Add RM_SetClientNameById and RM_GetClientNameById (#10839)

Adding Module APIs to let the module read and set the client name of an arbitrary connection.

4 files changed, 64 insertions, 15 deletions

diff --git a/src/module.c b/src/module.c
index 084ee5fd5..f81b2c042 100644
--- a/src/module.c
+++ b/src/module.c
@@ -3373,6 +3373,40 @@ int RM_GetClientInfoById(void *ci, uint64_t id) {
     return modulePopulateClientInfoStructure(ci,client,structver);
 }
 
+/* Returns the name of the client connection with the given ID.
+ *
+ * If the client ID does not exist or if the client has no name associated with
+ * it, NULL is returned. */
+RedisModuleString *RM_GetClientNameById(RedisModuleCtx *ctx, uint64_t id) {
+    client *client = lookupClientByID(id);
+    if (client == NULL || client->name == NULL) return NULL;
+    robj *name = client->name;
+    incrRefCount(name);
+    autoMemoryAdd(ctx, REDISMODULE_AM_STRING, name);
+    return name;
+}
+
+/* Sets the name of the client with the given ID. This is equivalent to the client calling
+ * `CLIENT SETNAME name`.
+ *
+ * Returns REDISMODULE_OK on success. On failure, REDISMODULE_ERR is returned
+ * and errno is set as follows:
+ *
+ * - ENOENT if the client does not exist
+ * - EINVAL if the name contains invalid characters */
+int RM_SetClientNameById(uint64_t id, RedisModuleString *name) {
+    client *client = lookupClientByID(id);
+    if (client == NULL) {
+        errno = ENOENT;
+        return REDISMODULE_ERR;
+    }
+    if (clientSetName(client, name) == C_ERR) {
+        errno = EINVAL;
+        return REDISMODULE_ERR;
+    }
+    return REDISMODULE_OK;
+}
+
 /* Publish a message to subscribers (see PUBLISH command). */
 int RM_PublishMessage(RedisModuleCtx *ctx, RedisModuleString *channel, RedisModuleString *message) {
     UNUSED(ctx);
@@ -12601,6 +12635,8 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(ServerInfoGetFieldUnsigned);
     REGISTER_API(ServerInfoGetFieldDouble);
     REGISTER_API(GetClientInfoById);
+    REGISTER_API(GetClientNameById);
+    REGISTER_API(SetClientNameById);
     REGISTER_API(PublishMessage);
     REGISTER_API(PublishMessageShard);
     REGISTER_API(SubscribeToServerEvent);
diff --git a/src/networking.c b/src/networking.c
index 44aa50642..8cace10d4 100644
--- a/src/networking.c
+++ b/src/networking.c
@@ -2832,18 +2832,9 @@ sds getAllClientsInfoString(int type) {
     return o;
 }
 
-/* This function implements CLIENT SETNAME, including replying to the
- * user with an error if the charset is wrong (in that case C_ERR is
- * returned). If the function succeeded C_OK is returned, and it's up
- * to the caller to send a reply if needed.
- *
- * Setting an empty string as name has the effect of unsetting the
- * currently set name: the client will remain unnamed.
- *
- * This function is also used to implement the HELLO SETNAME option. */
-int clientSetNameOrReply(client *c, robj *name) {
-    int len = sdslen(name->ptr);
-    char *p = name->ptr;
+/* Returns C_OK if the name has been set or C_ERR if the name is invalid. */
+int clientSetName(client *c, robj *name) {
+    int len = (name != NULL) ? sdslen(name->ptr) : 0;
 
     /* Setting the client name to an empty string actually removes
      * the current name. */
@@ -2856,11 +2847,9 @@ int clientSetNameOrReply(client *c, robj *name) {
     /* Otherwise check if the charset is ok. We need to do this otherwise
      * CLIENT LIST format will break. You should always be able to
      * split by space to get the different fields. */
+    char *p = name->ptr;
     for (int j = 0; j < len; j++) {
         if (p[j] < '!' || p[j] > '~') { /* ASCII is assumed. */
-            addReplyError(c,
-                "Client names cannot contain spaces, "
-                "newlines or special characters.");
             return C_ERR;
         }
     }
@@ -2870,6 +2859,25 @@ int clientSetNameOrReply(client *c, robj *name) {
     return C_OK;
 }
 
+/* This function implements CLIENT SETNAME, including replying to the
+ * user with an error if the charset is wrong (in that case C_ERR is
+ * returned). If the function succeeded C_OK is returned, and it's up
+ * to the caller to send a reply if needed.
+ *
+ * Setting an empty string as name has the effect of unsetting the
+ * currently set name: the client will remain unnamed.
+ *
+ * This function is also used to implement the HELLO SETNAME option. */
+int clientSetNameOrReply(client *c, robj *name) {
+    int result = clientSetName(c, name);
+    if (result == C_ERR) {
+        addReplyError(c,
+                      "Client names cannot contain spaces, "
+                      "newlines or special characters.");
+    }
+    return result;
+}
+
 /* Reset the client state to resemble a newly connected client.
  */
 void resetCommand(client *c) {
diff --git a/src/redismodule.h b/src/redismodule.h
index 899bb519d..e36d5f3c0 100644
--- a/src/redismodule.h
+++ b/src/redismodule.h
@@ -1000,6 +1000,8 @@ REDISMODULE_API void (*RedisModule_ChannelAtPosWithFlags)(RedisModuleCtx *ctx, i
 REDISMODULE_API unsigned long long (*RedisModule_GetClientId)(RedisModuleCtx *ctx) REDISMODULE_ATTR;
 REDISMODULE_API RedisModuleString * (*RedisModule_GetClientUserNameById)(RedisModuleCtx *ctx, uint64_t id) REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_GetClientInfoById)(void *ci, uint64_t id) REDISMODULE_ATTR;
+REDISMODULE_API RedisModuleString * (*RedisModule_GetClientNameById)(RedisModuleCtx *ctx, uint64_t id) REDISMODULE_ATTR;
+REDISMODULE_API int (*RedisModule_SetClientNameById)(uint64_t id, RedisModuleString *name) REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_PublishMessage)(RedisModuleCtx *ctx, RedisModuleString *channel, RedisModuleString *message) REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_PublishMessageShard)(RedisModuleCtx *ctx, RedisModuleString *channel, RedisModuleString *message) REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_GetContextFlags)(RedisModuleCtx *ctx) REDISMODULE_ATTR;
@@ -1426,6 +1428,8 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(ServerInfoGetFieldUnsigned);
     REDISMODULE_GET_API(ServerInfoGetFieldDouble);
     REDISMODULE_GET_API(GetClientInfoById);
+    REDISMODULE_GET_API(GetClientNameById);
+    REDISMODULE_GET_API(SetClientNameById);
     REDISMODULE_GET_API(PublishMessage);
     REDISMODULE_GET_API(PublishMessageShard);
     REDISMODULE_GET_API(SubscribeToServerEvent);
diff --git a/src/server.h b/src/server.h
index abaa5f046..6beae765b 100644
--- a/src/server.h
+++ b/src/server.h
@@ -2498,6 +2498,7 @@ char *getClientPeerId(client *client);
 char *getClientSockName(client *client);
 sds catClientInfoString(sds s, client *client);
 sds getAllClientsInfoString(int type);
+int clientSetName(client *c, robj *name);
 void rewriteClientCommandVector(client *c, int argc, ...);
 void rewriteClientCommandArgument(client *c, int i, robj *newval);
 void replaceClientCommandVector(client *c, int argc, robj **argv);