chore: add a tailscale router that uses the CoderVPN protocol

coder · ethanndickson · Nov 7, 2024 · Nov 6, 2024 · Nov 7, 2024 · 2dce0f1aab4a949972ab6b855013d46d3cb2a3fd
commit 2dce0f1aab4a949972ab6b855013d46d3cb2a3fd
diff --git a/tailnet/conn.go b/tailnet/conn.go
@@ -110,6 +110,8 @@ type Options struct {
 	// DNSConfigurator is optional, and is passed to the underlying wireguard
 	// engine.
 	DNSConfigurator dns.OSConfigurator
+	// Router is optional, and is passed to the underlying wireguard engine.
+	Router router.Router
 }
 
 // TelemetrySink allows tailnet.Conn to send network telemetry to the Coder
@@ -183,6 +185,7 @@ func NewConn(options *Options) (conn *Conn, err error) {
 		ListenPort:   options.ListenPort,
 		SetSubsystem: sys.Set,
 		DNS:          options.DNSConfigurator,
+		Router:       options.Router,
 	})
 	if err != nil {
 		return nil, xerrors.Errorf("create wgengine: %w", err)

diff --git a/vpn/router.go b/vpn/router.go
@@ -0,0 +1,105 @@
+package vpn
+
+import (
+	"net"
+	"net/netip"
+
+	"tailscale.com/wgengine/router"
+)
+
+func NewRouter(t *Tunnel) router.Router {
+	return &vpnRouter{tunnel: t}
+}
+
+type vpnRouter struct {
+	tunnel *Tunnel
+}
+
+func (*vpnRouter) Up() error {
+	// On macOS, the Desktop app will handle turning the VPN on and off.
+	// On Windows, this is a no-op.
+	return nil
+}
+
+func (v *vpnRouter) Set(cfg *router.Config) error {
+	req := convertRouterConfig(cfg)
+	return v.tunnel.ApplyNetworkSettings(v.tunnel.ctx, req)
+}
+
+func (*vpnRouter) Close() error {
+	// There's no cleanup that we need to initiate from within the dylib.
+	return nil
+}
+
+func convertRouterConfig(cfg *router.Config) *NetworkSettingsRequest {
+	v4LocalAddrs := make([]string, 0)
+	v6LocalAddrs := make([]string, 0)
+	for _, addrs := range cfg.LocalAddrs {
+		if addrs.Addr().Is4() {
+			v4LocalAddrs = append(v4LocalAddrs, addrs.String())
+		} else if addrs.Addr().Is6() {
+			v6LocalAddrs = append(v6LocalAddrs, addrs.String())
+		} else {
+			continue
+		}
+	}
+	v4Routes := make([]*NetworkSettingsRequest_IPv4Settings_IPv4Route, 0)
+	v6Routes := make([]*NetworkSettingsRequest_IPv6Settings_IPv6Route, 0)
+	for _, route := range cfg.Routes {
+		if route.Addr().Is4() {
+			v4Routes = append(v4Routes, convertToIPV4Route(route))
+		} else if route.Addr().Is6() {
+			v6Routes = append(v6Routes, convertToIPV6Route(route))
+		} else {
+			continue
+		}
+	}
+	v4ExcludedRoutes := make([]*NetworkSettingsRequest_IPv4Settings_IPv4Route, 0)
+	v6ExcludedRoutes := make([]*NetworkSettingsRequest_IPv6Settings_IPv6Route, 0)
+	for _, route := range cfg.LocalRoutes {
+		if route.Addr().Is4() {
+			v4ExcludedRoutes = append(v4ExcludedRoutes, convertToIPV4Route(route))
+		} else if route.Addr().Is6() {
+			v6ExcludedRoutes = append(v6ExcludedRoutes, convertToIPV6Route(route))
+		} else {
+			continue
+		}
+	}
+
+	return &NetworkSettingsRequest{
+		Mtu: uint32(cfg.NewMTU),
+		Ipv4Settings: &NetworkSettingsRequest_IPv4Settings{
+			Addrs:          v4LocalAddrs,
+			IncludedRoutes: v4Routes,
+			ExcludedRoutes: v4ExcludedRoutes,
+		},
+		Ipv6Settings: &NetworkSettingsRequest_IPv6Settings{
+			Addrs:          v6LocalAddrs,
+			IncludedRoutes: v6Routes,
+			ExcludedRoutes: v6ExcludedRoutes,
+		},
+		TunnelOverheadBytes: 0,  // N/A
+		TunnelRemoteAddress: "", // N/A
+	}
+}
+
+func convertToIPV4Route(route netip.Prefix) *NetworkSettingsRequest_IPv4Settings_IPv4Route {
+	return &NetworkSettingsRequest_IPv4Settings_IPv4Route{
+		Destination: route.Addr().String(),
+		Mask:        prefixToSubnetMask(route),
+		Router:      "", // N/A
+	}
+}
+
+func convertToIPV6Route(route netip.Prefix) *NetworkSettingsRequest_IPv6Settings_IPv6Route {
+	return &NetworkSettingsRequest_IPv6Settings_IPv6Route{
+		Destination:  route.Addr().String(),
+		PrefixLength: uint32(route.Bits()),
+		Router:       "", // N/A
+	}
+}
+
+func prefixToSubnetMask(prefix netip.Prefix) string {
+	maskBytes := net.CIDRMask(prefix.Masked().Bits(), net.IPv4len*8)
+	return net.IP(maskBytes).String()
+}
diff --git a/vpn/router_internal_test.go b/vpn/router_internal_test.go
@@ -0,0 +1,74 @@
+package vpn
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"tailscale.com/wgengine/router"
+)
+
+func TestConvertRouterConfig(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		cfg      *router.Config
+		expected *NetworkSettingsRequest
+	}{
+		{
+			name: "IPv4 and IPv6 configuration",
+			cfg: &router.Config{
+				LocalAddrs:  []netip.Prefix{netip.MustParsePrefix("100.64.0.1/32"), netip.MustParsePrefix("fd7a:115c:a1e0::1/128")},
+				Routes:      []netip.Prefix{netip.MustParsePrefix("192.168.0.0/24"), netip.MustParsePrefix("fd00::/64")},
+				LocalRoutes: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8"), netip.MustParsePrefix("2001:db8::/32")},
+				NewMTU:      1500,
+			},
+			expected: &NetworkSettingsRequest{
+				Mtu: 1500,
+				Ipv4Settings: &NetworkSettingsRequest_IPv4Settings{
+					Addrs: []string{"100.64.0.1/32"},
+					IncludedRoutes: []*NetworkSettingsRequest_IPv4Settings_IPv4Route{
+						{Destination: "192.168.0.0", Mask: "255.255.255.0", Router: ""},
+					},
+					ExcludedRoutes: []*NetworkSettingsRequest_IPv4Settings_IPv4Route{
+						{Destination: "10.0.0.0", Mask: "255.0.0.0", Router: ""},
+					},
+				},
+				Ipv6Settings: &NetworkSettingsRequest_IPv6Settings{
+					Addrs: []string{"fd7a:115c:a1e0::1/128"},
+					IncludedRoutes: []*NetworkSettingsRequest_IPv6Settings_IPv6Route{
+						{Destination: "fd00::", PrefixLength: 64, Router: ""},
+					},
+					ExcludedRoutes: []*NetworkSettingsRequest_IPv6Settings_IPv6Route{
+						{Destination: "2001:db8::", PrefixLength: 32, Router: ""},
+					},
+				},
+			},
+		},
+		{
+			name: "Empty",
+			cfg:  &router.Config{},
+			expected: &NetworkSettingsRequest{
+				Ipv4Settings: &NetworkSettingsRequest_IPv4Settings{
+					Addrs:          []string{},
+					IncludedRoutes: []*NetworkSettingsRequest_IPv4Settings_IPv4Route{},
+					ExcludedRoutes: []*NetworkSettingsRequest_IPv4Settings_IPv4Route{},
+				},
+				Ipv6Settings: &NetworkSettingsRequest_IPv6Settings{
+					Addrs:          []string{},
+					IncludedRoutes: []*NetworkSettingsRequest_IPv6Settings_IPv6Route{},
+					ExcludedRoutes: []*NetworkSettingsRequest_IPv6Settings_IPv6Route{},
+				},
+			},
+		},
+	}
+	//nolint:paralleltest // outdated rule
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			result := convertRouterConfig(tt.cfg)
+			require.Equal(t, tt.expected, result)
+		})
+	}
+}