code review 6295096: Added RequestSubsystem(), according to RFC 4254 Section...

ssh/session.go

Index: ssh/session.go 
=================================================================== 
--- a/ssh/session.go 
+++ b/ssh/session.go 
@@ -85,6 +85,14 @@ 
	Value string 
 } 
 
+// RFC 4254 Section 6.5. 
+type subsystemRequestMsg struct { 
+	PeersId uint32 
+	Request string 
+	WantReply bool 
+	Subsystem string 
+} 
+ 
 // Setenv sets an environment variable that will be applied to any 
 // command executed by Shell or Run. 
 func (s *Session) Setenv(name, value string) error { 
@@ -136,6 +144,21 @@ 
	return s.waitForResponse() 
 } 
 
+// RequestSubsystem requests the association of a subsystem with the session on the remote host. 
+// A subsystem is a predefined command that runs in the background when the ssh session is initiated 
+func (s *Session) RequestSubsystem(subsystem string) error { 
+	req := subsystemRequestMsg{ 
+	PeersId: s.remoteId, 
+	Request: "subsystem", 
+	WantReply: true, 
+	Subsystem: subsystem, 
+	} 
+	if err := s.writePacket(marshal(msgChannelRequest, req)); err != nil { 
+	return err 
+	} 
+	return s.waitForResponse() 
+} 
+ 
 // RFC 4254 Section 6.9. 
 type signalMsg struct { 
	PeersId uint32