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halfpipe.cc
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halfpipe.cc
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// --------------------------------------------------------------------------
// "THE BEER-WARE LICENSE" (Revision 42):
// pcapr wrote this file. As long as you retain this notice you can do whatever
// you want with this stuff. If we meet some day, and you think this stuff is
// worth it, you can buy us a beer in return.
//
// http://www.pcapr.net
// http://twitter.com/pcapr
// http://labs.mudynamics.com
// --------------------------------------------------------------------------
#include "halfpipe.h"
#if defined(__APPLE__) && defined(__MACH__)
#include <ifaddrs.h>
#include <net/if_dl.h>
#elif defined(__linux)
#error "This OS not supported at the moment"
#endif
HalfPipe::HalfPipe(std::string ifname, clock_t timeout)
:_ifname(ifname), _timeout(timeout)
{
_pcap = 0;
}
HalfPipe::~HalfPipe()
{
close();
}
/*
* HalfPipe::_get_mac()
* --------------------
* Get the MAC address of the interface corresponding to this half pipe. We
* need this to identify packets intended for 'this' host
*/
int
HalfPipe::_get_mac()
{
#if defined(__APPLE__) && defined(__MACH__)
struct ifaddrs *ifap = 0;
if (::getifaddrs(&ifap) < 0)
return -1;
for (struct ifaddrs *p = ifap; p; p = p->ifa_next) {
if (_ifname == p->ifa_name && p->ifa_addr->sa_family == AF_LINK) {
struct sockaddr_dl *sdp = (struct sockaddr_dl*) p->ifa_addr;
::memcpy(&_mac, sdp->sdl_data + sdp->sdl_nlen, sizeof _mac);
break;
}
}
::freeifaddrs(ifap);
#else
#error "Dunno how to get MAC address of an interface on this OS"
#endif
return 0;
}
/*
* HalfPipe::open()
* ----------------
* Open the half pipe (before we can read/write)
*/
int
HalfPipe::open()
{
if (_pcap)
return 0;
if (_get_mac() < 0) {
fprintf(stderr, "bummer: can't get mac for %s\n",
_ifname.c_str());
return -1;
}
char eb[PCAP_ERRBUF_SIZE];
_pcap = ::pcap_open_live(_ifname.c_str(), 65535, 1, _timeout, eb);
if (_pcap == 0) {
fprintf(stderr, "bummer: pcap_open_live(%s) failed\n\t %s\n",
_ifname.c_str(), eb);
return -1;
}
// Ignore packets from this host (just need the incoming ones)
if (::pcap_setdirection(_pcap, PCAP_D_IN) < 0) {
fprintf(stderr, "bummer: pcap_set_direction(%s) failed\n",
_ifname.c_str());
goto bummer;
}
return 0;
bummer:
close();
return -1;
}
void
HalfPipe::close()
{
if (_pcap) {
::pcap_close(_pcap);
_pcap = 0;
}
}
/*
* HalfPipe::read()
* ----------------
* Read a packet from the half pipe.
*/
int
HalfPipe::read(uint8_t *bytes, size_t size, Type &type)
{
if (_pcap == 0 || bytes == 0 || size == 0)
return -1;
struct pcap_pkthdr phdr;
struct pcap_pkthdr *php = &phdr;
const uint8_t *bptr = 0;
int ret = ::pcap_next_ex(_pcap, &php, &bptr);
if (ret == 0)
return 0;
// Truncated read
if (ret < 0 || php->len < sizeof _mac)
return -1;
int nread = std::min(size_t(php->len), size);
::memcpy(bytes, bptr, nread);
const eth_addr_t broadcast = {{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }};
eth_addr_t dst;
::memcpy(&dst, bytes, sizeof dst);
// Classify the packet based on the MAC address
if (::memcmp(&dst, &_mac, sizeof _mac) == 0) {
type = Host;
} else if (::memcmp(&dst, &broadcast, sizeof dst) == 0) {
type = Broadcast;
} else if (dst.addr[0] == 0x1) {
type = Multicast;
} else {
type = Other;
}
return nread;
}
/*
* HalfPipe::write()
* -----------------
* Write a packet through this half pipe into the interface
*/
int
HalfPipe::write(const uint8_t *bytes, size_t size)
{
if (_pcap == 0 || bytes == 0 || size == 0)
return -1;
if (::pcap_inject(_pcap, bytes, size) != int(size))
return -1;
return 0;
}