io: Make peer_addr fallible (#755)

The `io::PeerAddr` trait assumes that the peer addr lookup is infallible,
panicking the process when the call fails. In practice, however, this
call can fail when a system is under load.

This change modifies the `io::PeerAddr` trait to allow this lookup to
fail. When it fails, we propagate this failure to the connection's task.

linkerd/io/src/boxed.rs

@@ -1,4 +1,4 @@
-use super::{internal::Io, AsyncRead, AsyncWrite, PeerAddr, Poll};
+use super::{internal::Io, AsyncRead, AsyncWrite, PeerAddr, Poll, Result};
 use bytes::{Buf, BufMut};
 use std::{mem::MaybeUninit, pin::Pin, task::Context};
 
@@ -15,7 +15,7 @@ impl BoxedIo {
 }
 
 impl PeerAddr for BoxedIo {
-    fn peer_addr(&self) -> std::net::SocketAddr {
+    fn peer_addr(&self) -> Result<std::net::SocketAddr> {
         self.0.peer_addr()
     }
 }
@@ -106,8 +106,8 @@ mod tests {
     struct WriteBufDetector;
 
     impl PeerAddr for WriteBufDetector {
-        fn peer_addr(&self) -> std::net::SocketAddr {
-            ([0, 0, 0, 0], 0).into()
+        fn peer_addr(&self) -> Result<std::net::SocketAddr> {
+            Ok(([0, 0, 0, 0], 0).into())
         }
     }
 

linkerd/io/src/lib.rs

@@ -16,38 +16,38 @@ pub use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
 pub type Poll<T> = std::task::Poll<Result<T>>;
 
 pub trait PeerAddr {
-    fn peer_addr(&self) -> SocketAddr;
+    fn peer_addr(&self) -> Result<SocketAddr>;
 }
 
 impl PeerAddr for tokio::net::TcpStream {
-    fn peer_addr(&self) -> SocketAddr {
-        tokio::net::TcpStream::peer_addr(self).expect("TcpStream must have a peer address")
+    fn peer_addr(&self) -> Result<SocketAddr> {
+        tokio::net::TcpStream::peer_addr(self)
     }
 }
 
 impl<T: PeerAddr> PeerAddr for tokio_rustls::client::TlsStream<T> {
-    fn peer_addr(&self) -> SocketAddr {
+    fn peer_addr(&self) -> Result<SocketAddr> {
         self.get_ref().0.peer_addr()
     }
 }
 
 impl<T: PeerAddr> PeerAddr for tokio_rustls::server::TlsStream<T> {
-    fn peer_addr(&self) -> SocketAddr {
+    fn peer_addr(&self) -> Result<SocketAddr> {
         self.get_ref().0.peer_addr()
     }
 }
 
 #[cfg(feature = "tokio-test")]
 impl PeerAddr for tokio_test::io::Mock {
-    fn peer_addr(&self) -> SocketAddr {
-        ([0, 0, 0, 0], 0).into()
+    fn peer_addr(&self) -> Result<SocketAddr> {
+        Ok(([0, 0, 0, 0], 0).into())
     }
 }
 
 #[cfg(feature = "tokio-test")]
 impl PeerAddr for tokio::io::DuplexStream {
-    fn peer_addr(&self) -> SocketAddr {
-        ([0, 0, 0, 0], 0).into()
+    fn peer_addr(&self) -> Result<SocketAddr> {
+        Ok(([0, 0, 0, 0], 0).into())
     }
 }
 mod internal {

linkerd/io/src/prefixed.rs

@@ -1,10 +1,9 @@
 use crate::{internal::Io, PeerAddr, Poll};
 use bytes::{Buf, BufMut, Bytes};
+use pin_project::pin_project;
 use std::{cmp, io};
 use std::{mem::MaybeUninit, pin::Pin, task::Context};
-use tokio::io::{AsyncRead, AsyncWrite};
-
-use pin_project::pin_project;
+use tokio::io::{AsyncRead, AsyncWrite, Result};
 
 /// A TcpStream where the initial reads will be served from `prefix`.
 #[pin_project]
@@ -28,7 +27,7 @@ impl<S: AsyncRead + AsyncWrite> PrefixedIo<S> {
 }
 
 impl<S: PeerAddr> PeerAddr for PrefixedIo<S> {
-    fn peer_addr(&self) -> std::net::SocketAddr {
+    fn peer_addr(&self) -> Result<std::net::SocketAddr> {
         self.io.peer_addr()
     }
 }

linkerd/io/src/sensor.rs

@@ -6,7 +6,7 @@ use pin_project::pin_project;
 use std::mem::MaybeUninit;
 use std::pin::Pin;
 use std::task::Context;
-use tokio::io::{AsyncRead, AsyncWrite};
+use tokio::io::{AsyncRead, AsyncWrite, Result};
 
 pub trait Sensor {
     fn record_read(&mut self, sz: usize);
@@ -106,7 +106,7 @@ impl<T: Io, S: Sensor + Send> Io for SensorIo<T, S> {
 }
 
 impl<T: PeerAddr, S> PeerAddr for SensorIo<T, S> {
-    fn peer_addr(&self) -> std::net::SocketAddr {
+    fn peer_addr(&self) -> Result<std::net::SocketAddr> {
         self.io.peer_addr()
     }
 }

linkerd/proxy/http/src/detect.rs

@@ -158,21 +158,20 @@ where
                     svc
                 };
 
-                let (svc, closed) = SetClientHandle::new(io.peer_addr(), http1);
-
-                let mut conn = self
-                    .server
-                    .clone()
-                    .http1_only(true)
-                    .serve_connection(
-                        io,
-                        // Enable support for HTTP upgrades (CONNECT and websockets).
-                        HyperServerSvc::new(upgrade::Service::new(svc, self.drain.clone())),
-                    )
-                    .with_upgrades();
-
+                let mut server = self.server.clone();
                 let drain = self.drain.clone();
                 Box::pin(async move {
+                    let (svc, closed) = SetClientHandle::new(io.peer_addr()?, http1);
+
+                    let mut conn = server
+                        .http1_only(true)
+                        .serve_connection(
+                            io,
+                            // Enable support for HTTP upgrades (CONNECT and websockets).
+                            HyperServerSvc::new(upgrade::Service::new(svc, drain.clone())),
+                        )
+                        .with_upgrades();
+
                     tokio::select! {
                         res = &mut conn => {
                             debug!(?res, "The client is shutting down the connection");
@@ -208,16 +207,15 @@ where
                     svc
                 };
 
-                let (svc, closed) = SetClientHandle::new(io.peer_addr(), h2);
-
-                let mut conn = self
-                    .server
-                    .clone()
-                    .http2_only(true)
-                    .serve_connection(io, HyperServerSvc::new(svc));
-
+                let mut server = self.server.clone();
                 let drain = self.drain.clone();
                 Box::pin(async move {
+                    let (svc, closed) = SetClientHandle::new(io.peer_addr()?, h2);
+
+                    let mut conn = server
+                        .http2_only(true)
+                        .serve_connection(io, HyperServerSvc::new(svc));
+
                     tokio::select! {
                         res = &mut conn => {
                             debug!(?res, "The client is shutting down the connection");