50 lines
1.7 KiB
Markdown
50 lines
1.7 KiB
Markdown
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EDNS
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====
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Extension Mechanisms for DNS
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This document will give some hints to litterature about edns
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and how it's done in this project.
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* https://tools.ietf.org/html/rfc6891
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* https://en.wikipedia.org/wiki/Extension_mechanisms_for_DNS
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OPT RR, 41/0x29
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---------------
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OPT RR MAY be placed anywhere in the additional data section,
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it MUST be the only OPT RR in that message.
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###Wireformat
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Wireformat is described in section 6.1.2 of RFC6891
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Fixed part
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```
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+------------+--------------+------------------------------+
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| Field Name | Field Type | Description |
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+------------+--------------+------------------------------+
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| NAME | domain name | MUST be 0 (root domain) |
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| TYPE | u_int16_t | OPT (41) |
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| CLASS | u_int16_t | requestor's UDP payload size |
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| TTL | u_int32_t | extended RCODE and flags |
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| RDLEN | u_int16_t | length of all RDATA |
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| RDATA | octet stream | {attribute,value} pairs |
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+------------+--------------+------------------------------+
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```
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Varable part
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```
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+0 (MSB) +1 (LSB)
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+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
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0: | OPTION-CODE |
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+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
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2: | OPTION-LENGTH |
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+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
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4: | |
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/ OPTION-DATA /
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/ /
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+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
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```
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