analyzer: quic: some optimizations

analyzer/udp/internal/quic/payload.go

@@ -2,11 +2,13 @@ package quic
 
 import (
 	"bytes"
+	"container/list"
 	"crypto"
 	"errors"
 	"fmt"
 	"io"
 	"sort"
+	"sync"
 
 	"github.com/quic-go/quic-go/quicvarint"
 	"golang.org/x/crypto/hkdf"
@@ -16,10 +18,30 @@ var defaultPNMaxGuesses = []int64{
 	0, 1, 2, 3, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096,
 }
 
+const (
+	initialSecretLabelClientIn = "client in"
+	initialSecretLabelServerIn = "server in"
+)
+
+const initialProtectorCacheSize = 512
+
+var initialProtectorCache = newInitialPacketProtectorCache(initialProtectorCacheSize)
+
+type DecryptSuccessHint struct {
+	ConnectionID    []byte
+	SecretLabel     string
+	PacketNumberMax int64
+}
+
 type ReadCryptoFramesOptions struct {
 	AdditionalConnectionIDs [][]byte
 	TryServerSecret         bool
 	PacketNumberMaxGuesses  []int64
+	PreferredConnectionID   []byte
+	PreferredSecretLabel    string
+	PreferredPNMax          int64
+	HasPreferredPNMax       bool
+	SuccessHint             *DecryptSuccessHint
 }
 
 func ReadCryptoPayload(packet []byte) ([]byte, error) {
@@ -61,33 +83,18 @@ func ReadCryptoFramesWithOptions(packet []byte, opts *ReadCryptoFramesOptions) (
 	}
 	packetView := packet[:offset+hdr.Length]
 
-	candidateConnIDs := [][]byte{hdr.DestConnectionID}
-	if opts != nil {
-		candidateConnIDs = append(candidateConnIDs, opts.AdditionalConnectionIDs...)
-	}
-	candidateConnIDs = uniqueNonEmptyConnectionIDs(candidateConnIDs)
-
-	pnMaxGuesses := defaultPNMaxGuesses
-	if opts != nil && len(opts.PacketNumberMaxGuesses) > 0 {
-		pnMaxGuesses = opts.PacketNumberMaxGuesses
-	}
-
-	labels := []string{"client in"}
-	if opts != nil && opts.TryServerSecret {
-		labels = append(labels, "server in")
-	}
+	candidateConnIDs := collectConnectionIDCandidates(hdr, opts)
+	pnMaxGuesses := collectPacketNumberMaxGuesses(opts)
+	labels := collectSecretLabels(opts)
 
 	var lastErr error
 	for _, connID := range candidateConnIDs {
-		initialSecret := hkdf.Extract(crypto.SHA256.New, connID, getSalt(hdr.Version))
 		for _, label := range labels {
-			secret := hkdfExpandLabel(crypto.SHA256.New, initialSecret, label, []byte{}, crypto.SHA256.Size())
-			key, err := NewInitialProtectionKey(secret, hdr.Version)
+			pp, err := getOrCreateInitialPacketProtector(hdr.Version, connID, label)
 			if err != nil {
-				lastErr = fmt.Errorf("NewInitialProtectionKey: %w", err)
+				lastErr = err
 				continue
 			}
-			pp := NewPacketProtector(key)
 			for _, pnMax := range pnMaxGuesses {
 				packetCopy := append([]byte(nil), packetView...)
 				unProtectedPayload, err := pp.UnProtect(packetCopy, offset, pnMax)
@@ -100,6 +107,11 @@ func ReadCryptoFramesWithOptions(packet []byte, opts *ReadCryptoFramesOptions) (
 					lastErr = err
 					continue
 				}
+				if opts != nil && opts.SuccessHint != nil {
+					opts.SuccessHint.ConnectionID = append(opts.SuccessHint.ConnectionID[:0], connID...)
+					opts.SuccessHint.SecretLabel = label
+					opts.SuccessHint.PacketNumberMax = pnMax
+				}
 				return frs, nil
 			}
 		}
@@ -337,6 +349,68 @@ func skipN(r *bytes.Reader, n uint64) error {
 	return err
 }
 
+func collectConnectionIDCandidates(hdr *Header, opts *ReadCryptoFramesOptions) [][]byte {
+	ids := make([][]byte, 0, 2)
+	if opts != nil && len(opts.PreferredConnectionID) > 0 {
+		ids = append(ids, opts.PreferredConnectionID)
+	}
+	ids = append(ids, hdr.DestConnectionID)
+	if opts != nil {
+		ids = append(ids, opts.AdditionalConnectionIDs...)
+	}
+	return uniqueNonEmptyConnectionIDs(ids)
+}
+
+func collectPacketNumberMaxGuesses(opts *ReadCryptoFramesOptions) []int64 {
+	guesses := defaultPNMaxGuesses
+	if opts != nil && len(opts.PacketNumberMaxGuesses) > 0 {
+		guesses = opts.PacketNumberMaxGuesses
+	}
+	if opts == nil || !opts.HasPreferredPNMax {
+		return uniqueInt64PreserveOrder(guesses)
+	}
+	out := make([]int64, 0, len(guesses)+1)
+	out = append(out, opts.PreferredPNMax)
+	out = append(out, guesses...)
+	return uniqueInt64PreserveOrder(out)
+}
+
+func collectSecretLabels(opts *ReadCryptoFramesOptions) []string {
+	labels := []string{initialSecretLabelClientIn}
+	if opts != nil && opts.TryServerSecret {
+		labels = append(labels, initialSecretLabelServerIn)
+	}
+	if opts == nil || opts.PreferredSecretLabel == "" {
+		return labels
+	}
+	return prependStringIfPresent(labels, opts.PreferredSecretLabel)
+}
+
+func prependStringIfPresent(base []string, preferred string) []string {
+	if preferred == "" {
+		return base
+	}
+	has := false
+	for _, s := range base {
+		if s == preferred {
+			has = true
+			break
+		}
+	}
+	if !has {
+		return base
+	}
+	out := make([]string, 0, len(base))
+	out = append(out, preferred)
+	for _, s := range base {
+		if s == preferred {
+			continue
+		}
+		out = append(out, s)
+	}
+	return out
+}
+
 func uniqueNonEmptyConnectionIDs(ids [][]byte) [][]byte {
 	out := make([][]byte, 0, len(ids))
 	seen := make(map[string]struct{}, len(ids))
@@ -354,6 +428,103 @@ func uniqueNonEmptyConnectionIDs(ids [][]byte) [][]byte {
 	return out
 }
 
+func uniqueInt64PreserveOrder(values []int64) []int64 {
+	out := make([]int64, 0, len(values))
+	seen := make(map[int64]struct{}, len(values))
+	for _, v := range values {
+		if _, ok := seen[v]; ok {
+			continue
+		}
+		seen[v] = struct{}{}
+		out = append(out, v)
+	}
+	return out
+}
+
+type initialPacketProtectorCacheKey struct {
+	Version uint32
+	ConnID  string
+	Label   string
+}
+
+type initialPacketProtectorCacheEntry struct {
+	Key   initialPacketProtectorCacheKey
+	Value *PacketProtector
+}
+
+type initialPacketProtectorCache struct {
+	mutex    sync.Mutex
+	capacity int
+	ll       *list.List
+	items    map[initialPacketProtectorCacheKey]*list.Element
+}
+
+func newInitialPacketProtectorCache(capacity int) *initialPacketProtectorCache {
+	if capacity <= 0 {
+		capacity = 1
+	}
+	return &initialPacketProtectorCache{
+		capacity: capacity,
+		ll:       list.New(),
+		items:    make(map[initialPacketProtectorCacheKey]*list.Element, capacity),
+	}
+}
+
+func (c *initialPacketProtectorCache) Get(key initialPacketProtectorCacheKey) (*PacketProtector, bool) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	elem, ok := c.items[key]
+	if !ok {
+		return nil, false
+	}
+	c.ll.MoveToFront(elem)
+	return elem.Value.(*initialPacketProtectorCacheEntry).Value, true
+}
+
+func (c *initialPacketProtectorCache) Add(key initialPacketProtectorCacheKey, value *PacketProtector) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	if elem, ok := c.items[key]; ok {
+		entry := elem.Value.(*initialPacketProtectorCacheEntry)
+		entry.Value = value
+		c.ll.MoveToFront(elem)
+		return
+	}
+	elem := c.ll.PushFront(&initialPacketProtectorCacheEntry{
+		Key:   key,
+		Value: value,
+	})
+	c.items[key] = elem
+	for c.ll.Len() > c.capacity {
+		oldest := c.ll.Back()
+		if oldest == nil {
+			break
+		}
+		c.ll.Remove(oldest)
+		delete(c.items, oldest.Value.(*initialPacketProtectorCacheEntry).Key)
+	}
+}
+
+func getOrCreateInitialPacketProtector(version uint32, connID []byte, label string) (*PacketProtector, error) {
+	key := initialPacketProtectorCacheKey{
+		Version: version,
+		ConnID:  string(connID),
+		Label:   label,
+	}
+	if cached, ok := initialProtectorCache.Get(key); ok {
+		return cached, nil
+	}
+	initialSecret := hkdf.Extract(crypto.SHA256.New, connID, getSalt(version))
+	secret := hkdfExpandLabel(crypto.SHA256.New, initialSecret, label, []byte{}, crypto.SHA256.Size())
+	protectionKey, err := NewInitialProtectionKey(secret, version)
+	if err != nil {
+		return nil, fmt.Errorf("NewInitialProtectionKey: %w", err)
+	}
+	protector := NewPacketProtector(protectionKey)
+	initialProtectorCache.Add(key, protector)
+	return protector, nil
+}
+
 // assembleCryptoFrames assembles multiple crypto frames into a single slice (if possible).
 // It returns an error if the frames cannot be assembled. This can happen if the frames are not contiguous.
 func assembleCryptoFrames(frames []CryptoFrame) []byte {