Thanks for your answers.
I just tried to compile the libnl, but some errors occured, so I'm just continuing without it.
But I've looked at the html documentation and it seems to be very good.

I repaired the main() function by adding the

rtMsg->rtm_family = AF_INET;
rtMsg->rtm_dst_len = 16;

but every request on any dst address in the routing table gives me this output:
Destination             Gateway         Interface               Source          Netmask
127.0.0.1               *.*.*.*                         lo              255.255.255.255

The 'rtm_dst_len = 16' should mean the mask of the route I'm looking for, correct? The whole code before sending the packet is below:


     /* Create Socket */
     if((sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0)
         perror("Socket Creation: ");

     /* Initialize the buffer */
     memset(msgBuf, 0, BUFSIZE);

     /* point the header and the msg structure pointers into the buffer */
     nlMsg = (struct nlmsghdr *)msgBuf;
     rtMsg = (struct rtmsg *)NLMSG_DATA(nlMsg);
     rtMsg->rtm_family = AF_INET;
     rtMsg->rtm_dst_len = 16;

     /* Fill in the nlmsg header*/
     nlMsg->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)); // Length of message.
     nlMsg->nlmsg_type = RTM_GETROUTE;   // Get the routes from kernel routing table .
     nlMsg->nlmsg_flags = NLM_F_REQUEST;   // The message is a request for dump.
     nlMsg->nlmsg_seq = msgSeq++;   // Sequence of the message packet.
     nlMsg->nlmsg_pid = getpid();   // PID of process sending the request.

     char *cp;
     unsigned int xx[4]; int i = 0;
     unsigned char *ap = (unsigned char *)xx;
     for (cp = argv[1], i = 0; *cp; cp++) {
         if (*cp <= '9' && *cp >= '0') {
             ap[i] = 10*ap[i] + (*cp-'0');
             continue;
         }
         if (*cp == '.' && ++i <= 3)
             continue;
         return -1;
     }

     NetlinkAddAttr(nlMsg, sizeof(nlMsg), RTA_DST, &xx, 4);




On Fri, 17 Jun 2005, Thomas Graf wrote:

* Tom?? Macek [ref] 2005-06-17 20:57

quoted

Part of my routing table is here:

3.3.0.0         *               255.255.0.0     U     0      0        0 eth1
default         meric           0.0.0.0         UG    0      0        0 eth0

Ommiting NLM_F_DUMP and typing './a.out 3.3.0.0' gives

Error in recieved packet: Success
Read From Socket Failed...

Bcause you don't set rtm_dst_len to the prefix length or 32,
and rtm_family (AF_INET). You could also use libnl, probably
easier to use.