Abusing the "home" flag to force IPv6 source address selection

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


Hello,

I have googled for how to select a specific source among a number of
candidates, and have found two recommended ways based on RFC3484:

1) set the preferred address with a /128 mask on the outgoing interface

2) deprecate all other equal or better addresses by setting the
   preferred lifetime to 0

However, none of these can be used if the preferred address is coming
from a prefix delegated via DHCPv6-PD, and the uplink/WAN interface is
supposed to have a dynamically assigned (SLAAC) global address.  This is
my situation.

RFC3633 forbids using any part of the delegated prefix for the
uplink/WAN interface:

  "the requesting router MUST NOT assign any delegated prefixes or
   subnets from the delegated prefix(es) to the link through which it
   received the DHCP message from the delegating router."

so option 1) is out of the question.

And I believe there is no way to deprecate a dynamically assigned
address.  You can deprecate it, but the status will change with the next
RA received, so option 2) is out of the question as well.

So I looked for other options in RFC3484 and found that setting the
"home" flag on the preferred source address does indeed work, without
needing to change anything on the outgoing interface.  So it looks like
an excellent way to mark the preferred source address, completely
ignoring outgoing interface and prefix lengths.

However, I wonder if this has any unwanted side effects?  Exactly what
is this flag changing?  Or is it just a flag, which only affects address
selection? 

Note:  I do not use mobile IPv6, so there is no chance that this will
disturb that.



BjÃrn
--
To unsubscribe from this list: send the line "unsubscribe linux-net" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Netdev]     [Ethernet Bridging]     [Linux 802.1Q VLAN]     [Linux Wireless]     [Kernel Newbies]     [Security]     [Linux for Hams]     [Netfilter]     [Git]     [Bugtraq]     [Photo]     [Yosemite]     [Yosemite News and Information]     [MIPS Linux]     [ARM Linux]     [Linux RAID]     [Linux PCI]     [Linux Admin]     [Samba]     [Video 4 Linux]     [Linux Resources]

Add to Google