Example #1
0
/*Unshim removes the shim layer from an IPv4 packet, if it's present.*/
func Unshim(ipLayer *layers.IPv4) *RouteRecord {
	if Shimmed(ipLayer) {
		/*Remove the route record from the payload*/
		ipPayload := bytes.NewBuffer(ipLayer.LayerPayload())
		var rr RouteRecord
		rr.ReadFrom(ipPayload)

		ipLayer.Length -= uint16(rr.Len())
		ipLayer.Protocol = layers.IPProtocol(rr.Protocol)
		ipLayer.Checksum = 0
		ipLayer.Payload = ipPayload.Bytes()

		return &rr
	}

	return nil
}
Example #2
0
/*Shim inserts the given router into the shim layer route record of the given
IPv4 packet, creating a new route record if it's not already present.*/
func Shim(ipLayer *layers.IPv4, r Router) {
	ipPayload := bytes.NewBuffer(ipLayer.LayerPayload())
	var modifiedIPPayload bytes.Buffer

	var rr RouteRecord

	if Shimmed(ipLayer) {
		rr.ReadFrom(ipPayload)
		ipLayer.Length -= uint16(rr.Len())
	} else {
		rr.Protocol = uint8(ipLayer.Protocol)
	}

	/*Add the specified router to the route record and put the record at the
	beginning of the payload.*/
	rr.AddRouter(r)
	rr.WriteTo(&modifiedIPPayload)
	ipPayload.WriteTo(&modifiedIPPayload)

	ipLayer.Length += uint16(rr.Len())
	ipLayer.Protocol = layers.IPProtocol(IPProtocolAITFRouteRecord)
	ipLayer.Checksum = 0
	ipLayer.Payload = modifiedIPPayload.Bytes()
}