Multicast traffic

[Mari Carmen Garro]

Hello,

I would like to make multicast traffic pass through WANem but I have seen that there is a lack of multicast support and I have to write a program to sniff incoming multicast packets and re-send them using raw sockets. Then, I have some questions related to this.

First of all, since I'm using the LiveCD, how do I run a program on WANem? Should I perform an HDD install of WANEM first?

And concerning to sniffing incoming multicast packets, what are the best practises for doing that? Should I use netfilter hooks? Where should I re-inject packets sniffed?

I would be grateful if someone could help me.

Thanks in advance,

Mari Carmen  

[buzzLightYear]

Here is how you can run your program in WANem Live CD. Boot through CD. When WANem is up 'n running, do a 'exit2shell' from the WANem command prompt. FTP your program/code to WANem and then run it as a normal program.

Please refer the links below for some multicasting best practices;
http://www.netcraftsmen.net/resources/archived-articles/283-ip-multicast-best-practices-and-control.html

You may want to google for more information about the multicasting best practices.

[Mari Carmen Garro]

Thank you very much. I'll try what you suggest to run a program.

However, these best practises aren't what I was asking for. My question was related to what mknambiar said in another post:

"Wanem does not forward multicast packets. If you badly need to do this then you have to write a program which will run on wanem, which will sniff incoming multicast packets and re-send them using raw sockets."

I would like to know what are the best practises for this sniffing: where I should re-inject packets sniffed, if I have to use netfilter hooks, …, because I don't know exactly how to do it.

Thanks,

Mari Carmen

[M K Nambiar]

Hi,

You can try this piece of c code. Just replace the MAC address in it to the MAC address of your WANem outgoing interface.

Compile it with the -lpcap flag.

All the best.

Regards,
M.K.Nambiar

---

#include<stdio.h>
#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/tcp.h>
#include<netinet/in.h>
#include<netinet/ip.h>
#include<arpa/inet.h>
#include<net/if.h>
#include<netinet/if_ether.h>

#include<pcap.h>
#include<netdb.h>
#include<stdlib.h>

#define MAXLINE 1600

      /* Setting Packet Filter-Only TCP Packets are allowed */

#define  CMD "ip multicast and not ether src 00:0E:0C:42:64:37" //Your WANem MAC address here

int sockfd,datalink,dlen;

int snaplen=1600;

pcap_t *pd;

unsigned int len;

char datagram;

char *device;

/* struct pcap_pkthdr pcap_t; */
struct tcpiphdr *tcp_check(char *ptr,unsigned int *);

struct tcpiphdr *tcp_read(void);

struct sockaddr_in sip,dip;

struct sockaddr_in emuladdr;

char *next_pcap(int *);

struct sockaddr *dest,*sa;

struct addrinfo *aip;

int DLHLength;

main(void)
{
sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_TCP);
printf("\nSocket Created……..");
  
{                             
int one = 1;
const int *val = &one;
if (setsockopt (sockfd, IPPROTO_IP, IP_HDRINCL, val, sizeof (one)) < 0)
printf ("Warning: Cannot set HDRINCL!\n");
}

open_pcap();
}

static char sstr,dstr;     
void process_packet(unsigned char *user, const struct pcap_pkthdr *h, const unsigned char *p)
{

char *ptr;
      

struct ether_header     *eptr;
struct ip *ip;

ptr = (char *)p;
ptr=ptr+DLHLength;
       
       ip = (struct ip *) ptr;

       len=ntohs(ip->ip_len);

sip.sin_addr.s_addr = (ip->ip_src.s_addr);
dip.sin_addr.s_addr = (ip->ip_dst.s_addr);
              
        dlen=sizeof(emuladdr);
   
        sendto(sockfd,ip,len,0,(struct sockaddr *) &dip,dlen);
}

open_pcap(void)
{
unsigned int localnet, netmask;
char cmd, errbuf,str1, str2;

struct bpf_program fcode;
        struct ether_header     *eptr;

if (device == NULL) {
if ( (device = pcap_lookupdev(errbuf)) == NULL)
printf("pcap_lookup: %s", errbuf);
}
/* 4hardcode: promisc=0, to_ms=0 */
if ( (pd = pcap_open_live(device, snaplen,0, 0, errbuf)) == NULL)
printf("pcap_open_live: %s", errbuf);

   if (pcap_lookupnet(device, &localnet, &netmask, errbuf) < 0)
printf("pcap_lookupnet: %s", errbuf);
      
        strcpy(cmd,CMD);
if (pcap_compile(pd, &fcode, cmd, 0, netmask) < 0)
printf("pcap_compile: %s", pcap_geterr(pd));

if (pcap_setfilter(pd, &fcode) < 0)
printf("pcap_setfilter: %s", pcap_geterr(pd));

if ( (datalink = pcap_datalink(pd)) < 0)
printf("pcap_datalink: %s", pcap_geterr(pd));

        switch (datalink)
        {
                case DLT_NULL:  /* loopback header = 4 bytes */
                        DLHLength=4;
                        break;

                case DLT_EN10MB:
                        DLHLength=14;
                        break;

                case DLT_SLIP:  /* SLIP header = 24 bytes */
                        DLHLength=24;
                        break;

                case DLT_PPP:   /* PPP header = 24 bytes */
                        DLHLength=24;
                        break;
         }
 
if (pcap_loop(pd, -1, process_packet, NULL) < 0) {
printf("pcap loop falied for reason = %s\n", pcap_geterr(pd));
exit(1);
}

pcap_close(pd);
}
/* end open_pcap */

---

[Mari Carmen Garro]

Thank you very much M.K.Nambiar.
I am going to try with this piece of c code. It will be very helpful surely.

Best regards,
Mari Carmen.

[RobertCeus]

Hi Mari Carmen.
If you write a program to make it work with multicast, please tell me.
I am very interested in it!!!

Good luck!

[Allan Guerriero]

If you look at a previous post of mine. If you install the latest version of Knoppix then do the software updates, you can also do an "apt-get install pimd". After this you just need to modify sysctl will enable multicast forwarding. If you are doing bridging then you need to make a script to set multicast_snooping to 0 in on bootup.

[markfm2]

Any chance someone with a working multicast patch will send that back to the developers, maybe get an updated wanem released with multicast support?