Co-authored-by: Ashvitha Sridharan <ashvitha.sridharan@hashicorp.com>
Co-authored-by: Freddy <freddygv@users.noreply.github.com>
Add a new envoy flag: "envoy_hcp_metrics_bind_socket_dir", a directory
where a unix socket will be created with the name
`<namespace>_<proxy_id>.sock` to forward Envoy metrics.
If set, this will configure:
- In bootstrap configuration a local stats_sink and static cluster.
These will forward metrics to a loopback listener sent over xDS.
- A dynamic listener listening at the socket path that the previously
defined static cluster is sending metrics to.
- A dynamic cluster that will forward traffic received at this listener
to the hcp-metrics-collector service.
Reasons for having a static cluster pointing at a dynamic listener:
- We want to secure the metrics stream using TLS, but the stats sink can
only be defined in bootstrap config. With dynamic listeners/clusters
we can use the proxy's leaf certificate issued by the Connect CA,
which isn't available at bootstrap time.
- We want to intelligently route to the HCP collector. Configuring its
addreess at bootstrap time limits our flexibility routing-wise. More
on this below.
Reasons for defining the collector as an upstream in `proxycfg`:
- The HCP collector will be deployed as a mesh service.
- Certificate management is taken care of, as mentioned above.
- Service discovery and routing logic is automatically taken care of,
meaning that no code changes are required in the xds package.
- Custom routing rules can be added for the collector using discovery
chain config entries. Initially the collector is expected to be
deployed to each admin partition, but in the future could be deployed
centrally in the default partition. These config entries could even be
managed by HCP itself.
* Leverage ServiceResolver ConnectTimeout for route timeouts to make TerminatingGateway upstream timeouts configurable
* Regenerate golden files
* Add RequestTimeout field
* Add changelog entry
* Include secret type when building resources from config snapshot
* First pass at generating envoy secrets from api-gateway snapshot
* Update comments for xDS update order
* Add secret type + corresponding golden files to existing tests
* Initialize test helpers for testing api-gateway resource generation
* Generate golden files for new api-gateway xDS resource test
* Support ADS for TLS certificates on api-gateway
* Configure TLS on api-gateway listeners
* Inline TLS cert code
* update tests
* Add SNI support so we can have multiple certificates
* Remove commented out section from helper
* regen deep-copy
* Add tcp tls test
---------
Co-authored-by: Nathan Coleman <nathan.coleman@hashicorp.com>
* Simple API Gateway e2e test for tcp routes
* Drop DNSSans since we don't front the Gateway with a leaf cert
* WIP listener tests for api-gateway
* Return early if no routes
* Add back in leaf cert to testing
* Fix merge conflicts
* Re-add kind to setup
* Fix iteration over listener upstreams
* New tcp listener test
* Add tests for API Gateway with TCP and HTTP routes
* Move zero-route check back
* Drop generateIngressDNSSANs
* Check for chains not routes
---------
Co-authored-by: Andrew Stucki <andrew.stucki@hashicorp.com>
* Add Tproxy support to Envoy Extensions (this is needed for service to service validation)
* Add validation for Envoy configuration for an upstream service
* Use both /config_dump and /cluster to validate Envoy configuration
This is because of a bug in Envoy where the EndpointsConfigDump does not
include a cluster_name, making it impossible to match an endpoint to
verify it exists.
This removes endpoints support for builtin extensions since only the
validate plugin was using it, and it is no longer used. It also removes
test cases for endpoint validation. Endpoints validation now only occurs
in the top level test from config_dump and clusters json files.
Co-authored-by: Eric <eric@haberkorn.co>
* updated builtin extension to parse region directly from ARN
- added a unit test
- added some comments/light refactoring
* updated golden files with proper ARNs
- ARNs need to be right format now that they are being processed
* updated tests and integration tests
- removed 'region' from all EnvoyExtension arguments
- added properly formatted ARN which includes the same region found in the removed "Region" field: 'us-east-1'
* extensions: refactor PluginConfiguration into a more generic type
ExtensionConfiguration
Also:
* adds endpoints configuration to lambda golden tests
* uses string constant for builtin/aws/lambda
Co-authored-by: Eric <eric@haberkorn.co>
* feat(ingress-gateway): support outlier detection of upstream service for ingress gateway
* changelog
Co-authored-by: Eric Haberkorn <erichaberkorn@gmail.com>
* Fix mesh gateway proxy-defaults not affecting upstreams.
* Clarify distinction with upstream settings
Top-level mesh gateway mode in proxy-defaults and service-defaults gets
merged into NodeService.Proxy.MeshGateway, and only gets merged with
the mode attached to an an upstream in proxycfg/xds.
* Fix mgw mode usage for peered upstreams
There were a couple issues with how mgw mode was being handled for
peered upstreams.
For starters, mesh gateway mode from proxy-defaults
and the top-level of service-defaults gets stored in
NodeService.Proxy.MeshGateway, but the upstream watch for peered data
was only considering the mesh gateway config attached in
NodeService.Proxy.Upstreams[i]. This means that applying a mesh gateway
mode via global proxy-defaults or service-defaults on the downstream
would not have an effect.
Separately, transparent proxy watches for peered upstreams didn't
consider mesh gateway mode at all.
This commit addresses the first issue by ensuring that we overlay the
upstream config for peered upstreams as we do for non-peered. The second
issue is addressed by re-using setupWatchesForPeeredUpstream when
handling transparent proxy updates.
Note that for transparent proxies we do not yet support mesh gateway
mode per upstream, so the NodeService.Proxy.MeshGateway mode is used.
* Fix upstream mesh gateway mode handling in xds
This commit ensures that when determining the mesh gateway mode for
peered upstreams we consider the NodeService.Proxy.MeshGateway config as
a baseline.
In absense of this change, setting a mesh gateway mode via
proxy-defaults or the top-level of service-defaults will not have an
effect for peered upstreams.
* Merge service/proxy defaults in cfg resolver
Previously the mesh gateway mode for connect proxies would be
merged at three points:
1. On servers, in ComputeResolvedServiceConfig.
2. On clients, in MergeServiceConfig.
3. On clients, in proxycfg/xds.
The first merge returns a ServiceConfigResponse where there is a
top-level MeshGateway config from proxy/service-defaults, along with
per-upstream config.
The second merge combines per-upstream config specified at the service
instance with per-upstream config specified centrally.
The third merge combines the NodeService.Proxy.MeshGateway
config containing proxy/service-defaults data with the per-upstream
mode. This third merge is easy to miss, which led to peered upstreams
not considering the mesh gateway mode from proxy-defaults.
This commit removes the third merge, and ensures that all mesh gateway
config is available at the upstream. This way proxycfg/xds do not need
to do additional overlays.
* Ensure that proxy-defaults is considered in wc
Upstream defaults become a synthetic Upstream definition under a
wildcard key "*". Now that proxycfg/xds expect Upstream definitions to
have the final MeshGateway values, this commit ensures that values from
proxy-defaults/service-defaults are the default for this synthetic
upstream.
* Add changelog.
Co-authored-by: freddygv <freddy@hashicorp.com>
* Regenerate golden files.
* Backport from ENT: "Avoid race"
Original commit: 5006c8c858b0e332be95271ef9ba35122453315b
Original author: freddygv
* Backport from ENT: "chore: fix flake peerstream test"
Original commit: b74097e7135eca48cc289798c5739f9ef72c0cc8
Original author: DanStough
* ingress-gateways: don't log error when registering gateway
Previously, when an ingress gateway was registered without a
corresponding ingress gateway config entry, an error was logged
because the watch on the config entry returned a nil result.
This is expected so don't log an error.
* Configure Envoy alpn_protocols based on service protocol
* define alpnProtocols in a more standard way
* http2 protocol should be h2 only
* formatting
* add test for getAlpnProtocol()
* create changelog entry
* change scope is connect-proxy
* ignore errors on ParseProxyConfig; fixes linter
* add tests for grpc and http2 public listeners
* remove newlines from PR
* Add alpn_protocol configuration for ingress gateway
* Guard against nil tlsContext
* add ingress gateway w/ TLS tests for gRPC and HTTP2
* getAlpnProtocols: add TCP protocol test
* add tests for ingress gateway with grpc/http2 and per-listener TLS config
* add tests for ingress gateway with grpc/http2 and per-listener TLS config
* add Gateway level TLS config with mixed protocol listeners to validate ALPN
* update changelog to include ingress-gateway
* add http/1.1 to http2 ALPN
* go fmt
* fix test on custom-trace-listener
This commit adds the xDS resources needed for INBOUND traffic from peer
clusters:
- 1 filter chain for all inbound peering requests.
- 1 cluster for all inbound peering requests.
- 1 endpoint per voting server with the gRPC TLS port configured.
There is one filter chain and cluster because unlike with WAN
federation, peer clusters will not attempt to dial individual servers.
Peer clusters will only dial the local mesh gateway addresses.
* feat(ingress gateway: support configuring limits in ingress-gateway config entry
- a new Defaults field with max_connections, max_pending_connections, max_requests
is added to ingress gateway config entry
- new field max_connections, max_pending_connections, max_requests in
individual services to overwrite the value in Default
- added unit test and integration test
- updated doc
Co-authored-by: Chris S. Kim <ckim@hashicorp.com>
Co-authored-by: Jeff Boruszak <104028618+boruszak@users.noreply.github.com>
Co-authored-by: Dan Stough <dan.stough@hashicorp.com>
* draft commit
* add changelog, update test
* remove extra param
* fix test
* update type to account for nil value
* add test for custom passive health check
* update comments and tests
* update description in docs
* fix missing commas
* add golden files
* add support to http in tgateway egress destination
* fix slice sorting to include both address and port when using server_names
* fix listener loop for http destination
* fix routes to generate a route per port and a virtualhost per port-address combination
* sort virtual hosts list to have a stable order
* extract redundant serviceNode
Now that peered upstreams can generate envoy resources (#13758), we need a way to disambiguate local from peered resources in our metrics. The key difference is that datacenter and partition will be replaced with peer, since in the context of peered resources partition is ambiguous (could refer to the partition in a remote cluster or one that exists locally). The partition and datacenter of the proxy will always be that of the source service.
Regexes were updated to make emitting datacenter and partition labels mutually exclusive with peer labels.
Listener filter names were updated to better match the existing regex.
Cluster names assigned to peered upstreams were updated to be synthesized from local peer name (it previously used the externally provided primary SNI, which contained the peer name from the other side of the peering). Integration tests were updated to assert for the new peer labels.
Peered upstreams has a separate loop in xds from discovery chain upstreams. This PR adds similar but slightly modified code to add filters for peered upstream listeners, clusters, and endpoints in the case of transparent proxy.
Because peerings are pairwise, between two tuples of (datacenter,
partition) having any exported reference via a discovery chain that
crosses out of the peered datacenter or partition will ultimately not be
able to work for various reasons. The biggest one is that there is no
way in the ultimate destination to configure an intention that can allow
an external SpiffeID to access a service.
This PR ensures that a user simply cannot do this, so they won't run
into weird situations like this.
When the protocol is http-like, and an intention has a peered source
then the normal RBAC mTLS SAN field check is replaces with a joint combo
of:
mTLS SAN field must be the service's local mesh gateway leaf cert
AND
the first XFCC header (from the MGW) must have a URI field that matches the original intention source
Also:
- Update the regex program limit to be much higher than the teeny
defaults, since the RBAC regex constructions are more complicated now.
- Fix a few stray panics in xds generation.
This is only configured in xDS when a service with an L7 protocol is
exported.
They also load any relevant trust bundles for the peered services to
eventually use for L7 SPIFFE validation during mTLS termination.
When converting from Consul intentions to xds RBAC rules, services imported from other peers must encode additional data like partition (from the remote cluster) and trust domain.
This PR updates the PeeringTrustBundle to hold the sending side's local partition as ExportedPartition. It also updates RBAC code to encode SpiffeIDs of imported services with the ExportedPartition and TrustDomain.
Mesh gateways can use hostnames in their tagged addresses (#7999). This is useful
if you were to expose a mesh gateway using a cloud networking load balancer appliance
that gives you a DNS name but no reliable static IPs.
Envoy cannot accept hostnames via EDS and those must be configured using CDS.
There was already logic when configuring gateways in other locations in the code, but
given the illusions in play for peering the downstream of a peered service wasn't aware
that it should be doing that.
Also:
- ensuring that we always try to use wan-like addresses to cross peer boundaries.
Mesh gateways will now enable tcp connections with SNI names including peering information so that those connections may be proxied.
Note: this does not change the callers to use these mesh gateways.
Envoy's SPIFFE certificate validation extension allows for us to
validate against different root certificates depending on the trust
domain of the dialing proxy.
If there are any trust bundles from peers in the config snapshot then we
use the SPIFFE validator as the validation context, rather than the
usual TrustedCA.
The injected validation config includes the local root certificates as
well.
For mTLS to work between two proxies in peered clusters with different root CAs,
proxies need to configure their outbound listener to use different root certificates
for validation.
Up until peering was introduced proxies would only ever use one set of root certificates
to validate all mesh traffic, both inbound and outbound. Now an upstream proxy
may have a leaf certificate signed by a CA that's different from the dialing proxy's.
This PR makes changes to proxycfg and xds so that the upstream TLS validation
uses different root certificates depending on which cluster is being dialed.
Description
Add x-fowarded-client-cert information on trusted incoming connections.
Envoy provides support forwarding and annotating the
x-forwarded-client-cert header via the forward_client_cert_details
set_current_client_cert_details filter fields. It would be helpful for
consul to support this directly in its config. The escape hatches are
a bit cumbersome for this purpose.
This has been implemented on incoming connections to envoy. Outgoing
(from the local service through the sidecar) will not have a
certificate, and so are left alone.
A service on an incoming connection will now get headers something like this:
```
X-Forwarded-Client-Cert:[By=spiffe://efad7282-d9b2-3298-f6d8-38b37fb58df3.consul/ns/default/dc/dc1/svc/counting;Hash=61ad5cbdfcb50f5a3ec0ca60923d61613c149a9d4495010a64175c05a0268ab2;Cert="-----BEGIN%20CERTIFICATE-----%0AMIICHDCCAcOgAwIBAgIBCDAKBggqhkjOPQQDAjAxMS8wLQYDVQQDEyZwcmktMTli%0AYXdyb2YuY29uc3VsLmNhLmVmYWQ3MjgyLmNvbnN1bDAeFw0yMjA0MjkwMzE0NTBa%0AFw0yMjA1MDIwMzE0NTBaMAAwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAARVIZ7Y%0AZEXfbOGBfxGa7Vuok1MIng%2FuzLQK2xLVlSTIPDbO5hstTGP%2B%2FGx182PYFP3jYqk5%0Aq6rYWe1wiPNMA30Io4H8MIH5MA4GA1UdDwEB%2FwQEAwIDuDAdBgNVHSUEFjAUBggr%0ABgEFBQcDAgYIKwYBBQUHAwEwDAYDVR0TAQH%2FBAIwADApBgNVHQ4EIgQgrp4q50oX%0AHHghMbxz5Bk8OJFWMdfgH0Upr350WlhyxvkwKwYDVR0jBCQwIoAgUe6uERAIj%2FLM%0AyuFzDc3Wbp9TGAKBJYAwyhF14ToOQCMwYgYDVR0RAQH%2FBFgwVoZUc3BpZmZlOi8v%0AZWZhZDcyODItZDliMi0zMjk4LWY2ZDgtMzhiMzdmYjU4ZGYzLmNvbnN1bC9ucy9k%0AZWZhdWx0L2RjL2RjMS9zdmMvZGFzaGJvYXJkMAoGCCqGSM49BAMCA0cAMEQCIDwb%0AFlchufggNTijnQ5SUcvTZrWlZyq%2FrdVC20nbbmWLAiAVshNNv1xBqJI1NmY2HI9n%0AgRMfb8aEPVSuxEHhqy57eQ%3D%3D%0A-----END%20CERTIFICATE-----%0A";Chain="-----BEGIN%20CERTIFICATE-----%0AMIICHDCCAcOgAwIBAgIBCDAKBggqhkjOPQQDAjAxMS8wLQYDVQQDEyZwcmktMTli%0AYXdyb2YuY29uc3VsLmNhLmVmYWQ3MjgyLmNvbnN1bDAeFw0yMjA0MjkwMzE0NTBa%0AFw0yMjA1MDIwMzE0NTBaMAAwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAARVIZ7Y%0AZEXfbOGBfxGa7Vuok1MIng%2FuzLQK2xLVlSTIPDbO5hstTGP%2B%2FGx182PYFP3jYqk5%0Aq6rYWe1wiPNMA30Io4H8MIH5MA4GA1UdDwEB%2FwQEAwIDuDAdBgNVHSUEFjAUBggr%0ABgEFBQcDAgYIKwYBBQUHAwEwDAYDVR0TAQH%2FBAIwADApBgNVHQ4EIgQgrp4q50oX%0AHHghMbxz5Bk8OJFWMdfgH0Upr350WlhyxvkwKwYDVR0jBCQwIoAgUe6uERAIj%2FLM%0AyuFzDc3Wbp9TGAKBJYAwyhF14ToOQCMwYgYDVR0RAQH%2FBFgwVoZUc3BpZmZlOi8v%0AZWZhZDcyODItZDliMi0zMjk4LWY2ZDgtMzhiMzdmYjU4ZGYzLmNvbnN1bC9ucy9k%0AZWZhdWx0L2RjL2RjMS9zdmMvZGFzaGJvYXJkMAoGCCqGSM49BAMCA0cAMEQCIDwb%0AFlchufggNTijnQ5SUcvTZrWlZyq%2FrdVC20nbbmWLAiAVshNNv1xBqJI1NmY2HI9n%0AgRMfb8aEPVSuxEHhqy57eQ%3D%3D%0A-----END%20CERTIFICATE-----%0A";Subject="";URI=spiffe://efad7282-d9b2-3298-f6d8-38b37fb58df3.consul/ns/default/dc/dc1/svc/dashboard]
```
Closes#12852
Just like standard upstreams the order of applicability in descending precedence:
1. caller's `service-defaults` upstream override for destination
2. caller's `service-defaults` upstream defaults
3. destination's `service-resolver` ConnectTimeout
4. system default of 5s
Co-authored-by: mrspanishviking <kcardenas@hashicorp.com>
- `tls.incoming`: applies to the inbound mTLS targeting the public
listener on `connect-proxy` and `terminating-gateway` envoy instances
- `tls.outgoing`: applies to the outbound mTLS dialing upstreams from
`connect-proxy` and `ingress-gateway` envoy instances
Fixes#11966
Prior to this PR for the envoy xDS golden tests in the agent/xds package we
were hand-creating a proxycfg.ConfigSnapshot structure in the proper format for
input to the xDS generator. Over time this intermediate structure has gotten
trickier to build correctly for the various tests.
This PR proposes to switch to using the existing mechanism for turning a
structs.NodeService and a sequence of cache.UpdateEvent copies into a
proxycfg.ConfigSnapshot, as that is less error prone to construct and aligns
more with how the data arrives.
NOTE: almost all of this is in test-related code. I tried super hard to craft
correct event inputs to get the golden files to be the same, or similar enough
after construction to feel ok that i recreated the spirit of the original test
cases.
Transparent proxies can set up filter chains that allow direct
connections to upstream service instances. Services that can be dialed
directly are stored in the PassthroughUpstreams map of the proxycfg
snapshot.
Previously these addresses were not being cleaned up based on new
service health data. The list of addresses associated with an upstream
service would only ever grow.
As services scale up and down, eventually they will have instances
assigned to an IP that was previously assigned to a different service.
When IP addresses are duplicated across filter chain match rules the
listener config will be rejected by Envoy.
This commit updates the proxycfg snapshot management so that passthrough
addresses can get cleaned up when no longer associated with a given
upstream.
There is still the possibility of a race condition here where due to
timing an address is shared between multiple passthrough upstreams.
That concern is mitigated by #12195, but will be further addressed
in a follow-up.
The gist here is that now we use a value-type struct proxycfg.UpstreamID
as the map key in ConfigSnapshot maps where we used to use "upstream
id-ish" strings. These are internal only and used just for bidirectional
trips through the agent cache keyspace (like the discovery chain target
struct).
For the few places where the upstream id needs to be projected into xDS,
that's what (proxycfg.UpstreamID).EnvoyID() is for. This lets us ALWAYS
inject the partition and namespace into these things without making
stuff like the golden testdata diverge.
* xds: refactor ingress listener SDS configuration
* xds: update resolveListenerSDS call args in listeners_test
* ingress: add TLS min, max and cipher suites to GatewayTLSConfig
* xds: implement envoyTLSVersions and envoyTLSCipherSuites
* xds: merge TLS config
* xds: configure TLS parameters with ingress TLS context from leaf
* xds: nil check in resolveListenerTLSConfig validation
* xds: nil check in makeTLSParameters* functions
* changelog: add entry for TLS params on ingress config entries
* xds: remove indirection for TLS params in TLSConfig structs
* xds: return tlsContext, nil instead of ambiguous err
Co-authored-by: Chris S. Kim <ckim@hashicorp.com>
* xds: switch zero checks to types.TLSVersionUnspecified
* ingress: add validation for ingress config entry TLS params
* ingress: validate listener TLS config
* xds: add basic ingress with TLS params tests
* xds: add ingress listeners mixed TLS min version defaults precedence test
* xds: add more explicit tests for ingress listeners inheriting gateway defaults
* xds: add test for single TLS listener on gateway without TLS defaults
* xds: regen golden files for TLSVersionInvalid zero value, add TLSVersionAuto listener test
* types/tls: change TLSVersion to string
* types/tls: update TLSCipherSuite to string type
* types/tls: implement validation functions for TLSVersion and TLSCipherSuites, make some maps private
* api: add TLS params to GatewayTLSConfig, add tests
* api: add TLSMinVersion to ingress gateway config entry test JSON
* xds: switch to Envoy TLS cipher suite encoding from types package
* xds: fixup validation for TLSv1_3 min version with cipher suites
* add some kitchen sink tests and add a missing struct tag
* xds: check if mergedCfg.TLSVersion is in TLSVersionsWithConfigurableCipherSuites
* xds: update connectTLSEnabled comment
* xds: remove unsued resolveGatewayServiceTLSConfig function
* xds: add makeCommonTLSContextFromLeafWithoutParams
* types/tls: add LessThan comparator function for concrete values
* types/tls: change tlsVersions validation map from string to TLSVersion keys
* types/tls: remove unused envoyTLSCipherSuites
* types/tls: enable chacha20 cipher suites for Consul agent
* types/tls: remove insecure cipher suites from allowed config
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 and TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 are both explicitly listed as insecure and disabled in the Go source.
Refs https://cs.opensource.google/go/go/+/refs/tags/go1.17.3:src/crypto/tls/cipher_suites.go;l=329-330
* types/tls: add ValidateConsulAgentCipherSuites function, make direct lookup map private
* types/tls: return all unmatched cipher suites in validation errors
* xds: check that Envoy API value matching TLS version is found when building TlsParameters
* types/tls: check that value is found in map before appending to slice in MarshalEnvoyTLSCipherSuiteStrings
* types/tls: cast to string rather than fmt.Printf in TLSCihperSuite.String()
* xds: add TLSVersionUnspecified to list of configurable cipher suites
* structs: update note about config entry warning
* xds: remove TLS min version cipher suite unconfigurable test placeholder
* types/tls: update tests to remove assumption about private map values
Co-authored-by: R.B. Boyer <rb@hashicorp.com>
The duo of `makeUpstreamFilterChainForDiscoveryChain` and `makeListenerForDiscoveryChain` were really hard to reason about, and led to concealing a bug in their branching logic. There were several issues here:
- They tried to accomplish too much: determining filter name, cluster name, and whether RDS should be used.
- They embedded logic to handle significantly different kinds of upstream listeners (passthrough, prepared query, typical services, and catch-all)
- They needed to coalesce different data sources (Upstream and CompiledDiscoveryChain)
Rather than handling all of those tasks inside of these functions, this PR pulls out the RDS/clusterName/filterName logic.
This refactor also fixed a bug with the handling of [UpstreamDefaults](https://www.consul.io/docs/connect/config-entries/service-defaults#defaults). These defaults get stored as UpstreamConfig in the proxy snapshot with a DestinationName of "*", since they apply to all upstreams. However, this wildcard destination name must not be used when creating the name of the associated upstream cluster. The coalescing logic in the original functions here was in some situations creating clusters with a `*.` prefix, which is not a valid destination.
Fixes an issue described in #10132, where if two DCs are WAN federated
over mesh gateways, and the gateway in the non-primary DC is terminated
and receives a new IP address (as is commonly the case when running them
on ephemeral compute instances) the primary DC is unable to re-establish
its connection until the agent running on its own gateway is restarted.
This was happening because we always preferred gateways discovered by
the `Internal.ServiceDump` RPC (which would fail because there's no way
to dial the remote DC) over those discovered in the federation state,
which is replicated as long as the primary DC's gateway is reachable.
Andrew Stucki