[support] How do the tunnel work?

[tony chen]

Hi!everyone.

I'm doing about creating ipv6 tunnel and encountering a problem.
I wrote a program that was similar to "tunnalctl.c" in nepl.

As i run the NEPL and build up the tunnel ,the information is

Sun Nov 15 11:29:22 __tunnel_add: created tunnel ip6tnl3 (18) from
2001:a:b:0:0:0:0:1 to 2001:a:b:0:0:0:0:1000 user count 1
Sun Nov 15 11:29:22 tnl_dump: name: ip6tnl3
link: 3
proto: 41
encap_limit: 0
hop_limit: 64
flowinfo: 0
flags: 30009
laddr: 2001:a:b:0:0:0:0:1
raddr: 2001:a:b:0:0:0:0:1000
ifindex: 18
users: 1
Sun Nov 15 11:29:22 conf_home_addr_info: Home address 2001:a:b:0:0:0:0:1
Sun Nov 15 11:29:22 flag_hoa: set HoA 2001:a:b:0:0:0:0:1/128 iif 18 flags 12
preferred_time 4294967295 valid_time 4294967295
Sun Nov 15 11:29:22 conf_home_addr_info: Added new home_addr_info
successfully

I look at the ifconfig infomation about ip6tnl3:

ip6tnl3   Link encap:UNSPEC  HWaddr
20-01-00-0A-00-0B-00-00-00-00-00-00-00-00-00-00
          inet6 addr: fe80::212:f0ff:fe08:72ce/64 Scope:Link
          inet6 addr: 2001:a:b::1/128 Scope:Global
          UP POINTOPOINT RUNNING NOARP  MTU:1460  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

but I wrote my program following above information,and I use the tnl_dump to
get the tunnel information:
name: ip6tnl6
link: 0
proto: 41
encap_limit: 0
hop_limit: 64
flowinfo: 0
flags: 30009
laddr: 2001:a:b:0:0:0:0:1
raddr: 2001:0:0:0:0:0:0:1000
ifindex: 20
users: 1

It's right,
but I look at information of ifconfig of the ip6tnl6.

ip6tnl6   Link encap:UNSPEC  HWaddr
20-01-00-0A-00-0B-00-00-00-00-00-00-00-00-00-00
          inet6 addr: fe80::212:f0ff:fe08:72ce/64 Scope:Link
          UP POINTOPOINT RUNNING NOARP  MTU:1460  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)


the  inet6 addr: 2001:a:b::1/128 Scope:Global is gone!! Orz..

why?

This is my code below:

int main()
{
        const char basedev[] = "ip6tnl0";
    struct mip6_tnl *tnl = NULL;
    struct ifreq ifr;
    struct in6_addr *local, *remote;
    int link=0;

    if ((tnl_fd = socket(AF_INET6, SOCK_DGRAM, 0)) < 0)
        return -1;

    local=malloc( sizeof(struct in6_addr) );
    remote=malloc( sizeof(struct in6_addr) );
    if ((tnl = malloc(sizeof(struct mip6_tnl))) == NULL)
        return NULL;

    memset(local,0,sizeof(struct in6_addr));
    memset(remote,0,sizeof(struct in6_addr));

    inet_pton(AF_INET6, "2001:a:b::1", &(local->in6_u.u6_addr16));
    inet_pton(AF_INET6, "2001::1", &(remote->in6_u.u6_addr16));

    memset(tnl, 0, sizeof(struct mip6_tnl));
    tnl->users = 1;
    tnl->parm.proto = IPPROTO_IPV6;
    tnl->parm.flags = IP6_TNL_F_MIP6_DEV|IP6_TNL_F_IGN_ENCAP_LIMIT;
    tnl->parm.hop_limit = 64;
    tnl->parm.laddr = *local;
    tnl->parm.raddr = *remote;
    tnl->parm.link = link;

    strcpy(ifr.ifr_name, basedev);
    ifr.ifr_ifru.ifru_data = (void *)&tnl->parm;
    if (ioctl(tnl_fd, SIOCADDTUNNEL, &ifr) < 0) {
        printf("SIOCADDTUNNEL failed status %d %s\n",
         errno, strerror(errno));
        goto err;
    }
    if (!(tnl->parm.flags & IP6_TNL_F_MIP6_DEV)) {
        printf("tunnel exists,but isn't used for MIPv6\n");
        goto err;
    }
    strcpy(ifr.ifr_name, tnl->parm.name);
    if (ioctl(tnl_fd, SIOCGIFFLAGS, &ifr) < 0) {
        printf("SIOCGIFFLAGS failed status %d %s\n",
             errno, strerror(errno));
        goto err;
    }
    ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
    if (ioctl(tnl_fd, SIOCSIFFLAGS, &ifr) < 0) {
        printf("SIOCSIFFLAGS failed status %d %s\n",
             errno, strerror(errno));
        goto err;
    }
    if (!(tnl->ifindex = if_nametoindex(tnl->parm.name))) {
        printf("no device called %s\n", tnl->parm.name);
        goto err;
    }
    tnl_dump(tnl);


    return tnl;
err:
    free(tnl);
    return NULL;
}

Thank to  everybody viewing and replying.
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