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pcap.go
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pcap.go
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package pcap
/*
#cgo LDFLAGS: -lpcap
#include <stdlib.h>
#include <pcap.h>
// Workaround for not knowing how to cast to const u_char**
int hack_pcap_next_ex(pcap_t *p, struct pcap_pkthdr **pkt_header,
u_char **pkt_data) {
return pcap_next_ex(p, pkt_header, (const u_char **)pkt_data);
}
*/
import "C"
import (
"errors"
"net"
"syscall"
"unsafe"
)
type Pcap struct {
cptr *C.pcap_t
}
type Stat struct {
PacketsReceived uint32
PacketsDropped uint32
PacketsIfDropped uint32
}
type Interface struct {
Name string
Description string
Addresses []IFAddress
// TODO: add more elements
}
type IFAddress struct {
IP net.IP
Netmask net.IPMask
// TODO: add broadcast + PtP dst ?
}
func Openlive(device string, snaplen int32, promisc bool, timeout_ms int32) (handle *Pcap, err error) {
var buf *C.char
buf = (*C.char)(C.calloc(ERRBUF_SIZE, 1))
h := new(Pcap)
var pro int32
if promisc {
pro = 1
} else {
pro = 0
}
dev := C.CString(device)
defer C.free(unsafe.Pointer(dev))
h.cptr = C.pcap_open_live(dev, C.int(snaplen), C.int(pro), C.int(timeout_ms), buf)
if nil == h.cptr {
handle = nil
err = errors.New(C.GoString(buf))
} else {
handle = h
}
C.free(unsafe.Pointer(buf))
return
}
func Openoffline(file string) (handle *Pcap, err error) {
var buf *C.char
buf = (*C.char)(C.calloc(ERRBUF_SIZE, 1))
h := new(Pcap)
cf := C.CString(file)
defer C.free(unsafe.Pointer(cf))
h.cptr = C.pcap_open_offline(cf, buf)
if nil == h.cptr {
handle = nil
err = errors.New(C.GoString(buf))
} else {
handle = h
}
C.free(unsafe.Pointer(buf))
return
}
func (p *Pcap) Next() (pkt *Packet) {
rv, _ := p.NextEx()
return rv
}
func (p *Pcap) NextEx() (pkt *Packet, result int32) {
var pkthdr_ptr *C.struct_pcap_pkthdr
var pkthdr C.struct_pcap_pkthdr
var buf_ptr *C.u_char
var buf unsafe.Pointer
result = int32(C.hack_pcap_next_ex(p.cptr, &pkthdr_ptr, &buf_ptr))
buf = unsafe.Pointer(buf_ptr)
pkthdr = *pkthdr_ptr
if nil == buf {
pkt = nil
return
}
pkt = new(Packet)
pkt.Time.Sec = int32(pkthdr.ts.tv_sec)
pkt.Time.Usec = int32(pkthdr.ts.tv_usec)
pkt.Caplen = uint32(pkthdr.caplen)
pkt.Len = uint32(pkthdr.len)
pkt.Data = make([]byte, pkthdr.caplen)
for i := uint32(0); i < pkt.Caplen; i++ {
pkt.Data[i] = *(*byte)(unsafe.Pointer(uintptr(buf) + uintptr(i)))
}
return
}
func (p *Pcap) Geterror() error {
return errors.New(C.GoString(C.pcap_geterr(p.cptr)))
}
func (p *Pcap) Getstats() (stat *Stat, err error) {
var cstats _Ctype_struct_pcap_stat
if -1 == C.pcap_stats(p.cptr, &cstats) {
return nil, p.Geterror()
}
stats := new(Stat)
stats.PacketsReceived = uint32(cstats.ps_recv)
stats.PacketsDropped = uint32(cstats.ps_drop)
stats.PacketsIfDropped = uint32(cstats.ps_ifdrop)
return stats, nil
}
func (p *Pcap) Setfilter(expr string) (err error) {
var bpf _Ctype_struct_bpf_program
cexpr := C.CString(expr)
defer C.free(unsafe.Pointer(cexpr))
if -1 == C.pcap_compile(p.cptr, &bpf, cexpr, 1, 0) {
return p.Geterror()
}
if -1 == C.pcap_setfilter(p.cptr, &bpf) {
C.pcap_freecode(&bpf)
return p.Geterror()
}
C.pcap_freecode(&bpf)
return nil
}
func Version() string {
return C.GoString(C.pcap_lib_version())
}
func (p *Pcap) Datalink() int {
return int(C.pcap_datalink(p.cptr))
}
func (p *Pcap) Setdatalink(dlt int) error {
if -1 == C.pcap_set_datalink(p.cptr, C.int(dlt)) {
return p.Geterror()
}
return nil
}
func DatalinkValueToName(dlt int) error {
name := C.pcap_datalink_val_to_name(C.int(dlt))
if nil != name {
return errors.New(C.GoString(name))
}
return nil
}
func DatalinkValueToDescription(dlt int) error {
desc := C.pcap_datalink_val_to_description(C.int(dlt))
if nil != desc {
return errors.New(C.GoString(desc))
}
return nil
}
func Findalldevs() (ifs []Interface, err error) {
var buf *C.char
buf = (*C.char)(C.calloc(ERRBUF_SIZE, 1))
defer C.free(unsafe.Pointer(buf))
var alldevsp *C.pcap_if_t
if -1 == C.pcap_findalldevs((**C.pcap_if_t)(&alldevsp), buf) {
return nil, errors.New(C.GoString(buf))
}
defer C.pcap_freealldevs((*C.pcap_if_t)(alldevsp))
dev := alldevsp
var i uint32
for i = 0; dev != nil; dev = (*C.pcap_if_t)(dev.next) {
i++
}
ifs = make([]Interface, i)
dev = alldevsp
for j := uint32(0); dev != nil; dev = (*C.pcap_if_t)(dev.next) {
var iface Interface
iface.Name = C.GoString(dev.name)
iface.Description = C.GoString(dev.description)
iface.Addresses = findalladdresses(dev.addresses)
// TODO: add more elements
ifs[j] = iface
j++
}
return
}
func findalladdresses(addresses *_Ctype_struct_pcap_addr) (retval []IFAddress) {
// TODO - make it support more than IPv4 and IPv6?
retval = make([]IFAddress, 0, 1)
for curaddr := addresses; curaddr != nil; curaddr = (*_Ctype_struct_pcap_addr)(curaddr.next) {
var a IFAddress
var err error
a.IP, err = sockaddr_to_IP((*syscall.RawSockaddr)(unsafe.Pointer(curaddr.addr)))
if err != nil {
continue
}
a.Netmask, err = sockaddr_to_IP((*syscall.RawSockaddr)(unsafe.Pointer(curaddr.addr)))
if err != nil {
continue
}
retval = append(retval, a)
}
return
}
func sockaddr_to_IP(rsa *syscall.RawSockaddr) (IP []byte, err error) {
switch rsa.Family {
case syscall.AF_INET:
pp := (*syscall.RawSockaddrInet4)(unsafe.Pointer(rsa))
IP = make([]byte, 4)
for i := 0; i < len(IP); i++ {
IP[i] = pp.Addr[i]
}
return
case syscall.AF_INET6:
pp := (*syscall.RawSockaddrInet6)(unsafe.Pointer(rsa))
IP = make([]byte, 16)
for i := 0; i < len(IP); i++ {
IP[i] = pp.Addr[i]
}
return
}
err = errors.New("Unsupported address type")
return
}
func (p *Pcap) Inject(data []byte) (err error) {
buf := (*C.char)(C.malloc((C.size_t)(len(data))))
for i := 0; i < len(data); i++ {
*(*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(buf)) + uintptr(i))) = data[i]
}
if -1 == C.pcap_inject(p.cptr, unsafe.Pointer(buf), (C.size_t)(len(data))) {
err = p.Geterror()
}
C.free(unsafe.Pointer(buf))
return nil
}