Listeners associated with this Gateway. Listeners define
logical endpoints that are bound on this Gateway's addresses.
At least one Listener MUST be specified.
## Distinct Listeners
Each Listener in a set of Listeners (for example, in a single Gateway)
MUST be _distinct_, in that a traffic flow MUST be able to be assigned to
exactly one listener. (This section uses "set of Listeners" rather than
"Listeners in a single Gateway" because implementations MAY merge configuration
from multiple Gateways onto a single data plane, and these rules _also_
apply in that case).
Practically, this means that each listener in a set MUST have a unique
combination of Port, Protocol, and, if supported by the protocol, Hostname.
Some combinations of port, protocol, and TLS settings are considered
Core support and MUST be supported by implementations based on the objects
they support:
HTTPRoute
1. HTTPRoute, Port: 80, Protocol: HTTP
2. HTTPRoute, Port: 443, Protocol: HTTPS, TLS Mode: Terminate, TLS keypair provided
TLSRoute
1. TLSRoute, Port: 443, Protocol: TLS, TLS Mode: Passthrough
"Distinct" Listeners have the following property:
**The implementation can match inbound requests to a single distinct
Listener**.
When multiple Listeners share values for fields (for
example, two Listeners with the same Port value), the implementation
can match requests to only one of the Listeners using other
Listener fields.
When multiple listeners have the same value for the Protocol field, then
each of the Listeners with matching Protocol values MUST have different
values for other fields.
The set of fields that MUST be different for a Listener differs per protocol.
The following rules define the rules for what fields MUST be considered for
Listeners to be distinct with each protocol currently defined in the
Gateway API spec.
The set of listeners that all share a protocol value MUST have _different_
values for _at least one_ of these fields to be distinct:
* **HTTP, HTTPS, TLS**: Port, Hostname
* **TCP, UDP**: Port
One **very** important rule to call out involves what happens when an
implementation:
* Supports TCP protocol Listeners, as well as HTTP, HTTPS, or TLS protocol
Listeners, and
* sees HTTP, HTTPS, or TLS protocols with the same `port` as one with TCP
Protocol.
In this case all the Listeners that share a port with the
TCP Listener are not distinct and so MUST NOT be accepted.
If an implementation does not support TCP Protocol Listeners, then the
previous rule does not apply, and the TCP Listeners SHOULD NOT be
accepted.
Note that the `tls` field is not used for determining if a listener is distinct, because
Listeners that _only_ differ on TLS config will still conflict in all cases.
### Listeners that are distinct only by Hostname
When the Listeners are distinct based only on Hostname, inbound request
hostnames MUST match from the most specific to least specific Hostname
values to choose the correct Listener and its associated set of Routes.
Exact matches MUST be processed before wildcard matches, and wildcard
matches MUST be processed before fallback (empty Hostname value)
matches. For example, `"foo.example.com"` takes precedence over
`"*.example.com"`, and `"*.example.com"` takes precedence over `""`.
Additionally, if there are multiple wildcard entries, more specific
wildcard entries must be processed before less specific wildcard entries.
For example, `"*.foo.example.com"` takes precedence over `"*.example.com"`.
The precise definition here is that the higher the number of dots in the
hostname to the right of the wildcard character, the higher the precedence.
The wildcard character will match any number of characters _and dots_ to
the left, however, so `"*.example.com"` will match both
`"foo.bar.example.com"` _and_ `"bar.example.com"`.
## Handling indistinct Listeners
If a set of Listeners contains Listeners that are not distinct, then those
Listeners are _Conflicted_, and the implementation MUST set the "Conflicted"
condition in the Listener Status to "True".
The words "indistinct" and "conflicted" are considered equivalent for the
purpose of this documentation.
Implementations MAY choose to accept a Gateway with some Conflicted
Listeners only if they only accept the partial Listener set that contains
no Conflicted Listeners.
Specifically, an implementation MAY accept a partial Listener set subject to
the following rules:
* The implementation MUST NOT pick one conflicting Listener as the winner.
ALL indistinct Listeners must not be accepted for processing.
* At least one distinct Listener MUST be present, or else the Gateway effectively
contains _no_ Listeners, and must be rejected from processing as a whole.
The implementation MUST set a "ListenersNotValid" condition on the
Gateway Status when the Gateway contains Conflicted Listeners whether or
not they accept the Gateway. That Condition SHOULD clearly
indicate in the Message which Listeners are conflicted, and which are
Accepted. Additionally, the Listener status for those listeners SHOULD
indicate which Listeners are conflicted and not Accepted.
## General Listener behavior
Note that, for all distinct Listeners, requests SHOULD match at most one Listener.
For example, if Listeners are defined for "foo.example.com" and "*.example.com", a
request to "foo.example.com" SHOULD only be routed using routes attached
to the "foo.example.com" Listener (and not the "*.example.com" Listener).
This concept is known as "Listener Isolation", and it is an Extended feature
of Gateway API. Implementations that do not support Listener Isolation MUST
clearly document this, and MUST NOT claim support for the
`GatewayHTTPListenerIsolation` feature.
Implementations that _do_ support Listener Isolation SHOULD claim support
for the Extended `GatewayHTTPListenerIsolation` feature and pass the associated
conformance tests.
## Compatible Listeners
A Gateway's Listeners are considered _compatible_ if:
1. They are distinct.
2. The implementation can serve them in compliance with the Addresses
requirement that all Listeners are available on all assigned
addresses.
Compatible combinations in Extended support are expected to vary across
implementations. A combination that is compatible for one implementation
may not be compatible for another.
For example, an implementation that cannot serve both TCP and UDP listeners
on the same address, or cannot mix HTTPS and generic TLS listens on the same port
would not consider those cases compatible, even though they are distinct.
Implementations MAY merge separate Gateways onto a single set of
Addresses if all Listeners across all Gateways are compatible.
In a future release the MinItems=1 requirement MAY be dropped.
Support: Core
minItems: 1
maxItems: 64
allowedRoutes
object
AllowedRoutes defines the types of routes that MAY be attached to a
Listener and the trusted namespaces where those Route resources MAY be
present.
Although a client request may match multiple route rules, only one rule
may ultimately receive the request. Matching precedence MUST be
determined in order of the following criteria:
* The most specific match as defined by the Route type.
* The oldest Route based on creation timestamp. For example, a Route with
a creation timestamp of "2020-09-08 01:02:03" is given precedence over
a Route with a creation timestamp of "2020-09-08 01:02:04".
* If everything else is equivalent, the Route appearing first in
alphabetical order (namespace/name) should be given precedence. For
example, foo/bar is given precedence over foo/baz.
All valid rules within a Route attached to this Listener should be
implemented. Invalid Route rules can be ignored (sometimes that will mean
the full Route). If a Route rule transitions from valid to invalid,
support for that Route rule should be dropped to ensure consistency. For
example, even if a filter specified by a Route rule is invalid, the rest
of the rules within that Route should still be supported.
Support: Core
kinds
[]object
Kinds specifies the groups and kinds of Routes that are allowed to bind
to this Gateway Listener. When unspecified or empty, the kinds of Routes
selected are determined using the Listener protocol.
A RouteGroupKind MUST correspond to kinds of Routes that are compatible
with the application protocol specified in the Listener's Protocol field.
If an implementation does not support or recognize this resource type, it
MUST set the "ResolvedRefs" condition to False for this Listener with the
"InvalidRouteKinds" reason.
Support: Core
maxItems: 8
group
string
Group is the group of the Route.
pattern: ^$|^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$
maxLength: 253
kind
string required
Kind is the kind of the Route.
pattern: ^[a-zA-Z]([-a-zA-Z0-9]*[a-zA-Z0-9])?$
minLength: 1
maxLength: 63
namespaces
object
Namespaces indicates namespaces from which Routes may be attached to this
Listener. This is restricted to the namespace of this Gateway by default.
Support: Core
from
string
From indicates where Routes will be selected for this Gateway. Possible
values are:
* All: Routes in all namespaces may be used by this Gateway.
* Selector: Routes in namespaces selected by the selector may be used by
this Gateway.
* Same: Only Routes in the same namespace may be used by this Gateway.
Support: Core
enum: All, Selector, Same
selector
object
Selector must be specified when From is set to "Selector". In that case,
only Routes in Namespaces matching this Selector will be selected by this
Gateway. This field is ignored for other values of "From".
Support: Core
matchExpressions
[]object
matchExpressions is a list of label selector requirements. The requirements are ANDed.
key
string required
key is the label key that the selector applies to.
operator
string required
operator represents a key's relationship to a set of values.
Valid operators are In, NotIn, Exists and DoesNotExist.
values
[]string
values is an array of string values. If the operator is In or NotIn,
the values array must be non-empty. If the operator is Exists or DoesNotExist,
the values array must be empty. This array is replaced during a strategic
merge patch.
matchLabels
object
matchLabels is a map of {key,value} pairs. A single {key,value} in the matchLabels
map is equivalent to an element of matchExpressions, whose key field is "key", the
operator is "In", and the values array contains only "value". The requirements are ANDed.
hostname
string
Hostname specifies the virtual hostname to match for protocol types that
define this concept. When unspecified, all hostnames are matched. This
field is ignored for protocols that don't require hostname based
matching.
Implementations MUST apply Hostname matching appropriately for each of
the following protocols:
* TLS: The Listener Hostname MUST match the SNI.
* HTTP: The Listener Hostname MUST match the Host header of the request.
* HTTPS: The Listener Hostname SHOULD match both the SNI and Host header.
Note that this does not require the SNI and Host header to be the same.
The semantics of this are described in more detail below.
To ensure security, Section 11.1 of RFC-6066 emphasizes that server
implementations that rely on SNI hostname matching MUST also verify
hostnames within the application protocol.
Section 9.1.2 of RFC-7540 provides a mechanism for servers to reject the
reuse of a connection by responding with the HTTP 421 Misdirected Request
status code. This indicates that the origin server has rejected the
request because it appears to have been misdirected.
To detect misdirected requests, Gateways SHOULD match the authority of
the requests with all the SNI hostname(s) configured across all the
Gateway Listeners on the same port and protocol:
* If another Listener has an exact match or more specific wildcard entry,
the Gateway SHOULD return a 421.
* If the current Listener (selected by SNI matching during ClientHello)
does not match the Host:
* If another Listener does match the Host the Gateway SHOULD return a
421.
* If no other Listener matches the Host, the Gateway MUST return a
404.
For HTTPRoute and TLSRoute resources, there is an interaction with the
`spec.hostnames` array. When both listener and route specify hostnames,
there MUST be an intersection between the values for a Route to be
accepted. For more information, refer to the Route specific Hostnames
documentation.
Hostnames that are prefixed with a wildcard label (`*.`) are interpreted
as a suffix match. That means that a match for `*.example.com` would match
both `test.example.com`, and `foo.test.example.com`, but not `example.com`.
Support: Core
pattern: ^(\*\.)?[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$
minLength: 1
maxLength: 253
name
string required
Name is the name of the Listener. This name MUST be unique within a
Gateway.
Support: Core
pattern: ^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$
minLength: 1
maxLength: 253
port
integer required
Port is the network port. Multiple listeners may use the
same port, subject to the Listener compatibility rules.
Support: Core
format: int32
minimum: 1
maximum: 65535
protocol
string required
Protocol specifies the network protocol this listener expects to receive.
Support: Core
pattern: ^[a-zA-Z0-9]([-a-zA-Z0-9]*[a-zA-Z0-9])?$|[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*\/[A-Za-z0-9]+$
minLength: 1
maxLength: 255
tls
object
TLS is the TLS configuration for the Listener. This field is required if
the Protocol field is "HTTPS" or "TLS". It is invalid to set this field
if the Protocol field is "HTTP", "TCP", or "UDP".
The association of SNIs to Certificate defined in ListenerTLSConfig is
defined based on the Hostname field for this listener.
The GatewayClass MUST use the longest matching SNI out of all
available certificates for any TLS handshake.
Support: Core
certificateRefs
[]object
CertificateRefs contains a series of references to Kubernetes objects that
contains TLS certificates and private keys. These certificates are used to
establish a TLS handshake for requests that match the hostname of the
associated listener.
A single CertificateRef to a Kubernetes Secret has "Core" support.
Implementations MAY choose to support attaching multiple certificates to
a Listener, but this behavior is implementation-specific.
References to a resource in different namespace are invalid UNLESS there
is a ReferenceGrant in the target namespace that allows the certificate
to be attached. If a ReferenceGrant does not allow this reference, the
"ResolvedRefs" condition MUST be set to False for this listener with the
"RefNotPermitted" reason.
This field is required to have at least one element when the mode is set
to "Terminate" (default) and is optional otherwise.
CertificateRefs can reference to standard Kubernetes resources, i.e.
Secret, or implementation-specific custom resources.
Support: Core - A single reference to a Kubernetes Secret of type kubernetes.io/tls
Support: Implementation-specific (More than one reference or other resource types)
maxItems: 64
group
string
Group is the group of the referent. For example, "gateway.networking.k8s.io".
When unspecified or empty string, core API group is inferred.
pattern: ^$|^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$
maxLength: 253
kind
string
Kind is kind of the referent. For example "Secret".
pattern: ^[a-zA-Z]([-a-zA-Z0-9]*[a-zA-Z0-9])?$
minLength: 1
maxLength: 63
name
string required
Name is the name of the referent.
minLength: 1
maxLength: 253
namespace
string
Namespace is the namespace of the referenced object. When unspecified, the local
namespace is inferred.
Note that when a namespace different than the local namespace is specified,
a ReferenceGrant object is required in the referent namespace to allow that
namespace's owner to accept the reference. See the ReferenceGrant
documentation for details.
Support: Core
pattern: ^[a-z0-9]([-a-z0-9]*[a-z0-9])?$
minLength: 1
maxLength: 63
mode
string
Mode defines the TLS behavior for the TLS session initiated by the client.
There are two possible modes:
- Terminate: The TLS session between the downstream client and the
Gateway is terminated at the Gateway. This mode requires certificates
to be specified in some way, such as populating the certificateRefs
field.
- Passthrough: The TLS session is NOT terminated by the Gateway. This
implies that the Gateway can't decipher the TLS stream except for
the ClientHello message of the TLS protocol. The certificateRefs field
is ignored in this mode.
Support: Core
enum: Terminate, Passthrough
options
object
Options are a list of key/value pairs to enable extended TLS
configuration for each implementation. For example, configuring the
minimum TLS version or supported cipher suites.
A set of common keys MAY be defined by the API in the future. To avoid
any ambiguity, implementation-specific definitions MUST use
domain-prefixed names, such as `example.com/my-custom-option`.
Un-prefixed names are reserved for key names defined by Gateway API.
Support: Implementation-specific