Remove panic when failing to get remote address (#107)

The listener *already* got the remote address when it was accepted, but we drop the value by using `TcpListener::incoming`. By the time we call `socket.peer_addr()`, the connection may have been closed, and thus we were panicking.

By removing the panic here, later code should notice that the connection is closed (when a `read` finds EOF), and it should be dropped gracefully.

For the same reasons (that the connection might already be closed), this reduces the `error!` from `get_original_dst` to just a `warn!`, just as `set_nodelay` is a `warn!`. No need to yell in that case.

Closes https://github.com/linkerd/linkerd2/issues/1787

Signed-off-by: Sean McArthur <sean@buoyant.io>

src/transport/addr_info.rs

@@ -77,7 +77,7 @@ mod linux {
         );
         if ret != 0 {
             let e = io::Error::last_os_error();
-            error!("failed to read SO_ORIGINAL_DST: {:?}", e);
+            warn!("failed to read SO_ORIGINAL_DST: {:?}", e);
             return Err(e);
         }
 

src/transport/connection.rs

@@ -1,7 +1,7 @@
 /// Tokio-level (not Tower-level) proxy-specific networking.
 
 use bytes::{Buf, BytesMut};
-use futures::{*, future::Either};
+use futures::{Async, Future, IntoFuture, Poll, Stream, future::{self, Either}, stream};
 use std;
 use std::cmp;
 use std::io;
@@ -186,13 +186,15 @@ impl BoundPort {
             // background reactor if `listen_and_fold` is called before we've
             // initialized the runtime.
             TcpListener::from_std(inner, &Handle::current())
-        }).and_then(move |listener|
+        }).and_then(move |mut listener| {
-            listener.incoming()
+            let incoming = stream::poll_fn(move || {
-                .take(connection_limit)
+                let ret = try_ready!(listener.poll_accept());
-                .and_then(move |socket| {
+                Ok(Async::Ready(Some(ret)))
-                    let remote_addr = socket.peer_addr()
+            });
-                        .expect("couldn't get remote addr!");
 
+            incoming
+                .take(connection_limit)
+                .and_then(move |(socket, remote_addr)| {
                     // TODO: On Linux and most other platforms it would be better
                     // to set the `TCP_NODELAY` option on the bound socket and
                     // then have the listening sockets inherit it. However, that
@@ -225,7 +227,7 @@ impl BoundPort {
                 })
                 .filter_map(|x| x)
                 .fold(initial, f)
-        )
+        })
         .map(|_| ())
     }
 }