reintroduced ClientInfo because it does appear to work.

Most likely some error elsewhere caused it not to work previously

pkg/comms/agentlistener.go

@@ -41,7 +41,7 @@ func (listener AgentListener) Accept() (net.Conn, error) {
 		conn.Close()
 		return nil, err
 	}
-	conn = NewLocalAddrHackConn(conn, clientId)
+	conn = NewLocalAddrHackConn(conn, clientId.ClientId)
 	return conn, nil
 }
 

pkg/comms/agentlistener_test.go

@@ -19,7 +19,7 @@ func (s *AgentServerTestSuite) Test_clientIdPassedAsLocalAddr() {
 		func() any {
 			connection, err := serverChannel.Session.OpenStream()
 			s.Nil(err)
-			err = SendClientInfo(connection, clientId)
+			err = SendClientInfo(connection, ClientInfo{ClientId: clientId})
 			s.Nil(err)
 			return nil
 		})

pkg/comms/agentserver.go

@@ -1,7 +1,6 @@
 package comms
 
 import (
-	"encoding/binary"
 	"fmt"
 	"github.com/hashicorp/yamux"
 	"io"
@@ -227,31 +226,18 @@ func CheckProtocolVersion(role Role, channel GOBChannel) error {
 // decorates the yamux Session (which is a listener) and uses this connection to exchange some
 // metadata before the connection is handed back to SSH.
 
-// Cannot use GOB for sending clientinfo since this involves mixing of buffered reads by
-// GOB with ather reads. Alternatively, we could wrap the GOB message and encode its length,
-// and then read the exacct number of bytes when decodeing. But since the clientInfo is just
-// a string, this is easier.
-func SendClientInfo(conn io.Writer, info string) error {
-	err := binary.Write(conn, binary.BigEndian, uint32(len(info)))
-	if err != nil {
-		return err
-	}
-	_, err = conn.Write([]byte(info))
-	return err
+func SendClientInfo(conn io.ReadWriter, info ClientInfo) error {
+	channel := NewGOBChannel(conn)
+	return SendWithTimeout(channel, info)
 }
 
-func ReceiveClientInfo(conn io.Reader) (string, error) {
-	var length uint32
-	err := binary.Read(conn, binary.BigEndian, &length)
+func ReceiveClientInfo(conn io.ReadWriter) (ClientInfo, error) {
+	channel := NewGOBChannel(conn)
+	clientInfo, err := ReceiveWithTimeout[ClientInfo](channel)
 	if err != nil {
-		return "", err
+		return ClientInfo{}, err
 	}
-	bytes := make([]byte, length)
-	_, err = io.ReadFull(conn, bytes)
-	if err != nil {
-		return "", err
-	}
-	return string(bytes), nil
+	return clientInfo, nil
 }
 
 // message sent on the initial connection from server to agent to confirm the registration

pkg/comms/agentserver_test.go

@@ -64,11 +64,11 @@ func TestAgentServerTestSuite(t *testing.T) {
 func (s *AgentServerTestSuite) TestClientInfoEncodeDecode() {
 	for _, clientId := range []string{"abc", "djkdfadfha"} {
 		buf := &bytes.Buffer{}
-		err := SendClientInfo(buf, clientId)
+		err := SendClientInfo(buf, ClientInfo{ClientId: clientId})
 		s.Nil(err)
 		clientIdReceived, err := ReceiveClientInfo(buf)
 		s.Nil(err)
-		s.Equal(clientId, clientIdReceived)
+		s.Equal(clientId, clientIdReceived.ClientId)
 	}
 }
 

pkg/comms/events.go

@@ -29,6 +29,10 @@ type EnvironmentInfo struct {
 	Shell    string
 }
 
+type ClientInfo struct {
+	ClientId string
+}
+
 type SessionInfo struct {
 	ClientId string
 

pkg/server/admin/admin.go

@@ -180,7 +180,7 @@ func (admin *Admin) AddClient(publicId models.RendezVousId, clientConn iowrapper
 
 	// Before using this connection for SSH we use it to send client metadata to the
 	// agent
-	err = comms.SendClientInfo(agentConn, string(client.Info.ClientId))
+	err = comms.SendClientInfo(agentConn, comms.ClientInfo{ClientId: string(client.Info.ClientId)})
 	if err != nil {
 		return nil, err
 	}