Toy VPN handling congestion control
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#include <linux/if.h>
#include <linux/if_tun.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <cstdlib>
#include <cstring>
#include "TunDevice.hpp"
static const size_t TUN_MTU = 1500; // TODO determine this cleanly
TunDevice::TunDevice(const std::string& dev)
{
struct ifreq ifr;
int fd;
if( (fd = open("/dev/net/tun", O_RDWR)) < 0 ) {
throw TunDevice::InitializationError(
"Cannot open /dev/net/tun", errno, true);
}
memset(&ifr, 0, sizeof(ifr));
/* Flags: IFF_TUN - TUN device (no Ethernet headers)
* IFF_TAP - TAP device
*
* IFF_NO_PI - Do not provide packet information
*/
ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
if(!dev.empty()) {
if(dev.size() >= IFNAMSIZ - 2)
throw TunDevice::InitializationError("Device name is too long.");
strncpy(ifr.ifr_name, dev.c_str(), IFNAMSIZ-1);
}
if(ioctl(fd, TUNSETIFF, (void *) &ifr) < 0){
close(fd);
throw TunDevice::InitializationError(
"Tunnel interface failed [TUNSETIFF]", errno, true);
}
_dev_name = ifr.ifr_name;
_fd = fd;
// Bring interface up
kdebugf("Bringing interface up...\n");
int sockfd = socket(AF_INET, SOCK_DGRAM, 0); // Any socket will do
if(ioctl(sockfd, SIOCGIFFLAGS, (void*) &ifr) < 0) {
close(fd);
close(sockfd);
throw TunDevice::InitializationError(
"Could not get tunnel interface flags", errno, true);
}
ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
if(ioctl(sockfd, SIOCSIFFLAGS, (void*) &ifr) < 0) {
close(fd);
close(sockfd);
throw TunDevice::InitializationError(
"Could not bring tunnel interface up", errno, true);
}
close(sockfd);
// The device is now fully set up
_poll_fd.fd = _fd;
_poll_fd.events = POLLIN;
}
TunDevice::~TunDevice() {
close(_fd);
}
uint16_t TunDevice::get_mtu() const {
int sockfd = socket(AF_INET, SOCK_DGRAM, 0); // Any socket will do
struct ifreq ifr;
ifr.ifr_addr.sa_family = AF_INET6;
strncpy(ifr.ifr_name, _dev_name.c_str(), sizeof(ifr.ifr_name)-1);
if (ioctl(sockfd, SIOCGIFMTU, (caddr_t)&ifr) < 0)
return 0;
close(sockfd);
return ifr.ifr_mtu;
}
bool TunDevice::set_mtu(uint16_t mtu) {
int sockfd = socket(AF_INET, SOCK_DGRAM, 0); // Any socket will do
struct ifreq ifr;
ifr.ifr_addr.sa_family = AF_INET6;
strncpy(ifr.ifr_name, _dev_name.c_str(), sizeof(ifr.ifr_name)-1);
ifr.ifr_mtu = mtu;
if (ioctl(sockfd, SIOCSIFMTU, (caddr_t)&ifr) < 0)
return false;
close(sockfd);
return true;
}
size_t TunDevice::poll_packet(char* read_buffer, size_t buf_size, int timeout) {
int poll_rc = poll(&_poll_fd, 1, timeout);
if(poll_rc < 0) {
if(errno == EINTR) // Interrupt.
return 0;
throw TunDevice::NetError(
"Error polling from interface", errno, true);
}
else if(poll_rc == 0 || (_poll_fd.revents & POLLIN) == 0) {
// Nothing to read
return 0;
}
return this->read(read_buffer, buf_size);
}
size_t TunDevice::read(char* read_buffer, size_t buf_size) {
int nread = ::read(_fd, read_buffer, buf_size);
if(nread < 0) {
throw TunDevice::NetError(
"Error reading from interface", errno, true);
}
_last_read_size = nread;
return _last_read_size;
}
size_t TunDevice::write(const char* data, size_t len) {
int nwritten = ::write(_fd, data, len);
if(nwritten < 0) {
throw TunDevice::NetError(
"Error writing to interface: ", errno, true);
}
return nwritten;
}