ACL: use a fixed table for command IDs.

src/acl.c

@@ -93,3 +93,20 @@ int ACLCheckUserCredentials(robj *username, robj *password) {
         return C_ERR;
     }
 }
+
+/* For ACL purposes, every user has a bitmap with the commands that such
+ * user is allowed to execute. In order to populate the bitmap, every command
+ * should have an assigned ID (that is used to index the bitmap). This function
+ * creates such an ID: it uses sequential IDs, reusing the same ID for the same
+ * command name, so that a command retains the same ID in case of modules that
+ * are unloaded and later reloaded. */
+unsigned long ACLGetCommandID(const char *cmdname) {
+    static rax *map = NULL;
+    unsigned long nextid = 0;
+
+    if (map == NULL) map = raxNew();
+    void *id = raxFind(map,(unsigned char*)cmdname,strlen(cmdname));
+    if (id != raxNotFound) return (unsigned long)id;
+    raxInsert(map,(unsigned char*)cmdname,strlen(cmdname),(void*)nextid,NULL);
+    return nextid++;
+}

src/server.c

@@ -2224,8 +2224,7 @@ void populateCommandTable(void) {
             f++;
         }
 
-        c->id = j; /* Sequential ID for each command. Used for ACLs. */
+        c->id = ACLGetCommandID(c->name); /* Assign the ID used for ACL. */
-
         retval1 = dictAdd(server.commands, sdsnew(c->name), c);
         /* Populate an additional dictionary that will be unaffected
          * by rename-command statements in redis.conf. */

src/server.h

@@ -1352,6 +1352,14 @@ typedef struct {
     dictIterator *di;
 } setTypeIterator;
 
+/* This structure represents a Redis user. This is useful for ACLs, the
+ * user is associated to the connection after the connection is authenticated.
+ * If there is no associated user, the connection uses the default user. */
+#define USER_MAX_COMMAND_BIT 1024
+typedef struct user {
+    uint64_t allowed_commands[USER_MAX_COMMAND_BIT/64];
+} user;
+
 /* Structure to hold hash iteration abstraction. Note that iteration over
  * hashes involves both fields and values. Because it is possible that
  * not both are required, store pointers in the iterator to avoid
@@ -1655,6 +1663,7 @@ void receiveChildInfo(void);
 
 /* acl.c -- Authentication related prototypes. */
 int ACLCheckUserCredentials(robj *username, robj *password);
+unsigned long ACLGetCommandID(const char *cmdname);
 
 /* Sorted sets data type */