2000-12-07 02:04:34

by Daniel Chemko

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Subject: Multicast problems on 2.4.0?

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <netinet/in.h>

#define TEST_PORT 12345
#define SEND_PORT 12345
#define BUFSIZE 512
#define USAGE_STMT "Usage: argv[0] <address> <message>\n"

int main(int argc, char* argv[])
int i, s, duh;
struct sockaddr_in saddr;
char buf[BUFSIZE];

if (argc != 3)
return -1;

s = socket(PF_INET, SOCK_DGRAM, 0);
if (s == -1)
printf("argv[0]: cannot get socket descriptor\n");
return -1;

saddr.sin_family = AF_INET;
saddr.sin_port = htons(SEND_PORT);
saddr.sin_addr.s_addr = INADDR_ANY;

/*if (bind(s, &saddr, sizeof(struct sockaddr_in)) == -1)
printf("argv[0]: could not name socket\n");
return -1;

saddr.sin_port = htons(TEST_PORT);
saddr.sin_addr.s_addr = inet_addr(argv[1]);
strcpy(buf, argv[2]);
duh = sizeof(struct sockaddr_in);
sendto(s, buf, strlen(buf)+1, 0, &saddr, duh);

getmcast.c (1.35 kB)
udpsend.c (966.00 B)
cerf89x0.c (25.53 kB)
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2000-12-07 20:32:35

by Frank van Maarseveen

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Subject: Re: Multicast problems on 2.4.0?

On Thu, Dec 07, 2000 at 05:34:44AM -0800, Daniel Chemko wrote:
> Hello,
> I am doing development work on the 2.4.0 kernel, and can not seem to get
> multicasting to work.
I frequently experiment with "zebra" (http://www.zebra.org) routing engine
and multicasting works for me (2.4.0-test11), according to tcpdump and
observed behavior.

If you have multiple interfaces with the same IP address (point-to-point
interfaces: same local address) then it is possible that the packets go
out via the wrong interface. This has bitten me once.