fix: Introduce protocol-compliant check for maximum packet size

pojntfx · pojntfx · commit d85fb666c360 · 2023-05-18T01:56:01.000+02:00
diff --git a/pkg/server/nbd.go b/pkg/server/nbd.go
@@ -16,6 +16,10 @@ var (
 	ErrInvalidBlocksize = errors.New("invalid blocksize")
 )
 
+const (
+	maximumPacketSize = 32 * 1024 * 1024 // Support for a 32M maximum packet size is expected: https://sourceforge.net/p/nbd/mailman/message/35081223/
+)
+
 type Export struct {
 	Name        string
 	Description string
@@ -46,7 +50,7 @@ func Handle(conn net.Conn, exports []Export, options *Options) error {
 	}
 
 	if options.MaximumBlockSize == 0 {
-		options.MaximumBlockSize = 0xffffffff
+		options.MaximumBlockSize = maximumPacketSize
 	}
 
 	// Negotiation
@@ -312,7 +316,7 @@ n:
 	}
 
 	// Transmission
-	b := make([]byte, options.MaximumBlockSize)
+	b := make([]byte, maximumPacketSize)
 	for {
 		var requestHeader protocol.TransmissionRequestHeader
 		if err := binary.Read(conn, binary.BigEndian, &requestHeader); err != nil {

Original file line number	Diff line number	Diff line change
`@@ -16,6 +16,10 @@ var (`
`16`	`16`	`ErrInvalidBlocksize = errors.New("invalid blocksize")`
`17`	`17`	`)`
`18`	`18`
	`19`	`+const (`
	`20`	`+ maximumPacketSize = 32 * 1024 * 1024 // Support for a 32M maximum packet size is expected: https://sourceforge.net/p/nbd/mailman/message/35081223/`
	`21`	`+)`
	`22`	`+`
`19`	`23`	`type Export struct {`
`20`	`24`	`Name string`
`21`	`25`	`Description string`
`@@ -46,7 +50,7 @@ func Handle(conn net.Conn, exports []Export, options *Options) error {`
`46`	`50`	`}`
`47`	`51`
`48`	`52`	`if options.MaximumBlockSize == 0 {`
`49`		`- options.MaximumBlockSize = 0xffffffff`
	`53`	`+ options.MaximumBlockSize = maximumPacketSize`
`50`	`54`	`}`
`51`	`55`
`52`	`56`	`// Negotiation`
`@@ -312,7 +316,7 @@ n:`
`312`	`316`	`}`
`313`	`317`
`314`	`318`	`// Transmission`
`315`		`- b := make([]byte, options.MaximumBlockSize)`
	`319`	`+ b := make([]byte, maximumPacketSize)`
`316`	`320`	`for {`
`317`	`321`	`var requestHeader protocol.TransmissionRequestHeader`
`318`	`322`	`if err := binary.Read(conn, binary.BigEndian, &requestHeader); err != nil {`