Support sending "[email protected]" requests (#527)

Author: handewo

russh/src/client/encrypted.rs

@@ -731,6 +731,9 @@ impl Session {
                     Some(GlobalRequestResponse::Keepalive) => {
                         // ignore keepalives
                     }
+                    Some(GlobalRequestResponse::NoMoreSessions) => {
+                        debug!("[email protected] requests success");
+                    }
                     Some(GlobalRequestResponse::TcpIpForward(return_channel)) => {
                         let result = if r.is_empty() {
                             // If a specific port was requested, the reply has no data
@@ -767,6 +770,9 @@ impl Session {
                     Some(GlobalRequestResponse::Keepalive) => {
                         // ignore keepalives
                     }
+                    Some(GlobalRequestResponse::NoMoreSessions) => {
+                        warn!("[email protected] requests failure");
+                    }
                     Some(GlobalRequestResponse::TcpIpForward(return_channel)) => {
                         let _ = return_channel.send(None);
                     }

russh/src/client/mod.rs

@@ -200,6 +200,9 @@ pub enum Msg {
     Keepalive {
         want_reply: bool,
     },
+    NoMoreSessions {
+        want_reply: bool,
+    },
 }
 
 impl From<(ChannelId, ChannelMsg)> for Msg {
@@ -834,6 +837,14 @@ impl<H: Handler> Handle<H> {
             .await
             .map_err(|_| Error::SendError)
     }
+
+    /// Send a no-more-sessions request to the remote peer.
+    pub async fn no_more_sessions(&self, want_reply: bool) -> Result<(), Error> {
+        self.sender
+            .send(Msg::NoMoreSessions { want_reply })
+            .await
+            .map_err(|_| Error::SendError)
+    }
 }
 
 impl<H: Handler> Future for Handle<H> {
@@ -1376,6 +1387,9 @@ impl Session {
             Msg::Keepalive { want_reply } => {
                 let _ = self.send_keepalive(want_reply);
             }
+            Msg::NoMoreSessions { want_reply } => {
+                let _ = self.no_more_sessions(want_reply);
+            }
             msg => {
                 // should be unreachable, since the receiver only gets
                 // messages from methods implemented within russh

russh/src/client/session.rs

@@ -414,6 +414,19 @@ impl Session {
         Ok(())
     }
 
+    pub fn no_more_sessions(&mut self, want_reply: bool) -> Result<(), crate::Error> {
+        self.open_global_requests
+            .push_back(crate::session::GlobalRequestResponse::NoMoreSessions);
+        if let Some(ref mut enc) = self.common.encrypted {
+            push_packet!(enc.write, {
+                msg::GLOBAL_REQUEST.encode(&mut enc.write)?;
+                "[email protected]".encode(&mut enc.write)?;
+                (want_reply as u8).encode(&mut enc.write)?;
+            });
+        }
+        Ok(())
+    }
+
     pub fn data(&mut self, channel: ChannelId, data: CryptoVec) -> Result<(), crate::Error> {
         if let Some(ref mut enc) = self.common.encrypted {
             enc.data(channel, data, self.kex.active())

russh/src/session.rs

@@ -585,6 +585,8 @@ pub(crate) struct NewKeys {
 pub(crate) enum GlobalRequestResponse {
     /// request was for Keepalive, ignore result
     Keepalive,
+    /// request was for NoMoreSessions, disallow additional sessions
+    NoMoreSessions,
     /// request was for TcpIpForward, sends Some(port) for success or None for failure
     TcpIpForward(oneshot::Sender<Option<u32>>),
     /// request was for CancelTcpIpForward, sends true for success or false for failure