More table

infra/conf/transport_internet.go

@@ -6,6 +6,7 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"math"
+	"math/big"
 	"net/netip"
 	"net/url"
 	"os"
@@ -381,6 +382,14 @@ func (c *SplitHTTPConfig) Build() (proto.Message, error) {
 	}
 
 	if c.SessionIDTable != "" {
+		if predefined, ok := splithttp.PredefinedTable[c.SessionIDTable]; ok {
+			c.SessionIDTable = predefined
+		}
+		room := roomSize(len(c.SessionIDTable), c.SessionIDLength.From, c.SessionIDLength.To)
+		// 2.1B possiblities should be enough
+		if room.Cmp(big.NewInt(2<<30)) < 0 {
+			return nil, errors.New("sessionIDTable or sessionIDLength is too small")
+		}
 		if c.SessionIDLength.From <= 0 {
 			return nil, errors.New("sessionIDLength.from must be greater than 0")
 		}
@@ -454,6 +463,17 @@ func (c *SplitHTTPConfig) Build() (proto.Message, error) {
 	return config, nil
 }
 
+func roomSize(tableSize int, min, max int32) *big.Int {
+	base := big.NewInt(int64(tableSize))
+	sum := new(big.Int)
+	term := new(big.Int)
+	for k := min; k <= max; k++ {
+		term.Exp(base, big.NewInt(int64(k)), nil)
+		sum.Add(sum, term)
+	}
+	return sum
+}
+
 const (
 	Byte     = 1
 	Kilobyte = 1024 * Byte

transport/internet/splithttp/config.go

@@ -488,22 +488,23 @@ func (c *RangeConfig) rand() int32 {
 }
 
 // predefined
-var (
+var PredefinedTable = map[string]string{
-	base62Table   = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+	"number":   "0123456789",
-	hexTable      = "0123456789abcdef"
+	"base62":   "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz",
-	hexTableUpper = "0123456789ABCDEF"
+	"base36":   "0123456789abcdefghijklmnopqrstuvwxyz",
-)
+	"BASE36":   "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ",
+	"hex":      "0123456789abcdef",
+	"HEX":      "0123456789ABCDEF",
+	"Alphabet": "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz",
+	"ALPHABET": "ABCDEFGHIJKLMNOPQRSTUVWXYZ",
+	"alphabet": "abcdefghijklmnopqrstuvwxyz",
+}
 
 func (c *Config) GenerateSessionID() string {
 	length := c.SessionIDLength.rand()
 	table := c.SessionIDTable
-	switch table {
+	if predefined, ok := PredefinedTable[table]; ok {
-	case "base62":
+		table = predefined
-		table = base62Table
-	case "hex":
-		table = hexTable
-	case "HEX":
-		table = hexTableUpper
 	}
 	if table != "" && length > 0 {
 		id := make([]byte, length)