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Fix EDNS0 compliance (#2357)

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* Fix EDNS0 compliance

Do SizeAndDo in the server (ScrubWriter) and remove all uses of this
from the plugins. Also *always* do it. This is to get into compliance
for https://dnsflagday.net/.

The pkg/edns0 now exports the EDNS0 options we understand; this is
exported to allow plugins add things there. The *rewrite* plugin used
this to add custom EDNS0 option codes that the server needs to
understand.

This also needs a new release of miekg/dns because it triggered a
race-condition that was basicly there forever.

See:
* https://github.com/miekg/dns/issues/857
* https://github.com/miekg/dns/pull/859

Running a test instance and pointing the https://ednscomp.isc.org/ednscomp
to it shows the tests are now fixed:

~~~
EDNS Compliance Tester
Checking: 'miek.nl' as at 2018-12-01T17:53:15Z

miek.nl. @147.75.204.203 (drone.coredns.io.): dns=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=ok ednsflags=ok docookie=ok edns512tcp=ok optlist=ok
miek.nl. @2604:1380:2002:a000::1 (drone.coredns.io.): dns=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=ok ednsflags=ok docookie=ok edns512tcp=ok optlist=ok

All Ok
Codes
ok - test passed.
~~~

Signed-off-by: Miek Gieben <miek@miek.nl>

Signed-off-by: Miek Gieben <miek@miek.nl>

* typos in comments

Signed-off-by: Miek Gieben <miek@miek.nl>
This commit is contained in:
Miek Gieben 2018-12-06 21:18:11 +00:00 • committed by GitHub
parent f51c110511
commit fc667b98e0
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16 changed files with 113 additions and 20 deletions
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27
plugin/pkg/edns/edns.go
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@ -3,10 +3,37 @@ package edns
import (
"errors"
"sync"
"github.com/miekg/dns"
)
var sup = &supported{m: make(map[uint16]struct{})}
type supported struct {
m map[uint16]struct{}
sync.RWMutex
}
// SetSupportedOption adds a new supported option the set of EDNS0 options that we support. Plugins typically call
// this in their setup code to signal support for a new option.
// By default we support:
// dns.EDNS0NSID, dns.EDNS0EXPIRE, dns.EDNS0COOKIE, dns.EDNS0TCPKEEPALIVE, dns.EDNS0PADDING. These
// values are not in this map and checked directly in the server.
func SetSupportedOption(option uint16) {
sup.Lock()
sup.m[option] = struct{}{}
sup.Unlock()
}
// SupportedOption returns true if the option code is supported as an extra EDNS0 option.
func SupportedOption(option uint16) bool {
sup.RLock()
_, ok := sup.m[option]
sup.RUnlock()
return ok
}
// Version checks the EDNS version in the request. If error
// is nil everything is OK and we can invoke the plugin. If non-nil, the
// returned Msg is valid to be returned to the client (and should). For some