Introduce connection layer framework

Use connTypeRegister() to register a connection type into redis, and
query connection by connectionByType() via type.

With this change, we can hide TLS specified methods into connection
type:
- void tlsInit(void);
- void tlsCleanup(void);
- int tlsConfigure(redisTLSContextConfig *ctx_config);
- int isTlsConfigured(void);

Merge isTlsConfigured & tlsConfigure, use an argument *reconfigure*
to distinguish:
   tlsConfigure(&server.tls_ctx_config)
-> onnTypeConfigure(CONN_TYPE_TLS, &server.tls_ctx_config, 1)

   isTlsConfigured() && tlsConfigure(&server.tls_ctx_config)
-> connTypeConfigure(CONN_TYPE_TLS, &server.tls_ctx_config, 0)

Finally, we can remove USE_OPENSSL from config.c. If redis is built
without TLS, and still run redis with TLS, then redis reports:
 # Missing implement of connection type 1
 # Failed to configure TLS. Check logs for more info.

The log can be optimised, let's leave it in the future. Maybe we can
use connection type as a string.

Although uninitialized fields of a static struct are zero, we still
set them as NULL explicitly in socket.c, let them clear to read & maintain:
    .init = NULL,
    .cleanup = NULL,
    .configure = NULL,

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>

9 files changed, 169 insertions, 36 deletions

diff --git a/src/Makefile b/src/Makefile
index ca08f5b2e..f5736514e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -316,7 +316,7 @@ endif
 
 REDIS_SERVER_NAME=redis-server$(PROG_SUFFIX)
 REDIS_SENTINEL_NAME=redis-sentinel$(PROG_SUFFIX)
-REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o eval.o bio.o rio.o rand.o memtest.o syscheck.o crcspeed.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o lolwut6.o acl.o tracking.o socket.o tls.o sha256.o timeout.o setcpuaffinity.o monotonic.o mt19937-64.o resp_parser.o call_reply.o script_lua.o script.o functions.o function_lua.o commands.o strl.o
+REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o eval.o bio.o rio.o rand.o memtest.o syscheck.o crcspeed.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o lolwut6.o acl.o tracking.o socket.o tls.o sha256.o timeout.o setcpuaffinity.o monotonic.o mt19937-64.o resp_parser.o call_reply.o script_lua.o script.o functions.o function_lua.o commands.o strl.o connection.o
 REDIS_CLI_NAME=redis-cli$(PROG_SUFFIX)
 REDIS_CLI_OBJ=anet.o adlist.o dict.o redis-cli.o zmalloc.o release.o ae.o redisassert.o crcspeed.o crc64.o siphash.o crc16.o monotonic.o cli_common.o mt19937-64.o strl.o
 REDIS_BENCHMARK_NAME=redis-benchmark$(PROG_SUFFIX)
diff --git a/src/config.c b/src/config.c
index f98225cbe..7b8c4b75c 100644
--- a/src/config.c
+++ b/src/config.c
@@ -30,6 +30,7 @@
 
 #include "server.h"
 #include "cluster.h"
+#include "connection.h"
 
 #include <fcntl.h>
 #include <sys/stat.h>
@@ -2571,13 +2572,12 @@ int updateClusterHostname(const char **err) {
     return 1;
 }
 
-#ifdef USE_OPENSSL
 static int applyTlsCfg(const char **err) {
     UNUSED(err);
 
     /* If TLS is enabled, try to configure OpenSSL. */
     if ((server.tls_port || server.tls_replication || server.tls_cluster)
-            && tlsConfigure(&server.tls_ctx_config) == C_ERR) {
+         && connTypeConfigure(CONN_TYPE_TLS, &server.tls_ctx_config, 1) == C_ERR) {
         *err = "Unable to update TLS configuration. Check server logs.";
         return 0;
     }
@@ -2586,7 +2586,7 @@ static int applyTlsCfg(const char **err) {
 
 static int applyTLSPort(const char **err) {
     /* Configure TLS in case it wasn't enabled */
-    if (!isTlsConfigured() && tlsConfigure(&server.tls_ctx_config) == C_ERR) {
+    if (connTypeConfigure(CONN_TYPE_TLS, &server.tls_ctx_config, 0) == C_ERR) {
         *err = "Unable to update TLS configuration. Check server logs.";
         return 0;
     }
@@ -2599,8 +2599,6 @@ static int applyTLSPort(const char **err) {
     return 1;
 }
 
-#endif  /* USE_OPENSSL */
-
 static int setConfigDirOption(standardConfig *config, sds *argv, int argc, const char **err) {
     UNUSED(config);
     if (argc != 1) {
@@ -3109,7 +3107,6 @@ standardConfig static_configs[] = {
     createOffTConfig("auto-aof-rewrite-min-size", NULL, MODIFIABLE_CONFIG, 0, LLONG_MAX, server.aof_rewrite_min_size, 64*1024*1024, MEMORY_CONFIG, NULL, NULL),
     createOffTConfig("loading-process-events-interval-bytes", NULL, MODIFIABLE_CONFIG | HIDDEN_CONFIG, 1024, INT_MAX, server.loading_process_events_interval_bytes, 1024*1024*2, INTEGER_CONFIG, NULL, NULL),
 
-#ifdef USE_OPENSSL
     createIntConfig("tls-port", NULL, MODIFIABLE_CONFIG, 0, 65535, server.tls_port, 0, INTEGER_CONFIG, NULL, applyTLSPort), /* TCP port. */
     createIntConfig("tls-session-cache-size", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.tls_ctx_config.session_cache_size, 20*1024, INTEGER_CONFIG, NULL, applyTlsCfg),
     createIntConfig("tls-session-cache-timeout", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.tls_ctx_config.session_cache_timeout, 300, INTEGER_CONFIG, NULL, applyTlsCfg),
@@ -3130,7 +3127,6 @@ standardConfig static_configs[] = {
     createStringConfig("tls-protocols", NULL, MODIFIABLE_CONFIG, EMPTY_STRING_IS_NULL, server.tls_ctx_config.protocols, NULL, NULL, applyTlsCfg),
     createStringConfig("tls-ciphers", NULL, MODIFIABLE_CONFIG, EMPTY_STRING_IS_NULL, server.tls_ctx_config.ciphers, NULL, NULL, applyTlsCfg),
     createStringConfig("tls-ciphersuites", NULL, MODIFIABLE_CONFIG, EMPTY_STRING_IS_NULL, server.tls_ctx_config.ciphersuites, NULL, NULL, applyTlsCfg),
-#endif
 
     /* Special configs */
     createSpecialConfig("dir", NULL, MODIFIABLE_CONFIG | PROTECTED_CONFIG | DENY_LOADING_CONFIG, setConfigDirOption, getConfigDirOption, rewriteConfigDirOption, NULL),
diff --git a/src/connection.c b/src/connection.c
new file mode 100644
index 000000000..958c9b818
--- /dev/null
+++ b/src/connection.c
@@ -0,0 +1,102 @@
+/* ==========================================================================
+ * connection.c - connection layer framework
+ * --------------------------------------------------------------------------
+ * Copyright (C) 2022  zhenwei pi
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to permit
+ * persons to whom the Software is furnished to do so, subject to the
+ * following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+ * NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.
+ * ==========================================================================
+ */
+
+#include "server.h"
+#include "connection.h"
+
+static ConnectionType *connTypes[CONN_TYPE_MAX];
+
+int connTypeRegister(ConnectionType *ct) {
+    int type = ct->get_type(NULL);
+
+    /* unknown connection type as a fatal error */
+    if (type >= CONN_TYPE_MAX) {
+        serverPanic("Unsupported connection type %d", type);
+    }
+
+    if (connTypes[type] == ct) {
+        serverLog(LL_WARNING, "Connection type %d already registered", type);
+        return C_OK;
+    }
+
+    serverLog(LL_VERBOSE, "Connection type %d registered", type);
+    connTypes[type] = ct;
+
+    if (ct->init) {
+        ct->init();
+    }
+
+    return C_OK;
+}
+
+int connTypeInitialize() {
+    /* currently socket connection type is necessary  */
+    serverAssert(RedisRegisterConnectionTypeSocket() == C_OK);
+
+    /* may fail if without BUILD_TLS=yes */
+    RedisRegisterConnectionTypeTLS();
+
+    return C_OK;
+}
+
+ConnectionType *connectionByType(int type) {
+    ConnectionType *ct;
+
+    serverAssert(type < CONN_TYPE_MAX);
+
+    ct = connTypes[type];
+    if (!ct) {
+        serverLog(LL_WARNING, "Missing implement of connection type %d", type);
+    }
+
+    return ct;
+}
+
+void connTypeCleanup(int type) {
+    ConnectionType *ct = connectionByType(type);
+
+    if (ct && ct->cleanup) {
+        ct->cleanup();
+    }
+}
+
+void connTypeCleanupAll() {
+    int type;
+
+    for (type = 0; type < CONN_TYPE_MAX; type++) {
+        connTypeCleanup(type);
+    }
+}
+
+int connTypeConfigure(int type, void *priv, int reconfigure) {
+    ConnectionType *ct = connectionByType(type);
+
+    if (ct && ct->configure) {
+        return ct->configure(priv, reconfigure);
+    }
+
+    return C_ERR;
+}
diff --git a/src/connection.h b/src/connection.h
index a7c4c0cf4..b3eb6cc20 100644
--- a/src/connection.h
+++ b/src/connection.h
@@ -54,8 +54,9 @@ typedef enum {
 #define CONN_FLAG_CLOSE_SCHEDULED   (1<<0)      /* Closed scheduled by a handler */
 #define CONN_FLAG_WRITE_BARRIER     (1<<1)      /* Write barrier requested */
 
-#define CONN_TYPE_SOCKET            1
-#define CONN_TYPE_TLS               2
+#define CONN_TYPE_SOCKET            0
+#define CONN_TYPE_TLS               1
+#define CONN_TYPE_MAX               2
 
 typedef void (*ConnectionCallbackFunc)(struct connection *conn);
 
@@ -63,6 +64,11 @@ typedef struct ConnectionType {
     /* connection type */
     int (*get_type)(struct connection *conn);
 
+    /* connection type initialize & finalize & configure */
+    void (*init)(void); /* auto-call during register */
+    void (*cleanup)(void);
+    int (*configure)(void *priv, int reconfigure);
+
     /* ae & accept & listen & error & address handler */
     void (*ae_handler)(struct aeEventLoop *el, int fd, void *clientData, int mask);
     int (*addr)(connection *conn, char *ip, size_t ip_len, int *port, int remote);
@@ -329,4 +335,24 @@ sds connTLSGetPeerCert(connection *conn);
 int tlsHasPendingData();
 int tlsProcessPendingData();
 
+/* Initialize the redis connection framework */
+int connTypeInitialize();
+
+/* Register a connection type into redis connection framework */
+int connTypeRegister(ConnectionType *ct);
+
+/* Configure a connection type. A typical case is to configure TLS.
+ * @priv is connection type specified,
+ * @reconfigure is boolean type to specify if overwrite the original config */
+int connTypeConfigure(int type, void *priv, int reconfigure);
+
+/* Cleanup a connection type. A typical case is to cleanup TLS. */
+void connTypeCleanup(int type);
+
+/* Walk all the connection type, and cleanup them all if possible */
+void connTypeCleanupAll();
+
+int RedisRegisterConnectionTypeSocket();
+int RedisRegisterConnectionTypeTLS();
+
 #endif  /* __REDIS_CONNECTION_H */
diff --git a/src/sentinel.c b/src/sentinel.c
index 7f2ef7e16..b1c180d41 100644
--- a/src/sentinel.c
+++ b/src/sentinel.c
@@ -848,7 +848,7 @@ void sentinelRunPendingScripts(void) {
             sj->pid = 0;
         } else if (pid == 0) {
             /* Child */
-            tlsCleanup();
+            connTypeCleanupAll();
             execve(sj->argv[0],sj->argv,environ);
             /* If we are here an error occurred. */
             _exit(2); /* Don't retry execution. */
diff --git a/src/server.c b/src/server.c
index f8dbb0972..fe8d9bb81 100644
--- a/src/server.c
+++ b/src/server.c
@@ -2447,7 +2447,7 @@ void initServer(void) {
     }
 
     if ((server.tls_port || server.tls_replication || server.tls_cluster)
-                && tlsConfigure(&server.tls_ctx_config) == C_ERR) {
+         && connTypeConfigure(CONN_TYPE_TLS, &server.tls_ctx_config, 1) == C_ERR) {
         serverLog(LL_WARNING, "Failed to configure TLS. Check logs for more info.");
         exit(1);
     }
@@ -6944,7 +6944,7 @@ int main(int argc, char **argv) {
     ACLInit(); /* The ACL subsystem must be initialized ASAP because the
                   basic networking code and client creation depends on it. */
     moduleInitModulesSystem();
-    tlsInit();
+    connTypeInitialize();
 
     /* Store the executable path and arguments in a safe place in order
      * to be able to restart the server later. */
diff --git a/src/server.h b/src/server.h
index c0f68c73f..ffcc7aff2 100644
--- a/src/server.h
+++ b/src/server.h
@@ -3579,12 +3579,6 @@ void swapMainDbWithTempDb(redisDb *tempDb);
         _serverLog(level, __VA_ARGS__);\
     } while(0)
 
-/* TLS stuff */
-void tlsInit(void);
-void tlsCleanup(void);
-int tlsConfigure(redisTLSContextConfig *ctx_config);
-int isTlsConfigured(void);
-
 #define redisDebug(fmt, ...) \
     printf("DEBUG %s:%d > " fmt "\n", __FILE__, __LINE__, __VA_ARGS__)
 #define redisDebugMark() \
diff --git a/src/socket.c b/src/socket.c
index 2ef29e1d4..d93882cce 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -352,6 +352,11 @@ ConnectionType CT_Socket = {
     /* connection type */
     .get_type = connSocketGetType,
 
+    /* connection type initialize & finalize & configure */
+    .init = NULL,
+    .cleanup = NULL,
+    .configure = NULL,
+
     /* ae & accept & listen & error & address handler */
     .ae_handler = connSocketEventHandler,
     .addr = connSocketAddr,
@@ -409,3 +414,7 @@ int connRecvTimeout(connection *conn, long long ms) {
     return anetRecvTimeout(NULL, conn->fd, ms);
 }
 
+int RedisRegisterConnectionTypeSocket()
+{
+    return connTypeRegister(&CT_Socket);
+}
diff --git a/src/tls.c b/src/tls.c
index 442824dcd..4078fd307 100644
--- a/src/tls.c
+++ b/src/tls.c
@@ -141,7 +141,7 @@ static void initCryptoLocks(void) {
 }
 #endif /* USE_CRYPTO_LOCKS */
 
-void tlsInit(void) {
+static void tlsInit(void) {
     /* Enable configuring OpenSSL using the standard openssl.cnf
      * OPENSSL_config()/OPENSSL_init_crypto() should be the first 
      * call to the OpenSSL* library.
@@ -169,7 +169,7 @@ void tlsInit(void) {
     pending_list = listCreate();
 }
 
-void tlsCleanup(void) {
+static void tlsCleanup(void) {
     if (redis_tls_ctx) {
         SSL_CTX_free(redis_tls_ctx);
         redis_tls_ctx = NULL;
@@ -281,12 +281,20 @@ error:
 
 /* Attempt to configure/reconfigure TLS. This operation is atomic and will
  * leave the SSL_CTX unchanged if fails.
+ * @priv: config of redisTLSContextConfig.
+ * @reconfigure: if true, ignore the previous configure; if false, only
+ *               configure from @ctx_config if redis_tls_ctx is NULL.
  */
-int tlsConfigure(redisTLSContextConfig *ctx_config) {
+static int tlsConfigure(void *priv, int reconfigure) {
+    redisTLSContextConfig *ctx_config = (redisTLSContextConfig *)priv;
     char errbuf[256];
     SSL_CTX *ctx = NULL;
     SSL_CTX *client_ctx = NULL;
 
+    if (!reconfigure && redis_tls_ctx) {
+        return C_OK;
+    }
+
     if (!ctx_config->cert_file) {
         serverLog(LL_WARNING, "No tls-cert-file configured!");
         goto error;
@@ -406,12 +414,6 @@ error:
     return C_ERR;
 }
 
-/* Return 1 if TLS was already configured, 0 otherwise.
- */
-int isTlsConfigured(void) {
-    return redis_tls_ctx != NULL;
-}
-
 #ifdef TLS_DEBUGGING
 #define TLSCONN_DEBUG(fmt, ...) \
     serverLog(LL_DEBUG, "TLSCONN: " fmt, __VA_ARGS__)
@@ -1066,6 +1068,11 @@ ConnectionType CT_TLS = {
     /* connection type */
     .get_type = connTLSGetType,
 
+    /* connection type initialize & finalize & configure */
+    .init = tlsInit,
+    .cleanup = tlsCleanup,
+    .configure = tlsConfigure,
+
     /* ae & accept & listen & error & address handler */
     .ae_handler = tlsEventHandler,
     .addr = connTLSAddr,
@@ -1090,17 +1097,16 @@ ConnectionType CT_TLS = {
     .sync_readline = connTLSSyncReadLine,
 };
 
-#else   /* USE_OPENSSL */
-
-void tlsInit(void) {
+int RedisRegisterConnectionTypeTLS()
+{
+    return connTypeRegister(&CT_TLS);
 }
 
-void tlsCleanup(void) {
-}
+#else   /* USE_OPENSSL */
 
-int tlsConfigure(redisTLSContextConfig *ctx_config) {
-    UNUSED(ctx_config);
-    return C_OK;
+int RedisRegisterConnectionTypeTLS()
+{
+    return C_ERR;
 }
 
 connection *connCreateTLS(void) {