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Old 11-26-2010, 08:27 AM   #1
Lobinho
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Registered: May 2010
Distribution: Ubuntu
Posts: 72

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Problem to set gateway using c++ program


Hi,

I'm trying to set the gateway with my c++ program. My function receive the gateway on the first parameter.

The return of execution of ioctl() is 0, so it's working good, but when I run the "route" command on console, the configured gateway isn't there.

Check the output and the function below:


$ route
Quote:
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.0 * 255.0.0.0 U 0 0 0 eth0
Code:
int gateWayConfig(string gateWay) {
    int result = ERROR; //retorno da função
    try {
        int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
        gateWay = formatIp(gateWay); //converts 192.168.000.001 to 192.168.0.1

        if (sockfd > 0) {
            struct sockaddr_in *dst, *gw, *mask;
            struct rtentry route;

            printf("gateway: %s\n", gateWay.c_str());
            printf("gateway: %d\n", inet_addr(gateWay.c_str()));

            memset(&route, 0, sizeof (struct rtentry));

            dst = (struct sockaddr_in *) (&(route.rt_dst));
            gw = (struct sockaddr_in *) (&(route.rt_gateway));
            mask = (struct sockaddr_in *) (&(route.rt_genmask));

            // Make sure we're talking about IP here
            dst->sin_family = AF_INET;
            gw->sin_family = AF_INET;
            mask->sin_family = AF_INET;

            // Set up the data for removing the default route
            dst->sin_addr.s_addr = 0;
            gw->sin_addr.s_addr = 0;
            mask->sin_addr.s_addr = 0;
            route.rt_flags = RTF_UP | RTF_GATEWAY;

            // Remove the default route
            ioctl(sockfd, SIOCDELRT, &route);

            // Set up the data for adding the default route
            dst->sin_addr.s_addr = 0;
            gw->sin_addr.s_addr = inet_addr(gateWay.c_str());
            mask->sin_addr.s_addr = 0;
            route.rt_metric = 1;
            route.rt_flags = RTF_UP | RTF_GATEWAY;

            // Remove this route if it already exists
            ioctl(sockfd, SIOCDELRT, &route);

            // Add the default route
            if (ioctl(sockfd, SIOCADDRT, &route) == -1) {
                // *** The error never occurs ***
                fprintf(stderr, "Adding default route: %d", errno);
            }
            shutdown(sockfd, SHUT_RDWR);
            close(sockfd);
        }
        printf("result: %d\n", result); 
        
    } catch (...) {

    }
    return result;
}

Could someone help me to solve this issue?

I tried to use system() function to set the gateway using:
system("route del default");
system("route add default gw 10.100.40.1 dev eth0");

But didn't work too. :/


Thanks in advance

Last edited by Lobinho; 11-26-2010 at 08:34 AM.
 
Old 11-26-2010, 09:55 AM   #2
Sergei Steshenko
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Did you run as root ?
 
Old 11-26-2010, 10:14 AM   #3
Lobinho
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Registered: May 2010
Distribution: Ubuntu
Posts: 72

Original Poster
Rep: Reputation: 18
Hi Sergei,

Yes, I was running the program as root. I discovered right now the problem: I was setting interface down to set mac address and the gateway config was going to hell with the "ifconfig eth0 down" command. :P

sorry, my fault. Thanks anyway.
 
Old 11-26-2010, 10:14 AM   #4
Lobinho
Member
 
Registered: May 2010
Distribution: Ubuntu
Posts: 72

Original Poster
Rep: Reputation: 18
Hi Sergei,

Yes, I was running the program as root. I discovered right now the problem: I was setting interface down to set mac address and the gateway config was going to hell with the "ifconfig eth0 down" command. :P

sorry, my fault. Thanks anyway.
 
  


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