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206 lines
4.4 KiB
Groff
206 lines
4.4 KiB
Groff
.\" Generated by Mmark Markdown Processer - mmark.miek.nl
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.TH "COREDNS-GRPC" 7 "March 2021" "CoreDNS" "CoreDNS Plugins"
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.SH "NAME"
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.PP
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\fIgrpc\fP - facilitates proxying DNS messages to upstream resolvers via gRPC protocol.
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.SH "DESCRIPTION"
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.PP
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The \fIgrpc\fP plugin supports gRPC and TLS.
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.PP
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This plugin can only be used once per Server Block.
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.SH "SYNTAX"
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.PP
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In its most basic form:
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.PP
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.RS
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.nf
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grpc FROM TO...
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.fi
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.RE
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.IP \(bu 4
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\fBFROM\fP is the base domain to match for the request to be proxied.
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.IP \(bu 4
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\fBTO...\fP are the destination endpoints to proxy to. The number of upstreams is
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limited to 15.
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.PP
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Multiple upstreams are randomized (see \fB\fCpolicy\fR) on first use. When a proxy returns an error
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the next upstream in the list is tried.
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.PP
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Extra knobs are available with an expanded syntax:
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.PP
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.RS
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.nf
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grpc FROM TO... {
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except IGNORED\_NAMES...
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tls CERT KEY CA
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tls\_servername NAME
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policy random|round\_robin|sequential
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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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\fBFROM\fP and \fBTO...\fP as above.
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.IP \(bu 4
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\fBIGNORED_NAMES\fP in \fB\fCexcept\fR is a space-separated list of domains to exclude from proxying.
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Requests that match none of these names will be passed through.
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.IP \(bu 4
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\fB\fCtls\fR \fBCERT\fP \fBKEY\fP \fBCA\fP define the TLS properties for TLS connection. From 0 to 3 arguments can be
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provided with the meaning as described below
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.RS
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.IP \(en 4
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\fB\fCtls\fR - no client authentication is used, and the system CAs are used to verify the server certificate
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.IP \(en 4
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\fB\fCtls\fR \fBCA\fP - no client authentication is used, and the file CA is used to verify the server certificate
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.IP \(en 4
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\fB\fCtls\fR \fBCERT\fP \fBKEY\fP - client authentication is used with the specified cert/key pair.
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The server certificate is verified with the system CAs
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.IP \(en 4
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\fB\fCtls\fR \fBCERT\fP \fBKEY\fP \fBCA\fP - client authentication is used with the specified cert/key pair.
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The server certificate is verified using the specified CA file
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.RE
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.IP \(bu 4
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\fB\fCtls_servername\fR \fBNAME\fP allows you to set a server name in the TLS configuration; for instance 9.9.9.9
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needs this to be set to \fB\fCdns.quad9.net\fR. Multiple upstreams are still allowed in this scenario,
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but they have to use the same \fB\fCtls_servername\fR. E.g. mixing 9.9.9.9 (QuadDNS) with 1.1.1.1
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(Cloudflare) will not work.
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.IP \(bu 4
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\fB\fCpolicy\fR specifies the policy to use for selecting upstream servers. The default is \fB\fCrandom\fR.
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.PP
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Also note the TLS config is "global" for the whole grpc proxy if you need a different
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\fB\fCtls-name\fR for different upstreams you're out of luck.
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.SH "METRICS"
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.PP
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If monitoring is enabled (via the \fIprometheus\fP plugin) then the following metric are exported:
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.IP \(bu 4
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\fB\fCcoredns_grpc_request_duration_seconds{to}\fR - duration per upstream interaction.
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.IP \(bu 4
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\fB\fCcoredns_grpc_requests_total{to}\fR - query count per upstream.
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.IP \(bu 4
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\fB\fCcoredns_grpc_responses_total{to, rcode}\fR - count of RCODEs per upstream.
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and we are randomly (this always uses the \fB\fCrandom\fR policy) spraying to an upstream.
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.SH "EXAMPLES"
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.PP
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Proxy all requests within \fB\fCexample.org.\fR to a nameserver running on a different port:
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.PP
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.RS
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.nf
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example.org {
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grpc . 127.0.0.1:9005
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}
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.fi
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.RE
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.PP
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Load balance all requests between three resolvers, one of which has a IPv6 address.
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.PP
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.RS
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.nf
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\&. {
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grpc . 10.0.0.10:53 10.0.0.11:1053 [2003::1]:53
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}
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.fi
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.RE
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.PP
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Forward everything except requests to \fB\fCexample.org\fR
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.PP
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.RS
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.nf
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\&. {
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grpc . 10.0.0.10:1234 {
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except example.org
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}
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}
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.fi
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.RE
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.PP
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Proxy everything except \fB\fCexample.org\fR using the host's \fB\fCresolv.conf\fR's nameservers:
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.PP
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.RS
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.nf
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\&. {
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grpc . /etc/resolv.conf {
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except example.org
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}
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}
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.fi
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.RE
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.PP
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Proxy all requests to 9.9.9.9 using the TLS protocol, and cache every answer for up to 30
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seconds. Note the \fB\fCtls_servername\fR is mandatory if you want a working setup, as 9.9.9.9 can't be
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used in the TLS negotiation.
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.PP
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.RS
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.nf
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\&. {
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grpc . 9.9.9.9 {
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tls\_servername dns.quad9.net
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}
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cache 30
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}
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.fi
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.RE
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.PP
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Or with multiple upstreams from the same provider
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.PP
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.RS
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.nf
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\&. {
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grpc . 1.1.1.1 1.0.0.1 {
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tls\_servername cloudflare\-dns.com
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}
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cache 30
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}
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.fi
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.RE
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.SH "BUGS"
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.PP
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The TLS config is global for the whole grpc proxy if you need a different \fB\fCtls_servername\fR for
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different upstreams you're out of luck.
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