avoid using sendfile if tls-replication is enabled

this obviously broke the tests, but went unnoticed so far since tls
wasn't often tested.

src/replication.c

@@ -1032,39 +1032,46 @@ void sendBulkToSlave(connection *conn) {
         }
     }
 
-    /* If the preamble was already transferred, send the RDB bulk data. */
+    /* If the preamble was already transferred, send the RDB bulk data.
+     * try to use sendfile system call if supported, unless tls is enabled.
+     * fallback to normal read+write otherwise. */
+    nwritten = 0;
 #if HAVE_SENDFILE
-    if ((nwritten = redis_sendfile(conn->fd,slave->repldbfd,
-        slave->repldboff,PROTO_IOBUF_LEN)) == -1)
-    {
-        if (errno != EAGAIN) {
-            serverLog(LL_WARNING,"Sendfile error sending DB to replica: %s",
-                strerror(errno));
-            freeClient(slave);
+    if (!server.tls_replication) {
+        if ((nwritten = redis_sendfile(conn->fd,slave->repldbfd,
+            slave->repldboff,PROTO_IOBUF_LEN)) == -1)
+        {
+            if (errno != EAGAIN) {
+                serverLog(LL_WARNING,"Sendfile error sending DB to replica: %s",
+                    strerror(errno));
+                freeClient(slave);
+            }
+            return;
         }
-        return;
     }
-#else
-    ssize_t buflen;
-    char buf[PROTO_IOBUF_LEN];
-
-    lseek(slave->repldbfd,slave->repldboff,SEEK_SET);
-    buflen = read(slave->repldbfd,buf,PROTO_IOBUF_LEN);
-    if (buflen <= 0) {
-        serverLog(LL_WARNING,"Read error sending DB to replica: %s",
-            (buflen == 0) ? "premature EOF" : strerror(errno));
-        freeClient(slave);
-        return;
-    }
-    if ((nwritten = connWrite(conn,buf,buflen)) == -1) {
-        if (connGetState(conn) != CONN_STATE_CONNECTED) {
-            serverLog(LL_WARNING,"Write error sending DB to replica: %s",
-                connGetLastError(conn));
+#endif
+    if (!nwritten) {
+        ssize_t buflen;
+        char buf[PROTO_IOBUF_LEN];
+
+        lseek(slave->repldbfd,slave->repldboff,SEEK_SET);
+        buflen = read(slave->repldbfd,buf,PROTO_IOBUF_LEN);
+        if (buflen <= 0) {
+            serverLog(LL_WARNING,"Read error sending DB to replica: %s",
+                (buflen == 0) ? "premature EOF" : strerror(errno));
             freeClient(slave);
+            return;
+        }
+        if ((nwritten = connWrite(conn,buf,buflen)) == -1) {
+            if (connGetState(conn) != CONN_STATE_CONNECTED) {
+                serverLog(LL_WARNING,"Write error sending DB to replica: %s",
+                    connGetLastError(conn));
+                freeClient(slave);
+            }
+            return;
         }
-        return;
     }
-#endif
+
     slave->repldboff += nwritten;
     server.stat_net_output_bytes += nwritten;
     if (slave->repldboff == slave->repldbsize) {