The problem with PuTTY Client

[ileamo]

I run example:

cargo run -p russh --example echoserver

It works as expected using OpenSSH's Client.
However with PuTTY, no data is sent.

Client versions:

[...DEBUG russh::ssh_read] Ok("SSH-2.0-PuTTY_Release_0.78\r\n") 
[...DEBUG russh::ssh_read] Ok("SSH-2.0-OpenSSH_for_Windows_8.1\r\n")

[ileamo]

After analyzing the PuTTY logs, I found that PuTTY does not start transferring data until it receives the SSH2_MSG_CHANNEL_WINDOW_ADJUST packet from the server.
Unfortunately, I did not find a public function in russh crate that sends this packet, so I added my own dirty function for testing.

With the following fixes, the echoserver example worked as expected with the PuTTY client:

diff --git a/russh/examples/echoserver.rs b/russh/examples/echoserver.rs
index 356f1b3..16e294d 100644
--- a/russh/examples/echoserver.rs
+++ b/russh/examples/echoserver.rs
@@ -80,6 +80,30 @@ impl server::Handler for Server {
         Ok((self, server::Auth::Accept))
     }
 
+    async fn pty_request(
+        self,
+        channel: ChannelId,
+        _term: &str,
+        _col_width: u32,
+        _row_height: u32,
+        _pix_width: u32,
+        _pix_height: u32,
+        _modes: &[(Pty, u32)],
+        mut session: Session,
+    ) -> Result<(Self, Session), Self::Error> {
+        session.channel_window_adjust(channel);
+        Ok((self, session))
+    }
+
     async fn data(
         mut self,
         channel: ChannelId,
diff --git a/russh/src/server/session.rs b/russh/src/server/session.rs
index 9bb2025..dc72df5 100644
--- a/russh/src/server/session.rs
+++ b/russh/src/server/session.rs
@@ -605,6 +605,23 @@ impl Session {
         }
     }
 
+    pub fn channel_window_adjust(&mut self, channel: ChannelId) {
+        if let Some(ref mut enc) = self.common.encrypted {
+            if let Some(channel) = enc.channels.get_mut(&channel) {
+                assert!(channel.confirmed);
+                if channel.wants_reply {
+                    channel.wants_reply = false;
+                    debug!("channel_window_adjust {:?}", channel);
+                    push_packet!(enc.write, {
+                        enc.write.push(msg::CHANNEL_WINDOW_ADJUST);
+                        enc.write.push_u32_be(0x100);
+                        enc.write.push_u32_be(0x200000);
+                    });
+                }
+            }
+        }
+    }
+
     /// Send a "failure" reply to a global request.
     pub fn channel_failure(&mut self, channel: ChannelId) {
         if let Some(ref mut enc) = self.common.encrypted {