consul: fixup expected consul tagged_addresses when using ipv6 (#15411)

This PR is a continuation of #14917, where we missed the ipv6 cases.

Consul auto-inserts tagged_addresses for keys
- lan_ipv4
- wan_ipv4
- lan_ipv6
- wan_ipv6

even though the service registration coming from Nomad does not contain such
elements. When doing the differential between services Nomad expects to be
registered vs. the services actually registered into Consul, we must first
purge these automatically inserted tagged_addresses if they do not exist in
the Nomad view of the Consul service.

.changelog/15411.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+consul: Fixed a bug where services would continuously re-register when using ipv6
+```

command/agent/consul/service_client.go

@@ -225,6 +225,12 @@ func maybeTweakTaggedAddresses(wanted *api.AgentServiceRegistration, existing *a
 		if _, exists := wanted.TaggedAddresses["wan_ipv4"]; !exists {
 			delete(existing.TaggedAddresses, "wan_ipv4")
 		}
+		if _, exists := wanted.TaggedAddresses["lan_ipv6"]; !exists {
+			delete(existing.TaggedAddresses, "lan_ipv6")
+		}
+		if _, exists := wanted.TaggedAddresses["wan_ipv6"]; !exists {
+			delete(existing.TaggedAddresses, "wan_ipv6")
+		}
 	}
 }
 

command/agent/consul/service_client_test.go

@@ -13,8 +13,115 @@ import (
 	"github.com/hashicorp/nomad/nomad/structs"
 	"github.com/shoenig/test/must"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/exp/maps"
 )
 
+func TestSyncLogic_maybeTweakTaggedAddresses(t *testing.T) {
+	ci.Parallel(t)
+
+	cases := []struct {
+		name     string
+		wanted   map[string]api.ServiceAddress
+		existing map[string]api.ServiceAddress
+		id       string
+		exp      []string
+	}{
+		{
+			name:   "not managed by nomad",
+			id:     "_nomad-other-hello",
+			wanted: map[string]api.ServiceAddress{
+				// empty
+			},
+			existing: map[string]api.ServiceAddress{
+				"lan_ipv4": {},
+				"wan_ipv4": {},
+				"custom":   {},
+			},
+			exp: []string{"lan_ipv4", "wan_ipv4", "custom"},
+		},
+		{
+			name: "remove defaults",
+			id:   "_nomad-task-hello",
+			wanted: map[string]api.ServiceAddress{
+				"lan_custom": {},
+				"wan_custom": {},
+			},
+			existing: map[string]api.ServiceAddress{
+				"lan_ipv4":   {},
+				"wan_ipv4":   {},
+				"lan_ipv6":   {},
+				"wan_ipv6":   {},
+				"lan_custom": {},
+				"wan_custom": {},
+			},
+			exp: []string{"lan_custom", "wan_custom"},
+		},
+		{
+			name: "overridden defaults",
+			id:   "_nomad-task-hello",
+			wanted: map[string]api.ServiceAddress{
+				"lan_ipv4": {},
+				"wan_ipv4": {},
+				"lan_ipv6": {},
+				"wan_ipv6": {},
+				"custom":   {},
+			},
+			existing: map[string]api.ServiceAddress{
+				"lan_ipv4": {},
+				"wan_ipv4": {},
+				"lan_ipv6": {},
+				"wan_ipv6": {},
+				"custom":   {},
+			},
+			exp: []string{"lan_ipv4", "wan_ipv4", "lan_ipv6", "wan_ipv6", "custom"},
+		},
+		{
+			name: "applies to nomad client",
+			id:   "_nomad-client-12345",
+			wanted: map[string]api.ServiceAddress{
+				"custom": {},
+			},
+			existing: map[string]api.ServiceAddress{
+				"lan_ipv4": {},
+				"wan_ipv4": {},
+				"lan_ipv6": {},
+				"wan_ipv6": {},
+				"custom":   {},
+			},
+			exp: []string{"custom"},
+		},
+		{
+			name: "applies to nomad server",
+			id:   "_nomad-server-12345",
+			wanted: map[string]api.ServiceAddress{
+				"custom": {},
+			},
+			existing: map[string]api.ServiceAddress{
+				"lan_ipv4": {},
+				"wan_ipv4": {},
+				"lan_ipv6": {},
+				"wan_ipv6": {},
+				"custom":   {},
+			},
+			exp: []string{"custom"},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			asr := &api.AgentServiceRegistration{
+				ID:              tc.id,
+				TaggedAddresses: maps.Clone(tc.wanted),
+			}
+			as := &api.AgentService{
+				TaggedAddresses: maps.Clone(tc.existing),
+			}
+			maybeTweakTaggedAddresses(asr, as)
+			must.MapContainsKeys(t, as.TaggedAddresses, tc.exp)
+		})
+	}
+}
+
 func TestSyncLogic_agentServiceUpdateRequired(t *testing.T) {
 	ci.Parallel(t)