How to modify linklocal address of an ethernet interface

Nov. 7, 2012

      Hi,

I have written a sample code to modify the link-local address of an Ethernet interface.
The code snippet is -

    while(1) {
        printf("\n1.Add Link Local\n2.Modify LinkLocal\n");
        scanf("%d", &ch);
        switch(ch) {
            case 1:
            {
                add_linklocaladdr(fd, NLM_F_CREATE|NLM_F_EXCL);
                break;
            }
            case 2:
            {
                add_linklocaladdr(fd, NLM_F_REPLACE);
                break;
            }
-------------
-------------
void add_linklocaladdr(int fd, int flags)) {
-------------
-------------
    nlh = (struct nlmsghdr *)buf;
    len = MSG_ALIGN(sizeof(struct nlmsghdr));
    nlh->nlmsg_len   = len;
    nlh->nlmsg_type  = RTM_NEWADDR;
    nlh->nlmsg_flags = NLM_F_REQUEST | flag;
    nlh->nlmsg_seq = 1;

    ifadr = nlmsg_put_extra_header(nlh, sizeof(struct ifaddrmsg));
    ifadr->ifa_family    = AF_INET6;
    ifadr->ifa_prefixlen = 0x40 ; /*hardcoded*/
    ifadr->ifa_flags     = IFA_F_PERMANENT;;
    ifadr->ifa_scope     = RT_SCOPE_HOST;
    ifadr->ifa_index     = 2;

    /*Push 'struct nlattr' */
    attr_put(nlh, IFA_ADDRESS, dst);

When I execute case 1 (add link-local), a new ipv6 ip is getting added.
I want to modify an existing link local address in case2, but it's not working.
Can anybody help me correcting this code for case2.

Thanks & Regards
Murali Annamneni

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