[ECOS] Cannot sendto multicast using FreeBSD stack

[Chad Handrich]

Andrew Lunn wrote:
> 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
>
>   

It appears that you are correct. Using ioctl to add a route with the 
parameters you specified seems to be working. My thanks.


Chad


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