MXS-1220: Allow binding to a specific address

The admin interface can now bind to a specific network interface.

Documentation/Getting-Started/Configuration-Guide.md

@@ -172,6 +172,12 @@ write or modify the data in the backend server. The default is 2 seconds.
 auth_write_timeout=10
 ```
 
+#### `admin_host`
+
+The network interface where the HTTP admin interface listens on. The default
+value is the IPv6 address `::` which listens on all available network
+interfaces.
+
 #### `admin_port`
 
 The port where the HTTP admin interface listens on. The default value is port

include/maxscale/config.h

@@ -28,10 +28,12 @@ MXS_BEGIN_DECLS
 
 /** Default port where the REST API listens */
 #define DEFAULT_ADMIN_HTTP_PORT 8989
+#define DEFAULT_ADMIN_HOST      "::"
 
 #define _RELEASE_STR_LENGTH     256     /**< release len */
 #define MAX_ADMIN_USER_LEN      1024
 #define MAX_ADMIN_PW_LEN        1024
+#define MAX_ADMIN_HOST_LEN      1024
 
 /**
  * Common configuration parameters names
@@ -42,6 +44,7 @@ MXS_BEGIN_DECLS
  */
 extern const char CN_ADDRESS[];
 extern const char CN_ADMIN_AUTH[];
+extern const char CN_ADMIN_HOST[];
 extern const char CN_ADMIN_PASSWORD[];
 extern const char CN_ADMIN_PORT[];
 extern const char CN_ADMIN_USER[];
@@ -156,6 +159,7 @@ typedef struct
     char*         qc_args;                             /**< Arguments for the query classifier */
     char          admin_user[MAX_ADMIN_USER_LEN];      /**< Admin interface user */
     char          admin_password[MAX_ADMIN_PW_LEN];    /**< Admin interface password */
+    char          admin_host[MAX_ADMIN_HOST_LEN];      /**< Admin interface host */
     uint16_t      admin_port;                          /**< Admin interface port */
     bool          admin_auth;                          /**< Admin interface authentication */
 } MXS_CONFIG;

server/core/admin.cc

@@ -11,11 +11,17 @@
  * Public License.
  */
 
+/**
+ * @file The embedded HTTP protocol administrative interface
+ */
 #include "maxscale/admin.hh"
 
 #include <climits>
 #include <new>
 #include <microhttpd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
 
 #include <maxscale/atomic.h>
 #include <maxscale/debug.h>
@@ -180,16 +186,64 @@ int handle_client(void *cls,
     return client->process(url, method, upload_data, upload_data_size);
 }
 
+static bool host_to_sockaddr(const char* host, uint16_t port, struct sockaddr_storage* addr)
+{
+    struct addrinfo *ai = NULL, hint = {};
+    int rc;
+    hint.ai_socktype = SOCK_STREAM;
+    hint.ai_family = AF_UNSPEC;
+    hint.ai_flags = AI_ALL;
+
+    if ((rc = getaddrinfo(host, NULL, &hint, &ai)) != 0)
+    {
+        MXS_ERROR("Failed to obtain address for host %s: %s", host, gai_strerror(rc));
+        return false;
+    }
+
+    /* Take the first one */
+    if (ai)
+    {
+        memcpy(addr, ai->ai_addr, ai->ai_addrlen);
+
+        if (addr->ss_family == AF_INET)
+        {
+            struct sockaddr_in *ip = (struct sockaddr_in*)addr;
+            ip->sin_port = htons(port);
+        }
+        else if (addr->ss_family == AF_INET6)
+        {
+            struct sockaddr_in6 *ip = (struct sockaddr_in6*)addr;
+            ip->sin6_port = htons(port);
+        }
+    }
+
+    freeaddrinfo(ai);
+    return true;
+}
+
 bool mxs_admin_init()
 {
-    http_daemon = MHD_start_daemon(MHD_USE_EPOLL_INTERNALLY_LINUX_ONLY | MHD_USE_DUAL_STACK,
+    struct sockaddr_storage addr;
-                                   config_get_global_options()->admin_port,
-                                   NULL, NULL,
-                                   handle_client, NULL,
-                                   MHD_OPTION_NOTIFY_COMPLETED, close_client, NULL,
-                                   MHD_OPTION_END);
-    return http_daemon != NULL;
 
+    if (host_to_sockaddr(config_get_global_options()->admin_host,
+                         config_get_global_options()->admin_port,
+                         &addr))
+    {
+        int options = MHD_USE_EPOLL_INTERNALLY_LINUX_ONLY;
+
+        if (addr.ss_family == AF_INET6)
+        {
+            options |= MHD_USE_DUAL_STACK;
+        }
+
+        // The port argument is ignored and the port in the struct sockaddr is used instead
+        http_daemon = MHD_start_daemon(options, 0,  NULL, NULL, handle_client, NULL,
+                                       MHD_OPTION_NOTIFY_COMPLETED, close_client, NULL,
+                                       MHD_OPTION_SOCK_ADDR, &addr,
+                                       MHD_OPTION_END);
+    }
+
+    return http_daemon != NULL;
 }
 
 void mxs_admin_shutdown()

server/core/config.cc

@@ -53,6 +53,7 @@ using std::string;
 
 const char CN_ADDRESS[]                       = "address";
 const char CN_ADMIN_AUTH[]                    = "admin_auth";
+const char CN_ADMIN_HOST[]                    = "admin_host";
 const char CN_ADMIN_PASSWORD[]                = "admin_password";
 const char CN_ADMIN_PORT[]                    = "admin_port";
 const char CN_ADMIN_USER[]                    = "admin_user";
@@ -1520,6 +1521,10 @@ handle_global_item(const char *name, const char *value)
     {
         gateway.admin_port = atoi(value);
     }
+    else if (strcmp(name, CN_ADMIN_HOST) == 0)
+    {
+        strcpy(gateway.admin_host, value);
+    }
     else if (strcmp(name, CN_ADMIN_AUTH) == 0)
     {
         gateway.admin_auth = config_truth_value(value);
@@ -1746,6 +1751,7 @@ global_defaults()
     gateway.skip_permission_checks = false;
     gateway.admin_port = DEFAULT_ADMIN_HTTP_PORT;
     gateway.admin_auth = false;
+    strcpy(gateway.admin_host, DEFAULT_ADMIN_HOST);
     strcpy(gateway.admin_user, INET_DEFAULT_USERNAME);
     strcpy(gateway.admin_password, INET_DEFAULT_PASSWORD);
 

server/core/gateway.cc

@@ -1982,6 +1982,18 @@ int main(int argc, char **argv)
         }
     }
 
+    if (mxs_admin_init())
+    {
+        MXS_NOTICE("Started REST API on [%s]:%u", cnf->admin_host, cnf->admin_port);
+    }
+    else
+    {
+        const char* logerr = "Failed to initialize admin interface";
+        print_log_n_stderr(true, true, logerr, logerr, 0);
+        rc = MAXSCALE_INTERNALERROR;
+        goto return_main;
+    }
+
     MXS_NOTICE("MaxScale started with %d server threads.", config_threadcount());
     /**
      * Successful start, notify the parent process that it can exit.
@@ -1992,14 +2004,6 @@ int main(int argc, char **argv)
         write_child_exit_code(daemon_pipe[1], rc);
     }
 
-    if (!mxs_admin_init())
-    {
-        const char* logerr = "Failed to initialize admin interface";
-        print_log_n_stderr(true, true, logerr, logerr, 0);
-        rc = MAXSCALE_INTERNALERROR;
-        goto return_main;
-    }
-
     /*<
      * Run worker 0 in the main thread.
      */