Upload dockerd configuration over HTTP

Author: killenheladagen

README.md

@@ -209,6 +209,21 @@ has a significantly higher inference time when using a small and slow SD card.
 To get more informed about specifications, check the
 [SD Card Standards](https://www.sdcard.org/developers/sd-standard-overview/).
 
+## Additional configuration
+
+For even more control over the dockerd daemon,
+a configuration file can be uploaded to the device using HTTP.
+
+```sh
+curl --anyauth -u "root:$DEVICE_PASSWORD" -F [email protected] -X POST \
+  http://$DEVICE_IP/local/dockerdwrapper/daemon.json
+```
+
+The complete specification of this file can be found in the Docker reference, in section
+[Daemon configuration file](https://docs.docker.com/reference/cli/dockerd/#daemon-configuration-file).
+
+The dockerd service will automatically restart after a new configuration file has been uploaded.
+
 ## Using the Docker ACAP
 
 The Docker ACAP does not contain the docker client binary. This means that all

app/app_paths.h

@@ -2,3 +2,5 @@
 
 #define APP_DIRECTORY "/usr/local/packages/" APP_NAME
 #define APP_LOCALDATA APP_DIRECTORY "/localdata"
+
+#define DAEMON_JSON "daemon.json"

app/dockerdwrapper.c

@@ -487,7 +487,7 @@ static bool start_dockerd(const struct settings* settings, struct app_state* app
                               args_len - args_offset,
                               "%s %s",
                               "dockerd",
-                              "--config-file " APP_LOCALDATA "/daemon.json");
+                              "--config-file " APP_LOCALDATA "/" DAEMON_JSON);
 
     g_strlcpy(msg, "Starting dockerd", msg_len);
 

app/html/index.html

@@ -15,5 +15,10 @@ <h2>Remove TLS certificates and keys</h2>
       curl --anyauth -u $DEVICE_USER:$DEVICE_PASSWORD -X DELETE http://$DEVICE_IP/local/dockerdwrapper/server-cert.pem<br>
       curl --anyauth -u $DEVICE_USER:$DEVICE_PASSWORD -X DELETE http://$DEVICE_IP/local/dockerdwrapper/server-key.pem<br>
     </code>
+    <h2>Check and upload dockerd configuration</h2>
+    <code>
+      curl --anyauth -u $DEVICE_USER:$DEVICE_PASSWORD http://$DEVICE_IP/local/dockerdwrapper/daemon.json<br>
+      curl --anyauth -u $DEVICE_USER:$DEVICE_PASSWORD -F [email protected] -X POST http://$DEVICE_IP/local/dockerdwrapper/daemon.json.pem<br>
+    </code>
   </body>
 </html>

app/http_request.c

@@ -8,6 +8,7 @@
 #define HTTP_200_OK                    "200 OK"
 #define HTTP_204_NO_CONTENT            "204 No Content"
 #define HTTP_400_BAD_REQUEST           "400 Bad Request"
+#define HTTP_403_FORBIDDEN             "403 Forbidden"
 #define HTTP_404_NOT_FOUND             "404 Not Found"
 #define HTTP_405_METHOD_NOT_ALLOWED    "405 Method Not Allowed"
 #define HTTP_422_UNPROCESSABLE_CONTENT "422 Unprocessable Content"
@@ -93,6 +94,25 @@ static void post_request(FCGX_Request* request,
         log_error("Failed to remove %s: %s", temp_file, strerror(errno));
 }
 
+static void get_request(FCGX_Request* request, const char* filename) {
+    if (strcmp(filename, DAEMON_JSON) != 0) {
+        response_msg(request, HTTP_403_FORBIDDEN, "Resource is write-only");
+        return;
+    }
+
+    g_autofree char* contents = NULL;
+    gsize length;
+    GError* error = NULL;
+    const char* full_path = APP_LOCALDATA "/" DAEMON_JSON;
+    if (!g_file_get_contents(full_path, &contents, &length, &error)) {
+        log_error("Failed to read %s: %s.", full_path, error->message);
+        response_msg(request, HTTP_404_NOT_FOUND, "Could not read file");
+        return;
+    }
+
+    response(request, HTTP_200_OK, "application/json", contents);
+}
+
 static void delete_request(FCGX_Request* request, const char* filename) {
     if (!exists_in_localdata(filename))
         response_msg(request, HTTP_404_NOT_FOUND, "File not found in localdata");
@@ -130,6 +150,8 @@ void http_request_callback(void* request_void_ptr, void* restart_dockerd_context
 
         if (strcmp(method, "POST") == 0)
             post_request(request, filename, restart_dockerd_context_void_ptr);
+        else if (strcmp(method, "GET") == 0)
+            get_request(request, filename);
         else if (strcmp(method, "DELETE") == 0)
             delete_request(request, filename);
         else

app/manifest.json

@@ -58,6 +58,11 @@
             ],
             "settingPage": "index.html",
             "httpConfig": [
+                {
+                    "access": "admin",
+                    "name": "daemon.json",
+                    "type": "fastCgi"
+                },
                 {
                     "access": "admin",
                     "name": "ca.pem",