TUN-2607: add RPC stream helpers

connection/rpc.go

@@ -0,0 +1,49 @@
+package connection
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/sirupsen/logrus"
+	rpc "zombiezen.com/go/capnproto2/rpc"
+
+	"github.com/cloudflare/cloudflared/h2mux"
+	"github.com/cloudflare/cloudflared/tunnelrpc"
+	tunnelpogs "github.com/cloudflare/cloudflared/tunnelrpc/pogs"
+)
+
+// NewRPCClient creates and returns a new RPC client, which will communicate
+// using a stream on the given muxer
+func NewRPCClient(
+	ctx context.Context,
+	muxer *h2mux.Muxer,
+	logger *logrus.Entry,
+	openStreamTimeout time.Duration,
+) (client tunnelpogs.TunnelServer_PogsClient, err error) {
+	openStreamCtx, openStreamCancel := context.WithTimeout(ctx, openStreamTimeout)
+	defer openStreamCancel()
+	stream, err := muxer.OpenRPCStream(openStreamCtx)
+	if err != nil {
+		return
+	}
+
+	if !isRPCStreamResponse(stream.Headers) {
+		stream.Close()
+		err = fmt.Errorf("rpc: bad response headers: %v", stream.Headers)
+		return
+	}
+
+	conn := rpc.NewConn(
+		tunnelrpc.NewTransportLogger(logger, rpc.StreamTransport(stream)),
+		tunnelrpc.ConnLog(logger),
+	)
+	client = tunnelpogs.TunnelServer_PogsClient{Client: conn.Bootstrap(ctx), Conn: conn}
+	return client, nil
+}
+
+func isRPCStreamResponse(headers []h2mux.Header) bool {
+	return len(headers) == 1 &&
+		headers[0].Name == ":status" &&
+		headers[0].Value == "200"
+}