Платформа ЦРНП "Мирокод" для разработки проектов
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62 lines
1.9 KiB
62 lines
1.9 KiB
package dns |
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// MsgAcceptFunc is used early in the server code to accept or reject a message with RcodeFormatError. |
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// It returns a MsgAcceptAction to indicate what should happen with the message. |
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type MsgAcceptFunc func(dh Header) MsgAcceptAction |
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// DefaultMsgAcceptFunc checks the request and will reject if: |
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// |
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// * isn't a request (don't respond in that case) |
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// |
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// * opcode isn't OpcodeQuery or OpcodeNotify |
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// |
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// * Zero bit isn't zero |
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// |
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// * has more than 1 question in the question section |
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// |
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// * has more than 1 RR in the Answer section |
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// |
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// * has more than 0 RRs in the Authority section |
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// |
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// * has more than 2 RRs in the Additional section |
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// |
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var DefaultMsgAcceptFunc MsgAcceptFunc = defaultMsgAcceptFunc |
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// MsgAcceptAction represents the action to be taken. |
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type MsgAcceptAction int |
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// Allowed returned values from a MsgAcceptFunc. |
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const ( |
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MsgAccept MsgAcceptAction = iota // Accept the message |
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MsgReject // Reject the message with a RcodeFormatError |
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MsgIgnore // Ignore the error and send nothing back. |
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MsgRejectNotImplemented // Reject the message with a RcodeNotImplemented |
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) |
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func defaultMsgAcceptFunc(dh Header) MsgAcceptAction { |
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if isResponse := dh.Bits&_QR != 0; isResponse { |
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return MsgIgnore |
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} |
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// Don't allow dynamic updates, because then the sections can contain a whole bunch of RRs. |
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opcode := int(dh.Bits>>11) & 0xF |
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if opcode != OpcodeQuery && opcode != OpcodeNotify { |
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return MsgRejectNotImplemented |
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} |
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if dh.Qdcount != 1 { |
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return MsgReject |
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} |
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// NOTIFY requests can have a SOA in the ANSWER section. See RFC 1996 Section 3.7 and 3.11. |
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if dh.Ancount > 1 { |
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return MsgReject |
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} |
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// IXFR request could have one SOA RR in the NS section. See RFC 1995, section 3. |
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if dh.Nscount > 1 { |
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return MsgReject |
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} |
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if dh.Arcount > 2 { |
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return MsgReject |
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} |
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return MsgAccept |
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}
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