feat(agent): add second SSH listener on port 22 (#16627)

Fixes: https://github.com/coder/internal/issues/377

Added an additional SSH listener on port 22, so the agent now listens on both, port one and port 22.

---
Change-Id: Ifd986b260f8ac317e37d65111cd4e0bd1dc38af8
Signed-off-by: Thomas Kosiewski <tk@coder.com>

codersdk/workspacesdk/agentconn.go

@@ -165,6 +165,12 @@ func (c *AgentConn) ReconnectingPTY(ctx context.Context, id uuid.UUID, height, w
 // SSH pipes the SSH protocol over the returned net.Conn.
 // This connects to the built-in SSH server in the workspace agent.
 func (c *AgentConn) SSH(ctx context.Context) (*gonet.TCPConn, error) {
+	return c.SSHOnPort(ctx, AgentSSHPort)
+}
+
+// SSHOnPort pipes the SSH protocol over the returned net.Conn.
+// This connects to the built-in SSH server in the workspace agent on the specified port.
+func (c *AgentConn) SSHOnPort(ctx context.Context, port uint16) (*gonet.TCPConn, error) {
 	ctx, span := tracing.StartSpan(ctx)
 	defer span.End()
 
@@ -172,17 +178,23 @@ func (c *AgentConn) SSH(ctx context.Context) (*gonet.TCPConn, error) {
 		return nil, xerrors.Errorf("workspace agent not reachable in time: %v", ctx.Err())
 	}
 
-	c.Conn.SendConnectedTelemetry(c.agentAddress(), tailnet.TelemetryApplicationSSH)
-	return c.Conn.DialContextTCP(ctx, netip.AddrPortFrom(c.agentAddress(), AgentSSHPort))
+	c.SendConnectedTelemetry(c.agentAddress(), tailnet.TelemetryApplicationSSH)
+	return c.DialContextTCP(ctx, netip.AddrPortFrom(c.agentAddress(), port))
 }
 
 // SSHClient calls SSH to create a client that uses a weak cipher
 // to improve throughput.
 func (c *AgentConn) SSHClient(ctx context.Context) (*ssh.Client, error) {
+	return c.SSHClientOnPort(ctx, AgentSSHPort)
+}
+
+// SSHClientOnPort calls SSH to create a client on a specific port
+// that uses a weak cipher to improve throughput.
+func (c *AgentConn) SSHClientOnPort(ctx context.Context, port uint16) (*ssh.Client, error) {
 	ctx, span := tracing.StartSpan(ctx)
 	defer span.End()
 
-	netConn, err := c.SSH(ctx)
+	netConn, err := c.SSHOnPort(ctx, port)
 	if err != nil {
 		return nil, xerrors.Errorf("ssh: %w", err)
 	}

codersdk/workspacesdk/workspacesdk.go

@@ -31,6 +31,7 @@ var ErrSkipClose = xerrors.New("skip tailnet close")
 
 const (
 	AgentSSHPort             = tailnet.WorkspaceAgentSSHPort
+	AgentStandardSSHPort     = tailnet.WorkspaceAgentStandardSSHPort
 	AgentReconnectingPTYPort = tailnet.WorkspaceAgentReconnectingPTYPort
 	AgentSpeedtestPort       = tailnet.WorkspaceAgentSpeedtestPort
 	// AgentHTTPAPIServerPort serves a HTTP server with endpoints for e.g.