vendor.github.com.miekg.dns.acceptfunc.go Maven / Gradle / Ivy
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package dns
// MsgAcceptFunc is used early in the server code to accept or reject a message with RcodeFormatError.
// It returns a MsgAcceptAction to indicate what should happen with the message.
type MsgAcceptFunc func(dh Header) MsgAcceptAction
// DefaultMsgAcceptFunc checks the request and will reject if:
//
// * isn't a request (don't respond in that case)
//
// * opcode isn't OpcodeQuery or OpcodeNotify
//
// * does not have exactly 1 question in the question section
//
// * has more than 1 RR in the Answer section
//
// * has more than 0 RRs in the Authority section
//
// * has more than 2 RRs in the Additional section
var DefaultMsgAcceptFunc MsgAcceptFunc = defaultMsgAcceptFunc
// MsgAcceptAction represents the action to be taken.
type MsgAcceptAction int
// Allowed returned values from a MsgAcceptFunc.
const (
MsgAccept MsgAcceptAction = iota // Accept the message
MsgReject // Reject the message with a RcodeFormatError
MsgIgnore // Ignore the error and send nothing back.
MsgRejectNotImplemented // Reject the message with a RcodeNotImplemented
)
func defaultMsgAcceptFunc(dh Header) MsgAcceptAction {
if isResponse := dh.Bits&_QR != 0; isResponse {
return 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 != OpcodeQuery && opcode != OpcodeNotify {
return MsgRejectNotImplemented
}
if dh.Qdcount != 1 {
return 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 MsgReject
}
// IXFR request could have one SOA RR in the NS section. See RFC 1995, section 3.
if dh.Nscount > 1 {
return MsgReject
}
if dh.Arcount > 2 {
return MsgReject
}
return MsgAccept
}