Pull request 306: 6510-mapped-addr

Updates AdguardTeam/AdGuardHome#6510.

Squashed commit of the following:

commit 9dae89e
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Dec 8 19:08:32 2023 +0300

    netutil: unmap v4-in-v6 addrs

Author: ainar-g

internal/netutil/udp_unix.go

@@ -44,7 +44,9 @@ func udpSetOptions(c *net.UDPConn) (err error) {
 func udpGetDstFromOOB(oob []byte) (dst netip.Addr, err error) {
 	cm6 := &ipv6.ControlMessage{}
 	if cm6.Parse(oob) == nil && cm6.Dst != nil {
-		return netutil.IPToAddr(cm6.Dst, netutil.AddrFamilyIPv6)
+		// Linux maps IPv4 addresses to IPv6 ones by default, so we can get an
+		// IPv4 dst from an IPv6 control-message.
+		return netutil.IPToAddrNoMapped(cm6.Dst)
 	}
 
 	cm4 := &ipv4.ControlMessage{}