tor-browser

commit d673d2a47124bbf7f250cb86f6e1b5aafd76b6dd
parent e0b9d3d67032ec26a9ac82dc84dba9e924761de5
Author: Max Leonard Inden <mail@max-inden.de>
Date:   Wed, 12 Nov 2025 09:36:04 +0000

Bug 1909910 - enable QUIC PMTUD r=necko-reviewers,kershaw

Differential Revision: https://phabricator.services.mozilla.com/D223575

Diffstat:
M
modules/libpref/init/StaticPrefList.yaml
 | 
7
+++++++
M
netwerk/socket/neqo_glue/src/lib.rs
 | 
2
++
M
testing/web-platform/tests/webtransport/datagrams.https.any.js
 | 
26
+++++++++++++++++++-------

3 files changed, 28 insertions(+), 7 deletions(-)
diff --git a/modules/libpref/init/StaticPrefList.yaml b/modules/libpref/init/StaticPrefList.yaml
@@ -15422,6 +15422,13 @@
   value: 30
   mirror: always
 
+# Whether to enable Packetization Layer Path MTU Discovery.
+- name: network.http.http3.pmtud
+  type: RelaxedAtomicBool
+  value: true
+  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
diff --git a/netwerk/socket/neqo_glue/src/lib.rs b/netwerk/socket/neqo_glue/src/lib.rs
@@ -423,6 +423,8 @@ impl NeqoHttp3Conn {
         let pmtud_enabled =
             // Check if PMTUD is explicitly enabled,
             pmtud_enabled
+            // or enabled via pref,
+            || static_prefs::pref!("network.http.http3.pmtud")
             // but disable PMTUD if NSPR is used (socket == None) or
             // transmitted UDP datagrams might get fragmented by the IP layer.
             && socket.as_ref().map_or(false, |s| !s.may_fragment());
diff --git a/testing/web-platform/tests/webtransport/datagrams.https.any.js b/testing/web-platform/tests/webtransport/datagrams.https.any.js
@@ -199,13 +199,25 @@ promise_test(async t => {
   const writer = wt.datagrams.writable.getWriter();
   const reader = wt.datagrams.readable.getReader();
 
-  // Write and read max-size datagram.
-  await writer.write(new Uint8Array(wt.datagrams.maxDatagramSize+1));
-  // This should resolve with no datagram sent, which is hard to test for.
-  // Wait for incoming datagrams to arrive, and if they do, fail.
-  const result = await Promise.race([reader.read(), wait(500)]);
-  assert_equals(result, undefined);
-}, 'Fail to transfer max-size+1 datagram');
+  let maxDatagramSize = wt.datagrams.maxDatagramSize;
+
+  while (true) {
+    // Write and read max-size datagram.
+    await writer.write(new Uint8Array(maxDatagramSize + 1));
+    // This should resolve with no datagram sent, which is hard to test for.
+    // Wait for incoming datagrams to arrive, and if they do, fail.
+    const result = await Promise.race([reader.read(), wait(500)]);
+    if (result === undefined) {
+      return; // Success, no datagram received, exit the test early.
+    }
+
+    // Maybe QUIC's PMTUD increased the max-size datagram in the meantime. If
+    // so, try again.
+    const currentMaxDatagramSize = wt.datagrams.maxDatagramSize;
+    assert_greater_than(currentMaxDatagramSize, maxDatagramSize);
+    maxDatagramSize = currentMaxDatagramSize;
+  }
+}, 'Fail to transfer max-size+1 datagram, handle PMTUD increases');
 
 promise_test(async t => {
   // Make a WebTransport connection, but session is not necessarily established.