Ruby Raw Socket on Linux (ruby 1.9.3, linux x86_64)

raw_sock.rb

require 'socket'

ETH_P_ALL             = 0x0300 # linux/if_ether.h(network byte order)
SIOCGIFINDEX          = 0x8933 # bits/ioctls.h
SOL_PACKET            = 0x0107 # bits/socket.h
PACKET_ADD_MEMBERSHIP = 0x0001 # netpacket/packet.h
PACKET_MR_PROMISC     = 0x0001 # netpacket/packet.h
IFREQ_SIZE            = 0x0028 # sizeof(ifreq) on 64bit
IFINDEX_SIZE          = 0x0004 # sizeof(ifreq.ifr_ifindex) on 64bit
SOCKADDR_LL_SIZE      = 0x0014 # sizeof(sockaddr_ll) on 64bit
PACKET_MREQ_SIZE      = 0x0010 # sizeof(packet_mreq) on 64bit

# listen interface name
if_name = 'eth0'

# open raw socket
socket = Socket.open(Socket::PF_PACKET, Socket::SOCK_RAW, ETH_P_ALL)

# get interface number
ifreq = [if_name].pack('a' + IFREQ_SIZE.to_s)
socket.ioctl(SIOCGIFINDEX, ifreq)
if_num = ifreq[Socket::IFNAMSIZ, IFINDEX_SIZE]

# bind
sll = [Socket::AF_PACKET].pack('s')
sll << [ETH_P_ALL].pack('s')
sll << if_num
sll << ("\x00" * (SOCKADDR_LL_SIZE - sll.length))
socket.bind sll

# set promiscuous mode
mreq = if_num.dup
mreq << [PACKET_MR_PROMISC].pack('s')
mreq << ("\x00" * (PACKET_MREQ_SIZE - mreq.length))
socket.setsockopt(SOL_PACKET, PACKET_ADD_MEMBERSHIP, mreq)

# receive packet
data = socket.recvfrom(1024*4)

show_constants.c

#include <stdio.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netpacket/packet.h>
 
int main(int argc, char **argv) {
    struct ifreq ifr;
    struct sockaddr_ll sll;
    struct packet_mreq mreq;

    printf("ETH_P_ALL             = %#06x\n", htons(ETH_P_ALL));
    printf("SIOCGIFINDEX          = %#06x\n", SIOCGIFINDEX);
    printf("SOL_PACKET            = %#06x\n", SOL_PACKET);
    printf("PACKET_ADD_MEMBERSHIP = %#06x\n", PACKET_ADD_MEMBERSHIP);
    printf("PACKET_MR_PROMISC     = %#06x\n", PACKET_MR_PROMISC);
    printf("IFREQ_SIZE            = %#06zx\n", sizeof(ifr));
    printf("IFINDEX_SIZE          = %#06zx\n", sizeof(ifr.ifr_ifindex));
    printf("SOCKADDR_LL_SIZE      = %#06zx\n", sizeof(sll));
    printf("PACKET_MREQ_SIZE      = %#06zx\n", sizeof(mreq));
 
    return 0;
}