(untested) Merge commit e56ad81 from https://github.com/jzelinskie/chihaya

* rename/replace redis keys

frontend/http/frontend.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 	"net"
 	"net/http"
+	"net/netip"
 	"time"
 
 	"github.com/julienschmidt/httprouter"
@@ -282,12 +283,12 @@ func (f *Frontend) announceRoute(w http.ResponseWriter, r *http.Request, ps http
 	if f.EnableRequestTiming {
 		start = time.Now()
 	}
-	var af *bittorrent.AddressFamily
+	var addr netip.Addr
 	defer func() {
 		if f.EnableRequestTiming {
-			recordResponseDuration("announce", af, err, time.Since(start))
+			recordResponseDuration("announce", addr, err, time.Since(start))
 		} else {
-			recordResponseDuration("announce", af, err, time.Duration(0))
+			recordResponseDuration("announce", addr, err, time.Duration(0))
 		}
 	}()
 
@@ -296,8 +297,7 @@ func (f *Frontend) announceRoute(w http.ResponseWriter, r *http.Request, ps http
 		WriteError(w, err)
 		return
 	}
-	af = new(bittorrent.AddressFamily)
-	*af = req.IP.AddressFamily
+	addr = req.AddrPort.Addr()
 
 	ctx := injectRouteParamsToContext(context.Background(), ps)
 	ctx, resp, err := f.logic.HandleAnnounce(ctx, req)
@@ -323,12 +323,12 @@ func (f *Frontend) scrapeRoute(w http.ResponseWriter, r *http.Request, ps httpro
 	if f.EnableRequestTiming {
 		start = time.Now()
 	}
-	var af *bittorrent.AddressFamily
+	var addr netip.Addr
 	defer func() {
 		if f.EnableRequestTiming {
-			recordResponseDuration("scrape", af, err, time.Since(start))
+			recordResponseDuration("scrape", addr, err, time.Since(start))
 		} else {
-			recordResponseDuration("scrape", af, err, time.Duration(0))
+			recordResponseDuration("scrape", addr, err, time.Duration(0))
 		}
 	}()
 
@@ -345,18 +345,12 @@ func (f *Frontend) scrapeRoute(w http.ResponseWriter, r *http.Request, ps httpro
 		return
 	}
 
-	reqIP := net.ParseIP(host)
-	if reqIP.To4() != nil {
-		req.AddressFamily = bittorrent.IPv4
-	} else if len(reqIP) == net.IPv6len { // implies reqIP.To4() == nil
-		req.AddressFamily = bittorrent.IPv6
-	} else {
+	addr, err = netip.ParseAddr(host)
+	if err != nil || addr.IsUnspecified() {
 		log.Error("http: invalid IP: neither v4 nor v6", log.Fields{"RemoteAddr": r.RemoteAddr})
 		WriteError(w, bittorrent.ErrInvalidIP)
 		return
 	}
-	af = new(bittorrent.AddressFamily)
-	*af = req.AddressFamily
 
 	ctx := injectRouteParamsToContext(context.Background(), ps)
 	ctx, resp, err := f.logic.HandleScrape(ctx, req)

frontend/http/parser.go

@@ -2,8 +2,8 @@ package http
 
 import (
 	"errors"
-	"net"
 	"net/http"
+	"net/netip"
 
 	"github.com/sot-tech/mochi/bittorrent"
 )
@@ -28,6 +28,16 @@ const (
 	defaultMaxScrapeInfoHashes = 50
 )
 
+var (
+	errNoInfoHash                 = bittorrent.ClientError("no info hash supplied")
+	errMultipleInfoHashes         = bittorrent.ClientError("multiple info hashes supplied")
+	errInvalidPeerID              = bittorrent.ClientError("peer ID invalid or not provided")
+	errInvalidParameterLeft       = bittorrent.ClientError("parameter 'left' invalid or not provided")
+	errInvalidParameterDownloaded = bittorrent.ClientError("parameter 'downloaded' invalid or not provided")
+	errInvalidParameterUploaded   = bittorrent.ClientError("parameter 'uploaded' invalid or not provided")
+	errInvalidParameterNumWant    = bittorrent.ClientError("parameter 'num want' invalid or not provided")
+)
+
 // ParseAnnounce parses an bittorrent.AnnounceRequest from an http.Request.
 func ParseAnnounce(r *http.Request, opts ParseOptions) (*bittorrent.AnnounceRequest, error) {
 	qp, err := bittorrent.ParseURLData(r.RequestURI)
@@ -41,9 +51,8 @@ func ParseAnnounce(r *http.Request, opts ParseOptions) (*bittorrent.AnnounceRequ
 	var eventStr string
 	eventStr, request.EventProvided = qp.String("event")
 	if request.EventProvided {
-		request.Event, err = bittorrent.NewEvent(eventStr)
-		if err != nil {
-			return nil, bittorrent.ClientError("failed to provide valid client event")
+		if request.Event, err = bittorrent.NewEvent(eventStr); err != nil {
+			return nil, err
 		}
 	} else {
 		request.Event = bittorrent.None
@@ -56,17 +65,17 @@ func ParseAnnounce(r *http.Request, opts ParseOptions) (*bittorrent.AnnounceRequ
 	// Parse the infohash from the request.
 	infoHashes := qp.InfoHashes()
 	if len(infoHashes) < 1 {
-		return nil, bittorrent.ClientError("no info_hash parameter supplied")
+		return nil, errNoInfoHash
 	}
 	if len(infoHashes) > 1 {
-		return nil, bittorrent.ClientError("multiple info_hash parameters supplied")
+		return nil, errMultipleInfoHashes
 	}
 	request.InfoHash = infoHashes[0]
 
 	// Parse the PeerID from the request.
 	peerID, ok := qp.String("peer_id")
 	if !ok {
-		return nil, bittorrent.ClientError("failed to parse parameter: peer_id")
+		return nil, errInvalidPeerID
 	}
 	request.Peer.ID, err = bittorrent.NewPeerID([]byte(peerID))
 	if err != nil {
@@ -75,25 +84,25 @@ func ParseAnnounce(r *http.Request, opts ParseOptions) (*bittorrent.AnnounceRequ
 	// Determine the number of remaining bytes for the client.
 	request.Left, err = qp.Uint("left", 64)
 	if err != nil {
-		return nil, bittorrent.ClientError("failed to parse parameter: left")
+		return nil, errInvalidParameterLeft
 	}
 
 	// Determine the number of bytes downloaded by the client.
 	request.Downloaded, err = qp.Uint("downloaded", 64)
 	if err != nil {
-		return nil, bittorrent.ClientError("failed to parse parameter: downloaded")
+		return nil, errInvalidParameterDownloaded
 	}
 
 	// Determine the number of bytes shared by the client.
 	request.Uploaded, err = qp.Uint("uploaded", 64)
 	if err != nil {
-		return nil, bittorrent.ClientError("failed to parse parameter: uploaded")
+		return nil, errInvalidParameterUploaded
 	}
 
 	// Determine the number of peers the client wants in the response.
 	numwant, err := qp.Uint("numwant", 32)
 	if err != nil && !errors.Is(err, bittorrent.ErrKeyNotFound) {
-		return nil, bittorrent.ClientError("failed to parse parameter: numwant")
+		return nil, errInvalidParameterNumWant
 	}
 	// If there were no errors, the user actually provided the numwant.
 	request.NumWantProvided = err == nil
@@ -102,21 +111,22 @@ func ParseAnnounce(r *http.Request, opts ParseOptions) (*bittorrent.AnnounceRequ
 	// Parse the port where the client is listening.
 	port, err := qp.Uint("port", 16)
 	if err != nil {
-		return nil, bittorrent.ClientError("failed to parse parameter: port")
+		return nil, bittorrent.ErrInvalidPort
 	}
-	request.Peer.Port = uint16(port)
 
 	// Parse the IP address where the client is listening.
-	request.Peer.IP.IP, request.IPProvided = requestedIP(r, qp, opts)
-	if request.Peer.IP.IP == nil {
-		return nil, bittorrent.ClientError("failed to parse peer IP address")
+	ip, spoofed, err := requestedIP(r, qp, opts)
+	if err != nil {
+		return nil, bittorrent.ErrInvalidIP
+	}
+	request.Peer.AddrPort = netip.AddrPortFrom(ip, uint16(port))
+	request.IPProvided = spoofed
+
+	if err = bittorrent.SanitizeAnnounce(request, opts.MaxNumWant, opts.DefaultNumWant); err != nil {
+		request = nil
 	}
 
-	if err := bittorrent.SanitizeAnnounce(request, opts.MaxNumWant, opts.DefaultNumWant); err != nil {
-		return nil, err
-	}
-
-	return request, nil
+	return request, err
 }
 
 // ParseScrape parses an bittorrent.ScrapeRequest from an http.Request.
@@ -128,7 +138,7 @@ func ParseScrape(r *http.Request, opts ParseOptions) (*bittorrent.ScrapeRequest,
 
 	infoHashes := qp.InfoHashes()
 	if len(infoHashes) < 1 {
-		return nil, bittorrent.ClientError("no info_hash parameter supplied")
+		return nil, errNoInfoHash
 	}
 
 	request := &bittorrent.ScrapeRequest{
@@ -144,27 +154,29 @@ func ParseScrape(r *http.Request, opts ParseOptions) (*bittorrent.ScrapeRequest,
 }
 
 // requestedIP determines the IP address for a BitTorrent client request.
-func requestedIP(r *http.Request, p bittorrent.Params, opts ParseOptions) (ip net.IP, provided bool) {
+func requestedIP(r *http.Request, p bittorrent.Params, opts ParseOptions) (netip.Addr, bool, error) {
 	if opts.AllowIPSpoofing {
 		if ipstr, ok := p.String("ip"); ok {
-			return net.ParseIP(ipstr), true
+			addr, err := netip.ParseAddr(ipstr)
+			return addr, true, err
 		}
 
 		if ipstr, ok := p.String("ipv4"); ok {
-			return net.ParseIP(ipstr), true
+			addr, err := netip.ParseAddr(ipstr)
+			return addr, true, err
 		}
 
 		if ipstr, ok := p.String("ipv6"); ok {
-			return net.ParseIP(ipstr), true
+			addr, err := netip.ParseAddr(ipstr)
+			return addr, true, err
 		}
 	}
 
-	if opts.RealIPHeader != "" {
-		if ip := r.Header.Get(opts.RealIPHeader); ip != "" {
-			return net.ParseIP(ip), false
-		}
+	if ipstr := r.Header.Get(opts.RealIPHeader); ipstr != "" && opts.RealIPHeader != "" {
+		addr, err := netip.ParseAddr(ipstr)
+		return addr, false, err
 	}
 
-	host, _, _ := net.SplitHostPort(r.RemoteAddr)
-	return net.ParseIP(host), false
+	addrPort, err := netip.ParseAddrPort(r.RemoteAddr)
+	return addrPort.Addr(), false, err
 }

frontend/http/prometheus.go

@@ -2,11 +2,13 @@ package http
 
 import (
 	"errors"
+	"net/netip"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
 
 	"github.com/sot-tech/mochi/bittorrent"
+	"github.com/sot-tech/mochi/pkg/metrics"
 )
 
 func init() {
@@ -24,7 +26,7 @@ var promResponseDurationMilliseconds = prometheus.NewHistogramVec(
 
 // recordResponseDuration records the duration of time to respond to a Request
 // in milliseconds.
-func recordResponseDuration(action string, af *bittorrent.AddressFamily, err error, duration time.Duration) {
+func recordResponseDuration(action string, addr netip.Addr, err error, duration time.Duration) {
 	var errString string
 	if err != nil {
 		var clientErr bittorrent.ClientError
@@ -35,16 +37,7 @@ func recordResponseDuration(action string, af *bittorrent.AddressFamily, err err
 		}
 	}
 
-	var afString string
-	if af == nil {
-		afString = "Unknown"
-	} else if *af == bittorrent.IPv4 {
-		afString = "IPv4"
-	} else if *af == bittorrent.IPv6 {
-		afString = "IPv6"
-	}
-
 	promResponseDurationMilliseconds.
-		WithLabelValues(action, afString, errString).
+		WithLabelValues(action, metrics.AddressFamily(addr), errString).
 		Observe(float64(duration.Nanoseconds()) / float64(time.Millisecond))
 }

frontend/http/writer.go

@@ -98,29 +98,25 @@ func WriteScrapeResponse(w http.ResponseWriter, resp *bittorrent.ScrapeResponse)
 }
 
 func compact4(peer bittorrent.Peer) (buf []byte) {
-	if ip := peer.IP.To4(); ip == nil {
-		panic("non-IPv4 IP for Peer in IPv4Peers")
-	} else {
-		buf = ip
-	}
-	buf = append(buf, byte(peer.Port>>8), byte(peer.Port))
+	ip := peer.AddrPort.Addr().As4()
+	buf = append(buf, ip[:]...)
+	port := peer.AddrPort.Port()
+	buf = append(buf, byte(port>>8), byte(port&0xff))
 	return
 }
 
 func compact6(peer bittorrent.Peer) (buf []byte) {
-	if ip := peer.IP.To16(); ip == nil {
-		panic("non-IPv6 IP for Peer in IPv6Peers")
-	} else {
-		buf = ip
-	}
-	buf = append(buf, byte(peer.Port>>8), byte(peer.Port))
+	ip := peer.AddrPort.Addr().As16()
+	buf = append(buf, ip[:]...)
+	port := peer.AddrPort.Port()
+	buf = append(buf, byte(port>>8), byte(port&0xff))
 	return
 }
 
 func dict(peer bittorrent.Peer) map[string]any {
 	return map[string]any{
 		"peer id": string(peer.ID[:]),
-		"ip":      peer.IP.String(),
-		"port":    peer.Port,
+		"ip":      peer.Addr(),
+		"port":    peer.Port(),
 	}
 }

frontend/udp/connection_id.go

@@ -4,7 +4,7 @@ import (
 	"crypto/hmac"
 	"encoding/binary"
 	"hash"
-	"net"
+	"net/netip"
 	"time"
 
 	"github.com/minio/sha256-simd"
@@ -19,14 +19,14 @@ const ttl = 2 * time.Minute
 // described by BEP 15.
 // This is a wrapper around creating a new ConnectionIDGenerator and generating
 // an ID. It is recommended to use the generator for performance.
-func NewConnectionID(ip net.IP, now time.Time, key string) []byte {
+func NewConnectionID(ip netip.Addr, now time.Time, key string) []byte {
 	return NewConnectionIDGenerator(key).Generate(ip, now)
 }
 
 // ValidConnectionID determines whether a connection identifier is legitimate.
 // This is a wrapper around creating a new ConnectionIDGenerator and validating
 // the ID. It is recommended to use the generator for performance.
-func ValidConnectionID(connectionID []byte, ip net.IP, now time.Time, maxClockSkew time.Duration, key string) bool {
+func ValidConnectionID(connectionID []byte, ip netip.Addr, now time.Time, maxClockSkew time.Duration, key string) bool {
 	return NewConnectionIDGenerator(key).Validate(connectionID, ip, now, maxClockSkew)
 }
 
@@ -85,13 +85,14 @@ func (g *ConnectionIDGenerator) reset() {
 // The generated ID is written to g.connID, which is also returned. g.connID
 // will be reused, so it must not be referenced after returning the generator
 // to a pool and will be overwritten be subsequent calls to Generate!
-func (g *ConnectionIDGenerator) Generate(ip net.IP, now time.Time) []byte {
+func (g *ConnectionIDGenerator) Generate(ip netip.Addr, now time.Time) []byte {
 	g.reset()
 
 	binary.BigEndian.PutUint32(g.connID, uint32(now.Unix()))
 
 	g.mac.Write(g.connID[:4])
-	g.mac.Write(ip)
+	ipBytes, _ := ip.MarshalBinary()
+	g.mac.Write(ipBytes)
 	g.scratch = g.mac.Sum(g.scratch)
 	copy(g.connID[4:8], g.scratch[:4])
 
@@ -100,7 +101,7 @@ func (g *ConnectionIDGenerator) Generate(ip net.IP, now time.Time) []byte {
 }
 
 // Validate validates the given connection ID for an IP and the current time.
-func (g *ConnectionIDGenerator) Validate(connectionID []byte, ip net.IP, now time.Time, maxClockSkew time.Duration) bool {
+func (g *ConnectionIDGenerator) Validate(connectionID []byte, ip netip.Addr, now time.Time, maxClockSkew time.Duration) bool {
 	ts := time.Unix(int64(binary.BigEndian.Uint32(connectionID[:4])), 0)
 	log.Debug("validating connection ID", log.Fields{"connID": connectionID, "ip": ip, "ts": ts, "now": now})
 	if now.After(ts.Add(ttl)) || ts.After(now.Add(maxClockSkew)) {
@@ -110,7 +111,8 @@ func (g *ConnectionIDGenerator) Validate(connectionID []byte, ip net.IP, now tim
 	g.reset()
 
 	g.mac.Write(connectionID[:4])
-	g.mac.Write(ip)
+	ipBytes, _ := ip.MarshalBinary()
+	g.mac.Write(ipBytes)
 	g.scratch = g.mac.Sum(g.scratch)
 	return hmac.Equal(g.scratch[:4], connectionID[4:])
 }

frontend/udp/connection_id_test.go

@@ -4,7 +4,7 @@ import (
 	"crypto/hmac"
 	"encoding/binary"
 	"fmt"
-	"net"
+	"net/netip"
 	"sync"
 	"testing"
 	"time"
@@ -24,18 +24,19 @@ var golden = []struct {
 }{
 	{0, 1, "127.0.0.1", "", true},
 	{0, 420420, "127.0.0.1", "", false},
-	{0, 0, "[::]", "", true},
+	{0, 0, "::1", "", true},
 }
 
 // simpleNewConnectionID generates a new connection ID the explicit way.
 // This is used to verify correct behaviour of the generator.
-func simpleNewConnectionID(ip net.IP, now time.Time, key string) []byte {
+func simpleNewConnectionID(ip netip.Addr, now time.Time, key string) []byte {
 	buf := make([]byte, 8)
 	binary.BigEndian.PutUint32(buf, uint32(now.Unix()))
 
 	mac := hmac.New(sha256.New, []byte(key))
 	mac.Write(buf[:4])
-	mac.Write(ip)
+	ipBytes, _ := ip.MarshalBinary()
+	mac.Write(ipBytes)
 	macBytes := mac.Sum(nil)[:4]
 	copy(buf[4:], macBytes)
 
@@ -48,8 +49,8 @@ func simpleNewConnectionID(ip net.IP, now time.Time, key string) []byte {
 func TestVerification(t *testing.T) {
 	for _, tt := range golden {
 		t.Run(fmt.Sprintf("%s created at %d verified at %d", tt.ip, tt.createdAt, tt.now), func(t *testing.T) {
-			cid := NewConnectionID(net.ParseIP(tt.ip), time.Unix(tt.createdAt, 0), tt.key)
-			got := ValidConnectionID(cid, net.ParseIP(tt.ip), time.Unix(tt.now, 0), time.Minute, tt.key)
+			cid := NewConnectionID(netip.MustParseAddr(tt.ip), time.Unix(tt.createdAt, 0), tt.key)
+			got := ValidConnectionID(cid, netip.MustParseAddr(tt.ip), time.Unix(tt.now, 0), time.Minute, tt.key)
 			if got != tt.valid {
 				t.Errorf("expected validity: %t got validity: %t", tt.valid, got)
 			}
@@ -60,8 +61,8 @@ func TestVerification(t *testing.T) {
 func TestGeneration(t *testing.T) {
 	for _, tt := range golden {
 		t.Run(fmt.Sprintf("%s created at %d", tt.ip, tt.createdAt), func(t *testing.T) {
-			want := simpleNewConnectionID(net.ParseIP(tt.ip), time.Unix(tt.createdAt, 0), tt.key)
-			got := NewConnectionID(net.ParseIP(tt.ip), time.Unix(tt.createdAt, 0), tt.key)
+			want := simpleNewConnectionID(netip.MustParseAddr(tt.ip), time.Unix(tt.createdAt, 0), tt.key)
+			got := NewConnectionID(netip.MustParseAddr(tt.ip), time.Unix(tt.createdAt, 0), tt.key)
 			require.Equal(t, want, got)
 		})
 	}
@@ -70,13 +71,13 @@ func TestGeneration(t *testing.T) {
 func TestReuseGeneratorGenerate(t *testing.T) {
 	for _, tt := range golden {
 		t.Run(fmt.Sprintf("%s created at %d", tt.ip, tt.createdAt), func(t *testing.T) {
-			cid := NewConnectionID(net.ParseIP(tt.ip), time.Unix(tt.createdAt, 0), tt.key)
+			cid := NewConnectionID(netip.MustParseAddr(tt.ip), time.Unix(tt.createdAt, 0), tt.key)
 			require.Len(t, cid, 8)
 
 			gen := NewConnectionIDGenerator(tt.key)
 
 			for i := 0; i < 3; i++ {
-				connID := gen.Generate(net.ParseIP(tt.ip), time.Unix(tt.createdAt, 0))
+				connID := gen.Generate(netip.MustParseAddr(tt.ip), time.Unix(tt.createdAt, 0))
 				require.Equal(t, cid, connID)
 			}
 		})
@@ -87,9 +88,9 @@ func TestReuseGeneratorValidate(t *testing.T) {
 	for _, tt := range golden {
 		t.Run(fmt.Sprintf("%s created at %d verified at %d", tt.ip, tt.createdAt, tt.now), func(t *testing.T) {
 			gen := NewConnectionIDGenerator(tt.key)
-			cid := gen.Generate(net.ParseIP(tt.ip), time.Unix(tt.createdAt, 0))
+			cid := gen.Generate(netip.MustParseAddr(tt.ip), time.Unix(tt.createdAt, 0))
 			for i := 0; i < 3; i++ {
-				got := gen.Validate(cid, net.ParseIP(tt.ip), time.Unix(tt.now, 0), time.Minute)
+				got := gen.Validate(cid, netip.MustParseAddr(tt.ip), time.Unix(tt.now, 0), time.Minute)
 				if got != tt.valid {
 					t.Errorf("expected validity: %t got validity: %t", tt.valid, got)
 				}
@@ -99,7 +100,7 @@ func TestReuseGeneratorValidate(t *testing.T) {
 }
 
 func BenchmarkSimpleNewConnectionID(b *testing.B) {
-	ip := net.ParseIP("127.0.0.1")
+	ip := netip.MustParseAddr("127.0.0.1")
 	key := "some random string that is hopefully at least this long"
 	createdAt := time.Now()
 
@@ -116,7 +117,7 @@ func BenchmarkSimpleNewConnectionID(b *testing.B) {
 }
 
 func BenchmarkNewConnectionID(b *testing.B) {
-	ip := net.ParseIP("127.0.0.1")
+	ip := netip.MustParseAddr("127.0.0.1")
 	key := "some random string that is hopefully at least this long"
 	createdAt := time.Now()
 
@@ -133,7 +134,7 @@ func BenchmarkNewConnectionID(b *testing.B) {
 }
 
 func BenchmarkConnectionIDGenerator_Generate(b *testing.B) {
-	ip := net.ParseIP("127.0.0.1")
+	ip := netip.MustParseAddr("127.0.0.1")
 	key := "some random string that is hopefully at least this long"
 	createdAt := time.Now()
 
@@ -155,7 +156,7 @@ func BenchmarkConnectionIDGenerator_Generate(b *testing.B) {
 }
 
 func BenchmarkValidConnectionID(b *testing.B) {
-	ip := net.ParseIP("127.0.0.1")
+	ip := netip.MustParseAddr("127.0.0.1")
 	key := "some random string that is hopefully at least this long"
 	createdAt := time.Now()
 	cid := NewConnectionID(ip, createdAt, key)
@@ -170,7 +171,7 @@ func BenchmarkValidConnectionID(b *testing.B) {
 }
 
 func BenchmarkConnectionIDGenerator_Validate(b *testing.B) {
-	ip := net.ParseIP("127.0.0.1")
+	ip := netip.MustParseAddr("127.0.0.1")
 	key := "some random string that is hopefully at least this long"
 	createdAt := time.Now()
 	cid := NewConnectionID(ip, createdAt, key)

frontend/udp/frontend.go

@@ -7,9 +7,9 @@ import (
 	"context"
 	"encoding/binary"
 	"errors"
-	"fmt"
 	"math/rand"
 	"net"
+	"net/netip"
 	"sync"
 	"time"
 
@@ -184,7 +184,7 @@ func (t *Frontend) serve() error {
 
 		// Read a UDP packet into a reusable buffer.
 		buffer := pool.Get()
-		n, addr, err := t.socket.ReadFromUDP(*buffer)
+		n, addrPort, err := t.socket.ReadFromUDPAddrPort(*buffer)
 		if err != nil {
 			pool.Put(buffer)
 			var netErr net.Error
@@ -206,24 +206,20 @@ func (t *Frontend) serve() error {
 			defer t.wg.Done()
 			defer pool.Put(buffer)
 
-			if ip := addr.IP.To4(); ip != nil {
-				addr.IP = ip
-			}
-
 			// Handle the request.
+			addr := addrPort.Addr()
 			var start time.Time
 			if t.EnableRequestTiming {
 				start = time.Now()
 			}
-			action, af, err := t.handleRequest(
-				// Make sure the IP is copied, not referenced.
-				Request{(*buffer)[:n], append([]byte{}, addr.IP...)},
-				ResponseWriter{t.socket, addr},
+			action, err := t.handleRequest(
+				Request{(*buffer)[:n], addr},
+				ResponseWriter{t.socket, addrPort},
 			)
 			if t.EnableRequestTiming {
-				recordResponseDuration(action, af, err, time.Since(start))
+				recordResponseDuration(action, addr, err, time.Since(start))
 			} else {
-				recordResponseDuration(action, af, err, time.Duration(0))
+				recordResponseDuration(action, addr, err, time.Duration(0))
 			}
 		}()
 	}
@@ -232,23 +228,23 @@ func (t *Frontend) serve() error {
 // Request represents a UDP payload received by a Tracker.
 type Request struct {
 	Packet []byte
-	IP     net.IP
+	IP     netip.Addr
 }
 
 // ResponseWriter implements the ability to respond to a Request via the
 // io.Writer interface.
 type ResponseWriter struct {
-	socket *net.UDPConn
-	addr   *net.UDPAddr
+	socket   *net.UDPConn
+	addrPort netip.AddrPort
 }
 
 // Write implements the io.Writer interface for a ResponseWriter.
 func (w ResponseWriter) Write(b []byte) (int, error) {
-	return w.socket.WriteToUDP(b, w.addr)
+	return w.socket.WriteToUDPAddrPort(b, w.addrPort)
 }
 
 // handleRequest parses and responds to a UDP Request.
-func (t *Frontend) handleRequest(r Request, w ResponseWriter) (actionName string, af *bittorrent.AddressFamily, err error) {
+func (t *Frontend) handleRequest(r Request, w ResponseWriter) (actionName string, err error) {
 	if len(r.Packet) < 16 {
 		// Malformed, no client packets are less than 16 bytes.
 		// We explicitly return nothing in case this is a DoS attempt.
@@ -283,16 +279,6 @@ func (t *Frontend) handleRequest(r Request, w ResponseWriter) (actionName string
 			return
 		}
 
-		af = new(bittorrent.AddressFamily)
-		if r.IP.To4() != nil {
-			*af = bittorrent.IPv4
-		} else if len(r.IP) == net.IPv6len { // implies r.IP.To4() == nil
-			*af = bittorrent.IPv6
-		} else {
-			// Should never happen - we got the IP straight from the UDP packet.
-			panic(fmt.Sprintf("udp: invalid IP: neither v4 nor v6, IP: %#v", r.IP))
-		}
-
 		WriteConnectionID(w, txID, gen.Generate(r.IP, timecache.Now()))
 
 	case announceActionID, announceV6ActionID:
@@ -304,8 +290,6 @@ func (t *Frontend) handleRequest(r Request, w ResponseWriter) (actionName string
 			WriteError(w, txID, err)
 			return
 		}
-		af = new(bittorrent.AddressFamily)
-		*af = req.IP.AddressFamily
 
 		var ctx context.Context
 		var resp *bittorrent.AnnounceResponse
@@ -315,7 +299,7 @@ func (t *Frontend) handleRequest(r Request, w ResponseWriter) (actionName string
 			return
 		}
 
-		WriteAnnounce(w, txID, resp, actionID == announceV6ActionID, req.IP.AddressFamily == bittorrent.IPv6)
+		WriteAnnounce(w, txID, resp, actionID == announceV6ActionID, r.IP.Is6())
 
 		go t.logic.AfterAnnounce(ctx, req, resp)
 
@@ -329,17 +313,6 @@ func (t *Frontend) handleRequest(r Request, w ResponseWriter) (actionName string
 			return
 		}
 
-		if r.IP.To4() != nil {
-			req.AddressFamily = bittorrent.IPv4
-		} else if len(r.IP) == net.IPv6len { // implies r.IP.To4() == nil
-			req.AddressFamily = bittorrent.IPv6
-		} else {
-			// Should never happen - we got the IP straight from the UDP packet.
-			panic(fmt.Sprintf("udp: invalid IP: neither v4 nor v6, IP: %#v", r.IP))
-		}
-		af = new(bittorrent.AddressFamily)
-		*af = req.AddressFamily
-
 		var ctx context.Context
 		var resp *bittorrent.ScrapeResponse
 		ctx, resp, err = t.logic.HandleScrape(context.Background(), req)

frontend/udp/parser.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"net"
+	"net/netip"
 	"sync"
 
 	"github.com/sot-tech/mochi/bittorrent"
@@ -41,8 +42,6 @@ var (
 	}
 
 	errMalformedPacket   = bittorrent.ClientError("malformed packet")
-	errMalformedIP       = bittorrent.ClientError("malformed IP address")
-	errMalformedEvent    = bittorrent.ClientError("malformed event ID")
 	errUnknownAction     = bittorrent.ClientError("unknown action ID")
 	errBadConnectionID   = bittorrent.ClientError("bad connection ID")
 	errUnknownOptionType = bittorrent.ClientError("unknown option type")
@@ -89,19 +88,23 @@ func ParseAnnounce(r Request, v6Action bool, opts ParseOptions) (*bittorrent.Ann
 
 	eventID := int(r.Packet[83])
 	if eventID >= len(eventIDs) {
-		return nil, errMalformedEvent
+		return nil, bittorrent.ErrUnknownEvent
 	}
 
 	ip := r.IP
 	ipProvided := false
-	if ipBytes := r.Packet[84:ipEnd]; opts.AllowIPSpoofing {
-		// Make sure the bytes are copied to a new slice.
-		copy(ip, ipBytes)
+	if opts.AllowIPSpoofing {
+		ipBytes := r.Packet[84:ipEnd]
+		spoofed, ok := netip.AddrFromSlice(ipBytes)
+		if !ok {
+			return nil, bittorrent.ErrInvalidIP
+		}
 		ipProvided = true
+		ip = spoofed
 	}
-	if !opts.AllowIPSpoofing && r.IP == nil {
+	if !opts.AllowIPSpoofing && r.IP.IsUnspecified() {
 		// We have no IP address to fallback on.
-		return nil, errMalformedIP
+		return nil, bittorrent.ErrInvalidIP
 	}
 
 	numWant := binary.BigEndian.Uint32(r.Packet[ipEnd+4 : ipEnd+8])
@@ -133,18 +136,17 @@ func ParseAnnounce(r Request, v6Action bool, opts ParseOptions) (*bittorrent.Ann
 		NumWantProvided: true,
 		EventProvided:   true,
 		Peer: bittorrent.Peer{
-			ID:   peerID,
-			IP:   bittorrent.IP{IP: ip},
-			Port: port,
+			ID:       peerID,
+			AddrPort: netip.AddrPortFrom(ip, port),
 		},
 		Params: params,
 	}
 
-	if err := bittorrent.SanitizeAnnounce(request, opts.MaxNumWant, opts.DefaultNumWant); err != nil {
-		return nil, err
+	if err = bittorrent.SanitizeAnnounce(request, opts.MaxNumWant, opts.DefaultNumWant); err != nil {
+		request = nil
 	}
 
-	return request, nil
+	return request, err
 }
 
 type buffer struct {

frontend/udp/prometheus.go

@@ -2,11 +2,13 @@ package udp
 
 import (
 	"errors"
+	"net/netip"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
 
 	"github.com/sot-tech/mochi/bittorrent"
+	"github.com/sot-tech/mochi/pkg/metrics"
 )
 
 func init() {
@@ -24,7 +26,7 @@ var promResponseDurationMilliseconds = prometheus.NewHistogramVec(
 
 // recordResponseDuration records the duration of time to respond to a UDP
 // Request in milliseconds.
-func recordResponseDuration(action string, af *bittorrent.AddressFamily, err error, duration time.Duration) {
+func recordResponseDuration(action string, addr netip.Addr, err error, duration time.Duration) {
 	var errString string
 	if err != nil {
 		var clientErr bittorrent.ClientError
@@ -35,16 +37,7 @@ func recordResponseDuration(action string, af *bittorrent.AddressFamily, err err
 		}
 	}
 
-	var afString string
-	if af == nil {
-		afString = "Unknown"
-	} else if *af == bittorrent.IPv4 {
-		afString = "IPv4"
-	} else if *af == bittorrent.IPv6 {
-		afString = "IPv6"
-	}
-
 	promResponseDurationMilliseconds.
-		WithLabelValues(action, afString, errString).
+		WithLabelValues(action, metrics.AddressFamily(addr), errString).
 		Observe(float64(duration.Nanoseconds()) / float64(time.Millisecond))
 }

frontend/udp/writer.go

@@ -49,8 +49,8 @@ func WriteAnnounce(w io.Writer, txID []byte, resp *bittorrent.AnnounceResponse,
 	}
 
 	for _, peer := range peers {
-		_, _ = buf.Write(peer.IP.IP)
-		_ = binary.Write(buf, binary.BigEndian, peer.Port)
+		_, _ = buf.Write(peer.Addr().AsSlice())
+		_ = binary.Write(buf, binary.BigEndian, peer.Port())
 	}
 
 	_, _ = w.Write(buf.Bytes())