buffer->size, (uint32)sequence));
-	TRACE(("  in: first: %lu, last: %lu, num: %lu, cont: %lu\n", (uint32)fFirstSequence, (uint32)fLastSequence, fNumBytes, fContiguousBytes));
+	TRACE(("  in: first: %lu, last: %lu, num: %lu, cont: %lu\n",
+		(uint32)fFirstSequence, (uint32)fLastSequence, fNumBytes, fContiguousBytes));
 
 	buffer->sequence = sequence;
 
@@ -80,14 +81,18 @@ BufferQueue::Add(net_buffer *buffer, tcp_sequence sequence)
 		// we usually just add the buffer to the end of the queue
 		fList.Add(buffer);
 
-		if (sequence == fLastSequence && fLastSequence - fFirstSequence == fNumBytes) {
+		if (sequence == fLastSequence
-			// there is no hole in the buffer, we can make the whole buffer available
+			&& fLastSequence - fFirstSequence == fNumBytes) {
+			// there is no hole in the buffer, we can make the whole buffer
+			// available
 			fContiguousBytes += buffer->size;
 		}
 
 		fLastSequence = sequence + buffer->size;
 		fNumBytes += buffer->size;
-		TRACE(("  out0: first: %lu, last: %lu, num: %lu, cont: %lu\n", (uint32)fFirstSequence, (uint32)fLastSequence, fNumBytes, fContiguousBytes));
+
+		TRACE(("  out0: first: %lu, last: %lu, num: %lu, cont: %lu\n",
+			(uint32)fFirstSequence, (uint32)fLastSequence, fNumBytes, fContiguousBytes));
 		return;
 	}
 
@@ -100,7 +105,7 @@ BufferQueue::Add(net_buffer *buffer, tcp_sequence sequence)
 		sequence = fFirstSequence;
 	}
 
-	// find for the place where to insert the buffer into the queue
+	// find the place where to insert the buffer into the queue
 
 	SegmentList::ReverseIterator iterator = fList.GetReverseIterator();
 	net_buffer *previous = NULL;
@@ -117,9 +122,9 @@ BufferQueue::Add(net_buffer *buffer, tcp_sequence sequence)
 	// check if we have duplicate data, and remove it if that is the case
 	if (previous != NULL) {
 		if (sequence == previous->sequence) {
-			// we already have at least part of this data - ignore new data whenever
+			// we already have at least part of this data - ignore new data
-			// it makes sense (because some TCP implementations send bogus data when
+			// whenever it makes sense (because some TCP implementations send
-			// probing the window)
+			// bogus data when probing the window)
 			if (previous->size >= buffer->size) {
 				gBufferModule->free(buffer);
 				buffer = NULL;
@@ -127,8 +132,10 @@ BufferQueue::Add(net_buffer *buffer, tcp_sequence sequence)
 				fList.Remove(previous);
 				gBufferModule->free(previous);
 			}
-		} else if (tcp_sequence(previous->sequence + previous->size) > sequence)
+		} else if (tcp_sequence(previous->sequence + previous->size) > sequence) {
-			gBufferModule->remove_header(buffer, previous->sequence + previous->size - sequence);
+			gBufferModule->remove_header(buffer,
+				previous->sequence + previous->size - sequence);
+		}
 	}
 
 	if (buffer != NULL && next != NULL
@@ -140,12 +147,15 @@ BufferQueue::Add(net_buffer *buffer, tcp_sequence sequence)
 
 			fList.Remove(remove);
 			gBufferModule->free(remove);
-		} else
+		} else {
-			gBufferModule->remove_trailer(buffer, next->sequence - (sequence + buffer->size));
+			gBufferModule->remove_trailer(buffer,
+				sequence + buffer->size - next->sequence);
+		}
 	}
 
 	if (buffer == NULL) {
-		TRACE(("  out1: first: %lu, last: %lu, num: %lu, cont: %lu\n", (uint32)fFirstSequence, (uint32)fLastSequence, fNumBytes, fContiguousBytes));
+		TRACE(("  out1: first: %lu, last: %lu, num: %lu, cont: %lu\n",
+			(uint32)fFirstSequence, (uint32)fLastSequence, fNumBytes, fContiguousBytes));
 		return;
 	}
 
@@ -164,10 +174,12 @@ BufferQueue::Add(net_buffer *buffer, tcp_sequence sequence)
 			fContiguousBytes += buffer->size;
 
 			buffer = (struct net_buffer *)buffer->link.next;
-		} while (buffer != NULL && fFirstSequence + fContiguousBytes == buffer->sequence);
+		} while (buffer != NULL
+			&& fFirstSequence + fContiguousBytes == buffer->sequence);
 	}
 
-	TRACE(("  out2: first: %lu, last: %lu, num: %lu, cont: %lu\n", (uint32)fFirstSequence, (uint32)fLastSequence, fNumBytes, fContiguousBytes));
+	TRACE(("  out2: first: %lu, last: %lu, num: %lu, cont: %lu\n",
+		(uint32)fFirstSequence, (uint32)fLastSequence, fNumBytes, fContiguousBytes));
 }
 
 

src/add-ons/kernel/network/protocols/tcp/TCPEndpoint.cpp

@@ -64,7 +64,7 @@
 
 #ifdef PROBE_TCP
 #	define PROBE(buffer, window) \
-	dprintf("TCP PROBE %llu %s %s %ld %lu %lu %lu %lu %lu %lu %lu %lu %lu %llu\n", \
+	dprintf("TCP PROBE %llu %s %s %ld snxt %lu suna %lu cw %lu sst %lu win %lu swin %lu smax-suna %lu savail %lu sqused %lu rto %llu\n", \
 		system_time(), PrintAddress(buffer->source), \
 		PrintAddress(buffer->destination), buffer->size, (uint32)fSendNext, \
 		(uint32)fSendUnacknowledged, fCongestionWindow, fSlowStartThreshold, \
@@ -1320,7 +1320,7 @@ TCPEndpoint::_SendQueued(bool force, uint32 sendWindow)
 
 
 int
-TCPEndpoint::_GetMSS(const sockaddr *address) const
+TCPEndpoint::_MaxSegmentSize(const sockaddr *address) const
 {
 	return next->module->get_mtu(next, address) - sizeof(tcp_header);
 }
@@ -1714,7 +1714,7 @@ TCPEndpoint::_PrepareSendPath(const sockaddr *peer)
 	// we are counting the SYN here
 	fSendQueue.SetInitialSequence(fSendNext + 1);
 
-	fReceiveMaxSegmentSize = _GetMSS(peer);
+	fReceiveMaxSegmentSize = _MaxSegmentSize(peer);
 
 	// Compute the window shift we advertise to our peer - if it doesn't support
 	// this option, this will be reset to 0 (when its SYN is received)

src/add-ons/kernel/network/protocols/tcp/TCPEndpoint.h

@@ -94,7 +94,7 @@ class TCPEndpoint : public net_protocol, public ProtocolSocket {
 			uint32 segmentMaxSize, uint32 flightSize);
 		status_t _SendQueued(bool force = false);
 		status_t _SendQueued(bool force, uint32 sendWindow);
-		int _GetMSS(const struct sockaddr *) const;
+		int _MaxSegmentSize(const struct sockaddr *) const;
 		status_t _ShutdownEgress(bool closing);
 		ssize_t _AvailableData() const;
 		void _NotifyReader();

src/add-ons/kernel/network/protocols/tcp/tcp.cpp

@@ -30,6 +30,7 @@
 #include <NetBufferUtilities.h>
 #include <NetUtilities.h>
 
+
 //#define TRACE_TCP
 #ifdef TRACE_TCP
 #	define TRACE(x) dprintf x