From 5ac736a14e3a6b6079fd9c3c1827b8967ba56f37 Mon Sep 17 00:00:00 2001
From: Mark Riddoch <Mark.Riddoch@skysql.com>
Date: Fri, 30 Jan 2015 14:55:14 +0000
Subject: [PATCH] Fix for CRC in fake rotate events

---
 server/modules/routing/binlog/blr_master.c | 22 +++++++++++---
 server/modules/routing/binlog/blr_slave.c  | 34 +++++++++-------------
 2 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/server/modules/routing/binlog/blr_master.c b/server/modules/routing/binlog/blr_master.c
index 9e3e2064c..3ce019558 100644
--- a/server/modules/routing/binlog/blr_master.c
+++ b/server/modules/routing/binlog/blr_master.c
@@ -681,6 +681,11 @@ static REP_HEADER	phdr;
 	}
 
 	pkt_length = gwbuf_length(pkt);
+	/*
+	 * Loop over all the packets while we still have some data
+	 * and the packet length is enough to hold a replication event
+	 * header.
+	 */
 	while (pkt && pkt_length > 24)
 	{
 		reslen = GWBUF_LENGTH(pkt);
@@ -708,6 +713,7 @@ static REP_HEADER	phdr;
 		{
 			len = EXTRACT24(pdata) + 4;
 		}
+		/* len is now the payload length for the packet we are working on */
 
 		if (reslen < len && pkt_length >= len)
 		{
@@ -787,10 +793,17 @@ static REP_HEADER	phdr;
 			n_bufs = 1;
 		}
 
+		/*
+		 * ptr now points at the current message in a contiguous buffer,
+		 * this buffer is either within the GWBUF or in a malloc'd
+		 * copy if the message straddles GWBUF's.
+		 */
+
 		if (len < BINLOG_EVENT_HDR_LEN)
 		{
 		char	*msg = "";
 
+			/* Packet is too small to be a binlog event */
 			if (ptr[4] == 0xfe)	/* EOF Packet */
 			{
 				msg = "end of file";
@@ -812,7 +825,7 @@ static REP_HEADER	phdr;
 
 			blr_extract_header(ptr, &hdr);
 
-			if (hdr.event_size != len - 5)
+			if (hdr.event_size != len - 5)	/* Sanity check */
 			{
 				LOGIF(LE,(skygw_log_write(
 				   LOGFILE_ERROR,
@@ -843,8 +856,10 @@ static REP_HEADER	phdr;
 			phdr = hdr;
 			if (hdr.ok == 0)
 			{
-#define CHECK_CRC	1
-#if CHECK_CRC
+				/*
+				 * First check that the checksum we calculate matches the
+				 * checksum in the packet we received.
+				 */
 				uint32_t	chksum, pktsum;
 
 				chksum = crc32(0L, NULL, 0);
@@ -870,7 +885,6 @@ static REP_HEADER	phdr;
 					blr_master_delayed_connect(router);
 					return;
 				}
-#endif
 				router->stats.n_binlogs++;
 				router->lastEventReceived = hdr.event_type;
 
diff --git a/server/modules/routing/binlog/blr_slave.c b/server/modules/routing/binlog/blr_slave.c
index f76b151d0..09de1892f 100644
--- a/server/modules/routing/binlog/blr_slave.c
+++ b/server/modules/routing/binlog/blr_slave.c
@@ -888,7 +888,8 @@ if (hkheartbeat - beat1 > 1) LOGIF(LE, (skygw_log_write(
 			LOGIF(LE, (skygw_log_write(LOGFILE_ERROR,
 				"Slave reached end of file for binlog file %s at %u "
 				"which is not the file currently being downloaded. "
-				"Master binlog is %s, %lu.",
+				"Master binlog is %s, %lu. This may be caused by a "
+				"previous failure of the master.",
 				slave->binlogfile, slave->binlog_pos,
 				router->binlog_name, router->binlog_position)));
 			if (blr_slave_fake_rotate(router, slave))
@@ -1014,11 +1015,7 @@ uint32_t	chksum;
 		return 0;
 
 	binlognamelen = strlen(slave->binlogfile);
-
-	if (slave->nocrc)
-		len = 19 + 8 + binlognamelen;
-	else
-		len = 19 + 8 + 4 + binlognamelen;
+	len = 19 + 8 + 4 + binlognamelen;
 
 	// Build a fake rotate event
 	resp = gwbuf_alloc(len + 5);
@@ -1037,20 +1034,17 @@ uint32_t	chksum;
 	memcpy(ptr, slave->binlogfile, binlognamelen);
 	ptr += binlognamelen;
 
-	if (!slave->nocrc)
-	{
-		/*
-		 * Now add the CRC to the fake binlog rotate event.
-		 *
-		 * The algorithm is first to compute the checksum of an empty buffer
-		 * and then the checksum of the event portion of the message, ie we do not
-		 * include the length, sequence number and ok byte that makes up the first
-		 * 5 bytes of the message. We also do not include the 4 byte checksum itself.
-		 */
-		chksum = crc32(0L, NULL, 0);
-		chksum = crc32(chksum, GWBUF_DATA(resp) + 5, hdr.event_size - 4);
-		encode_value(ptr, chksum, 32);
-	}
+	/*
+	 * Now add the CRC to the fake binlog rotate event.
+	 *
+	 * The algorithm is first to compute the checksum of an empty buffer
+	 * and then the checksum of the event portion of the message, ie we do not
+	 * include the length, sequence number and ok byte that makes up the first
+	 * 5 bytes of the message. We also do not include the 4 byte checksum itself.
+	 */
+	chksum = crc32(0L, NULL, 0);
+	chksum = crc32(chksum, GWBUF_DATA(resp) + 5, hdr.event_size - 4);
+	encode_value(ptr, chksum, 32);
 
 	slave->dcb->func.write(slave->dcb, resp);
 	return 1;