Add "antctl get bgproutes" agent command

[Atish-iaf]

Add antctl get bgproutes agent command to print the advertised BGP routes on the local Node.

The command is implemented using a new HTTP endpoint (/bgproutes), which will return a 404 Not Found error if no BGPPolicy has been applied on the Node.

For #6209

[antoninbas]

Not done reviewing it yet, but at a high-level I do not think we should be handling "received routes" at the moment. Unless I am mistaken, this is not a concept which is really relevant to the (current) Antrea BGP implementation.

[antoninbas]

we do not handle "received routes" in the Antrea BGP implementation, so I think this may be misleading to users
cc @hongliangl

[hongliangl]

we do not handle "received routes" in the Antrea BGP implementation

Exactly. At least right now, we don't care about the "received routes" from remote peers. In current implementation of BGPPolicy controller, we only advertise routes, for the "received routes", we do nothing.

[rajnkamr]

@hongliangl
To track, better to create a separate issue to support received routes for future use-case , as received routes can be important for scenarios involving multiple BGP peers, dynamic route management, or multi-cluster setups,
as of now for basic CNI and Kubernetes networking, the focus is primarily on what the cluster advertises !

[hongliangl]

we do not handle "received routes" in the Antrea BGP implementation

Exactly. At least right now, we don't care about the "received routes" from remote peers. In current implementation of BGPPolicy controller, we only advertise routes, for the "received routes", we do nothing.

[Atish-iaf]

/test-all

[antoninbas]

only a handful of nits, otherwise LGTM

[antoninbas]

one last comment, otherwise lgtm

[antoninbas]

let's use this variation:

		values := r.URL.Query()
		var ipv4Only, ipv6Only bool
		if values.Has("ipv4-only") {
				if values.Get("ipv4-only") != "" {
						// bad request
				}
				ipv4Only = true
		}
		if values.Has("ipv6-only") {
				if values.Get("ipv6-only") != "" {
						// bad request
				}
				ipv6Only = true
		}
		if ipv4Only && ipv6Only {
				// bad request
		}
		// ...
		bgpRoutes, err := bq.GetBGPRoutes(r.Context(), !ipv6Only, !ipv4Only)

I feel like the current validation is a bit too restrictive / low-level. We should accept both ipv4-only= and ipv4-only for example.

[Atish-iaf]

/test-all

[antoninbas]

/test-all

[XinShuYang]

/test-e2e
/test-conformance

[XinShuYang]

/test-conformance

[XinShuYang]

/test-all-features-conformance