ip6defrag

Documentation

Overview

Package ip6defrag implements a IPv6 defragmenter

Index

• Constants
• type IPv6Defragmenter
  • func NewIPv6Defragmenter() *IPv6Defragmenter
  • func (d *IPv6Defragmenter) DefragIPv6(in *layers.IPv6, inFragment *layers.IPv6Fragment) (*layers.IPv6, error)
  • func (d *IPv6Defragmenter) DefragIPv6WithTimestamp(in *layers.IPv6, inFragment *layers.IPv6Fragment, t time.Time) (*layers.IPv6, error)
  • func (d *IPv6Defragmenter) DiscardOlderThan(t time.Time) int

Constants

const (
	IPv6MaximumSize            = 65535
	IPv6MaximumFragmentOffset  = 8191
	IPv6MaximumFragmentListLen = 8191
)

Constants determining how to handle fragments.

Types

type IPv6Defragmenter

type IPv6Defragmenter struct {
	sync.RWMutex
	// contains filtered or unexported fields
}

IPv6Defragmenter is a struct which embedded a map of all fragment/packet.

func NewIPv6Defragmenter

func NewIPv6Defragmenter() *IPv6Defragmenter

NewIPv6Defragmenter returns a new IPv6Defragmenter with an initialized map.

func (*IPv6Defragmenter) DefragIPv6

func (d *IPv6Defragmenter) DefragIPv6(in *layers.IPv6, inFragment *layers.IPv6Fragment) (*layers.IPv6, error)

DefragIPv6 takes in an IPv6 packet with a fragment payload.

It do not modify the IPv6 layer in place, 'in' and 'inFragment' remains untouched. It returns a ready-to be used IPv6 layer.

If we don't have all fragments, it will return nil and store whatever internal information it needs to eventually defrag the packet.

If the IPv6 layer is the last fragment needed to reconstruct the packet, a new IPv6 layer will be returned, and will be set to the entire defragmented packet,

It use a map of all the running flows

Usage example:

func HandlePacket(in *layers.IPv6, inFragment *layers.IPv6Fragment) err {
    defragger := ip6defrag.NewIPv6Defragmenter()
    in, err := defragger.DefragIPv6(in, inFragment)
    if err != nil {
        return err
    } else if in == nil {
        return nil  // packet fragment, we don't have whole packet yet.
    }
    // At this point, we know that 'in' is defragmented.
    //It may be the same 'in' passed to
	   // HandlePacket, or it may not, but we don't really care :)
	   ... do stuff to 'in' ...
}

func (*IPv6Defragmenter) DefragIPv6WithTimestamp

func (d *IPv6Defragmenter) DefragIPv6WithTimestamp(in *layers.IPv6, inFragment *layers.IPv6Fragment, t time.Time) (*layers.IPv6, error)

DefragIPv6WithTimestamp provides functionality of DefragIPv6 with an additional timestamp parameter which is used for discarding old fragments instead of time.Now()

This is useful when operating on pcap files instead of live captured data

func (*IPv6Defragmenter) DiscardOlderThan

func (d *IPv6Defragmenter) DiscardOlderThan(t time.Time) int

DiscardOlderThan forgets all packets without any activity since time t. It returns the number of FragmentList aka number of fragment packets it has discarded.