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119 lines
4.2 KiB
Markdown
119 lines
4.2 KiB
Markdown
# Gateway sources
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The gateway-grcproute, gateway-httproute, gateway-tcproute, gateway-tlsroute, and gateway-udproute
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sources create DNS entries based on their respective `gateway.networking.k8s.io` resources.
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## Filtering the Routes considered
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These sources support the `--label-filter` flag, which filters \*Route resources
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by a set of labels.
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## Domain names
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To calculate the Domain names created from a *Route, this source first collects a set
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of [domain names from the *Route](#domain-names-from-route).
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It then iterates over each of the `status.parents` with
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a [matching Gateway](#matching-gateways) and at least one [matching listener](#matching-listeners).
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For each matching listener, if the
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listener has a `hostname`, it narrows the set of domain names from the \*Route to the portion
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that overlaps the `hostname`. If a matching listener does not have a `hostname`, it uses
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the un-narrowed set of domain names.
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### Domain names from Route
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The set of domain names from a \*Route is sourced from the following places:
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- If the \*Route is a GRPCRoute, HTTPRoute, or TLSRoute, adds each of the`spec.hostnames`.
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- Adds the hostnames from any `external-dns.alpha.kubernetes.io/hostname` annotation on the \*Route.
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This behavior is suppressed if the `--ignore-hostname-annotation` flag was specified.
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- If no endpoints were produced by the previous steps
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or the `--combine-fqdn-annotation` flag was specified, then adds hostnames
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generated from any`--fqdn-template` flag.
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- If no endpoints were produced by the previous steps, each
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attached Gateway listener will use its `hostname`, if present.
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### Matching Gateways
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Matching Gateways are discovered by iterating over the \*Route's `status.parents`:
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- Ignores parents with a `parentRef.group` other than
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`gateway.networking.k8s.io` or a `parentRef.kind` other than `Gateway`.
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- If the `--gateway-namespace` flag was specified, ignores parents with a `parentRef.namespace` other
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than the specified value.
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- If the `--gateway-label-filter` flag was specified, ignores parents whose Gateway does not match the
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specified label filter.
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- Ignores parents whose Gateway either does not exist or has not accepted the route.
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### Matching listeners
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Iterates over all listeners for the parent's `parentRef.sectionName`:
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- Ignores listeners whose `protocol` field does not match the kind of the \*Route per the following table:
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| kind | protocols |
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| --------- | ----------- |
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| GRPCRoute | HTTP, HTTPS |
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| HTTPRoute | HTTP, HTTPS |
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| TCPRoute | TCP |
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| TLSRoute | TLS |
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| UDPRoute | UDP |
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- If the parent's `parentRef.port` port is specified, ignores listeners without a matching `port`.
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- Ignores listeners which specify an `allowedRoutes` which does not allow the route.
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## Targets
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The targets of the DNS entries created from a \*Route are sourced from the following places:
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1. If a matching parent Gateway has an `external-dns.alpha.kubernetes.io/target` annotation, uses
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the values from that.
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2. Otherwise, iterates over that parent Gateway's `status.addresses`,
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adding each address's `value`.
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The targets from each parent Gateway matching the \*Route are then combined and de-duplicated.
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## Dualstack Routes
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Gateway resources may be served from an external-loadbalancer which may support both IPv4 and "dualstack" (both IPv4 and IPv6) interfaces.
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External DNS Controller uses the `external-dns.alpha.kubernetes.io/dualstack` annotation to determine this. If this annotation is
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set to `true` then ExternalDNS will create two records (one A record
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and one AAAA record) for each hostname associated with the Route resource.
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Example:
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```yaml
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apiVersion: gateway.networking.k8s.io/v1
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kind: HTTPRoute
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metadata:
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annotations:
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external-dns.alpha.kubernetes.io/dualstack: "true"
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name: echo
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spec:
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hostnames:
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- echoserver.example.org
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rules:
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- backendRefs:
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- group: ""
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kind: Service
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name: echo
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port: 1027
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weight: 1
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matches:
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- path:
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type: PathPrefix
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value: /echo
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```
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The above HTTPRoute resource is backed by a dualstack Gateway.
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ExternalDNS will create both an A `echoserver.example.org` record and
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an AAAA record of the same name, that each are aliases for the same LB.
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