implement path MTU discovery support

cloudflare · Mar 1, 2024 · 5387d47 · 5387d47
1 parent 45b59aa
commit 5387d47
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Showing 14 changed files with 695 additions and 36 deletions.
diff --git a/apps/src/args.rs b/apps/src/args.rs
@@ -477,6 +477,7 @@ pub struct ServerArgs {
     pub key: String,
     pub disable_gso: bool,
     pub disable_pacing: bool,
+    pub enable_pmtud: bool,
 }
 
 impl Args for ServerArgs {
@@ -491,6 +492,7 @@ impl Args for ServerArgs {
         let key = args.get_str("--key").to_string();
         let disable_gso = args.get_bool("--disable-gso");
         let disable_pacing = args.get_bool("--disable-pacing");
+        let enable_pmtud = args.get_bool("--enable-pmtud");
 
         ServerArgs {
             listen,
@@ -501,6 +503,7 @@ impl Args for ServerArgs {
             key,
             disable_gso,
             disable_pacing,
+            enable_pmtud,
         }
     }
 }
diff --git a/apps/src/bin/quiche-server.rs b/apps/src/bin/quiche-server.rs
@@ -108,6 +108,7 @@ fn main() {
 
     config.set_application_protos(&conn_args.alpns).unwrap();
 
+    config.discover_pmtu(args.enable_pmtud);
     config.set_max_idle_timeout(conn_args.idle_timeout);
     config.set_max_recv_udp_payload_size(max_datagram_size);
     config.set_max_send_udp_payload_size(max_datagram_size);

diff --git a/quiche/include/quiche.h b/quiche/include/quiche.h
@@ -161,6 +161,9 @@ void quiche_config_verify_peer(quiche_config *config, bool v);
 // Configures whether to send GREASE.
 void quiche_config_grease(quiche_config *config, bool v);
 
+// Configures whether to do path MTU discovery.
+void quiche_config_discover_pmtu(quiche_config *config, bool v);
+
 // Enables logging of secrets.
 void quiche_config_log_keys(quiche_config *config);
 

diff --git a/quiche/src/ffi.rs b/quiche/src/ffi.rs
@@ -210,6 +210,11 @@ pub extern fn quiche_config_grease(config: &mut Config, v: bool) {
     config.grease(v);
 }
 
+#[no_mangle]
+pub extern fn quiche_config_discover_pmtu(config: &mut Config, v: bool) {
+    config.discover_pmtu(v);
+}
+
 #[no_mangle]
 pub extern fn quiche_config_log_keys(config: &mut Config) {
     config.log_keys();

diff --git a/quiche/src/frame.rs b/quiche/src/frame.rs
@@ -60,7 +60,14 @@ pub enum Frame {
         len: usize,
     },
 
-    Ping,
+    Ping {
+        // Attach metadata to the Ping frame. This doesn't appear on the wire,
+        // but does tell us if this frame was part of a PMTUD probe and how
+        // large the probe was. This will only show up on sent frames and be
+        // None otherwise. This is the total size of the QUIC packet in the
+        // probe.
+        mtu_probe: Option<usize>,
+    },
 
     ACK {
         ack_delay: u64,
@@ -198,7 +205,7 @@ impl Frame {
                 Frame::Padding { len }
             },
 
-            0x01 => Frame::Ping,
+            0x01 => Frame::Ping { mtu_probe: None },
 
             0x02..=0x03 => parse_ack_frame(frame_type, b)?,
 
@@ -376,7 +383,7 @@ impl Frame {
                 }
             },
 
-            Frame::Ping => {
+            Frame::Ping { .. } => {
                 b.put_varint(0x01)?;
             },
 
@@ -595,7 +602,7 @@ impl Frame {
         match self {
             Frame::Padding { len } => *len,
 
-            Frame::Ping => 1,
+            Frame::Ping { .. } => 1,
 
             Frame::ACK {
                 ack_delay,
@@ -1024,8 +1031,8 @@ impl std::fmt::Debug for Frame {
                 write!(f, "PADDING len={len}")?;
             },
 
-            Frame::Ping => {
-                write!(f, "PING")?;
+            Frame::Ping { mtu_probe } => {
+                write!(f, "PING mtu_probe={mtu_probe:?}")?;
             },
 
             Frame::ACK {
@@ -1375,7 +1382,7 @@ mod tests {
     fn ping() {
         let mut d = [42; 128];
 
-        let frame = Frame::Ping;
+        let frame = Frame::Ping { mtu_probe: None };
 
         let wire_len = {
             let mut b = octets::OctetsMut::with_slice(&mut d);