feat(provider): specify interface name (#941)

.golangci.yaml

@@ -44,6 +44,8 @@ linters:
     - exportloopref # deprecated
 
     - dupl # somewhat unpredictable, and never leads to actual code changes
+    - goconst # never leads to actual code changes
+    - mnd # never leads to actual code changes
 
     - cyclop # can detect complicated code, but never leads to actual code changes
     - funlen # can detect complicated code, but never leads to actual code changes

internal/api/cloudflare_waf.go

@@ -22,8 +22,8 @@ import (
 // - An IPv6 CIDR ranges with a prefix from /4 to /64
 // For this updater, only the maximum values matter.
 var WAFListMaxBitLen = map[ipnet.Type]int{ //nolint:gochecknoglobals
-	ipnet.IP4: 32, //nolint:mnd
-	ipnet.IP6: 64, //nolint:mnd
+	ipnet.IP4: 32,
+	ipnet.IP6: 64,
 }
 
 func hintWAFListPermission(ppfmt pp.PP, err error) {

internal/config/config.go

@@ -51,14 +51,14 @@ func Default() *Config {
 		UpdateCron:         cron.MustNew("@every 5m"),
 		UpdateOnStart:      true,
 		DeleteOnStop:       false,
-		CacheExpiration:    time.Hour * 6, //nolint:mnd
+		CacheExpiration:    time.Hour * 6,
 		TTL:                api.TTLAuto,
 		ProxiedTemplate:    "false",
 		Proxied:            map[domain.Domain]bool{},
 		RecordComment:      "",
 		WAFListDescription: "",
-		DetectionTimeout:   time.Second * 5,  //nolint:mnd
-		UpdateTimeout:      time.Second * 30, //nolint:mnd
+		DetectionTimeout:   time.Second * 5,
+		UpdateTimeout:      time.Second * 30,
 		Monitor:            monitor.NewComposed(),
 		Notifier:           notifier.NewComposed(),
 	}

internal/config/env_provider.go

@@ -83,47 +83,60 @@ func ReadProvider(ppfmt pp.PP, key, keyDeprecated string, field *provider.Provid
 		return false
 	}
 
-	switch val {
-	case "cloudflare":
+	parts := strings.SplitN(val, ":", 2) // len(parts) >= 1 because val is not empty
+	for i := range parts {
+		parts[i] = strings.TrimSpace(parts[i])
+	}
+
+	switch {
+	case len(parts) == 1 && parts[0] == "cloudflare":
 		ppfmt.Noticef(
 			pp.EmojiUserError,
 			`%s=cloudflare is invalid; use %s=cloudflare.trace or %s=cloudflare.doh`,
 			key, key, key,
 		)
 		return false
-	case "cloudflare.trace":
+	case len(parts) == 1 && parts[0] == "cloudflare.trace":
 		*field = provider.NewCloudflareTrace()
 		return true
-	case "cloudflare.doh":
+	case len(parts) == 1 && parts[0] == "cloudflare.doh":
 		*field = provider.NewCloudflareDOH()
 		return true
-	case "ipify":
+	case len(parts) == 1 && parts[0] == "ipify":
 		ppfmt.Noticef(
 			pp.EmojiUserWarning,
 			`%s=ipify is deprecated; use %s=cloudflare.trace or %s=cloudflare.doh`,
 			key, key, key,
 		)
 		*field = provider.NewIpify()
 		return true
-	case "local":
+	case len(parts) == 1 && parts[0] == "local":
 		*field = provider.NewLocal()
 		return true
-	case "none":
-		*field = nil
+	case len(parts) == 2 && parts[0] == "local":
+		if parts[1] == "" {
+			ppfmt.Noticef(
+				pp.EmojiUserError,
+				`%s=local: must be followed by a network interface name`,
+				key,
+			)
+			return false
+		}
+		*field = provider.NewLocalWithInterface(parts[1])
 		return true
-	}
-
-	if strings.HasPrefix(val, "url:") {
-		url := strings.TrimSpace(strings.TrimPrefix(val, "url:"))
-		p, ok := provider.NewCustomURL(ppfmt, url)
+	case len(parts) == 2 && parts[0] == "url":
+		p, ok := provider.NewCustomURL(ppfmt, parts[1])
 		if ok {
 			*field = p
 		}
 		return ok
+	case len(parts) == 1 && parts[0] == "none":
+		*field = nil
+		return true
+	default:
+		ppfmt.Noticef(pp.EmojiUserError, "%s (%q) is not a valid provider", key, val)
+		return false
 	}
-
-	ppfmt.Noticef(pp.EmojiUserError, "%s (%q) is not a valid provider", key, val)
-	return false
 }
 
 // ReadProviderMap reads the environment variables IP4_PROVIDER and IP6_PROVIDER,

internal/config/env_provider_test.go

@@ -19,12 +19,13 @@ func TestReadProvider(t *testing.T) {
 	keyDeprecated := keyPrefix + "DEPRECATED"
 
 	var (
-		none   provider.Provider
-		doh    = provider.NewCloudflareDOH()
-		trace  = provider.NewCloudflareTrace()
-		local  = provider.NewLocal()
-		ipify  = provider.NewIpify()
-		custom = provider.MustNewCustomURL("https://url.io")
+		none          provider.Provider
+		doh           = provider.NewCloudflareDOH()
+		trace         = provider.NewCloudflareTrace()
+		local         = provider.NewLocal()
+		localLoopback = provider.NewLocalWithInterface("lo")
+		ipify         = provider.NewIpify()
+		custom        = provider.MustNewCustomURL("https://url.io")
 	)
 
 	for name, tc := range map[string]struct {
@@ -154,7 +155,18 @@ func TestReadProvider(t *testing.T) {
 		"cloudflare.doh":   {true, "    \tcloudflare.doh   ", false, "", none, doh, true, nil},
 		"none":             {true, "   none   ", false, "", trace, none, true, nil},
 		"local":            {true, "   local   ", false, "", trace, local, true, nil},
-		"custom":           {true, "   url:https://url.io   ", false, "", trace, custom, true, nil},
+		"local:lo":         {true, "   local   :  lo ", false, "", trace, localLoopback, true, nil},
+		"local:": {
+			true, "   local: ", false, "", trace, trace, false,
+			func(m *mocks.MockPP) {
+				m.EXPECT().Noticef(
+					pp.EmojiUserError,
+					`%s=local: must be followed by a network interface name`,
+					key,
+				)
+			},
+		},
+		"custom": {true, "   url:https://url.io   ", false, "", trace, custom, true, nil},
 		"ipify": {
 			true, "     ipify  ", false, "", trace, ipify, true,
 			func(m *mocks.MockPP) {

internal/config/env_waf.go

@@ -32,8 +32,8 @@ func ReadAndAppendWAFListNames(ppfmt pp.PP, key string, field *[]api.WAFList) bo
 	for _, val := range vals {
 		var list api.WAFList
 
-		parts := strings.SplitN(val, "/", 2) //nolint:mnd
-		if len(parts) != 2 {                 //nolint:mnd
+		parts := strings.SplitN(val, "/", 2)
+		if len(parts) != 2 {
 			ppfmt.Noticef(pp.EmojiUserError, `List %q should be in format "account-id/list-name"`, val)
 			return false
 		}

internal/pp/utils.go

@@ -25,7 +25,7 @@ func EnglishJoin(items []string) string {
 		return "(none)"
 	case 1:
 		return items[0]
-	case 2: //nolint:mnd
+	case 2:
 		return fmt.Sprintf("%s and %s", items[0], items[1])
 	default:
 		return fmt.Sprintf("%s, and %s", strings.Join(items[:l-1], ", "), items[l-1])

internal/provider/local_cloudflare.go

@@ -1,19 +1,12 @@
 package provider
 
-import (
-	"github.com/favonia/cloudflare-ddns/internal/ipnet"
-	"github.com/favonia/cloudflare-ddns/internal/provider/protocol"
-)
+import "github.com/favonia/cloudflare-ddns/internal/provider/protocol"
 
 // NewLocal creates a specialized Local provider that uses Cloudflare as the remote server.
 // (No actual UDP packets will be sent to Cloudflare.)
 func NewLocal() Provider {
-	return protocol.Local{
-		ProviderName: "local",
-		RemoteUDPAddr: map[ipnet.Type]string{
-			// 1.0.0.1 is used in case 1.1.1.1 is hijacked by the router
-			ipnet.IP4: "1.0.0.1:443",
-			ipnet.IP6: "[2606:4700:4700::1111]:443",
-		},
+	return protocol.LocalAuto{
+		ProviderName:  "local",
+		RemoteUDPAddr: "api.cloudflare.com:443",
 	}
 }

internal/provider/local_iface.go

@@ -0,0 +1,11 @@
+package provider
+
+import "github.com/favonia/cloudflare-ddns/internal/provider/protocol"
+
+// NewLocalWithInterface creates a protocol.LocalWithInterface provider.
+func NewLocalWithInterface(iface string) Provider {
+	return protocol.LocalWithInterface{
+		ProviderName:  "local:" + iface,
+		InterfaceName: iface,
+	}
+}

internal/provider/protocol/local_auto.go

@@ -0,0 +1,63 @@
+package protocol
+
+import (
+	"context"
+	"net"
+	"net/netip"
+
+	"github.com/favonia/cloudflare-ddns/internal/ipnet"
+	"github.com/favonia/cloudflare-ddns/internal/pp"
+)
+
+// LocalAuto detects the IP address by pretending to send out an UDP packet
+// and using the source IP address assigned by the system. In most cases
+// it will detect the IP address of the network interface toward the internet.
+// (No actual UDP packets will be sent out.)
+type LocalAuto struct {
+	// Name of the detection protocol.
+	ProviderName string
+
+	// The target of the hypothetical UDP packet to be sent.
+	RemoteUDPAddr string
+}
+
+// Name of the detection protocol.
+func (p LocalAuto) Name() string {
+	return p.ProviderName
+}
+
+// ExtractUDPAddr converts an address from [net.Interface.Addrs] to [netip.Addr].
+// The address will be unmapped.
+func ExtractUDPAddr(ppfmt pp.PP, addr net.Addr) (netip.Addr, bool) {
+	switch v := addr.(type) {
+	case *net.UDPAddr:
+		ip := v.AddrPort().Addr().Unmap()
+		if !ip.IsValid() {
+			ppfmt.Noticef(pp.EmojiImpossible, "Failed to parse UDP source address %q", v.IP.String())
+			return netip.Addr{}, false
+		}
+		return ip, ip.IsValid()
+	default:
+		ppfmt.Noticef(pp.EmojiImpossible, "Unexpected UDP source address data %q of type %T", addr.String(), addr)
+		return netip.Addr{}, false
+	}
+}
+
+// GetIP detects the IP address by pretending to send an UDP packet.
+// (No actual UDP packets will be sent out.)
+func (p LocalAuto) GetIP(_ context.Context, ppfmt pp.PP, ipNet ipnet.Type) (netip.Addr, Method, bool) {
+	conn, err := net.Dial(ipNet.UDPNetwork(), p.RemoteUDPAddr)
+	if err != nil {
+		ppfmt.Noticef(pp.EmojiError, "Failed to detect a local %s address: %v", ipNet.Describe(), err)
+		return netip.Addr{}, MethodUnspecified, false
+	}
+	defer conn.Close()
+
+	ip, ok := ExtractUDPAddr(ppfmt, conn.LocalAddr())
+	if !ok {
+		return netip.Addr{}, MethodUnspecified, false
+	}
+
+	normalizedIP, ok := ipNet.NormalizeDetectedIP(ppfmt, ip)
+	return normalizedIP, MethodPrimary, ok
+}