encode: make zstd checksum configurable (#7586)

* http: make zstd checksum configurable

* disable_checksum

caddytest/integration/caddyfile_adapt/encode_options.caddyfiletest

@@ -18,7 +18,9 @@ encode gzip zstd {
 
 # Long way with a block for each encoding
 encode {
-	zstd
+	zstd {
+		disable_checksum
+	}
 	gzip 5
 }
 
@@ -71,7 +73,9 @@ encode
 										"gzip": {
 											"level": 5
 										},
-										"zstd": {}
+										"zstd": {
+											"checksum": false
+										}
 									},
 									"handler": "encode",
 									"prefer": [

modules/caddyhttp/encode/caddyfile.go

@@ -41,7 +41,10 @@ func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error)
 //
 //	encode [<matcher>] <formats...> {
 //	    gzip           [<level>]
-//	    zstd
+//	    zstd           [<level>] {
+//	        level           <level>
+//	        disable_checksum
+//	    }
 //	    minimum_length <length>
 //	    # response matcher block
 //	    match {

modules/caddyhttp/encode/zstd/zstd.go

@@ -33,6 +33,10 @@ type Zstd struct {
 	// The compression level. Accepted values: fastest, better, best, default.
 	Level string `json:"level,omitempty"`
 
+	// Whether to include the optional 4-byte zstd frame checksum trailer.
+	// If unset, the upstream zstd library default is preserved.
+	Checksum *bool `json:"checksum,omitempty"`
+
 	// Compression level refer to type constants value from zstd.SpeedFastest to zstd.SpeedBestCompression
 	level zstd.EncoderLevel
 }
@@ -48,19 +52,48 @@ func (Zstd) CaddyModule() caddy.ModuleInfo {
 // UnmarshalCaddyfile sets up the handler from Caddyfile tokens.
 func (z *Zstd) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 	d.Next() // consume option name
-	if !d.NextArg() {
-		return nil
+	args := d.RemainingArgs()
+	switch len(args) {
+	case 0:
+	case 1:
+		if _, err := parseEncoderLevel(args[0]); err != nil {
+			return d.Err(err.Error())
+		}
+		z.Level = args[0]
+	default:
+		return d.ArgErr()
 	}
-	levelStr := d.Val()
-	if ok, _ := zstd.EncoderLevelFromString(levelStr); !ok {
-		return d.Errf("unexpected compression level, use one of '%s', '%s', '%s', '%s'",
-			zstd.SpeedFastest,
-			zstd.SpeedBetterCompression,
-			zstd.SpeedBestCompression,
-			zstd.SpeedDefault,
-		)
+
+	for nesting := d.Nesting(); d.NextBlock(nesting); {
+		switch d.Val() {
+		case "level":
+			args := d.RemainingArgs()
+			if len(args) != 1 {
+				return d.ArgErr()
+			}
+			if z.Level != "" {
+				return d.Err("compression level already specified")
+			}
+			if _, err := parseEncoderLevel(args[0]); err != nil {
+				return d.Err(err.Error())
+			}
+			z.Level = args[0]
+
+		case "disable_checksum":
+			if d.NextArg() {
+				return d.ArgErr()
+			}
+			if z.Checksum != nil {
+				return d.Err("checksum already specified")
+			}
+			disabled := false
+			z.Checksum = &disabled
+
+		default:
+			return d.Errf("unknown subdirective '%s'", d.Val())
+		}
 	}
-	z.Level = levelStr
+
 	return nil
 }
 
@@ -69,15 +102,11 @@ func (z *Zstd) Provision(ctx caddy.Context) error {
 	if z.Level == "" {
 		z.Level = zstd.SpeedDefault.String()
 	}
-	var ok bool
-	if ok, z.level = zstd.EncoderLevelFromString(z.Level); !ok {
-		return fmt.Errorf("unexpected compression level, use one of '%s', '%s', '%s', '%s'",
-			zstd.SpeedFastest,
-			zstd.SpeedDefault,
-			zstd.SpeedBetterCompression,
-			zstd.SpeedBestCompression,
-		)
+	level, err := parseEncoderLevel(z.Level)
+	if err != nil {
+		return err
 	}
+	z.level = level
 	return nil
 }
 
@@ -90,14 +119,45 @@ func (z Zstd) NewEncoder() encode.Encoder {
 	// The default of 8MB for the window is
 	// too large for many clients, so we limit
 	// it to 128K to lighten their load.
-	writer, _ := zstd.NewWriter(
-		nil,
-		zstd.WithWindowSize(128<<10),
+	writer, _ := zstd.NewWriter(nil, z.writerOptions(128<<10)...)
+	return writer
+}
+
+func (z Zstd) writerOptions(windowSize int) []zstd.EOption {
+	opts := []zstd.EOption{
+		zstd.WithWindowSize(windowSize),
 		zstd.WithEncoderConcurrency(1),
 		zstd.WithZeroFrames(true),
-		zstd.WithEncoderLevel(z.level),
+		zstd.WithEncoderLevel(z.encoderLevel()),
+	}
+	if z.Checksum != nil {
+		opts = append(opts, zstd.WithEncoderCRC(*z.Checksum))
+	}
+	return opts
+}
+
+func (z Zstd) encoderLevel() zstd.EncoderLevel {
+	if z.level != 0 {
+		return z.level
+	}
+	if z.Level != "" {
+		if level, err := parseEncoderLevel(z.Level); err == nil {
+			return level
+		}
+	}
+	return zstd.SpeedDefault
+}
+
+func parseEncoderLevel(level string) (zstd.EncoderLevel, error) {
+	if ok, encLevel := zstd.EncoderLevelFromString(level); ok {
+		return encLevel, nil
+	}
+	return 0, fmt.Errorf("unexpected compression level, use one of '%s', '%s', '%s', '%s'",
+		zstd.SpeedFastest,
+		zstd.SpeedBetterCompression,
+		zstd.SpeedBestCompression,
+		zstd.SpeedDefault,
 	)
-	return writer
 }
 
 // Interface guards