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plugin/rewrite: add rcode as a rewrite option (#6204)

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* plugin/forward add ignore_server_failure for masking upstream server faults

Signed-off-by: schou <pschou@users.noreply.github.com>

* Switch from a ignore_server_fail to a rewrite rcode type.

Signed-off-by: schou <pschou@users.noreply.github.com>

* trim down the tests

Signed-off-by: schou <pschou@users.noreply.github.com>

* fixing readme TTL and using map for rcode

Signed-off-by: schou <pschou@users.noreply.github.com>

* add newline

Signed-off-by: schou <pschou@users.noreply.github.com>

---------

Signed-off-by: schou <pschou@users.noreply.github.com>
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pschou
2023-08-26 22:20:12 -04:00
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parent 07c7dc82f0
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plugin/rewrite/README.md
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@@ -26,6 +26,7 @@ e.g., to rewrite ANY queries to HINFO, use `rewrite type ANY HINFO`.
* `edns0` - an EDNS0 option can be appended to the request as described below in the **EDNS0 Options** section.
* `ttl` - the TTL value in the _response_ is rewritten.
* `cname` - the CNAME target if the response has a CNAME record
* `rcode` - the response code (RCODE) value in the _response_ is rewritten.
* **TYPE** this optional element can be specified for a `name` or `ttl` field.
If not given type `exact` will be assumed. If options should be specified the
@@ -335,6 +336,61 @@ rewrite ttl example.com. 30-
rewrite ttl example.com. 30 # equivalent to rewrite ttl example.com. 30-30
```
### RCODE Field Rewrites
At times, the need to rewrite a RCODE value could arise. For example, a DNS server
may respond with a SERVFAIL instead of NOERROR records when AAAA records are requested.
In the below example, the rcode value the answer for `coredns.rocks` the replies with SERVFAIL
is being switched to NOERROR.
This example rewrites all the *.coredns.rocks domain SERVFAIL errors to NOERROR
```
rewrite continue {
rcode regex (.*)\.coredns\.rocks SERVFAIL NOERROR
}
```
The same result numeric values:
```
rewrite continue {
rcode regex (.*)\.coredns\.rocks 2 0
}
```
The syntax for the RCODE rewrite rule is as follows. The meaning of
`exact|prefix|suffix|substring|regex` is the same as with the name rewrite rules.
An omitted type is defaulted to `exact`.
```
rewrite [continue|stop] rcode [exact|prefix|suffix|substring|regex] STRING FROM TO
```
The values of FROM and TO can be any of the following, text value or numeric:
```
0 NOERROR
1 FORMERR
2 SERVFAIL
3 NXDOMAIN
4 NOTIMP
5 REFUSED
6 YXDOMAIN
7 YXRRSET
8 NXRRSET
9 NOTAUTH
10 NOTZONE
16 BADSIG
17 BADKEY
18 BADTIME
19 BADMODE
20 BADNAME
21 BADALG
22 BADTRUNC
23 BADCOOKIE
```
## EDNS0 Options
Using the FIELD edns0, you can set, append, or replace specific EDNS0 options in the request.