raw socket error with sendto: no error code [was: raw socket error with sendto: no such device]

Question

im stuck with sending a raw ethernet frame.

[edit]
I found some errors.
1. It has to be AF_PACKET in the socket call.
2. AF_PACKET doesnt have an option SOCK_PACKET, but SOCK_DGRAM and SOCK_RAW

With SOCK_DGRAM wireshark captures a malformed LLC packet.
But with SOCK_RAW no error message and no captured packet.

i dont find whats really going wrong.
[/edit]

the code:

if ((ethernet_socket = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL))) == -1)
    cout << "Ethernet Socket: "<< strerror(errno) << endl;

struct sockaddr_ll socket_address;
socket_address.sll_family   = PF_PACKET;
socket_address.sll_protocol = htons(ETH_P_IP);
socket_address.sll_ifindex=if_nametoindex("eth0");
socket_address.sll_hatype   = 1; // ARPHRD_ETHER
socket_address.sll_pkttype  = PACKET_OTHERHOST;
socket_address.sll_halen    = ETH_ALEN;
memcpy(socket_address.sll_addr,dest_mac_addr,ETH_ALEN);

int send_result = 0;

char *opt=(char*)malloc(4*sizeof(char));
strcpy(opt,"eth0");

if(setsockopt(ethernet_socket, SOL_SOCKET, SO_BINDTODEVICE, opt, 4)==-1)
    cout << "Could not bind socket to device: " << strerror(errno) << endl;

if ((send_result  
= sendto(ethernet_socket, &buffer, sizeof(buffer), 0,  
    (struct sockaddr*)&socket_address, sizeof(socket_address)))==-1){
        cout << "sendto error: "<< strerror(errno) << endl;
        return send_result;
}

regards Ck

Are you running as root? Last time I looked (years ago) you had to have privileges to use raw sockets. — Jim Garrison

chris-kuhr chris-kuhr · Accepted Answer · 2012-11-21T08:13:34

I found the solution how this works. i took a look at the source code of the Linux program PackEth.

the following code works for me.

if ((ethernet_socket = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL))) == -1)
    cout << "Ethernet Socket: "<< strerror(errno) << endl;  //errorhandling

memset(&ifr, 0, sizeof(ifr));
strncpy (ifr.ifr_name, "eth0", sizeof(ifr.ifr_name) - 1);
ifr.ifr_name[sizeof(ifr.ifr_name)-1] = '\0';


if (ioctl(ethernet_socket, SIOCGIFINDEX, &ifr) == -1) {
    cout << "No such interface:"<< strerror(errno) << endl;
    close(ethernet_socket);
}

ioctl(ethernet_socket, SIOCGIFFLAGS, &ifr);
if ( (ifr.ifr_flags & 0x1) == 0) {
    cout << "Interface is down: "<< strerror(errno) << endl;
    close(ethernet_socket);
}

ioctl(ethernet_socket, SIOCGIFINDEX, &ifr);


memset(&socket_address, 0, sizeof (socket_address));
socket_address.sll_family    = AF_PACKET;
socket_address.sll_ifindex   = ifr.ifr_ifindex;
socket_address.sll_protocol  = htons(ETH_P_ALL);

if ((raw_send = sendto(ethernet_socket, buffer, size_payload+14,0,(struct     sockaddr*)     
                           &socket_address, sizeof(socket_address)))==-1){
    cout << "sendto error: "<< strerror(errno) << endl;
    return raw_send;
}

raw socket error with sendto: no error code [was: raw socket error with sendto: no such device]

2 Answers