fix: set SSL properly for created dynamic backends (#1016)

Author: Guy Bedford

integration-tests/js-compute/fixtures/app/src/dynamic-backend.js

@@ -57,7 +57,11 @@ routes.set('/backend/timeout', async () => {
   );
   routes.set('/implicit-dynamic-backend/dynamic-backends-enabled', async () => {
     allowDynamicBackends(true);
-    await assertResolves(() => fetch('https://http-me.glitch.me/headers'));
+    await assertResolves(async () => {
+      await fetch('https://http-me.glitch.me/headers');
+      const backend = Backend.fromName('http-me.glitch.me');
+      strictEqual(backend.isSSL, true);
+    });
     await assertResolves(() => fetch('https://www.fastly.com'));
     enforceExplicitBackends();
     await assertRejects(() => fetch('https://www.fastly.com'));

runtime/fastly/builtins/backend.cpp

@@ -1694,7 +1694,9 @@ JSObject *Backend::create(JSContext *cx, JS::HandleObject request) {
   if (!name_js_str) {
     return nullptr;
   }
+  JS::RootedValue name(cx, JS::StringValue(name_js_str));
   std::string name_str((char *)slice.data, slice.len);
+  JS::SetReservedSlot(request, static_cast<uint32_t>(Request::Slots::Backend), name);
 
   // Check if we already constructed an implicit dynamic backend for this host.
   bool found;
@@ -1707,6 +1709,7 @@ JSObject *Backend::create(JSContext *cx, JS::HandleObject request) {
       return nullptr;
     }
     JS::RootedObject backend(cx, &already_built_backend.toObject());
+
     return backend;
   }
 
@@ -1722,7 +1725,6 @@ JSObject *Backend::create(JSContext *cx, JS::HandleObject request) {
 
   host_api::BackendConfig backend_config = default_backend_config.clone();
 
-  JS::RootedValue name(cx, JS::StringValue(name_js_str));
   auto host_backend = set_backend(cx, backend, name);
   if (!host_backend) {
     return nullptr;
@@ -1744,6 +1746,7 @@ JSObject *Backend::create(JSContext *cx, JS::HandleObject request) {
 
   auto use_ssl = origin.rfind("https://", 0) == 0;
   if (use_ssl) {
+    backend_config.use_ssl = true;
     if (!set_sni_hostname(cx, backend_config, name)) {
       return nullptr;
     }