[ECOS] Cannot sendto multicast using FreeBSD stack

Andrew Lunn andrew@lunn.ch
Thu Jan 10 14:53:00 GMT 2008


On Thu, Jan 10, 2008 at 09:29:05AM -0500, Chad Handrich wrote:
> Hello,
>
> I wrote about this problem previously, but still have not found a solution 
> (see the subject "Problem with multicast using FreeBSD stack" from 
> 11/29/07)
>
> I have eCos configured with the FreeBSD stack.  Everything is working 
> except a portion where I have to SEND multicast UDP packets using sendto(). 
>  In these instances, sendto() returns -1, and errno == EHOSTUNREACH.
>
> Here is my test multicast code that is failing:
>
>    struct in_addr interface_addr;
>
>    // eth0 is configured to be 89.89.200.181
>    inet_aton("89.89.200.181", &interface_addr);
>    setsockopt(skt, IPPROTO_IP, IP_MULTICAST_IF, &interface_addr, 
> sizeof(interface_addr));
>        struct in_addr multi_iface;
>    getsockopt(skt, IPPROTO_IP, IP_MULTICAST_IF, &multi_iface, 
> sizeof(multi_iface));
>    diag_printf("getsockopt specifies %s as multicast interface\n", 
> inet_ntoa(multi_iface));
>    // This outputs the string:     getsockopt specifies 89.89.200.181 as 
> multicast interface
>
>    // Sample data to send via multicast
>    char buf[5]; buf[0] = 0; buf[1] = 1; buf[2] = 2; buf[3] = 3; buf[4] = 4;
>      struct sockaddr_in to;
>    to.sin_family = AF_INET;
>    to.sin_port = htons(2222);
>    inet_aton("239.192.23.160", &(to.sin_addr));
>      int retval = sendto(skt, buf, 5, 0, (struct sockaddr *)&to, 
> sizeof(to));
>    diag_printf("post-sendto: errno=%d   retval=%d\n", errno, retval);
>    // This outputs the string:     post-sendto: errno=365   retval=-1
>    //  errno=365 corresponds to EHOSTUNREACH
>
>
> Any help to get this multicast sendto() to succeed would be greatly 
> appreciated.

Do you also add a multicast route? Typically on Linux you have to add
a route:

route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0

      Andrew

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