Fix for bug #13407 "Remote connecting crashes server" and couple of similar

problems which were introduced during work on WL#2787 "Add view definer/owner
to the view definition (.frm) to check privileges on used tables and stored
routines when using a VIEW."

In some cases it is better to use value from Security_context::host_or_ip
instead of value from Security_context::host since the latter can be NULL
in certain situations (When we can't resolve hostname or we have not done
this yet).

mysql-test/r/skip_name_resolve.result

@@ -5,3 +5,10 @@ GRANT USAGE ON *.* TO 'mysqltest_1'@'127.0.0.1/255.255.255.255'
 GRANT ALL PRIVILEGES ON `test`.* TO 'mysqltest_1'@'127.0.0.1/255.255.255.255'
 REVOKE ALL ON test.* FROM mysqltest_1@'127.0.0.1/255.255.255.255';
 DROP USER mysqltest_1@'127.0.0.1/255.255.255.255';
+select user();
+user()
+#
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+#	root	#	test	Sleep	#		NULL
+#	root	#	test	Query	#	NULL	show processlist

mysql-test/t/skip_name_resolve.test

@@ -8,3 +8,13 @@ REVOKE ALL ON test.* FROM mysqltest_1@'127.0.0.1/255.255.255.255';
 DROP USER mysqltest_1@'127.0.0.1/255.255.255.255';
 
 # End of 4.1 tests
+
+# Bug #13407 "Remote connecting crashes server".
+# Server crashed when one used USER() function in connection for which
+# was impossible to obtain peer hostname.
+connect (con1, 127.0.0.1, root, , test, $MASTER_MYPORT, );
+--replace_column 1 #
+select user();
+--replace_column 1 # 6 # 3 #
+show processlist;
+connection default;

sql/item_strfunc.cc

@@ -1608,7 +1608,7 @@ String *Item_func_user::val_str(String *str)
   else
   {
     user= thd->main_security_ctx.user;
-    host= thd->main_security_ctx.host;
+    host= thd->main_security_ctx.host_or_ip;
   }
 
   // For system threads (e.g. replication SQL thread) user may be empty

sql/mysqld.cc

@@ -4208,7 +4208,7 @@ pthread_handler_decl(handle_connections_shared_memory,arg)
       errmsg= 0;
       goto errorconn;
     }
-    thd->host= my_strdup(my_localhost,MYF(0)); /* Host is unknown */
+    thd->security_ctx->host= my_strdup(my_localhost, MYF(0)); /* Host is unknown */
     create_new_thread(thd);
     connect_number++;
     continue;

sql/sql_show.cc

@@ -1205,7 +1205,7 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
 			"%s:%u", tmp_sctx->host_or_ip, tmp->peer_port);
 	}
 	else
-	  thd_info->host= thd->strdup(tmp_sctx->host);
+	  thd_info->host= thd->strdup(tmp_sctx->host_or_ip);
         if ((thd_info->db=tmp->db))             // Safe test
           thd_info->db=thd->strdup(thd_info->db);
         thd_info->command=(int) tmp->command;