dns-suite.js/node_modules/dns-js/doc/edns.md

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2017-01-14 02:04:27 +00:00
EDNS
====
Extension Mechanisms for DNS
This document will give some hints to litterature about edns
and how it's done in this project.
* https://tools.ietf.org/html/rfc6891
* https://en.wikipedia.org/wiki/Extension_mechanisms_for_DNS
OPT RR, 41/0x29
---------------
OPT RR MAY be placed anywhere in the additional data section,
it MUST be the only OPT RR in that message.
###Wireformat
Wireformat is described in section 6.1.2 of RFC6891
Fixed part
```
+------------+--------------+------------------------------+
| Field Name | Field Type | Description |
+------------+--------------+------------------------------+
| NAME | domain name | MUST be 0 (root domain) |
| TYPE | u_int16_t | OPT (41) |
| CLASS | u_int16_t | requestor's UDP payload size |
| TTL | u_int32_t | extended RCODE and flags |
| RDLEN | u_int16_t | length of all RDATA |
| RDATA | octet stream | {attribute,value} pairs |
+------------+--------------+------------------------------+
```
Varable part
```
+0 (MSB) +1 (LSB)
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
0: | OPTION-CODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
2: | OPTION-LENGTH |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
4: | |
/ OPTION-DATA /
/ /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
```