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369 lines
8.2 KiB
Groff
369 lines
8.2 KiB
Groff
.\" Generated by Mmark Markdown Processer - mmark.miek.nl
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.TH "COREDNS-ETCD" 7 "April 2020" "CoreDNS" "CoreDNS Plugins"
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.SH "NAME"
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.PP
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\fIetcd\fP - enables SkyDNS service discovery from etcd.
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.SH "DESCRIPTION"
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.PP
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The \fIetcd\fP plugin implements the (older) SkyDNS service discovery service. It is \fInot\fP suitable as
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a generic DNS zone data plugin. Only a subset of DNS record types are implemented, and subdomains
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and delegations are not handled at all.
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.PP
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The data in the etcd instance has to be encoded as
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a message
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\[la]https://github.com/skynetservices/skydns/blob/2fcff74cdc9f9a7dd64189a447ef27ac354b725f/msg/service.go#L26\[ra]
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like SkyDNS
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\[la]https://github.com/skynetservices/skydns\[ra]. It works just like SkyDNS.
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.PP
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The etcd plugin makes extensive use of the \fIforward\fP plugin to forward and query other servers in the
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network.
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.SH "SYNTAX"
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.PP
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.RS
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.nf
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etcd [ZONES...]
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.fi
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.RE
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.IP \(bu 4
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\fBZONES\fP zones \fIetcd\fP should be authoritative for.
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.PP
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The path will default to \fB\fC/skydns\fR the local etcd3 proxy (http://localhost:2379
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\[la]http://localhost:2379\[ra]). If no zones are
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specified the block's zone will be used as the zone.
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.PP
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If you want to \fB\fCround robin\fR A and AAAA responses look at the \fB\fCloadbalance\fR plugin.
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.PP
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.RS
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.nf
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etcd [ZONES...] {
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fallthrough [ZONES...]
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path PATH
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endpoint ENDPOINT...
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credentials USERNAME PASSWORD
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tls CERT KEY CACERT
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}
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.fi
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.RE
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.IP \(bu 4
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\fB\fCfallthrough\fR If zone matches but no record can be generated, pass request to the next plugin.
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If \fB[ZONES...]\fP is omitted, then fallthrough happens for all zones for which the plugin
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is authoritative. If specific zones are listed (for example \fB\fCin-addr.arpa\fR and \fB\fCip6.arpa\fR), then only
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queries for those zones will be subject to fallthrough.
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.IP \(bu 4
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\fBPATH\fP the path inside etcd. Defaults to "/skydns".
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.IP \(bu 4
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\fBENDPOINT\fP the etcd endpoints. Defaults to "http://localhost:2379"
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\[la]http://localhost:2379"\[ra].
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.IP \(bu 4
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\fB\fCcredentials\fR is used to set the \fBUSERNAME\fP and \fBPASSWORD\fP for accessing the etcd cluster.
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.IP \(bu 4
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\fB\fCtls\fR followed by:
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.RS
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.IP \(en 4
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no arguments, if the server certificate is signed by a system-installed CA and no client cert is needed
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.IP \(en 4
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a single argument that is the CA PEM file, if the server cert is not signed by a system CA and no client cert is needed
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.IP \(en 4
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two arguments - path to cert PEM file, the path to private key PEM file - if the server certificate is signed by a system-installed CA and a client certificate is needed
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.IP \(en 4
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three arguments - path to cert PEM file, path to client private key PEM file, path to CA PEM
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file - if the server certificate is not signed by a system-installed CA and client certificate
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is needed.
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.RE
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.SH "SPECIAL BEHAVIOUR"
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.PP
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The \fIetcd\fP plugin leverages directory structure to look for related entries. For example
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an entry \fB\fC/skydns/test/skydns/mx\fR would have entries like \fB\fC/skydns/test/skydns/mx/a\fR,
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\fB\fC/skydns/test/skydns/mx/b\fR and so on. Similarly a directory \fB\fC/skydns/test/skydns/mx1\fR will have all
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\fB\fCmx1\fR entries.
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.PP
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With etcd3, support for hierarchical keys are
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dropped
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\[la]https://coreos.com/etcd/docs/latest/learning/api.html\[ra]. This means there are no directories
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but only flat keys with prefixes in etcd3. To accommodate lookups, etcdv3 plugin now does a lookup
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on prefix \fB\fC/skydns/test/skydns/mx/\fR to search for entries like \fB\fC/skydns/test/skydns/mx/a\fR etc, and
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if there is nothing found on \fB\fC/skydns/test/skydns/mx/\fR, it looks for \fB\fC/skydns/test/skydns/mx\fR to
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find entries like \fB\fC/skydns/test/skydns/mx1\fR.
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.PP
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This causes two lookups from CoreDNS to etcdv3 in certain cases.
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.SH "EXAMPLES"
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.PP
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This is the default SkyDNS setup, with everything specified in full:
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.PP
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.RS
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.nf
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skydns.local {
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etcd {
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path /skydns
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endpoint http://localhost:2379
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}
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prometheus
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cache
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loadbalance
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}
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\&. {
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forward . 8.8.8.8:53 8.8.4.4:53
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cache
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}
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.fi
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.RE
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.PP
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Or a setup where we use \fB\fC/etc/resolv.conf\fR as the basis for the proxy and the upstream
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when resolving external pointing CNAMEs.
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.PP
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.RS
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.nf
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skydns.local {
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etcd {
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path /skydns
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}
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cache
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}
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\&. {
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forward . /etc/resolv.conf
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cache
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}
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.fi
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.RE
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.PP
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Multiple endpoints are supported as well.
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.PP
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.RS
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.nf
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etcd skydns.local {
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endpoint http://localhost:2379 http://localhost:4001
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\&...
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.fi
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.RE
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.PP
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Before getting started with these examples, please setup \fB\fCetcdctl\fR (with \fB\fCetcdv3\fR API) as explained
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here
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\[la]https://coreos.com/etcd/docs/latest/dev-guide/interacting_v3.html\[ra]. This will help you to put
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sample keys in your etcd server.
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.PP
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If you prefer, you can use \fB\fCcurl\fR to populate the \fB\fCetcd\fR server, but with \fB\fCcurl\fR the
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endpoint URL depends on the version of \fB\fCetcd\fR. For instance, \fB\fCetcd v3.2\fR or before uses only
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[CLIENT-URL]/v3alpha/* while \fB\fCetcd v3.5\fR or later uses [CLIENT-URL]/v3/* . Also, Key and Value must
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be base64 encoded in the JSON payload. With \fB\fCetcdctl\fR these details are automatically taken care
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of. You can check this document
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\[la]https://github.com/coreos/etcd/blob/master/Documentation/dev-guide/api_grpc_gateway.md#notes\[ra]
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for details.
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.SS "REVERSE ZONES"
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.PP
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Reverse zones are supported. You need to make CoreDNS aware of the fact that you are also
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authoritative for the reverse. For instance if you want to add the reverse for 10.0.0.0/24, you'll
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need to add the zone \fB\fC0.0.10.in-addr.arpa\fR to the list of zones. Showing a snippet of a Corefile:
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.PP
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.RS
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.nf
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etcd skydns.local 10.0.0.0/24 {
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\&...
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.fi
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.RE
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.PP
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Next you'll need to populate the zone with reverse records, here we add a reverse for
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10.0.0.127 pointing to reverse.skydns.local.
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.PP
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.RS
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.nf
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% etcdctl put /skydns/arpa/in\-addr/10/0/0/127 '{"host":"reverse.skydns.local."}'
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.fi
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.RE
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.PP
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Querying with dig:
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.PP
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.RS
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.nf
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% dig @localhost \-x 10.0.0.127 +short
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reverse.skydns.local.
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.fi
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.RE
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.SS "ZONE NAME AS A RECORD"
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.PP
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The zone name itself can be used as an \fB\fCA\fR record. This behavior can be achieved by writing special
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entries to the ETCD path of your zone. If your zone is named \fB\fCskydns.local\fR for example, you can
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create an \fB\fCA\fR record for this zone as follows:
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.PP
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.RS
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.nf
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% etcdctl put /skydns/local/skydns/ '{"host":"1.1.1.1","ttl":60}'
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.fi
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.RE
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.PP
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If you query the zone name itself, you will receive the created \fB\fCA\fR record:
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.PP
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.RS
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.nf
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% dig +short skydns.local @localhost
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1.1.1.1
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.fi
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.RE
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.PP
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If you would like to use DNS RR for the zone name, you can set the following:
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.PP
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.RS
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.nf
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% etcdctl put /skydns/local/skydns/x1 '{"host":"1.1.1.1","ttl":60}'
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% etcdctl put /skydns/local/skydns/x2 '{"host":"1.1.1.2","ttl":60}'
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.fi
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.RE
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.PP
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If you query the zone name now, you will get the following response:
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.PP
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.RS
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.nf
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% dig +short skydns.local @localhost
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1.1.1.1
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1.1.1.2
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.fi
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.RE
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.SS "ZONE NAME AS AAAA RECORD"
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.PP
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If you would like to use \fB\fCAAAA\fR records for the zone name too, you can set the following:
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.PP
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.RS
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.nf
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% etcdctl put /skydns/local/skydns/x3 '{"host":"2003::8:1","ttl":60}'
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% etcdctl put /skydns/local/skydns/x4 '{"host":"2003::8:2","ttl":60}'
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.fi
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.RE
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.PP
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If you query the zone name for \fB\fCAAAA\fR now, you will get the following response:
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.PP
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.RS
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.nf
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% dig +short skydns.local AAAA @localhost
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2003::8:1
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2003::8:2
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.fi
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.RE
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.SS "SRV RECORD"
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.PP
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If you would like to use \fB\fCSRV\fR records, you can set the following:
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.PP
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.RS
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.nf
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% etcdctl put /skydns/local/skydns/x5 '{"host":"skydns\-local.server","ttl":60,"priority":10,"port":8080}'
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.fi
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.RE
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.PP
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Please notice that the key \fB\fChost\fR is the \fB\fCtarget\fR in \fB\fCSRV\fR, so it should be a domain name.
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.PP
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If you query the zone name for \fB\fCSRV\fR now, you will get the following response:
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.PP
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.RS
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.nf
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% dig +short skydns.local SRV @localhost
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10 100 8080 skydns\-local.server.
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.fi
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.RE
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.SS "TXT RECORD"
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.PP
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If you would like to use \fB\fCTXT\fR records, you can set the following:
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.PP
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.RS
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.nf
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% etcdctl put /skydns/local/skydns/x6 '{"ttl":60,"text":"this is a random text message."}'
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.fi
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.RE
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.PP
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If you query the zone name for \fB\fCTXT\fR now, you will get the following response:
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.PP
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.RS
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.nf
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% dig +short skydns.local TXT @localhost
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"this is a random text message."
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.fi
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.RE
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