Bug 1851908 - Add a preference to specify neqo's congestion control algorithm r=necko-reviewers,kershaw

We want to experiment with NewReno so expose this via pref.

Differential Revision: https://phabricator.services.mozilla.com/D187602

modules/libpref/init/StaticPrefList.yaml

@@ -12417,6 +12417,15 @@
   value: false
   mirror: always
 
+# The congestion control algorithm with which to configure neqo.
+# 0 => NewReno
+# 1 => Cubic
+- name: network.http.http3.cc_algorithm
+  type: RelaxedAtomicUint32
+  value: 1
+  mirror: always
+  rust: true
+
 # When true, a http request will be upgraded to https when HTTPS RR is
 # available.
 - name: network.dns.upgrade_with_https_rr

netwerk/socket/neqo_glue/src/lib.rs

@@ -124,10 +124,20 @@ impl NeqoHttp3Conn {
         } else {
             vec![quic_version]
         };
+
+        let cc_algorithm = match static_prefs::pref!("network.http.http3.cc_algorithm") {
+            0 => CongestionControlAlgorithm::NewReno,
+            1 => CongestionControlAlgorithm::Cubic,
+            _ => {
+                // Unknown preferences; default to Cubic
+                CongestionControlAlgorithm::Cubic
+            }
+        };
+
         #[allow(unused_mut)]
         let mut params = ConnectionParameters::default()
             .versions(quic_version, version_list)
-            .cc_algorithm(CongestionControlAlgorithm::Cubic)
+            .cc_algorithm(cc_algorithm)
             .max_data(max_data)
             .max_stream_data(StreamType::BiDi, false, max_stream_data)
             .grease(static_prefs::pref!("security.tls.grease_http3_enable"));
@@ -1338,9 +1348,9 @@ pub extern "C" fn neqo_http3conn_webtransport_set_sendorder(
 ) -> nsresult {
     match conn
         .conn
-	.webtransport_set_sendorder(StreamId::from(stream_id), sendorder)
+        .webtransport_set_sendorder(StreamId::from(stream_id), sendorder)
     {
-	Ok(()) => NS_OK,
-	Err(_) => NS_ERROR_UNEXPECTED,
+        Ok(()) => NS_OK,
+        Err(_) => NS_ERROR_UNEXPECTED,
     }
 }