It's straightforward to determine if an IP address is link-local or not
- for an already configured address.
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
state UP qlen 1000
link/ether 94:db:c9:3f:7c:20 brd ff:ff:ff:ff:ff:ff
inet 10.10.10.30/24 brd 10.10.10.255 *scope global* eth1
inet6 fe80::96db:c9ff:fe3f:7c20/64 *scope link *
valid_lft forever preferred_lft forever
This works uniformly for both ipv4 and ipv6 addresses (quite nice!)
However, for addresses which are not yet up (which is unfortunately what
you're concerned with), ipv6 link-local addresses take the form
fe80:: -- followed by 64-bits of MAC addresses (48 bit
MACs are padded out)
http://en.wikipedia.org/wiki/Link-local_address
MAC addresses never begin with 4 bytes of zeros, so the regular
expression to match this is pretty straightforward. This isn't a bad
approximation (but could easily be made better):
islinklocal() {
if
echo $1 | grep -i '^fe80::[^:]*:[^:]*:[^:]*:[^:]*$' >/dev/null
then
echo "$1 is link-local"
else
echo "$1 is NOT link-local"
fi
}
On 05/31/2012 12:29 AM, Keisuke MORI wrote:
> I would like to propose an enhancement of IPaddr2 to support IPv6 as
> well as IPv4.
>
> I've submitted this as a pull request #97 but also posting to the ML
> for a wider audience.
>
> I would appreciate your comments and suggestions for merging this into
> the upstream.
>
> ----
> [RFC] IPaddr2: Proposal patch to support the dual stack of IPv4 and IPv6.
> https://github.com/ClusterLabs/resource-agents/pull/97
>
>
> ## Benefits:
>
> * Unify the usage, behavior and the code maintenance between IPv4 and
> IPv6 on Linux.
>
> The usage of IPaddr2 and IPv6addr are similar but they have
> different parameters and different behaviors.
> In particular, they may choose a different interface depending
> on your configuration even if you provided similar parameters
> in the past.
>
> IPv6addr is written in C and rather hard to make improvements.
> As /bin/ip already supports both IPv4 and IPv6, we can share
> the most of the code of IPaddr2 written in bash.
>
> * usable for LVS on IPv6.
>
> IPv6addr does not support lvs_support=true and unfortunately
> there is no possible way to use LVS on IPv6 right now.
>
> IPaddr2(/bin/ip) works for LVS configurations without
> enabling lvs_support both for IPv4 and IPv6.
>
> (You don't have to remove an address on the loopback interface
> if the virtual address is assigned by using /bin/ip.)
>
> See also:
> http://www.gossamer-threads.com/lists/linuxha/dev/76429#76429
>
> * retire the old 'findif' binary.
>
> 'findif' binary is replaced by a shell script version of
> findif, originally developed by lge.
> See findif could be rewritten in shell :
> https://github.com/ClusterLabs/resource-agents/issues/53
>
> * easier support for other pending issues
>
> These pending issues can be fix based on this new IPaddr2.
> * Allow ipv6addr to mark new address as deprecated
> https://github.com/ClusterLabs/resource-agents/issues/68
> * New RA that controls IPv6 address in loopback interface
> https://github.com/ClusterLabs/resource-agents/pull/77
>
>
> ## Notes / Changes:
>
> * findif semantics changes
>
> There are some incompatibility in deciding which interface to
> be used when your configuration is ambiguous. But in reality
> it should not be a problem as long as it's configured properly.
>
> The changes mostly came from fixing a bug in the findif binary
> (returns a wrong broadcast) or merging the difference between
> (old)IPaddr2 and IPv6addr.
> See the ofct test cases for details.
> (case No.6, No.9, No.10, No.12, No.15 in IPaddr2v4 test cases)
>
> Other notable changes are described below.
>
> * "broadcast" parameter for IPv4
>
> "broadcast" parameter may be required along with "cidr_netmask"
> when you want use a different subnet mask from the static IP address.
> It's because doing such calculation is difficult in the shell
> script version of findif.
>
> See the ofct test cases for details.
> (case No.11, No.14, No.16, No.17 in IPaddr2v4 test cases)
>
> This limitation may be eliminated if we would remove
> brd options from the /bin/ip command line.
>
> * loopback(lo) now requires cidr_netmask or broadcast.
>
> See the ofct test case in the IPaddr2 ocft script.
> The reason is similar to the previous one.
>
> * loose error check for "nic" for a IPv6 link-local address.
>
> IPv6addr was able to check this, but in the shell script it is
> hard to determine a link-local address (requires bitmask calculation).
> I do not think it's worth to implement it in shell.
>
> * send_ua: a new binary
>
> We need one new binary as a replacement of send_arp for IPv6 support.
> IPv6addr.c is reused to make this command.
>
>
> Note that IPv6addr RA is still there and you can continue to use
> it for the backward compatibility.
>
>
> ## Acknowledgement
>
> Thanks to Tomo Nozawa-san for his hard work for writing and
> testing this patch.
>
> Thanks to Lars Ellenberg for the first findif.sh implementation.
> ----
>
> Best Regards,
>
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