Desthost: Add support for wildcard host entries

This change adds support for wildcard host entries to the desthost
backend manager. Useful if all domains below a certain domain should use
a specific backend.

cmd/agent/app/options/options.go

@@ -92,7 +92,7 @@ func (o *GrpcProxyAgentOptions) Flags() *pflag.FlagSet {
 	flags.DurationVar(&o.SyncIntervalCap, "sync-interval-cap", o.SyncIntervalCap, "The maximum interval for the SyncInterval to back off to when unable to connect to the proxy server")
 	flags.DurationVar(&o.KeepaliveTime, "keepalive-time", o.KeepaliveTime, "Time for gRPC agent server keepalive.")
 	flags.StringVar(&o.ServiceAccountTokenPath, "service-account-token-path", o.ServiceAccountTokenPath, "If non-empty proxy agent uses this token to prove its identity to the proxy server.")
-	flags.StringVar(&o.AgentIdentifiers, "agent-identifiers", o.AgentIdentifiers, "Identifiers of the agent that will be used by the server when choosing agent. N.B. the list of identifiers must be in URL encoded format. e.g.,host=localhost&host=node1.mydomain.com&cidr=127.0.0.1/16&ipv4=1.2.3.4&ipv4=5.6.7.8&ipv6=:::::&default-route=true")
+	flags.StringVar(&o.AgentIdentifiers, "agent-identifiers", o.AgentIdentifiers, "Identifiers of the agent that will be used by the server when choosing agent. N.B. the list of identifiers must be in URL encoded format. e.g.,host=localhost&host=node1.mydomain.com&cidr=127.0.0.1/16&ipv4=1.2.3.4&ipv4=5.6.7.8&ipv6=:::::&default-route=true. If a host starts with *. or . it will be treated as wildcard")
 	flags.BoolVar(&o.WarnOnChannelLimit, "warn-on-channel-limit", o.WarnOnChannelLimit, "Turns on a warning if the system is going to push to a full channel. The check involves an unsafe read.")
 	flags.BoolVar(&o.SyncForever, "sync-forever", o.SyncForever, "If true, the agent continues syncing, in order to support server count changes.")
 	return flags

pkg/server/desthost_backend_manager.go

@@ -18,6 +18,7 @@ package server
 
 import (
 	"context"
+	"strings"
 
 	"k8s.io/klog/v2"
 	"sigs.k8s.io/apiserver-network-proxy/pkg/agent"
@@ -49,6 +50,18 @@ func (dibm *DestHostBackendManager) Backend(ctx context.Context) (Backend, error
 			klog.V(5).InfoS("Get the backend through the DestHostBackendManager", "destHost", destHost)
 			return dibm.backends[destHost][0], nil
 		}
+
+		for backend := range dibm.backends {
+			// Ignore backends that do not have a leading dot after stripping a leading *, we don't want foo.com to match for barfoo.com
+			if !strings.HasPrefix(backend, ".") {
+				continue
+			}
+			klog.V(5).Infof("Checking for wildcard match", "backend", backend, "destHost", destHost)
+			if strings.HasSuffix(destHost, backend) && len(dibm.backends[backend]) > 0 {
+				klog.V(5).InfoS("Get the backend through wildcardmatching in the DestHostBackendManager", "destHost", destHost, "backend", backend)
+				return dibm.backends[backend][0], nil
+			}
+		}
 	}
 	return nil, &ErrNotFound{}
 }

pkg/server/desthost_backend_manager_test.go

@@ -0,0 +1,94 @@
+package server
+
+import (
+	"context"
+	"testing"
+
+	"sigs.k8s.io/apiserver-network-proxy/proto/agent"
+)
+
+type fakeAgent struct {
+	ctx context.Context
+	agent.AgentService_ConnectServer
+}
+
+func (fa *fakeAgent) Context() context.Context {
+	return fa.ctx
+}
+
+const contextNameKey key = iota
+
+func newNamedBackend(name string) *backend {
+	return &backend{
+		conn: &fakeAgent{
+			ctx: context.WithValue(context.Background(), contextNameKey, name),
+		},
+	}
+}
+
+func TestBackend(t *testing.T) {
+
+	testCases := []struct {
+		name                string
+		destHost            string
+		backends            map[string][]*backend
+		expectedBackendName string
+	}{
+		{
+			name:     "Literal match",
+			destHost: "sts.amazonaws.com",
+			backends: map[string][]*backend{
+				"sts.amazonaws.com": {newNamedBackend("sts.amazonaws.com")},
+			},
+			expectedBackendName: "sts.amazonaws.com",
+		},
+		{
+			name:     "Wildcard match",
+			destHost: "sts.amazonaws.com",
+			backends: map[string][]*backend{
+				".amazonaws.com": {newNamedBackend(".amazonaws.com")},
+			},
+			expectedBackendName: ".amazonaws.com",
+		},
+		{
+			name:     "Both literal and wildcard match, literal match takes precedence",
+			destHost: "sts.amazonaws.com",
+			backends: map[string][]*backend{
+				"sts.amazonaws.com": {newNamedBackend("sts.amazonaws.com")},
+				".amazonaws.com":    {newNamedBackend(".amazonaws.com")},
+			},
+			expectedBackendName: "sts.amazonaws.com",
+		},
+		{
+			name:     "No wildcard match when entry doesn't start with dot",
+			destHost: "foo-bar.com",
+			backends: map[string][]*backend{
+				"bar.com": {newNamedBackend("bar.com")},
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+
+			request := context.WithValue(context.Background(), destHost, tc.destHost)
+			mgr := NewDestHostBackendManager()
+			mgr.backends = tc.backends
+
+			matchExpected := tc.expectedBackendName != ""
+			match, err := mgr.Backend(request)
+			hadMatch := err == nil
+			if matchExpected != hadMatch {
+				t.Fatalf("expected a match: %t, got a match: %t", matchExpected, hadMatch)
+			}
+			if !matchExpected {
+				return
+			}
+
+			matchName := match.Context().Value(contextNameKey).(string)
+			if matchName != tc.expectedBackendName {
+				t.Errorf("expected to get backend %s, got %s", tc.expectedBackendName, matchName)
+			}
+		})
+	}
+}