Throw error for conflicting bcast tracking prefixes (#8176)

Throw an error if there are conflicting bcast tracking prefixes.

src/networking.c

@@ -2800,6 +2800,13 @@ NULL
                 return;
             }
 
+            if (options & CLIENT_TRACKING_BCAST) {
+                if (!checkPrefixCollisionsOrReply(c,prefix,numprefix)) {
+                    zfree(prefix);
+                    return;
+                }
+            }
+
             enableTracking(c,redir,options,prefix,numprefix);
         } else if (!strcasecmp(c->argv[2]->ptr,"off")) {
             disableTracking(c);

src/server.h

@@ -1849,6 +1849,7 @@ uint64_t trackingGetTotalItems(void);
 uint64_t trackingGetTotalKeys(void);
 uint64_t trackingGetTotalPrefixes(void);
 void trackingBroadcastInvalidationMessages(void);
+int checkPrefixCollisionsOrReply(client *c, robj **prefix, size_t numprefix);
 
 /* List data type */
 void listTypeTryConversion(robj *subject, robj *value);

src/tracking.c

@@ -99,6 +99,57 @@ void disableTracking(client *c) {
     }
 }
 
+static int stringCheckPrefix(unsigned char *s1, size_t s1_len, unsigned char *s2, size_t s2_len) {
+    size_t min_length = s1_len < s2_len ? s1_len : s2_len;
+    return memcmp(s1,s2,min_length) == 0;   
+}
+
+/* Check if any of the provided prefixes collide with one another or
+ * with an existing prefix for the client. A collision is defined as two 
+ * prefixes that will emit an invalidation for the same key. If no prefix 
+ * collision is found, 1 is return, otherwise 0 is returned and the client 
+ * has an error emitted describing the error. */
+int checkPrefixCollisionsOrReply(client *c, robj **prefixes, size_t numprefix) {
+    for (size_t i = 0; i < numprefix; i++) {
+        /* Check input list has no overlap with existing prefixes. */
+        if (c->client_tracking_prefixes) {
+            raxIterator ri;
+            raxStart(&ri,c->client_tracking_prefixes);
+            raxSeek(&ri,"^",NULL,0);
+            while(raxNext(&ri)) {
+                if (stringCheckPrefix(ri.key,ri.key_len,
+                    prefixes[i]->ptr,sdslen(prefixes[i]->ptr))) 
+                {
+                    sds collision = sdsnewlen(ri.key,ri.key_len);
+                    addReplyErrorFormat(c,
+                        "Prefix '%s' overlaps with an existing prefix '%s'. "
+                        "Prefixes for a single client must not overlap.",
+                        (unsigned char *)prefixes[i]->ptr,
+                        (unsigned char *)collision);
+                    sdsfree(collision);
+                    raxStop(&ri);
+                    return 0;
+                }
+            }
+            raxStop(&ri);
+        }
+        /* Check input has no overlap with itself. */
+        for (size_t j = i + 1; j < numprefix; j++) {
+            if (stringCheckPrefix(prefixes[i]->ptr,sdslen(prefixes[i]->ptr),
+                prefixes[j]->ptr,sdslen(prefixes[j]->ptr)))
+            {
+                addReplyErrorFormat(c,
+                    "Prefix '%s' overlaps with another provided prefix '%s'. "
+                    "Prefixes for a single client must not overlap.",
+                    (unsigned char *)prefixes[i]->ptr,
+                    (unsigned char *)prefixes[j]->ptr);
+                return i;
+            }
+        }
+    }
+    return -1;
+}
+
 /* Set the client 'c' to track the prefix 'prefix'. If the client 'c' is
  * already registered for the specified prefix, no operation is performed. */
 void enableBcastTrackingForPrefix(client *c, char *prefix, size_t plen) {

tests/unit/tracking.tcl

@@ -325,6 +325,24 @@ start_server {tags {"tracking"}} {
         assert {$ping_reply eq {PONG}}
     }
 
+    test {BCAST with prefix collisions throw errors} {
+        set r [redis_client] 
+        catch {$r CLIENT TRACKING ON BCAST PREFIX FOOBAR PREFIX FOO} output
+        assert_match {ERR Prefix 'FOOBAR'*'FOO'*} $output
+
+        catch {$r CLIENT TRACKING ON BCAST PREFIX FOO PREFIX FOOBAR} output
+        assert_match {ERR Prefix 'FOO'*'FOOBAR'*} $output
+
+        $r CLIENT TRACKING ON BCAST PREFIX FOO PREFIX BAR
+        catch {$r CLIENT TRACKING ON BCAST PREFIX FO} output
+        assert_match {ERR Prefix 'FO'*'FOO'*} $output
+
+        catch {$r CLIENT TRACKING ON BCAST PREFIX BARB} output
+        assert_match {ERR Prefix 'BARB'*'BAR'*} $output
+
+        $r CLIENT TRACKING OFF
+    }
+
     test {Tracking gets notification on tracking table key eviction} {
         $rd_redirection HELLO 2
         r CLIENT TRACKING off