CODEWITHSUNDEEP
linuxdriversrouteripv6
Yifan Sun
Yifan Sun

Reputation: 832

How to send a router advertisement correctly?

I am developing a IPv6 linux device driver without the equipment at hand. So I am now trying to cheat the kernel with a fake router advertisement message. 

unsigned char c[] = {0x33, 0x33, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 61, 0x86, 0xdd, //IPv6 type
            0x60, 0x00, 0x00, 0x00, //Version, ...
            0x00, 24, //payload length
            58,         //next header 
            255,        //hop limit 
            0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0xff, 0xfe, 0x00, 0x00, 0x3d, //source
            0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, //destination
            134, //type
            0, //code,
            0x7a, 0x2c, //checksum
            255, //current hop limit
            0x80, //flag
            0xff, 0xff,
            0x00, 0x00, 0x00, 0x00, //reachable timer
            0x00, 0x00, 0x00, 0x00,
            0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 61, //source link-layer address   
            };

I tried to use Tcpdump to grab this packet I send to the kernel. And I found that the kernel really get this packet. 

13:32:59.989851 00:00:00:00:00:3d (oui Ethernet) > 33:33:00:00:00:02 (oui Unknown), ethertype IPv6 (0x86dd), length 78: (hlim 255, next-header ICMPv6 (58) payload length: 24) fe80::200:ff:fe00:3d > ip6-allnodes: [icmp6 sum ok] ICMP6, router advertisement, length 24
    hop limit 255, Flags [managed], pref medium, router lifetime 65535s, reachable time 0s, retrans time 0s
      source link-address option (1), length 8 (1): 00:00:00:00:00:3d
        0x0000:  0000 0000 003d

But after that I use ip -6 neigh to examine whether the kernel have the fake node in the neighbor table. I cannot find it.

What is my problem? Any idea?

Upvotes: 8

Views: 3969

Answers (2)

Bruce Barnett
Bruce Barnett

Reputation: 948

Perhaps these hacking toolkits will be helpful

  1. IPv6-toolkit - the ra6 program fakes router advertisements
  2. THV-IPv6 - the *fake_advertise6* program

Upvotes: 1

jfg956
jfg956

Reputation: 16750

Why fake a router advertisement ?

What I would do in your situation is put a 2nd Linux on the same Ethernet link (in VMWare or any other virtual environment if you do not have a physical setup), install radvd on this 2nd Linux, and let radvd send router advertisement on the link.

Upvotes: 1

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