problem in Route add using netlink

[VijayaLakshmi Seshadri <viji_171@xxxxxxxxxxx>]

Hi all

 Iam trying to implement "route add " using netlink. The changes are not reflected in the routing table. I have given my code and screen shots of the routing tables.

 

Can anybody tell me is there any mistake iam making in defining the fields .

or any other mistake iam commiting

 

thanxs

 

viji

 

//////////////////////////////////// CODE //////////////////////////////////////////////////////

#include <asm/types.h>
#include <netinet/ether.h>
#include <netinet/in.h>
#include <net/if.h>
#include <stdio.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <sys/types.h>

#define BUFSIZE 192
struct route_info{
        u_int   dstAddr;
        u_int   srcAddr;
        u_int   gateWay;
        char    ifName[IF_NAMESIZE];
};

void fillRoute (struct route_info *rinfo, const char* dstAddr,
                const char* srcAddr, const char* gateway, const char* ifName)
{
        /* Convert from the standrad numbers and dots notation
           to binary data  */
        inet_aton("192.168.51.0", (struct in_addr *)&rinfo->dstAddr);
        inet_aton("192.168.51.90", (struct in_addr *)&rinfo->gateWay);
}

int addAttr (struct nlmsghdr *nlhdr, int maxlen, int type,
                void *data, int alen)
{
        struct rtattr *rta;
        int len = RTA_LENGTH(alen);
        if (NLMSG_ALIGN(nlhdr->nlmsg_len) + len > maxlen)
                return -1;
        rta = (struct rtattr*)((char *)nlhdr + NLMSG_ALIGN(nlhdr->nlmsg_len));
        rta->rta_type = type;
        rta->rta_len  = len;
        memcpy(RTA_DATA(rta), data, alen);
        nlhdr->nlmsg_len = NLMSG_ALIGN(nlhdr->nlmsg_len) + len;
        return 0;
}

int main()
{
        struct nlmsghdr *nlMsg;
        struct rtmsg *rtMsg;
        char dstAddr[30] ;
        char srcAddr[30] ;
        char gateway[30] ;
        char ifName[30];
        char msgBuf[BUFSIZE];
        struct route_info rinfo;
        int sock, len, msgSeq = 0;
        int val, i;

        /* Create Socket */
        if((sock = socket(AF_NETLINK, SOCK_RAW, 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);

        /* Fill in the nlmsg header*/
        nlMsg->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)); // Length ofmessage.

        nlMsg->nlmsg_type = RTM_NEWROUTE;                      // Get the routes from kernel routing table .

        nlMsg->nlmsg_flags = NLM_F_CREATE ;       // 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.
        rtMsg->rtm_family = AF_INET;
        rtMsg->rtm_table = RT_TABLE_UNSPEC;
        rtMsg->rtm_dst_len = 16;
        rtMsg->rtm_src_len = 16;
        rtMsg->rtm_scope = RT_SCOPE_UNIVERSE;
        rtMsg->rtm_type = RTN_UNICAST;
        rtMsg->rtm_protocol = RTPROT_UNSPEC;
        rtMsg->rtm_flags   = RTM_F_NOTIFY;

        fillRoute (&rinfo, dstAddr, srcAddr, gateway, ifName);
        addAttr (nlMsg, BUFSIZE, RTA_DST,
                        &rinfo.dstAddr, 4);
                addAttr (nlMsg, BUFSIZE, RTA_GATEWAY,
                        &rinfo.gateWay, 4);

        /* Send the request */
        if((val = send(sock, nlMsg, nlMsg->nlmsg_len,0 )) < 0){
                printf("Write To Socket Failed...\n");
                return -1;
        }
        printf (" No of Bytes sent %d \n", val);
        printf (" Value that is sent \n " );
        for (i =0 ; i < val ; i ++)
          printf ("%u", msgBuf[i]);
        printf ("\n");
        close(sock);
return 0;
}

//////////////////////////////////////////////////////////////////////////////////////////////////////////

                              OUTPUT

[root@vijdom]gcc netlink_addroute.c -o addroute

[root@vijdom]# ./addroute
 No of Bytes sent 44
 Value that is sent
 4400024004000042949672398800216160000101008010429496723242949672085108050429496723242949672085190

//////////////////////////////////////////////////////////////////////////////////////////////////////////

                              SCREEN SHOTS

 

Routing table before execution of program

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.51.0    *               255.255.255.0   U     0      0        0 eth0
169.254.0.0     *               255.255.0.0     U     0      0        0 eth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
default         embedded        0.0.0.0         UG    0      0        0 eth0

 

Routing table after the execution of program
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.51.0    *               255.255.255.0   U     0      0        0 eth0
169.254.0.0     *               255.255.0.0     U     0      0        0 eth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
default         embedded        0.0.0.0         UG    0      0        0 eth0

 

 

 

 

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