nat traversal requires multipath (#159)

* nat traversal requires multipath

* allow crate access, not ideal, but unavoidable

* satisfty MSRV limits

* pub all the way to the top

* update wasm-bindgen-test

Author: divagant-martian

Cargo.lock

@@ -30,6 +30,9 @@ mod transport;
 pub use transport::QlogConfig;
 pub use transport::{AckFrequencyConfig, IdleTimeout, MtuDiscoveryConfig, TransportConfig};
 
+#[cfg(doc)]
+pub use transport::DEFAULT_CONCURRENT_MULTIPATH_PATHS_WHEN_ENABLED;
+
 /// Global configuration for the endpoint, affecting all connections
 ///
 /// Default values should be suitable for most internet applications.

quinn-proto/src/config/mod.rs

@@ -12,6 +12,22 @@ use crate::{
     congestion, connection::qlog::QlogSink,
 };
 
+/// When multipath is required and has not been explicitly enabled, this value will be used for
+/// [`TransportConfig::max_concurrent_multipath_paths`].
+const DEFAULT_CONCURRENT_MULTIPATH_PATHS_WHEN_ENABLED_: NonZeroU32 = {
+    match NonZeroU32::new(4) {
+        Some(v) => v,
+        None => panic!("to enable multipath this must be positive, which clearly it is"),
+    }
+};
+
+/// When multipath is required and has not been explicitly enabled, this value will be used for
+///
+/// [`TransportConfig::max_concurrent_multipath_paths`].
+#[cfg(doc)]
+pub const DEFAULT_CONCURRENT_MULTIPATH_PATHS_WHEN_ENABLED: NonZeroU32 =
+    DEFAULT_CONCURRENT_MULTIPATH_PATHS_WHEN_ENABLED_;
+
 /// Parameters governing the core QUIC state machine
 ///
 /// Default values should be suitable for most internet applications. Applications protocols which
@@ -432,11 +448,28 @@ impl TransportConfig {
     ///
     /// Setting this to any nonzero value will enable the Nat Traversal Extension for QUIC,
     /// see <https://www.ietf.org/archive/id/draft-seemann-quic-nat-traversal-02.html>
+    ///
+    /// This implementation expects the multipath extension to be enabled as well. if not yet
+    /// enabled via [`Self::max_concurrent_multipath_paths`], a default value of
+    /// [`DEFAULT_CONCURRENT_MULTIPATH_PATHS_WHEN_ENABLED`] will be used.
     pub fn set_max_nat_traversal_concurrent_attempts(&mut self, max_concurrent: u32) -> &mut Self {
         self.nat_traversal_concurrency_limit = NonZeroU32::new(max_concurrent);
+        if max_concurrent != 0 && self.max_concurrent_multipath_paths.is_none() {
+            self.max_concurrent_multipath_paths(
+                DEFAULT_CONCURRENT_MULTIPATH_PATHS_WHEN_ENABLED_.get(),
+            );
+        }
         self
     }
 
+    /// Gets the maximum number of concurrent attempts for nat traversal
+    ///
+    /// If this is `Some`, the value is guaranteed to be non zero.
+    pub fn get_nat_traversal_concurrency_limit(&self) -> Option<VarInt> {
+        self.nat_traversal_concurrency_limit
+            .map(|non_zero| VarInt::from_u32(non_zero.get()))
+    }
+
     /// qlog capture configuration to use for a particular connection
     #[cfg(feature = "qlog")]
     pub fn qlog_stream(&mut self, stream: Option<QlogStream>) -> &mut Self {

quinn-proto/src/config/transport.rs

@@ -55,6 +55,8 @@ pub use connection::qlog::QlogStream;
 pub use rustls;
 
 mod config;
+#[cfg(doc)]
+pub use config::DEFAULT_CONCURRENT_MULTIPATH_PATHS_WHEN_ENABLED;
 #[cfg(feature = "qlog")]
 pub use config::QlogConfig;
 pub use config::{

quinn-proto/src/lib.rs

@@ -196,9 +196,7 @@ impl TransportParameters {
             }),
             address_discovery_role: config.address_discovery_role,
             initial_max_path_id: config.get_initial_max_path_id(),
-            nat_traversal: config
-                .nat_traversal_concurrency_limit
-                .map(|limit| VarInt::from_u32(limit.get())),
+            nat_traversal: config.get_nat_traversal_concurrency_limit(),
             ..Self::default()
         }
     }