feat(perfectprivacy): port forwarding support (#2378)

internal/provider/perfectprivacy/portforward.go

@@ -0,0 +1,43 @@
+package perfectprivacy
+
+import (
+	"context"
+	"net/netip"
+
+	"github.com/qdm12/gluetun/internal/provider/utils"
+)
+
+// PortForward calculates and returns the VPN server side ports forwarded.
+func (p *Provider) PortForward(_ context.Context,
+	objects utils.PortForwardObjects) (ports []uint16, err error) {
+	if !objects.InternalIP.IsValid() {
+		panic("internal ip is not set")
+	}
+
+	return internalIPToPorts(objects.InternalIP), nil
+}
+
+func (p *Provider) KeepPortForward(ctx context.Context,
+	_ utils.PortForwardObjects) (err error) {
+	<-ctx.Done()
+	return ctx.Err()
+}
+
+// See https://www.perfect-privacy.com/en/faq section
+// How are the default forwarding ports being calculated?
+func internalIPToPorts(internalIP netip.Addr) (ports []uint16) {
+	internalIPBytes := internalIP.AsSlice()
+	// Convert the internal IP address to a bit string
+	// and keep only the last 12 bits
+	last16Bits := internalIPBytes[len(internalIPBytes)-2:]
+	last12Bits := []byte{
+		last16Bits[0] & 0b00001111, // only keep 4 bits
+		last16Bits[1],
+	}
+	basePort := uint16(last12Bits[0])<<8 + uint16(last12Bits[1]) //nolint:gomnd
+	return []uint16{
+		10000 + basePort,
+		20000 + basePort,
+		30000 + basePort,
+	}
+}

internal/provider/perfectprivacy/portforward_test.go

@@ -0,0 +1,33 @@
+package perfectprivacy
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_internalIPToPorts(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		internalIP netip.Addr
+		ports      []uint16
+	}{
+		"example_case": {
+			internalIP: netip.AddrFrom4([4]byte{10, 0, 203, 88}),
+			ports:      []uint16{12904, 22904, 32904},
+		},
+	}
+
+	for name, testCase := range testCases {
+		testCase := testCase
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			ports := internalIPToPorts(testCase.internalIP)
+
+			assert.Equal(t, testCase.ports, ports)
+		})
+	}
+}

internal/provider/utils/portforward.go

@@ -13,6 +13,8 @@ type PortForwardObjects struct {
 	// Gateway is the VPN gateway IP address, used by Private Internet Access
 	// and ProtonVPN.
 	Gateway netip.Addr
+	// InternalIP is the VPN internal IP address assigned, used by Perfect Privacy.
+	InternalIP netip.Addr
 	// Client is used to query the VPN gateway for Private Internet Access.
 	Client *http.Client
 	// ServerName is used by Private Internet Access for port forwarding.