Bug #11766769: 59959: SMALL VALUES OF --MAX-ALLOWED-PACKET

ARE NOT BEING HONORED

max_allowed_packet works in conjunction with net_buffer_length.
max_allowed_packet is an upper bound of net_buffer_length.
So it doesn't make sense to set the upper limit lower than the value.
Added a warning (using ER_UNKNOWN_ERRROR and a specific message)
when this is done (in the log at startup and when setting either 
max_allowed_packet or the net_buffer_length variables)
Added a test case.
Fixed several tests that broke the above rule.

mysql-test/r/packet.result

@@ -3,6 +3,7 @@ set @net_buffer_length=@@global.net_buffer_length;
 set global max_allowed_packet=100;
 Warnings:
 Warning	1292	Truncated incorrect max_allowed_packet value: '100'
+Warning	1105	The value of 'max_allowed_packet' should be no less than the value of 'net_buffer_length'
 set global net_buffer_length=100;
 Warnings:
 Warning	1292	Truncated incorrect net_buffer_length value: '100'

mysql-test/r/variables.result

@@ -280,6 +280,7 @@ NET_BUFFER_LENGTH	1024
 set global net_buffer_length=2000000000;
 Warnings:
 Warning	1292	Truncated incorrect net_buffer_length value: '2000000000'
+Warning	1105	The value of 'max_allowed_packet' should be no less than the value of 'net_buffer_length'
 show global variables like 'net_buffer_length';
 Variable_name	Value
 net_buffer_length	1048576
@@ -502,6 +503,7 @@ set low_priority_updates=1;
 set global max_allowed_packet=100;
 Warnings:
 Warning	1292	Truncated incorrect max_allowed_packet value: '100'
+Warning	1105	The value of 'max_allowed_packet' should be no less than the value of 'net_buffer_length'
 set global max_binlog_cache_size=100;
 Warnings:
 Warning	1292	Truncated incorrect max_binlog_cache_size value: '100'
@@ -1059,6 +1061,8 @@ set global max_write_lock_count      =default;
 set global myisam_data_pointer_size  =@my_myisam_data_pointer_size;
 set global myisam_max_sort_file_size =@my_myisam_max_sort_file_size;
 set global net_buffer_length         =@my_net_buffer_length;
+Warnings:
+Warning	1105	The value of 'max_allowed_packet' should be no less than the value of 'net_buffer_length'
 set global net_write_timeout         =@my_net_write_timeout;
 set global net_read_timeout          =@my_net_read_timeout;
 set global query_cache_limit         =@my_query_cache_limit;
@@ -1547,4 +1551,27 @@ SET @@global.max_binlog_cache_size=DEFAULT;
 SET @@global.max_join_size=DEFAULT;
 SET @@global.key_buffer_size=@kbs;
 SET @@global.key_cache_block_size=@kcbs;
+#
+# Bug #11766769 : 59959: SMALL VALUES OF --MAX-ALLOWED-PACKET 
+#   ARE NOT BEING HONORED
+#
+CREATE TABLE t1 (a MEDIUMTEXT);
+SET GLOBAL max_allowed_packet=2048;
+Warnings:
+Warning	1105	The value of 'max_allowed_packet' should be no less than the value of 'net_buffer_length'
+SET GLOBAL net_buffer_length=4096;
+Warnings:
+Warning	1105	The value of 'max_allowed_packet' should be no less than the value of 'net_buffer_length'
+SHOW SESSION VARIABLES LIKE 'max_allowed_packet';
+Variable_name	Value
+max_allowed_packet	2048
+SHOW SESSION VARIABLES LIKE 'net_buffer_length';
+Variable_name	Value
+net_buffer_length	4096
+ERROR 08S01: Got a packet bigger than 'max_allowed_packet' bytes
+SELECT LENGTH(a) FROM t1;
+LENGTH(a)
+SET GLOBAL max_allowed_packet=default;
+SET GLOBAL net_buffer_length=default;
+DROP TABLE t1;
 End of 5.1 tests

mysql-test/suite/rpl/r/rpl_packet.result

@@ -49,6 +49,8 @@ SET @max_allowed_packet_2= @@session.max_allowed_packet;
 ==== clean up ====
 DROP TABLE t1;
 SET @@global.max_allowed_packet= 1024;
+Warnings:
+Warning	1105	The value of 'max_allowed_packet' should be no less than the value of 'net_buffer_length'
 SET @@global.net_buffer_length= 1024;
 DROP TABLE t1;
 RESET SLAVE;

mysql-test/suite/rpl/t/rpl_loaddata_map-master.opt

@@ -1 +1 @@
---read_buffer_size=12K --max_allowed_packet=8K
+--read_buffer_size=12K --max_allowed_packet=8K --net-buffer-length=8K

mysql-test/suite/rpl/t/rpl_loaddata_map-slave.opt

@@ -1 +1 @@
---max_allowed_packet=8K
+--max_allowed_packet=8K --net-buffer-length=8K