xmlstream: implement simple timeout logic

This allows to detect and handle dying streams without getting stuck
forever.

Timeouts are always wrong, though, so we put the burden of choosing the
right values (mostly) on the creator of a stream.

tokio-xmpp/src/xmlstream/initiator.rs

@@ -17,7 +17,7 @@ use xmpp_parsers::stream_features::StreamFeatures;
 use xso::{AsXml, FromXml};
 
 use super::{
-    common::{RawXmlStream, ReadXso, StreamHeader},
+    common::{RawXmlStream, ReadXso, ReadXsoError, StreamHeader},
     XmlStream,
 };
 
@@ -80,7 +80,22 @@ impl<Io: AsyncBufRead + AsyncWrite + Unpin> PendingFeaturesRecv<Io> {
             mut stream,
             header: _,
         } = self;
-        let features = ReadXso::read_from(Pin::new(&mut stream)).await?;
+        let features = loop {
+            match ReadXso::read_from(Pin::new(&mut stream)).await {
+                Ok(v) => break v,
+                Err(ReadXsoError::SoftTimeout) => (),
+                Err(ReadXsoError::Hard(e)) => return Err(e),
+                Err(ReadXsoError::Parse(e)) => {
+                    return Err(io::Error::new(io::ErrorKind::InvalidData, e))
+                }
+                Err(ReadXsoError::Footer) => {
+                    return Err(io::Error::new(
+                        io::ErrorKind::UnexpectedEof,
+                        "unexpected stream footer",
+                    ))
+                }
+            }
+        };
         Ok((features, XmlStream::wrap(stream)))
     }