Improvements and fixes to strchr_esc_mysql

The C style comments were not ignored and the -- style comments
did not check for the trailing whitespace and made return values char*.

The creation of a stored procedure would prevent sessions from using
any of the slave servers because readwritesplit would interpret
the creation statement as a multi-statement query.

Parts of modutil and readwritesplit now compare pointers to pointers instead of
converting pointers to integers.

server/core/modutil.c

@@ -34,6 +34,7 @@
 #include <mysql_client_server_protocol.h>
 #include <maxscale/poll.h>
 #include <modutil.h>
+#include <strings.h>
 
 /** These are used when converting MySQL wildcards to regular expressions */
 static SPINLOCK re_lock = SPINLOCK_INIT;
@@ -765,7 +766,7 @@ static void modutil_reply_routing_error(DCB*     backend_dcb,
  * @return Pointer to the first non-escaped, non-quoted occurrence of the character.
  * If the character is not found, NULL is returned.
  */
-void* strnchr_esc(char* ptr, char c, int len)
+char* strnchr_esc(char* ptr, char c, int len)
 {
     char* p = (char*)ptr;
     char* start = p;
@@ -804,27 +805,28 @@ void* strnchr_esc(char* ptr, char c, int len)
 /**
  * Find the first occurrence of a character in a string. This function ignores
  * escaped characters and all characters that are enclosed in single or double quotes.
- * Also MySQL style comment blocks are ignored.
+ * MySQL style comment blocks and identifiers in backticks are also ignored.
  * @param ptr Pointer to area of memory to inspect
  * @param c Character to search for
  * @param len Size of the memory area
  * @return Pointer to the first non-escaped, non-quoted occurrence of the character.
  * If the character is not found, NULL is returned.
  */
-void* strnchr_esc_mysql(char* ptr, char c, int len)
+char* strnchr_esc_mysql(char* ptr, char c, int len)
 {
     char* p = (char*) ptr;
-    char* start = p;
+    char* start = p, *end = start + len;
-    bool quoted = false, escaped = false, backtick = false;
+    bool quoted = false, escaped = false, backtick = false, comment = false;
     char qc;
 
-    while (p < start + len)
+    while (p < end)
     {
         if (escaped)
         {
             escaped = false;
         }
-        else
+        else if ((!comment && !quoted && !backtick) || (comment && *p == '*') ||
+                 (!comment && quoted && *p == qc) || (!comment && backtick && *p == '`'))
         {
             switch (*p)
             {
@@ -832,7 +834,7 @@ void* strnchr_esc_mysql(char* ptr, char c, int len)
                     escaped = true;
                     break;
 
-                case'\'':
+                case '\'':
                 case '"':
                     if (!quoted)
                     {
@@ -845,31 +847,47 @@ void* strnchr_esc_mysql(char* ptr, char c, int len)
                     }
                     break;
 
+                case '/':
+                    if (p + 1 < end && *(p + 1) == '*')
+                    {
+                        comment = true;
+                        p += 1;
+                    }
+                    break;
+
+                case '*':
+                    if (comment && p + 1 < end && *(p + 1) == '/')
+                    {
+                        comment = false;
+                        p += 1;
+                    }
+                    break;
+
                 case '`':
                     backtick = !backtick;
                     break;
 
                 case '#':
-                    if (!backtick)
+                    return NULL;
+
+                case '-':
+                    if (p + 2 < end && *(p + 1) == '-' &&
+                        isspace(*(p + 2)))
                     {
                         return NULL;
                     }
                     break;
 
-                case '-':
+                default:
-                    if (!backtick && p + 1 < start + len && *(p + 1) == '-')
-                    {
-                        return NULL;
-                    }
                     break;
             }
 
-            if (*p == c && !escaped && !quoted)
+            if (*p == c && !escaped && !quoted && !comment && !backtick)
             {
                 return p;
             }
-            p++;
         }
+        p++;
     }
     return NULL;
 }
@@ -883,7 +901,7 @@ bool is_mysql_comment_start(const char* start, int len)
 {
     const char *ptr = start;
 
-    while (ptr - start < len && isspace(*ptr))
+    while (ptr < start + len && (isspace(*ptr) || *ptr == ';'))
     {
         ptr++;
     }
@@ -891,7 +909,7 @@ bool is_mysql_comment_start(const char* start, int len)
     switch (*ptr)
     {
         case '-':
-            if (*(ptr + 1) == '-')
+            if (*(ptr + 1) == '-' && isspace(*(ptr + 2)))
             {
                 return true;
             }
@@ -910,6 +928,23 @@ bool is_mysql_comment_start(const char* start, int len)
     return false;
 }
 
+/**
+ * @brief Check if the token is the END part of a BEGIN ... END block.
+ * @param ptr String with at least three non-whitespace characters in it
+ * @return True if the token is the final part of a BEGIN .. END block
+ */
+bool is_mysql_sp_end(const char* start, int len)
+{
+    const char *ptr = start;
+
+    while (ptr < start + len && (isspace(*ptr) || *ptr == ';'))
+    {
+        ptr++;
+    }
+
+    return ptr < start + len - 3 && strncasecmp(ptr, "end", 3) == 0;
+}
+
 /**
  * Create a COM_QUERY packet from a string.
  * @param query Query to create.

server/include/modutil.h

@@ -69,8 +69,9 @@ int modutil_count_signal_packets(GWBUF*,int,int,int*);
 mxs_pcre2_result_t modutil_mysql_wildcard_match(const char* pattern, const char* string);
 
 /** Character and token searching functions */
-void* strnchr_esc(char* ptr, char c, int len);
+char* strnchr_esc(char* ptr, char c, int len);
-void* strnchr_esc_mysql(char* ptr, char c, int len);
+char* strnchr_esc_mysql(char* ptr, char c, int len);
 bool is_mysql_comment_start(const char* start, int len);
+bool is_mysql_sp_end(const char* start, int len);
 
 #endif

server/modules/routing/readwritesplit/readwritesplit.c

@@ -5366,11 +5366,19 @@ static void check_for_multi_stmt(ROUTER_CLIENT_SES* rses, GWBUF *buf,
 
         if ((ptr = strnchr_esc_mysql(data, ';', buflen)))
         {
-            ptr++;
+            /** Skip stored procedures etc. */
-            if (ptr - data < buflen && !is_mysql_comment_start(ptr, ptr - data))
+            while (ptr && is_mysql_sp_end(ptr, ptr - data))
             {
-                rses->forced_node = rses->rses_master_ref;
+                ptr = strnchr_esc_mysql(ptr + 1, ';',  ptr - data);
-                MXS_INFO("Multi-statement query, routing all future queries to master.");
+            }
+
+            if (ptr)
+            {
+                if (ptr < data + buflen && !is_mysql_comment_start(ptr, ptr - data))
+                {
+                    rses->forced_node = rses->rses_master_ref;
+                    MXS_INFO("Multi-statement query, routing all future queries to master.");
+                }
             }
         }
     }