preferred address

quinn-proto/src/config.rs

@@ -1,4 +1,10 @@
-use std::{fmt, num::TryFromIntError, sync::Arc, time::Duration};
+use std::{
+    fmt,
+    net::{SocketAddrV4, SocketAddrV6},
+    num::TryFromIntError,
+    sync::Arc,
+    time::Duration,
+};
 
 use thiserror::Error;
 
@@ -765,6 +771,9 @@ pub struct ServerConfig {
     /// Improves behavior for clients that move between different internet connections or suffer NAT
     /// rebinding. Enabled by default.
     pub(crate) migration: bool,
+
+    pub(crate) preferred_address_v4: Option<SocketAddrV4>,
+    pub(crate) preferred_address_v6: Option<SocketAddrV6>,
 }
 
 impl ServerConfig {
@@ -781,6 +790,9 @@ impl ServerConfig {
             retry_token_lifetime: Duration::from_secs(15),
 
             migration: true,
+
+            preferred_address_v4: None,
+            preferred_address_v6: None,
         }
     }
 
@@ -810,6 +822,20 @@ impl ServerConfig {
         self.migration = value;
         self
     }
+
+    /// The preferred IPv4 address that will be communicated to clients during handshaking.
+    /// If the client is able to reach this address, it will switch to it.
+    pub fn preferred_address_v4(&mut self, address: Option<SocketAddrV4>) -> &mut Self {
+        self.preferred_address_v4 = address;
+        self
+    }
+
+    /// The preferred IPv6 address that will be communicated to clients during handshaking.
+    /// If the client is able to reach this address, it will switch to it.
+    pub fn preferred_address_v6(&mut self, address: Option<SocketAddrV6>) -> &mut Self {
+        self.preferred_address_v6 = address;
+        self
+    }
 }
 
 #[cfg(feature = "rustls")]
@@ -849,6 +875,8 @@ impl fmt::Debug for ServerConfig {
             .field("token_key", &"[ elided ]")
             .field("retry_token_lifetime", &self.retry_token_lifetime)
             .field("migration", &self.migration)
+            .field("preferred_address_v4", &self.preferred_address_v4)
+            .field("preferred_address_v6", &self.preferred_address_v6)
             .finish()
     }
 }

quinn-proto/src/connection/cid_state.rs

@@ -28,21 +28,30 @@ pub(super) struct CidState {
 }
 
 impl CidState {
-    pub(crate) fn new(cid_len: usize, cid_lifetime: Option<Duration>, now: Instant) -> Self {
+    pub(crate) fn new(
+        cid_len: usize,
+        cid_lifetime: Option<Duration>,
+        now: Instant,
+        issued: u64,
+    ) -> Self {
         let mut active_seq = FxHashSet::default();
-        // Add sequence number of CID used in handshaking into tracking set
-        active_seq.insert(0);
+        // Add sequence number of CIDs used in handshaking into tracking set
+        for seq in 0..issued {
+            active_seq.insert(seq);
+        }
         let mut this = Self {
             retire_timestamp: VecDeque::new(),
-            issued: 1, // One CID is already supplied during handshaking
+            issued,
             active_seq,
             prev_retire_seq: 0,
             retire_seq: 0,
             cid_len,
             cid_lifetime,
         };
-        // Track lifetime of cid used in handshaking
-        this.track_lifetime(0, now);
+        // Track lifetime of CIDs used in handshaking
+        for seq in 0..issued {
+            this.track_lifetime(seq, now);
+        }
         this
     }
 

quinn-proto/src/connection/mod.rs

@@ -244,6 +244,7 @@ impl Connection {
         init_cid: ConnectionId,
         loc_cid: ConnectionId,
         rem_cid: ConnectionId,
+        pref_addr_cid: Option<ConnectionId>,
         remote: SocketAddr,
         local_ip: Option<IpAddr>,
         crypto: Box<dyn crypto::Session>,
@@ -275,7 +276,12 @@ impl Connection {
             crypto,
             handshake_cid: loc_cid,
             rem_handshake_cid: rem_cid,
-            local_cid_state: CidState::new(cid_gen.cid_len(), cid_gen.cid_lifetime(), now),
+            local_cid_state: CidState::new(
+                cid_gen.cid_len(),
+                cid_gen.cid_lifetime(),
+                now,
+                if pref_addr_cid.is_some() { 2 } else { 1 },
+            ),
             path: PathData::new(
                 remote,
                 config.initial_rtt,

quinn-proto/src/endpoint.rs

@@ -1,7 +1,7 @@
 use std::{
     collections::{hash_map, HashMap},
     convert::TryFrom,
-    fmt, iter,
+    fmt,
     net::{IpAddr, SocketAddr},
     ops::{Index, IndexMut},
     sync::Arc,
@@ -30,7 +30,7 @@ use crate::{
         ConnectionEvent, ConnectionEventInner, ConnectionId, EcnCodepoint, EndpointEvent,
         EndpointEventInner, IssuedCid,
     },
-    transport_parameters::TransportParameters,
+    transport_parameters::{PreferredAddress, TransportParameters},
     ResetToken, RetryToken, Side, Transmit, TransportConfig, TransportError, INITIAL_MTU,
     MAX_CID_SIZE, MIN_INITIAL_SIZE, RESET_TOKEN_SIZE,
 };
@@ -390,6 +390,7 @@ impl Endpoint {
             remote_id,
             loc_cid,
             remote_id,
+            None,
             FourTuple {
                 remote,
                 local_ip: None,
@@ -413,8 +414,8 @@ impl Endpoint {
         for _ in 0..num {
             let id = self.new_cid(ch);
             let meta = &mut self.connections[ch];
-            meta.cids_issued += 1;
             let sequence = meta.cids_issued;
+            meta.cids_issued += 1;
             meta.loc_cids.insert(sequence, id);
             ids.push(IssuedCid {
                 sequence,
@@ -506,6 +507,7 @@ impl Endpoint {
         mut incoming: Incoming,
         now: Instant,
         buf: &mut BytesMut,
+        server_config: Option<Arc<ServerConfig>>,
     ) -> Result<(ConnectionHandle, Connection), AcceptError> {
         let packet_number = incoming.packet.header.number.expand(0);
         let InitialHeader {
@@ -530,7 +532,8 @@ impl Endpoint {
             });
         }
 
-        let server_config = self.server_config.as_ref().unwrap().clone();
+        let server_config =
+            server_config.unwrap_or_else(|| self.server_config.as_ref().unwrap().clone());
 
         if incoming
             .crypto
@@ -562,6 +565,19 @@ impl Endpoint {
         params.stateless_reset_token = Some(ResetToken::new(&*self.config.reset_key, &loc_cid));
         params.original_dst_cid = Some(incoming.orig_dst_cid);
         params.retry_src_cid = incoming.retry_src_cid;
+        let mut pref_addr_cid = None;
+        if server_config.preferred_address_v4.is_some()
+            || server_config.preferred_address_v6.is_some()
+        {
+            let cid = self.new_cid(ch);
+            pref_addr_cid = Some(cid);
+            params.preferred_address = Some(PreferredAddress {
+                address_v4: server_config.preferred_address_v4,
+                address_v6: server_config.preferred_address_v6,
+                connection_id: cid,
+                stateless_reset_token: ResetToken::new(&*self.config.reset_key, &cid),
+            });
+        }
 
         let tls = server_config.crypto.clone().start_session(version, &params);
         let transport_config = server_config.transport.clone();
@@ -571,6 +587,7 @@ impl Endpoint {
             dst_cid,
             loc_cid,
             src_cid,
+            pref_addr_cid,
             incoming.addresses,
             now,
             tls,
@@ -718,6 +735,7 @@ impl Endpoint {
         init_cid: ConnectionId,
         loc_cid: ConnectionId,
         rem_cid: ConnectionId,
+        pref_addr_cid: Option<ConnectionId>,
         addresses: FourTuple,
         now: Instant,
         tls: Box<dyn crypto::Session>,
@@ -734,6 +752,7 @@ impl Endpoint {
             init_cid,
             loc_cid,
             rem_cid,
+            pref_addr_cid,
             addresses.remote,
             addresses.local_ip,
             tls,
@@ -745,10 +764,22 @@ impl Endpoint {
             path_validated,
         );
 
+        let mut cids_issued = 0;
+        let mut loc_cids = FxHashMap::default();
+
+        loc_cids.insert(cids_issued, loc_cid);
+        cids_issued += 1;
+
+        if let Some(cid) = pref_addr_cid {
+            debug_assert_eq!(cids_issued, 1, "preferred address cid seq must be 1");
+            loc_cids.insert(cids_issued, cid);
+            cids_issued += 1;
+        }
+
         let id = self.connections.insert(ConnectionMeta {
             init_cid,
-            cids_issued: 0,
-            loc_cids: iter::once((0, loc_cid)).collect(),
+            cids_issued,
+            loc_cids,
             addresses,
             reset_token: None,
         });

quinn-proto/src/tests/util.rs

@@ -456,7 +456,7 @@ impl TestEndpoint {
         now: Instant,
     ) -> Result<ConnectionHandle, ConnectionError> {
         let mut buf = BytesMut::new();
-        match self.endpoint.accept(incoming, now, &mut buf) {
+        match self.endpoint.accept(incoming, now, &mut buf, None) {
             Ok((ch, conn)) => {
                 self.connections.insert(ch, conn);
                 self.accepted = Some(Ok(ch));

quinn-proto/src/transport_parameters.rs

@@ -493,7 +493,7 @@ mod test {
             max_udp_payload_size: 1200u32.into(),
             preferred_address: Some(PreferredAddress {
                 address_v4: Some(SocketAddrV4::new(Ipv4Addr::LOCALHOST, 42)),
-                address_v6: None,
+                address_v6: Some(SocketAddrV6::new(Ipv6Addr::LOCALHOST, 24, 0, 0)),
                 connection_id: ConnectionId::new(&[0x42]),
                 stateless_reset_token: [0xab; RESET_TOKEN_SIZE].into(),
             }),

quinn/src/endpoint.rs

@@ -359,13 +359,19 @@ pub(crate) struct EndpointInner {
 }
 
 impl EndpointInner {
-    pub(crate) fn accept(&self, incoming: proto::Incoming) -> Result<Connecting, ConnectionError> {
+    pub(crate) fn accept(
+        &self,
+        incoming: proto::Incoming,
+        server_config: Option<Arc<ServerConfig>>,
+    ) -> Result<Connecting, ConnectionError> {
         let mut state = self.state.lock().unwrap();
         let mut response_buffer = BytesMut::new();
-        match state
-            .inner
-            .accept(incoming, Instant::now(), &mut response_buffer)
-        {
+        match state.inner.accept(
+            incoming,
+            Instant::now(),
+            &mut response_buffer,
+            server_config,
+        ) {
             Ok((handle, conn)) => {
                 let socket = state.socket.clone();
                 let runtime = state.runtime.clone();

quinn/src/incoming.rs

@@ -2,10 +2,11 @@ use std::{
     future::{Future, IntoFuture},
     net::{IpAddr, SocketAddr},
     pin::Pin,
+    sync::Arc,
     task::{Context, Poll},
 };
 
-use proto::ConnectionError;
+use proto::{ConnectionError, ServerConfig};
 use thiserror::Error;
 
 use crate::{
@@ -25,7 +26,20 @@ impl Incoming {
     /// Attempt to accept this incoming connection (an error may still occur)
     pub fn accept(mut self) -> Result<Connecting, ConnectionError> {
         let state = self.0.take().unwrap();
-        state.endpoint.accept(state.inner)
+        state.endpoint.accept(state.inner, None)
+    }
+
+    /// Accept this incoming connection using a custom configuration.
+    ///
+    /// See [`accept()`] for more details.
+    ///
+    /// [`accept()`]: Incoming::accept
+    pub fn accept_with(
+        mut self,
+        server_config: Arc<ServerConfig>,
+    ) -> Result<Connecting, ConnectionError> {
+        let state = self.0.take().unwrap();
+        state.endpoint.accept(state.inner, Some(server_config))
     }
 
     /// Reject this incoming connection attempt