On 12/9/2019 4:35 AM, jpb...@westvi.com wrote:
Hi -
How you want to incorporate IPv6 into LFS is your choice, of course -
my goal was to provide a 'nudge' to actually incorporating it, as I
think it needs to be included.
Nudge accepted. Thank you. :-)
For example, I agree that the /etc/sysconfig/network file is annoying
and can be easily ignored. If someone runs into that need (which is
highly unlikely) they can deal with it. I also agree that no specific
DNS provider should be mentioned in any reference to resolv.conf - my
note I emailed indicated what I, in particular, did.
My comment was in reference to the book, not your hint. We list Google's
IPv4 addresses in a note box.
Having said that, I admit to confusion as to the suggestion to use an
interface alias for the IPv6 configuration, because the concept no
longer exists in iproute2.Interface aliases are a concept from
net-tools, last updated (outside of BSD) in 2011, and the new Linux
package, iproute2 (which is what LFS uses) doesn't provide such
functionality, because it natively allows multiple addresses on a
single interface, without needing the interface alias concept. In
fact, supporting IPv6 requires this. (Yes, ipconfig is still used in
BSD - but not Linux.)
It still exists, but it is only there for backwards compatibility. I had
forgotten that as I hadn't used it in a long time. Thank you for
bringing it to my attention. We should probably consider killing the
ifup/ifdown dependency on the full name of the configuration file. Grab
`for IFACE in $@; do ls /etc/sysconfig/ifconfig-${$IFACE}{,.*} | sort
-u;....` or some such (and 'sort -ur' for ifdown), that way you can do
something like 'ifup eth0 eth1' if desired (drop a continue in there for
*.bak). I'll take a quick look at it in a couple of days unless you (and
no pressure here, just offering if you'd like since it is already fresh
in your memory), or somebody else has a quick suggestion.
So, the creation of 'ipv46-static' followed from a chain of
requirements. There could definitely be a flaw in the chain of
reasoning shown below, but I don't see that.
a) We use iproute2, not net-tools.
b) iproute2 doesn't have interface aliases - and the use of 'labels'
to try to 'feel like it' is a very ugly concept and doesn't mesh well
with the needs of /sbin/if[up,down] etc.
c) the network configuration model of LFS is a directory of
per-interface files named "ifconfig.<interfacename>' that are
referenced by the 'network' script in /etc/init.d
d) (b) and (c) combine to make it necessary that all of an interface's
network configuration be in one file, such as ifconfig.eth0
e) The "networks" script used by 'ifup' and 'ifdown' reference a
*single* service script.
f) (d) and (e) combine to require a script combining both IPv4&IPv6 -
ipv46-static.
All of the above is incorrect in that the functionality still exists,
but again, I had no idea that it was only there for backwards
compatibility. I had also forgotten that the ":x" get's dropped. I'm
thinking we should use ifconfig-${1}{,.whatever_except.bak}.
I'll add one other reason: Some other packages that reference netfilter
I don't think that is valid as it drops the extension, but perhaps I'm
misunderstanding. Either way, ifup and ifdown need a little TLC - good
catch there.
The reason for changes in "/sbin/ifdown" can now be understood:
/sbin/ifdown will bring the interface *down* if no
non-local/non-link-local addresses exist on it after at the end of
running the "service" script. I did this because this (in my mind)
most approximates what a user would want to see if they type "ifdown
eth0"
I hope this note better explains why I created ipv46-static.
Oh, it does. Thanks for the detailed explanation. I'm still of the mind
that they should be separated, but your choice of having a separate
dual-stack service file makes much more sense now. Again, for the
additional text in the book, I'd use the private range fdxx::/8 (this is
the closest equivalent to 10.0.0.0/8, private, not routable, don't
inadvertently open to the outside world, etc.). Something like
fd12:3456:789a:1::2/64. Regardless of whether the static example goes
into the book, at very least, disabling RD should be mentioned (a
potential security threat if your router is not setup correctly).
--DJ
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