dhcpv6: easier option parsing

- move option parsing to uio buffer library.
- move option code and length reading into FromBytes rather than
implementing it in each OptionParser.

1 files changed, 18 insertions, 66 deletions

diff --git a/dhcpv6/option_vendor_opts.go b/dhcpv6/option_vendor_opts.go
index f791ddf..027e7c3 100644
--- a/dhcpv6/option_vendor_opts.go
+++ b/dhcpv6/option_vendor_opts.go
@@ -1,39 +1,15 @@
 package dhcpv6
 
-/*
- This module defines the OptVendorOpts structure.
- https://tools.ietf.org/html/rfc3315#section-22.17
-
-				Option 17
-       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-      |      OPTION_VENDOR_OPTS       |           option-len          |
-      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-      |                       enterprise-number                       |
-      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-      .                                                               .
-      .                   option-data (sub-options)                   .
-      .                                                               .
-      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-
-				Sub-Option
-	 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-	|          opt-code             |             option-len        |
-	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-	.                                                               .
-	.                          option-data                          .
-	.                                                               .
-	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-*/
-
 import (
-	"encoding/binary"
-	"errors"
 	"fmt"
+
+	"github.com/u-root/u-root/pkg/uio"
 )
 
 // OptVendorOpts represents a DHCPv6 Status Code option
+//
+// This module defines the OptVendorOpts structure.
+// https://tools.ietf.org/html/rfc3315#section-22.17
 type OptVendorOpts struct {
 	EnterpriseNumber uint32
 	VendorOpts       Options
@@ -46,14 +22,12 @@ func (op *OptVendorOpts) Code() OptionCode {
 
 // ToBytes serializes the option and returns it as a sequence of bytes
 func (op *OptVendorOpts) ToBytes() []byte {
-	buf := make([]byte, 8)
-	binary.BigEndian.PutUint16(buf[0:2], uint16(OptionVendorOpts))
-	binary.BigEndian.PutUint16(buf[2:4], uint16(op.Length()))
-	binary.BigEndian.PutUint32(buf[4:8], uint32(op.EnterpriseNumber))
-	for _, opt := range op.VendorOpts {
-		buf = append(buf, opt.ToBytes()...)
-	}
-	return buf
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(uint16(OptionVendorOpts))
+	buf.Write16(uint16(op.Length()))
+	buf.Write32(uint32(op.EnterpriseNumber))
+	buf.WriteData(op.VendorOpts.ToBytes())
+	return buf.Data()
 }
 
 // Length returns the option length
@@ -75,41 +49,19 @@ func (op *OptVendorOpts) String() string {
 // ParseOptVendorOpts builds an OptVendorOpts structure from a sequence of bytes.
 // The input data does not include option code and length bytes.
 func ParseOptVendorOpts(data []byte) (*OptVendorOpts, error) {
-	opt := OptVendorOpts{}
-	if len(data) < 4 {
-		return nil, fmt.Errorf("Invalid vendor opts data length. Expected at least 4 bytes, got %v", len(data))
-	}
-	opt.EnterpriseNumber = binary.BigEndian.Uint32(data[:4])
-
-	if err := opt.VendorOpts.FromBytesWithParser(data[4:], vendParseOption); err != nil {
+	var opt OptVendorOpts
+	buf := uio.NewBigEndianBuffer(data)
+	opt.EnterpriseNumber = buf.Read32()
+	if err := opt.VendorOpts.FromBytesWithParser(buf.ReadAll(), vendParseOption); err != nil {
 		return nil, err
 	}
-	return &opt, nil
+	return &opt, buf.FinError()
 }
 
 // vendParseOption builds a GenericOption from a slice of bytes
 // We cannot use the existing ParseOption function in options.go because the
 // sub-options include codes specific to each vendor. There are overlaps in these
 // codes with RFC standard codes.
-func vendParseOption(dataStart []byte) (Option, error) {
-	// Parse a sequence of bytes as a single DHCPv6 option.
-	// Returns the option structure, or an error if any.
-
-	if len(dataStart) < 4 {
-		return nil, fmt.Errorf("Invalid DHCPv6 vendor option: less than 4 bytes")
-	}
-	code := OptionCode(binary.BigEndian.Uint16(dataStart[:2]))
-	length := int(binary.BigEndian.Uint16(dataStart[2:4]))
-	if len(dataStart) < length+4 {
-		return nil, fmt.Errorf("Invalid option length for vendor option %v. Declared %v, actual %v",
-			code, length, len(dataStart)-4,
-		)
-	}
-
-	optData := dataStart[4 : 4+length]
-	if len(optData) < 1 {
-		return nil, errors.New("vendParseOption: at least one vendor options data is required")
-	}
-
-	return &OptionGeneric{OptionCode: code, OptionData: optData}, nil
+func vendParseOption(code OptionCode, data []byte) (Option, error) {
+	return &OptionGeneric{OptionCode: code, OptionData: data}, nil
 }