48 lines
1.5 KiB
Go
48 lines
1.5 KiB
Go
package dnsforward
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import (
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"net"
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"net/netip"
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"github.com/AdguardTeam/dnsproxy/proxy"
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)
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// setupDNS64 initializes DNS64 settings, the NAT64 prefixes in particular. If
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// the DNS64 feature is enabled and no prefixes are configured, the default
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// Well-Known Prefix is used, just like Section 5.2 of RFC 6147 prescribes. Any
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// configured set of prefixes discards the default Well-Known prefix unless it
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// is specified explicitly. Each prefix also validated to be a valid IPv6
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// CIDR with a maximum length of 96 bits. The first specified prefix is then
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// used to synthesize AAAA records.
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func (s *Server) setupDNS64() {
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if !s.conf.UseDNS64 {
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return
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}
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if len(s.conf.DNS64Prefixes) == 0 {
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// dns64WellKnownPref is the default prefix to use in an algorithmic
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// mapping for DNS64.
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//
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// See https://datatracker.ietf.org/doc/html/rfc6052#section-2.1.
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dns64WellKnownPref := netip.MustParsePrefix("64:ff9b::/96")
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s.dns64Pref = dns64WellKnownPref
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} else {
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s.dns64Pref = s.conf.DNS64Prefixes[0]
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}
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}
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// mapDNS64 maps ip to IPv6 address using configured DNS64 prefix. ip must be a
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// valid IPv4. It panics, if there are no configured DNS64 prefixes, because
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// synthesis should not be performed unless DNS64 function enabled.
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func (s *Server) mapDNS64(ip netip.Addr) (mapped net.IP) {
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pref := s.dns64Pref.Masked().Addr().As16()
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ipData := ip.As4()
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mapped = make(net.IP, net.IPv6len)
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copy(mapped[:proxy.NAT64PrefixLength], pref[:])
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copy(mapped[proxy.NAT64PrefixLength:], ipData[:])
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return mapped
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}
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