int
Secondary_Ipaddr_Handler::init_netlink_request (
char* const ip_slash_netmask,
const char *const if_name,
Netlink_Request& net_req,
bool action)
{
ACE_OS::memset (&net_req, 0, sizeof(net_req));
// fill the request header
net_req.nhdr_.nlmsg_len =
NLMSG_LENGTH (sizeof(struct ifaddrmsg));
net_req.nhdr_.nlmsg_flags = NLM_F_REQUEST;
net_req.nhdr_.nlmsg_type = action ? RTM_NEWADDR : RTM_DELADDR;
net_req.ifa_.ifa_family = AF_INET;
int interface_index = -1;
if (get_if_index (if_name,
interface_index) == -1 || interface_index < 0)
{
ACE_OS::fprintf (stderr, "get_if_index () - failed\n");
return -1;
}
net_req.ifa_.ifa_index = interface_index;
Inet_Prefix local_prefix;
if (fill_inet_prefix (local_prefix,
ip_slash_netmask) == -1)
{
ACE_OS::fprintf (stderr, "fill_inet_prefix () - failed\n");
return -1;
}
fill_rtnetlink_request (net_req.nhdr_,
IFA_LOCAL,
&local_prefix.data,
local_prefix.bytelen);
net_req.ifa_.ifa_prefixlen = local_prefix.bitlen; // number of bits in netmask
net_req.ifa_.ifa_scope = 0;
return 0;
}
int main(int argc, char *argv[])
{
struct sockaddr_ll srcethaddr; /* man 7 packet */
struct sockaddr_ll bindethaddr; /* man 7 packet */
struct packet_mreq mr; /* man 7 packet */
struct ifreq ifr; /* man 7 netdevice */
int nbytes;
socklen_t addrlen;
/* how big should the buffer be?
*
* This can be determined by MTU. MTU can be obtained by an ioctl call:
*
* ioctl(socket, SIOCGIFMTU, &ifr)
*
* where socket is a socket descriptor, ifr is of type struct ifreq.
* More information can be found at manual page netdevice(7). Note that
* one needs to give ifr_name to invoke the ioctl call. If a program
* retrieves frames from more than one device, the maximum MTU among
* the devices should be used.
*
* In Linux, available network devices can be obtained in multiple
* methods, commonly,
* (1) by walking through the /proc/net/dev file.
* (2) by calling ioctl(...) with request SIOCGIFCONF
* (3) via rtnetlink socket
*
* MTU does not include header/trailer. For capturing Ethernet frames,
* the buffer size should be set no less than
* 6 + 6 + 2 + MTU = ETHER_HDR_LEN + MTU.
*
* Question: how does IEEE 802.1Q affect the required buffer size?
* */
int bufsize; /* how big should the buffer be? */
int ifindex; /* interface index */
setupsignal(SIGINT, cleanup); /* capture CTRL-C */
if (argc < 2) {
usage(argv[0]);
exit(1);
}
/* open a raw packet socket to capture all types of ethernet frames */
sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if (sockfd < 0) {
perror("socket(AF_PACKET, SOCK_RAW, ETH_P_ALL) failed");
exit(1);
}
/* obtain interface index from interface name */
if ((ifindex = get_if_index(sockfd, argv[1])) == -1) {
fprintf(stderr,
"failed to obtain interface index for interface %s\n",
argv[1]);
exit(1);
}
/* put the interface into promiscuous mode. man 7 packet */
memset(&mr, 0, sizeof(mr));
mr.mr_ifindex = ifindex;
mr.mr_type = PACKET_MR_PROMISC;
if (setsockopt(sockfd, SOL_PACKET,
PACKET_ADD_MEMBERSHIP, (char *)&mr, sizeof(mr)) != 0) {
perror("setsockopt(sockfd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, ...)");
exit(1);
}
/* bind the socket to the interface. see bind(2) and packet(7) */
memset(&bindethaddr, 0, sizeof(bindethaddr));
bindethaddr.sll_family = AF_PACKET;
bindethaddr.sll_protocol = htons(ETH_P_ALL);
bindethaddr.sll_ifindex = ifindex;
if (bind(sockfd,
(struct sockaddr*)&bindethaddr, sizeof(bindethaddr)) != 0) {
perror("bind(sockfd, &bindethaddr, sizeof(bindethaddr))");
exit(1);
}
/* obtain MTU. see netdevice(7) */
ifr.ifr_addr.sa_family = AF_PACKET;
safe_strncpy(ifr.ifr_name, argv[1], IFNAMSIZ);
if (ioctl(sockfd, SIOCGIFMTU, &ifr) != 0) {
perror("ioctl(sockfd, SIOCGIFMTU, &ifr)");
exit (1);
}
/* allocate buffer */
bufsize = ifr.ifr_mtu + ETHER_HDR_LEN;
if ((buf = malloc(bufsize)) == NULL) {
fprintf(stderr, "insufficient memory\n");
exit(1);
}
/* begin capturing */
memset(&srcethaddr, 0, sizeof(srcethaddr));
while (1) {
addrlen = sizeof(srcethaddr);
nbytes = recvfrom(sockfd, buf, bufsize,
0, (struct sockaddr*)&srcethaddr, &addrlen);
if (nbytes < 0) {
perror("recv(sockfd ...) failed");
exit (1);
}
/* dump captured frame */
printf("Captured at interface: %s frame from ", argv[1]);
dump_physical_address(srcethaddr.sll_halen, srcethaddr.sll_addr);
printf("\n");
dumpbuf(buf, nbytes);
/**
* flush the buffer so that we don't have to rely on stdbuf, as in
* sudo stdbuf -o 0 ./ethercap eth0 | tee frame_captured.txt
*/
fflush(stdout);
}
/* remove the interface's promiscuous mode */
setsockopt(sockfd, SOL_PACKET,
PACKET_DROP_MEMBERSHIP, (char *)&mr, sizeof(mr));
free(buf);
close(sockfd);
return 0;
}
