agent: expose the list of supported envoy versions on /v1/agent/self (#8545)

.changelog/8545.txt

@@ -0,0 +1,3 @@
+```release-note:feature
+agent: expose the list of supported envoy versions on /v1/agent/self
+```

agent/agent_endpoint.go

@@ -17,6 +17,7 @@ import (
 	"github.com/hashicorp/consul/agent/debug"
 	"github.com/hashicorp/consul/agent/structs"
 	token_store "github.com/hashicorp/consul/agent/token"
+	"github.com/hashicorp/consul/agent/xds/proxysupport"
 	"github.com/hashicorp/consul/api"
 	"github.com/hashicorp/consul/ipaddr"
 	"github.com/hashicorp/consul/lib"
@@ -38,6 +39,11 @@ type Self struct {
 	Member      serf.Member
 	Stats       map[string]map[string]string
 	Meta        map[string]string
+	XDS         *xdsSelf `json:"xDS,omitempty"`
+}
+
+type xdsSelf struct {
+	SupportedProxies map[string][]string
 }
 
 func (s *HTTPServer) AgentSelf(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
@@ -60,6 +66,15 @@ func (s *HTTPServer) AgentSelf(resp http.ResponseWriter, req *http.Request) (int
 		}
 	}
 
+	var xds *xdsSelf
+	if s.agent.grpcServer != nil {
+		xds = &xdsSelf{
+			SupportedProxies: map[string][]string{
+				"envoy": proxysupport.EnvoyVersions,
+			},
+		}
+	}
+
 	config := struct {
 		Datacenter string
 		NodeName   string
@@ -82,6 +97,7 @@ func (s *HTTPServer) AgentSelf(resp http.ResponseWriter, req *http.Request) (int
 		Member:      s.agent.LocalMember(),
 		Stats:       s.agent.Stats(),
 		Meta:        s.agent.State.Metadata(),
+		XDS:         xds,
 	}, nil
 }
 

agent/agent_endpoint_test.go

@@ -13,7 +13,6 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"os"
-	"reflect"
 	"strconv"
 	"strings"
 	"testing"
@@ -27,6 +26,7 @@ import (
 	"github.com/hashicorp/consul/agent/structs"
 	"github.com/hashicorp/consul/agent/token"
 	tokenStore "github.com/hashicorp/consul/agent/token"
+	"github.com/hashicorp/consul/agent/xds/proxysupport"
 	"github.com/hashicorp/consul/api"
 	"github.com/hashicorp/consul/lib"
 	"github.com/hashicorp/consul/sdk/testutil"
@@ -1209,39 +1209,65 @@ func TestAgent_Checks_ACLFilter(t *testing.T) {
 
 func TestAgent_Self(t *testing.T) {
 	t.Parallel()
-	a := NewTestAgent(t, `
+
+	cases := map[string]struct {
+		hcl       string
+		expectXDS bool
+	}{
+		"normal": {
+			hcl: `
 			node_meta {
 				somekey = "somevalue"
 			}
-	`)
+			`,
+			expectXDS: true,
+		},
+		"no grpc": {
+			hcl: `
+			node_meta {
+				somekey = "somevalue"
+			}
+			ports = {
+				grpc = -1
+			}
+			`,
+			expectXDS: false,
+		},
+	}
+
+	for name, tc := range cases {
+		tc := tc
+		t.Run(name, func(t *testing.T) {
+			a := NewTestAgent(t, tc.hcl)
 			defer a.Shutdown()
 
 			testrpc.WaitForTestAgent(t, a.RPC, "dc1")
 			req, _ := http.NewRequest("GET", "/v1/agent/self", nil)
 			obj, err := a.srv.AgentSelf(nil, req)
-	if err != nil {
-		t.Fatalf("err: %v", err)
-	}
+			require.NoError(t, err)
 
 			val := obj.(Self)
-	if int(val.Member.Port) != a.Config.SerfPortLAN {
-		t.Fatalf("incorrect port: %v", obj)
-	}
-
-	if val.DebugConfig["SerfPortLAN"].(int) != a.Config.SerfPortLAN {
-		t.Fatalf("incorrect port: %v", obj)
-	}
+			require.Equal(t, a.Config.SerfPortLAN, int(val.Member.Port))
+			require.Equal(t, a.Config.SerfPortLAN, val.DebugConfig["SerfPortLAN"].(int))
 
 			cs, err := a.GetLANCoordinate()
-	if err != nil {
-		t.Fatalf("err: %v", err)
-	}
-	if c := cs[a.config.SegmentName]; !reflect.DeepEqual(c, val.Coord) {
-		t.Fatalf("coordinates are not equal: %v != %v", c, val.Coord)
-	}
+			require.NoError(t, err)
+			require.Equal(t, cs[a.config.SegmentName], val.Coord)
+
 			delete(val.Meta, structs.MetaSegmentKey) // Added later, not in config.
-	if !reflect.DeepEqual(a.config.NodeMeta, val.Meta) {
-		t.Fatalf("meta fields are not equal: %v != %v", a.config.NodeMeta, val.Meta)
+			require.Equal(t, a.config.NodeMeta, val.Meta)
+
+			if tc.expectXDS {
+				require.NotNil(t, val.XDS, "xds component missing when gRPC is enabled")
+				require.Equal(t,
+					map[string][]string{"envoy": proxysupport.EnvoyVersions},
+					val.XDS.SupportedProxies,
+				)
+
+			} else {
+				require.Nil(t, val.XDS, "xds component should be missing when gRPC is disabled")
+			}
+		})
 	}
 }
 

agent/xds/proxysupport/proxysupport.go

@@ -2,6 +2,9 @@ package proxysupport
 
 // EnvoyVersions lists the latest officially supported versions of envoy.
 //
+// This list must be sorted by semver descending. Only one point release for
+// each major release should be present.
+//
 // see: https://www.consul.io/docs/connect/proxies/envoy#supported-versions
 var EnvoyVersions = []string{
 	"1.15.0",