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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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33
test/edns0_test.go Normal file
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@ -0,0 +1,33 @@
package test
import (
"testing"
"github.com/miekg/dns"
)
func TestEDNS0(t *testing.T) {
corefile := `.:0 {
whoami
}
`
i, udp, _, err := CoreDNSServerAndPorts(corefile)
if err != nil {
t.Fatalf("Could not get CoreDNS serving instance: %s", err)
}
defer i.Stop()
m := new(dns.Msg)
m.SetQuestion("example.org.", dns.TypeSOA)
m.SetEdns0(4096, true)
resp, err := dns.Exchange(m, udp)
if err != nil {
t.Fatalf("Expected to receive reply, but didn't: %v", err)
}
opt := resp.Extra[len(resp.Extra)-1]
if opt.Header().Rrtype != dns.TypeOPT {
t.Errorf("Last RR must be OPT record")
}
}