Build TLS as a loadable module

* Support BUILD_TLS=module to be loaded as a module via config file or
  command line. e.g. redis-server --loadmodule redis-tls.so
* Updates to redismodule.h to allow it to be used side by side with
  server.h by defining REDISMODULE_CORE_MODULE
* Changes to server.h, redismodule.h and module.c to avoid repeated
  type declarations (gcc 4.8 doesn't like these)
* Add a mechanism for non-ABI neutral modules (ones who include
  server.h) to refuse loading if they detect not being built together with
  redis (release.c)
* Fix wrong signature of RedisModuleDefragFunc, this could break
  compilation of a module, but not the ABI
* Move initialization of listeners in server.c to be after loading
  the modules
* Config TLS after initialization of listeners
* Init cluster after initialization of listeners
* Add TLS module to CI
* Fix a test suite race conditions:
  Now that the listeners are initialized later, it's not sufficient to
  wait for the PID message in the log, we need to wait for the "Server
  Initialized" message.
* Fix issues with moduleconfigs test as a result from start_server
  waiting for "Server Initialized"
* Fix issues with modules/infra test as a result of an additional module
  present

Notes about Sentinel:
Sentinel can't really rely on the tls module, since it uses hiredis to
initiate connections and depends on OpenSSL (won't be able to use any
other connection modules for that), so it was decided that when TLS is
built as a module, sentinel does not support TLS at all.
This means that it keeps using redis_tls_ctx and redis_tls_client_ctx directly.

Example code of config in redis-tls.so(may be use in the future):
RedisModuleString *tls_cfg = NULL;

void tlsInfo(RedisModuleInfoCtx *ctx, int for_crash_report) {
    UNUSED(for_crash_report);
    RedisModule_InfoAddSection(ctx, "");
    RedisModule_InfoAddFieldLongLong(ctx, "var", 42);
}

int tlsCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
{
    if (argc != 2) return RedisModule_WrongArity(ctx);
    return RedisModule_ReplyWithString(ctx, argv[1]);
}

RedisModuleString *getStringConfigCommand(const char *name, void *privdata) {
    REDISMODULE_NOT_USED(name);
    REDISMODULE_NOT_USED(privdata);
    return tls_cfg;
}

int setStringConfigCommand(const char *name, RedisModuleString *new, void *privdata, RedisModuleString **err) {
    REDISMODULE_NOT_USED(name);
    REDISMODULE_NOT_USED(err);
    REDISMODULE_NOT_USED(privdata);
    if (tls_cfg) RedisModule_FreeString(NULL, tls_cfg);
    RedisModule_RetainString(NULL, new);
    tls_cfg = new;
    return REDISMODULE_OK;
}

int RedisModule_OnLoad(void *ctx, RedisModuleString **argv, int argc)
{
    ....
    if (RedisModule_CreateCommand(ctx,"tls",tlsCommand,"",0,0,0) == REDISMODULE_ERR)
        return REDISMODULE_ERR;

    if (RedisModule_RegisterStringConfig(ctx, "cfg", "", REDISMODULE_CONFIG_DEFAULT, getStringConfigCommand, setStringConfigCommand, NULL, NULL) == REDISMODULE_ERR)
        return REDISMODULE_ERR;

    if (RedisModule_LoadConfigs(ctx) == REDISMODULE_ERR) {
        if (tls_cfg) {
            RedisModule_FreeString(ctx, tls_cfg);
            tls_cfg = NULL;
        }
        return REDISMODULE_ERR;
    }
    ...
}

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

1 files changed, 17 insertions, 0 deletions

diff --git a/TLS.md b/TLS.md
index 2d020d0ce..b9bce7edc 100644
--- a/TLS.md
+++ b/TLS.md
@@ -9,8 +9,14 @@ Getting Started
 To build with TLS support you'll need OpenSSL development libraries (e.g.
 libssl-dev on Debian/Ubuntu).
 
+To build TLS support as Redis built-in:
 Run `make BUILD_TLS=yes`.
 
+Or to build TLS as Redis module:
+Run `make BUILD_TLS=module`.
+
+Note that sentinel mode does not support TLS module.
+
 ### Tests
 
 To run Redis test suite with TLS, you'll need TLS support for TCL (i.e.
@@ -22,16 +28,27 @@ To run Redis test suite with TLS, you'll need TLS support for TCL (i.e.
 2. Run `./runtest --tls` or `./runtest-cluster --tls` to run Redis and Redis
    Cluster tests in TLS mode.
 
+3. Run `./runtest --tls-module` or `./runtest-cluster --tls-module` to
+   run Redis and Redis cluster tests in TLS mode with Redis module.
+
 ### Running manually
 
 To manually run a Redis server with TLS mode (assuming `gen-test-certs.sh` was
 invoked so sample certificates/keys are available):
 
+For TLS built-in mode:
     ./src/redis-server --tls-port 6379 --port 0 \
         --tls-cert-file ./tests/tls/redis.crt \
         --tls-key-file ./tests/tls/redis.key \
         --tls-ca-cert-file ./tests/tls/ca.crt
 
+For TLS module mode:
+    ./src/redis-server --tls-port 6379 --port 0 \
+        --tls-cert-file ./tests/tls/redis.crt \
+        --tls-key-file ./tests/tls/redis.key \
+        --tls-ca-cert-file ./tests/tls/ca.crt \
+        --loadmodule src/redis-tls.so
+
 To connect to this Redis server with `redis-cli`:
 
     ./src/redis-cli --tls \