TUN-4596: Add QUIC application protocol for QUIC stream handshake

- Vendored the capnproto library to cloudflared.
- Added capnproto schema defining application protocol.
- Added Pogs and application level read write of the protocol.

quic/quic_protocol_test.go

@@ -0,0 +1,88 @@
+package quic
+
+import (
+	"bytes"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConnectRequestData(t *testing.T) {
+	var tests = []struct {
+		name           string
+		hostname       string
+		connectionType ConnectionType
+		metadata       []Metadata
+	}{
+		{
+			name:           "Signature verified and request metadata is unmarshaled and read correctly",
+			hostname:       "tunnel.com",
+			connectionType: ConnectionTypeHTTP,
+			metadata: []Metadata{
+				Metadata{
+					Key: "key",
+					Val: "1234",
+				},
+			},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			b := &bytes.Buffer{}
+			err := WriteConnectRequestData(b, test.hostname, test.connectionType, test.metadata...)
+			require.NoError(t, err)
+			reqMeta, err := ReadConnectRequestData(b)
+			require.NoError(t, err)
+
+			assert.Equal(t, test.metadata, reqMeta.Metadata)
+			assert.Equal(t, test.hostname, reqMeta.Dest)
+			assert.Equal(t, test.connectionType, reqMeta.Type)
+		})
+	}
+}
+
+func TestConnectResponseMeta(t *testing.T) {
+	var tests = []struct {
+		name     string
+		err      error
+		metadata []Metadata
+	}{
+		{
+			name: "Signature verified and response metadata is unmarshaled and read correctly",
+			metadata: []Metadata{
+				Metadata{
+					Key: "key",
+					Val: "1234",
+				},
+			},
+		},
+		{
+			name: "If error is not empty, other fields should be blank",
+			err:  errors.New("something happened"),
+			metadata: []Metadata{
+				Metadata{
+					Key: "key",
+					Val: "1234",
+				},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			b := &bytes.Buffer{}
+			err := WriteConnectResponseData(b, test.err, test.metadata...)
+			require.NoError(t, err)
+			respMeta, err := ReadConnectResponseData(b)
+			require.NoError(t, err)
+
+			if respMeta.Error == "" {
+				assert.Equal(t, test.metadata, respMeta.Metadata)
+			} else {
+				assert.Equal(t, 0, len(respMeta.Metadata))
+			}
+		})
+	}
+}