feat: Dynamic upstream DNS resolution for proxy hosts

backend/internal/nginx.js

@@ -9,6 +9,30 @@ import { debug, nginx as logger } from "../logger.js";
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = dirname(__filename);
 
+/**
+ * Returns the DNS resolver address to use in nginx `resolver` directives.
+ * Priority: NGINX_RESOLVER env var → first nameserver in /etc/resolv.conf → 127.0.0.11
+ *
+ * @returns {String}
+ */
+const getUpstreamResolver = () => {
+	if (process.env.NGINX_RESOLVER) {
+		return process.env.NGINX_RESOLVER;
+	}
+
+	try {
+		const resolvConf = fs.readFileSync("/etc/resolv.conf", { encoding: "utf8" });
+		const match = resolvConf.match(/^\s*nameserver\s+(\S+)/m);
+		if (match) {
+			return match[1];
+		}
+	} catch (_err) {
+		// ignore — fall through to default
+	}
+
+	return "127.0.0.11";
+};
+
 const internalNginx = {
 	/**
 	 * This will:
@@ -160,6 +184,8 @@ const internalNginx = {
 						{ http2_support: host.http2_support },
 						{ hsts_enabled: host.hsts_enabled },
 						{ hsts_subdomains: host.hsts_subdomains },
+						{ dynamic_upstream_resolve: host.dynamic_upstream_resolve },
+						{ upstream_resolver: host.upstream_resolver },
 						{ access_list: host.access_list },
 						{ certificate: host.certificate },
 						host.locations[i],
@@ -241,6 +267,9 @@ const internalNginx = {
 			// Set the IPv6 setting for the host
 			host.ipv6 = internalNginx.ipv6Enabled();
 
+			// Set the upstream resolver (used when dynamic_upstream_resolve is enabled)
+			host.upstream_resolver = getUpstreamResolver();
+
 			locationsPromise.then(() => {
 				renderEngine
 					.parseAndRender(template, host)

backend/migrations/20260131163528_trust_forwarded_proto.js

@@ -10,7 +10,7 @@ const migrateName = "trust_forwarded_proto";
  * @param   {Object} knex
  * @returns {Promise}
  */
-const up = (knex) => {
+const up = function (knex) {
     logger.info(`[${migrateName}] Migrating Up...`);
 
     return knex.schema
@@ -28,7 +28,7 @@ const up = (knex) => {
  * @param   {Object} knex
  * @returns {Promise}
  */
-const down = (knex) => {
+const down = function (knex) {
     logger.info(`[${migrateName}] Migrating Down...`);
 
     return knex.schema

backend/migrations/20260414000000_dynamic_upstream_resolve.js

@@ -0,0 +1,43 @@
+import { migrate as logger } from "../logger.js";
+
+const migrateName = "dynamic_upstream_resolve";
+
+/**
+ * Migrate
+ *
+ * @see http://knexjs.org/#Schema
+ *
+ * @param   {Object} knex
+ * @returns {Promise}
+ */
+const up = (knex) => {
+    logger.info(`[${migrateName}] Migrating Up...`);
+
+    return knex.schema
+        .alterTable('proxy_host', (table) => {
+            table.tinyint('dynamic_upstream_resolve').notNullable().defaultTo(0);
+        })
+        .then(() => {
+            logger.info(`[${migrateName}] proxy_host Table altered`);
+        });
+};
+
+/**
+ * Undo Migrate
+ *
+ * @param   {Object} knex
+ * @returns {Promise}
+ */
+const down = (knex) => {
+    logger.info(`[${migrateName}] Migrating Down...`);
+
+    return knex.schema
+        .alterTable('proxy_host', (table) => {
+            table.dropColumn('dynamic_upstream_resolve');
+        })
+        .then(() => {
+            logger.info(`[${migrateName}] proxy_host Table altered`);
+        });
+};
+
+export { up, down };

backend/models/proxy_host.js

@@ -21,6 +21,7 @@ const boolFields = [
 	"enabled",
 	"hsts_enabled",
 	"hsts_subdomains",
+	"dynamic_upstream_resolve",
 	"trust_forwarded_proto",
 ];
 

backend/schema/components/proxy-host-object.json

@@ -22,6 +22,7 @@
 		"enabled",
 		"locations",
 		"hsts_enabled",
+		"dynamic_upstream_resolve",
 		"hsts_subdomains",
 		"trust_forwarded_proto"
 	],
@@ -147,6 +148,11 @@
 			"description": "Trust the forwarded headers",
 			"example": false
 		},
+		"dynamic_upstream_resolve": {
+			"type": "boolean",
+			"description": "Resolve upstream host dynamically using resolver directive",
+			"example": false
+		},
 		"certificate": {
 			"oneOf": [
 				{

backend/schema/paths/nginx/proxy-hosts/get.json

@@ -53,6 +53,7 @@
 										"nginx_err": null
 									},
 									"allow_websocket_upgrade": false,
+									"dynamic_upstream_resolve": false,
 									"http2_support": false,
 									"forward_scheme": "http",
 									"enabled": true,

backend/schema/paths/nginx/proxy-hosts/hostID/get.json

@@ -50,6 +50,7 @@
 									"nginx_err": null
 								},
 								"allow_websocket_upgrade": false,
+								"dynamic_upstream_resolve": false,								
 								"http2_support": false,
 								"forward_scheme": "http",
 								"enabled": true,

backend/schema/paths/nginx/proxy-hosts/hostID/put.json

@@ -59,6 +59,9 @@
 						"trust_forwarded_proto": {
     						"$ref": "../../../../components/proxy-host-object.json#/properties/trust_forwarded_proto"
 						},
+						"dynamic_upstream_resolve": {
+							"$ref": "../../../../components/proxy-host-object.json#/properties/dynamic_upstream_resolve"
+						},
 						"http2_support": {
 							"$ref": "../../../../components/proxy-host-object.json#/properties/http2_support"
 						},
@@ -119,6 +122,7 @@
 									"nginx_err": null
 								},
 								"allow_websocket_upgrade": false,
+								"dynamic_upstream_resolve": false,								
 								"http2_support": false,
 								"forward_scheme": "http",
 								"enabled": true,

backend/schema/paths/nginx/proxy-hosts/post.json

@@ -51,6 +51,9 @@
 						"trust_forwarded_proto": {
     						"$ref": "../../../components/proxy-host-object.json#/properties/trust_forwarded_proto"
 						},
+						"dynamic_upstream_resolve": {
+							"$ref": "../../../components/proxy-host-object.json#/properties/dynamic_upstream_resolve"
+						},
 						"http2_support": {
 							"$ref": "../../../components/proxy-host-object.json#/properties/http2_support"
 						},
@@ -116,6 +119,7 @@
 								"advanced_config": "",
 								"meta": {},
 								"allow_websocket_upgrade": false,
+								"dynamic_upstream_resolve": false,								
 								"http2_support": false,
 								"forward_scheme": "http",
 								"enabled": true,

backend/templates/_location.conf

@@ -7,7 +7,12 @@
     proxy_set_header X-Forwarded-For    $remote_addr;
     proxy_set_header X-Real-IP		$remote_addr;
 
+    {% if dynamic_upstream_resolve == 1 or dynamic_upstream_resolve == true %}
+    set $upstream_host "{{ forward_host }}";
+    proxy_pass       {{ forward_scheme }}://$upstream_host:{{ forward_port }}{{ forward_path }};
+    {% else %}
     proxy_pass       {{ forward_scheme }}://{{ forward_host }}:{{ forward_port }}{{ forward_path }};
+    {% endif %}
 
     {% include "_access.conf" %}
     {% include "_assets.conf" %}

backend/templates/proxy_host.conf

@@ -9,6 +9,10 @@ server {
   set $server         "{{ forward_host }}";
   set $port           {{ forward_port }};
 
+  {% if dynamic_upstream_resolve == 1 or dynamic_upstream_resolve == true %}
+  resolver {{ upstream_resolver }} valid=10s;
+  {% endif %}
+
 {% include "_listen.conf" %}
 {% include "_certificates.conf" %}
 {% include "_assets.conf" %}

frontend/src/api/backend/models.ts

@@ -128,6 +128,7 @@ export interface ProxyHost {
 	hstsEnabled: boolean;
 	hstsSubdomains: boolean;
 	trustForwardedProto: boolean;
+	dynamicUpstreamResolve: boolean;
 	// Expansions:
 	owner?: User;
 	accessList?: AccessList;

frontend/src/hooks/useProxyHost.ts

@@ -25,6 +25,7 @@ const fetchProxyHost = (id: number | "new") => {
 			hstsEnabled: false,
 			hstsSubdomains: false,
 			trustForwardedProto: false,
+			dynamicUpstreamResolve: false,
 		} as ProxyHost);
 	}
 	return getProxyHost(id, ["owner"]);

frontend/src/locale/src/en.json

@@ -437,6 +437,12 @@
 	"host.flags.websockets-upgrade": {
 		"defaultMessage": "Websockets Support"
 	},
+	"host.flags.dynamic-upstream-resolve": {
+		"defaultMessage": "Dynamic Upstream Resolve"
+	},
+	"host.flags.dynamic-upstream-resolve-description": {
+		"defaultMessage": "Resolves upstream hostnames dynamically at request time. The DNS resolver is auto-detected from /etc/resolv.conf, or can be overridden with the NGINX_RESOLVER environment variable. Defaults to 127.0.0.11 (Docker bridge DNS) if no resolver is found."
+	},
 	"host.forward-port": {
 		"defaultMessage": "Forward Port"
 	},

frontend/src/locale/src/fr.json

@@ -437,6 +437,12 @@
 	"host.flags.websockets-upgrade": {
 		"defaultMessage": "Prise en charge de Websockets"
 	},
+	"host.flags.dynamic-upstream-resolve": {
+		"defaultMessage": "Résolution dynamique de l'upstream"
+	},
+	"host.flags.dynamic-upstream-resolve-description": {
+		"defaultMessage": "Résout les noms d'hôtes upstream dynamiquement à chaque requête. Le résolveur DNS est détecté automatiquement depuis /etc/resolv.conf, ou peut être remplacé via la variable d'environnement NGINX_RESOLVER. Par défaut : 127.0.0.11 (DNS Docker bridge) si aucun résolveur n'est trouvé."
+	},
 	"host.forward-port": {
 		"defaultMessage": "Port de redirection"
 	},

frontend/src/modals/ProxyHostModal.tsx

@@ -89,6 +89,7 @@ const ProxyHostModal = EasyModal.create(({ id, visible, remove }: Props) => {
 							hstsEnabled: data?.hstsEnabled || false,
 							hstsSubdomains: data?.hstsSubdomains || false,
 							trustForwardedProto: data?.trustForwardedProto || false,
+							dynamicUpstreamResolve: data?.dynamicUpstreamResolve || false,
 							// Advanced tab
 							advancedConfig: data?.advancedConfig || "",
 							meta: data?.meta || {},
@@ -328,6 +329,32 @@ const ProxyHostModal = EasyModal.create(({ id, visible, remove }: Props) => {
 																</span>
 															</label>
 														</div>
+														<div>
+															<label className="row" htmlFor="dynamicUpstreamResolve">
+																<span className="col">
+																	<T id="host.flags.dynamic-upstream-resolve" />
+																	<div className="small text-muted mt-1">
+																		<T id="host.flags.dynamic-upstream-resolve-description" />
+																	</div>
+																</span>
+																<span className="col-auto">
+																	<Field name="dynamicUpstreamResolve" type="checkbox">
+																		{({ field }: any) => (
+																			<label className="form-check form-check-single form-switch">
+																				<input
+																					{...field}
+																					id="dynamicUpstreamResolve"
+																					className={cn("form-check-input", {
+																						"bg-lime": field.checked,
+																					})}
+																					type="checkbox"
+																				/>
+																			</label>
+																		)}
+																	</Field>
+																</span>
+															</label>
+														</div>
 													</div>
 												</div>
 											</div>

test/cypress/e2e/api/ProxyHosts.cy.js

@@ -24,15 +24,16 @@ describe('Proxy Hosts endpoints', () => {
 				meta:           {
 					dns_challenge: false
 				},
-				advanced_config:         '',
-				locations:               [],
-				block_exploits:          false,
-				caching_enabled:         false,
-				allow_websocket_upgrade: false,
-				http2_support:           false,
-				hsts_enabled:            false,
-				hsts_subdomains:         false,
-				ssl_forced:              false
+				advanced_config:          '',
+				locations:                [],
+				block_exploits:           false,
+				caching_enabled:          false,
+				allow_websocket_upgrade:  false,
+				http2_support:            false,
+				hsts_enabled:             false,
+				hsts_subdomains:          false,
+				ssl_forced:               false,
+				dynamic_upstream_resolve: false,
 			}
 		}).then((data) => {
 			cy.validateSwaggerSchema('post', 201, '/nginx/proxy-hosts', data);
@@ -45,4 +46,37 @@ describe('Proxy Hosts endpoints', () => {
 		});
 	});
 
+	it('Should be able to create a proxy host with dynamic upstream resolve enabled', () => {
+		cy.task('backendApiPost', {
+			token: token,
+			path:  '/api/nginx/proxy-hosts',
+			data:  {
+				domain_names:   ['dynamic-resolve.example.com'],
+				forward_scheme: 'http',
+				forward_host:   'my.node',
+				forward_port:   8080,
+				access_list_id: '0',
+				certificate_id: 0,
+				meta:           {
+					dns_challenge: false
+				},
+				advanced_config:          '',
+				locations:                [],
+				block_exploits:           false,
+				caching_enabled:          false,
+				allow_websocket_upgrade:  false,
+				http2_support:            false,
+				hsts_enabled:             false,
+				hsts_subdomains:          false,
+				ssl_forced:               false,
+				dynamic_upstream_resolve: true,
+			}
+		}).then((data) => {
+			cy.validateSwaggerSchema('post', 201, '/nginx/proxy-hosts', data);
+			expect(data).to.have.property('id');
+			expect(data.id).to.be.greaterThan(0);
+			expect(data).to.have.property('dynamic_upstream_resolve', true);
+		});
+	});
+
 });