alignedbuff

Documentation

Overview

Package alignedbuff implements encoding and decoding aligned data elements to/from buffers in native endianess.

Note

The alignment/padding as implemented in this package must match that of kernel's and user space C implementations for a particular architecture (bit size). Please see also the "dummy structure" _xt_align (https://elixir.bootlin.com/linux/v5.17.7/source/include/uapi/linux/netfilter/x_tables.h#L93) as well as the associated XT_ALIGN C preprocessor macro.

In particular, we rely on the Go compiler to follow the same architecture alignments as the C compiler(s) on Linux.

Index

• Variables
• type AlignedBuff
  • func New() AlignedBuff
  • func NewWithData(data []byte) AlignedBuff
  • func (a *AlignedBuff) BytesAligned32(size int) ([]byte, error)
  • func (a *AlignedBuff) Data() []byte
  • func (a *AlignedBuff) Int32() (int32, error)
  • func (a *AlignedBuff) PutBytesAligned32(data []byte, size int)
  • func (a *AlignedBuff) PutInt32(v int32)
  • func (a *AlignedBuff) PutString(v string)
  • func (a *AlignedBuff) PutUint(v uint)
  • func (a *AlignedBuff) PutUint16(v uint16)
  • func (a *AlignedBuff) PutUint16BE(v uint16)
  • func (a *AlignedBuff) PutUint32(v uint32)
  • func (a *AlignedBuff) PutUint64(v uint64)
  • func (a *AlignedBuff) PutUint8(v uint8)
  • func (a *AlignedBuff) String() (string, error)
  • func (a *AlignedBuff) StringWithLength(len int) (string, error)
  • func (a *AlignedBuff) Uint() (uint, error)
  • func (a *AlignedBuff) Uint16() (uint16, error)
  • func (a *AlignedBuff) Uint16BE() (uint16, error)
  • func (a *AlignedBuff) Uint32() (uint32, error)
  • func (a *AlignedBuff) Uint64() (uint64, error)
  • func (a *AlignedBuff) Uint8() (uint8, error)

Variables

var ErrEOF = errors.New("not enough data left")

ErrEOF signals trying to read beyond the available payload information.

Types

type AlignedBuff

type AlignedBuff struct {
	// contains filtered or unexported fields
}

AlignedBuff implements marshalling and unmarshalling information in platform/architecture native endianess and data type alignment. It additionally covers some of the nftables-xtables translation-specific idiosyncracies to the extend needed in order to properly marshal and unmarshal Match and Target expressions, and their Info payload in particular.

func New

func New() AlignedBuff

New returns a new AlignedBuff for marshalling aligned data in native endianess.

func NewWithData

func NewWithData(data []byte) AlignedBuff

NewWithData returns a new AlignedBuff for unmarshalling the passed data in native endianess.

func (*AlignedBuff) BytesAligned32

func (a *AlignedBuff) BytesAligned32(size int) ([]byte, error)

BytesAligned32 unmarshals the given amount of bytes starting with the native alignment for uint32 data types. It returns ErrEOF when trying to read beyond the payload.

BytesAligned32 is used to unmarshal IP addresses for different IP versions, which are always aligned the same way as the native alignment for uint32.

func (*AlignedBuff) Data

func (a *AlignedBuff) Data() []byte

Data returns the properly padded info payload data written before by calling the various Uint8, Uint16, ... marshalling functions.

func (*AlignedBuff) Int32

func (a *AlignedBuff) Int32() (int32, error)

Int32 unmarshals an int32 in native endianess and alignment. It returns ErrEOF when trying to read beyond the payload.

func (*AlignedBuff) PutBytesAligned32

func (a *AlignedBuff) PutBytesAligned32(data []byte, size int)

PutBytesAligned32 marshals the given bytes starting with the native alignment for uint32 data types. It additionaly adds padding to reach the specified size.

PutBytesAligned32 is used to marshal IP addresses for different IP versions, which are always aligned the same way as the native alignment for uint32.

func (*AlignedBuff) PutInt32

func (a *AlignedBuff) PutInt32(v int32)

PutInt32 marshals an int32 in native endianess and alignment.

func (*AlignedBuff) PutString

func (a *AlignedBuff) PutString(v string)

PutString marshals a string.

func (*AlignedBuff) PutUint

func (a *AlignedBuff) PutUint(v uint)

PutUint marshals an uint in native endianess and alignment for the C "unsigned int" type. Please note that on 64bit platforms, the size and alignment of C's and Go's unsigned integer data types differ, so we encapsulate this difference here.

func (*AlignedBuff) PutUint16

func (a *AlignedBuff) PutUint16(v uint16)

PutUint16 marshals an uint16 in native endianess and alignment.

func (*AlignedBuff) PutUint16BE

func (a *AlignedBuff) PutUint16BE(v uint16)

PutUint16BE marshals an uint16 in "network" (=big endian) endianess and native uint16 alignment.

func (*AlignedBuff) PutUint32

func (a *AlignedBuff) PutUint32(v uint32)

PutUint32 marshals an uint32 in native endianess and alignment.

func (*AlignedBuff) PutUint64

func (a *AlignedBuff) PutUint64(v uint64)

PutUint64 marshals an uint64 in native endianess and alignment.

func (*AlignedBuff) PutUint8

func (a *AlignedBuff) PutUint8(v uint8)

PutUint8 marshals an uint8 in native endianess and alignment.

func (*AlignedBuff) String

func (a *AlignedBuff) String() (string, error)

String unmarshals a null terminated string

func (*AlignedBuff) StringWithLength

func (a *AlignedBuff) StringWithLength(len int) (string, error)

StringWithLength unmarshals a string of a given length (for non-null terminated strings)

func (*AlignedBuff) Uint

func (a *AlignedBuff) Uint() (uint, error)

Uint unmarshals an uint in native endianess and alignment for the C "unsigned int" type. It returns ErrEOF when trying to read beyond the payload. Please note that on 64bit platforms, the size and alignment of C's and Go's unsigned integer data types differ, so we encapsulate this difference here.

func (*AlignedBuff) Uint16

func (a *AlignedBuff) Uint16() (uint16, error)

Uint16 unmarshals an uint16 in native endianess and alignment. It returns ErrEOF when trying to read beyond the payload.

func (*AlignedBuff) Uint16BE

func (a *AlignedBuff) Uint16BE() (uint16, error)

Uint16BE unmarshals an uint16 in "network" (=big endian) endianess and native uint16 alignment. It returns ErrEOF when trying to read beyond the payload.

func (*AlignedBuff) Uint32

func (a *AlignedBuff) Uint32() (uint32, error)

Uint32 unmarshals an uint32 in native endianess and alignment. It returns ErrEOF when trying to read beyond the payload.

func (*AlignedBuff) Uint64

func (a *AlignedBuff) Uint64() (uint64, error)

Uint64 unmarshals an uint64 in native endianess and alignment. It returns ErrEOF when trying to read beyond the payload.

func (*AlignedBuff) Uint8

func (a *AlignedBuff) Uint8() (uint8, error)

Uint8 unmarshals an uint8 in native endianess and alignment. It returns ErrEOF when trying to read beyond the payload.