DEVELOPMENT ENVIRONMENT

~liljamo/felu

35694256108aae7dbf72677359edd17ef94ba666 — Jonni Liljamo a month ago 5234e58
feat: modified msgAcceptFunc to facilitate dynamic updates
1 files changed, 48 insertions(+), 2 deletions(-)

M internal/dns/server.go
M internal/dns/server.go => internal/dns/server.go +48 -2
@@ 18,9 18,55 @@ func Run(addr string, net string) error {
	dns.HandleFunc(config.FeluConfig.DNSPattern, handleDNSRequest)

	server := &dns.Server{
		Addr: addr,
		Net:  net,
		Addr:          addr,
		Net:           net,
		MsgAcceptFunc: msgAcceptFunc,
	}

	return server.ListenAndServe()
}

// https://github.com/miekg/dns/blob/b77d1ed8e9282cadf21c4124f53a660fed55c8ca/types.go#L192
const _QR = 1 << 15 // query/response (response=1)

// Otherwise the same as the original, but:
//
//	1: Commented out dynamic update rejection.
//	2: Commented out dh.Nscount > 1, for dynamic updates.
//
// TODO: Consider looking this over properly, and maybe ditching the default.
//
// https://github.com/miekg/dns/blob/b77d1ed8e9282cadf21c4124f53a660fed55c8ca/acceptfunc.go
func msgAcceptFunc(dh dns.Header) dns.MsgAcceptAction {
	if isResponse := dh.Bits&_QR != 0; isResponse {
		return dns.MsgIgnore
	}

	/*
		// Don't allow dynamic updates, because then the sections can contain a whole bunch of RRs.
		opcode := int(dh.Bits>>11) & 0xF
		if opcode != dns.OpcodeQuery && opcode != dns.OpcodeNotify {
			return dns.MsgRejectNotImplemented
		}
	*/

	if dh.Qdcount != 1 {
		return dns.MsgReject
	}
	// NOTIFY requests can have a SOA in the ANSWER section. See RFC 1996 Section 3.7 and 3.11.
	if dh.Ancount > 1 {
		return dns.MsgReject
	}
	/*
		// IXFR request could have one SOA RR in the NS section. See RFC 1995, section 3.
		if dh.Nscount > 1 {
			return dns.MsgReject
		}
	*/

	if dh.Arcount > 2 {
		return dns.MsgReject
	}

	return dns.MsgAccept
}