traefik/vendor/github.com/miekg/dns/acceptfunc.go

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2019-01-07 17:30:06 +00:00
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
// * Zero bit isn't zero
// * has more than 1 question in the question section
// * has more than 0 RRs 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
const (
MsgAccept MsgAcceptAction = iota // Accept the message
MsgReject // Reject the message with a RcodeFormatError
MsgIgnore // Ignore the error and send nothing back.
)
var defaultMsgAcceptFunc = func(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 MsgReject
}
if isZero := dh.Bits&_Z != 0; isZero {
return MsgReject
}
if dh.Qdcount != 1 {
return MsgReject
}
if dh.Ancount != 0 {
return MsgReject
}
if dh.Nscount != 0 {
return MsgReject
}
if dh.Arcount > 2 {
return MsgReject
}
return MsgAccept
}