MAC address of an IPv6 address

Hi All,

I am writing a program that tests the health of a NIC card. I am
creating a NDD socket (Data Link Access) which I will use to send ICMP
ECHO packets to a given host. This means that my application has to
build the entire packet and I have to create and add the IP/IPv6,
ICMP/
6, and MAC headers in my application. I got things to work for IP, but
I am stuck with IPv6:

1) How do I find the MAC address for an IPv6 remote host? For IP, I
use the SIOCGARP ioctl and get the MAC adress from the ARP cache. But
IPv6 does not use ARP. there is something called neighbor discovery
for IPv6, but I could not find any programatic interface to use it ..

2) How do I do a broadcast ping in IPv6? In v4, I just put the
broadcast address in the destination addr fiend of the IP header and
things worked, but what do I do for v6?

Thanks in advance for your help.

Jigs

Jigs wrote:
> Hi All,
> [snip]
ping6 ?
>
> 2) How do I do a broadcast ping in IPv6? In v4, I just put the
> broadcast address in the destination addr fiend of the IP header and
> things worked, but what do I do for v6?

MAC address is part of the IPv6 address - no more ARP!

>
> Thanks in advance for your help.
>
> Jigs
>
Steve

SadOldGit wrote:
> Jigs wrote:
>> Hi All,
>> [snip]
> ping6 ?
>> 2) How do I do a broadcast ping in IPv6? In v4, I just put the
>> broadcast address in the destination addr fiend of the IP header and
>> things worked, but what do I do for v6?
>
> MAC address is part of the IPv6 address - no more ARP!

When jou set the ip address manually it is not.

--
Hans

Hans wrote:
> SadOldGit wrote:
>> Jigs wrote:
>>> Hi All,
>>> [snip]
>> ping6 ?
>>> 2) How do I do a broadcast ping in IPv6? In v4, I just put the
>>> broadcast address in the destination addr fiend of the IP header and
>>> things worked, but what do I do for v6?
>>
>> MAC address is part of the IPv6 address - no more ARP!
>
> When jou set the ip address manually it is not.
>

"When IEEE 802 48bit MAC addresses are available (on an interface or a
node), an implementation should use them to create interface
identifiers due to their availability and uniqueness properties."
RFC2373

OK, it doesn't say must!

SadOldGit wrote:
> Hans wrote:
>> SadOldGit wrote:
>>> Jigs wrote:
>>>> Hi All,
>>>> [snip]
>>> ping6 ?
>>>> 2) How do I do a broadcast ping in IPv6? In v4, I just put the
>>>> broadcast address in the destination addr fiend of the IP header and
>>>> things worked, but what do I do for v6?
>>> MAC address is part of the IPv6 address - no more ARP!
>> When jou set the ip address manually it is not.
>>
>
> "When IEEE 802 48bit MAC addresses are available (on an interface or a
> node), an implementation should use them to create interface
> identifiers due to their availability and uniqueness properties."
> RFC2373
>
> OK, it doesn't say must!

Should is almost must. By the way:

bash-3.1# ip addr -6 show dev eth0
2: eth0: <BROADCAST,MULTICAST,NOTRAILERS,UP,10000> mtu 1500 qdisc
pfifo_fast qlen 1000
link/ether 00:11:43:61:8d:db brd ff:ff:ff:ff:ff:ff
inet6 2001:888:1639::4/48 scope global
valid_lft forever preferred_lft forever
inet6 fe80::211:43ff:fe61:8ddb/64 scope link
valid_lft forever preferred_lft forever
bash-3.1#

The global scope is mac-free, but the scope link is not. And on another
pc of mine every bridge-port (except eth3) seems to have its own ip6
addr whether i like it or not:

bash-3.1# brctl show
bridge name bridge id STP enabled interfaces
br0 8000.003018a54f01 no eth0
eth1
eth2
eth3
bash-3.1# ip -6 addr show
1: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qlen 1000
inet6 fe80::230:18ff:fea5:ebfd/64 scope link
valid_lft forever preferred_lft forever
2: lo: <LOOPBACK,UP,10000> mtu 16436
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qlen 1000
inet6 fe80::230:18ff:fea5:4f01/64 scope link
valid_lft forever preferred_lft forever
4: eth2: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qlen 1000
inet6 fe80::230:18ff:fea5:4f02/64 scope link
valid_lft forever preferred_lft forever
7: br0: <BROADCAST,MULTICAST,UP,10000> mtu 1500
inet6 2001:888:1639::2/48 scope global
valid_lft forever preferred_lft forever
inet6 fe80::230:18ff:fea5:4f01/64 scope link
valid_lft forever preferred_lft forever

--
Hans

Hans wrote:
> SadOldGit wrote:
>> Hans wrote:
>>> SadOldGit wrote:
>>>> Jigs wrote:
>>>>> Hi All,
>>>>> [snip]
>>>> ping6 ?
>>>>> 2) How do I do a broadcast ping in IPv6? In v4, I just put the
>>>>> broadcast address in the destination addr fiend of the IP header and
>>>>> things worked, but what do I do for v6?
>>>> MAC address is part of the IPv6 address - no more ARP!
>>> When jou set the ip address manually it is not.
>>>
>>
>> "When IEEE 802 48bit MAC addresses are available (on an interface or a
>> node), an implementation should use them to create interface
>> identifiers due to their availability and uniqueness properties."
>> RFC2373
>>
>> OK, it doesn't say must!
>
> Should is almost must. By the way:
>
> bash-3.1# ip addr -6 show dev eth0
> 2: eth0: <BROADCAST,MULTICAST,NOTRAILERS,UP,10000> mtu 1500 qdisc
> pfifo_fast qlen 1000
> link/ether 00:11:43:61:8d:db brd ff:ff:ff:ff:ff:ff
> inet6 2001:888:1639::4/48 scope global
> valid_lft forever preferred_lft forever
> inet6 fe80::211:43ff:fe61:8ddb/64 scope link
> valid_lft forever preferred_lft forever
> bash-3.1#
>
> The global scope is mac-free, but the scope link is not. And on another
> pc of mine every bridge-port (except eth3) seems to have its own ip6
> addr whether i like it or not:
>
> bash-3.1# brctl show
> bridge name bridge id STP enabled interfaces
> br0 8000.003018a54f01 no eth0
> eth1
> eth2
> eth3
> bash-3.1# ip -6 addr show
> 1: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qlen 1000
> inet6 fe80::230:18ff:fea5:ebfd/64 scope link
> valid_lft forever preferred_lft forever
> 2: lo: <LOOPBACK,UP,10000> mtu 16436
> inet6 ::1/128 scope host
> valid_lft forever preferred_lft forever
> 3: eth1: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qlen 1000
> inet6 fe80::230:18ff:fea5:4f01/64 scope link
> valid_lft forever preferred_lft forever
> 4: eth2: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qlen 1000
> inet6 fe80::230:18ff:fea5:4f02/64 scope link
> valid_lft forever preferred_lft forever
> 7: br0: <BROADCAST,MULTICAST,UP,10000> mtu 1500
> inet6 2001:888:1639::2/48 scope global
> valid_lft forever preferred_lft forever
> inet6 fe80::230:18ff:fea5:4f01/64 scope link
> valid_lft forever preferred_lft forever
>

Thanks Hans - I must check that out on mine