fix(frontend): allow resolution of v6 addresses. (backport release-3.5.x) (#18261)

Co-authored-by: Ashwanth <iamashwanth@gmail.com>

Author: loki-gh-app[bot]

docs/sources/shared/configuration.md

@@ -2713,6 +2713,10 @@ The `frontend` block configures the Loki query-frontend.
 # CLI flag: -frontend.instance-interface-names
 [instance_interface_names: <list of strings> | default = [<private network interfaces>]]
 
+# Enable using a IPv6 instance address (default false).
+# CLI flag: -frontend.instance-enable-ipv6
+[instance_enable_ipv6: <boolean> | default = false]
+
 # Defines the encoding for requests to and responses from the scheduler and
 # querier. Can be 'json' or 'protobuf' (defaults to 'json').
 # CLI flag: -frontend.encoding

pkg/lokifrontend/frontend/config.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 
 	"github.com/go-kit/log"
+	"github.com/grafana/dskit/netutil"
 	"github.com/grafana/dskit/ring"
 	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus"
@@ -13,7 +14,6 @@ import (
 	v1 "github.com/grafana/loki/v3/pkg/lokifrontend/frontend/v1"
 	v2 "github.com/grafana/loki/v3/pkg/lokifrontend/frontend/v2"
 	"github.com/grafana/loki/v3/pkg/querier/queryrange/queryrangebase"
-	"github.com/grafana/loki/v3/pkg/util"
 )
 
 // This struct combines several configuration options together to preserve backwards compatibility.
@@ -48,7 +48,7 @@ func InitFrontend(cfg CombinedFrontendConfig, ring ring.ReadRing, limits v1.Limi
 	case cfg.FrontendV2.SchedulerAddress != "" || ring != nil:
 		// If query-scheduler address is configured, use Frontend.
 		if cfg.FrontendV2.Addr == "" {
-			addr, err := util.GetFirstAddressOf(cfg.FrontendV2.InfNames, log)
+			addr, err := netutil.GetFirstAddressOf(cfg.FrontendV2.InfNames, log, cfg.FrontendV2.EnableIPv6)
 			if err != nil {
 				return nil, nil, nil, errors.Wrap(err, "failed to get frontend address")
 			}

pkg/lokifrontend/frontend/v2/frontend.go

@@ -51,7 +51,8 @@ type Config struct {
 	GracefulShutdownTimeout time.Duration     `yaml:"graceful_shutdown_timeout"`
 
 	// Used to find local IP address, that is sent to scheduler and querier-worker.
-	InfNames []string `yaml:"instance_interface_names" doc:"default=[<private network interfaces>]"`
+	InfNames   []string `yaml:"instance_interface_names" doc:"default=[<private network interfaces>]"`
+	EnableIPv6 bool     `yaml:"instance_enable_ipv6"`
 
 	// If set, address is not computed from interfaces.
 	Addr string `yaml:"address" doc:"hidden"`
@@ -69,6 +70,7 @@ func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
 
 	cfg.InfNames = netutil.PrivateNetworkInterfacesWithFallback([]string{"eth0", "en0"}, util_log.Logger)
 	f.Var((*flagext.StringSlice)(&cfg.InfNames), "frontend.instance-interface-names", "Name of network interface to read address from. This address is sent to query-scheduler and querier, which uses it to send the query response back to query-frontend.")
+	f.BoolVar(&cfg.EnableIPv6, "frontend.instance-enable-ipv6", false, "Enable using a IPv6 instance address (default false).")
 	f.StringVar(&cfg.Addr, "frontend.instance-addr", "", "IP address to advertise to querier (via scheduler) (resolved via interfaces by default).")
 	f.IntVar(&cfg.Port, "frontend.instance-port", 0, "Port to advertise to querier (via scheduler) (defaults to server.grpc-listen-port).")