Merge pull request #201 from Bytom/v0.1

[bytom/vapor.git] / vendor / github.com / miekg / dns / acceptfunc.go

diff --git a/vendor/github.com/miekg/dns/acceptfunc.go b/vendor/github.com/miekg/dns/acceptfunc.go
new file mode 100644 (file)
index 0000000..78c076c
--- /dev/null
+++ b/vendor/github.com/miekg/dns/acceptfunc.go
@@ -0,0 +1,56 @@
+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 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
+
+const (
+       MsgAccept MsgAcceptAction = iota // Accept the message
+       MsgReject                        // Reject the message with a RcodeFormatError
+       MsgIgnore                        // Ignore the error and send nothing back.
+)
+
+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 MsgReject
+       }
+
+       if isZero := dh.Bits&_Z != 0; isZero {
+               return MsgReject
+       }
+       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
+}