hotfix(pmtud): detect IPv6 usage in VPN connection

internal/vpn/ipv6.go

@@ -0,0 +1,48 @@
+package vpn
+
+import (
+	"github.com/qdm12/gluetun/internal/configuration/settings"
+	"github.com/qdm12/gluetun/internal/constants/vpn"
+	"github.com/qdm12/gluetun/internal/netlink"
+)
+
+func (l *Loop) isIPv6Used(settings settings.VPN) bool {
+	if !l.ipv6SupportLevel.IsSupported() {
+		return false
+	}
+	switch settings.Type {
+	case vpn.AmneziaWg:
+		for _, prefix := range settings.AmneziaWg.Wireguard.Addresses {
+			if prefix.Addr().Is6() {
+				return true
+			}
+		}
+		return false
+	case vpn.OpenVPN:
+		link, err := l.netLinker.LinkByName(settings.OpenVPN.Interface)
+		if err != nil {
+			l.logger.Warnf("assuming IPv6 is not supported, cannot get OpenVPN link by name: %v", err)
+			return false
+		}
+		ipv6Prefixes, err := l.netLinker.AddrList(link.Index, netlink.FamilyV6)
+		if err != nil {
+			l.logger.Warnf("assuming IPv6 is not supported, cannot list OpenVPN link addresses: %v", err)
+			return false
+		}
+		for _, prefix := range ipv6Prefixes {
+			if prefix.Addr().IsGlobalUnicast() && !prefix.Addr().IsPrivate() {
+				return true
+			}
+		}
+		return false
+	case vpn.Wireguard:
+		for _, prefix := range settings.Wireguard.Addresses {
+			if prefix.Addr().Is6() {
+				return true
+			}
+		}
+		return false
+	default:
+		panic("vpn type not implemented: " + settings.Type)
+	}
+}