Fix server getting completely choked up on even a little of DoS

* If client count is unbearable, immediately delete denied clients * Re-prioritize the checking order of things about incoming clients * Remove a huge CPU-wasting exception in ReliablePacketBuffer
minetest · Aug 4, 2013 · e6687be · e6687be
1 parent 8831669
commit e6687be
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Showing 4 changed files with 229 additions and 168 deletions.
diff --git a/src/connection.cpp b/src/connection.cpp
@@ -207,12 +207,13 @@ RPBSearchResult ReliablePacketBuffer::notFound()
 {
 	return m_list.end();
 }
-u16 ReliablePacketBuffer::getFirstSeqnum()
+bool ReliablePacketBuffer::getFirstSeqnum(u16 *result)
 {
 	if(empty())
-		throw NotFoundException("Buffer is empty");
+		return false;
 	BufferedPacket p = *m_list.begin();
-	return readU16(&p.data[BASE_HEADER_SIZE+1]);
+	*result = readU16(&p.data[BASE_HEADER_SIZE+1]);
+	return true;
 }
 BufferedPacket ReliablePacketBuffer::popFirst()
 {
@@ -700,7 +701,7 @@ void Connection::receive()
 
 	bool single_wait_done = false;
 
-	for(;;)
+	for(u32 loop_i=0; loop_i<1000; loop_i++) // Limit in case of DoS
 	{
 	try{
 		/* Check if some buffer has relevant data */
@@ -1245,17 +1246,16 @@ bool Connection::checkIncomingBuffers(Channel *channel, u16 &peer_id,
 {
 	u16 firstseqnum = 0;
 	// Clear old packets from start of buffer
-	try{
 	for(;;){
-		firstseqnum = channel->incoming_reliables.getFirstSeqnum();
+		bool found = channel->incoming_reliables.getFirstSeqnum(&firstseqnum);
+		if(!found)
+			break;
 		if(seqnum_higher(channel->next_incoming_seqnum, firstseqnum))
 			channel->incoming_reliables.popFirst();
 		else
 			break;
 	}
 	// This happens if all packets are old
-	}catch(con::NotFoundException)
-	{}
 
 	if(channel->incoming_reliables.empty() == false)
 	{

diff --git a/src/connection.h b/src/connection.h
@@ -281,7 +281,7 @@ class ReliablePacketBuffer
 	u32 size();
 	RPBSearchResult findPacket(u16 seqnum);
 	RPBSearchResult notFound();
-	u16 getFirstSeqnum();
+	bool getFirstSeqnum(u16 *result);
 	BufferedPacket popFirst();
 	BufferedPacket popSeqnum(u16 seqnum);
 	void insert(BufferedPacket &p);