RE: [Xen-devel] [PATCH] get dhcp working for network-nat (Take 2)

["Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>]

I just noticed a small bug in this that could cause some problems,
but am not sure how to fix it.  It seems that when a domain
is "xm destroy'ed" the cleanup method dhcp_remove_entry() is
invoked, but this doesn't happen when a domain exits (or
reboots) on its own accord.  This is especially noticeable for
domains that have "on_reboot=restart"... the DHCPDARGS= line
in /etc/sysconfig/dhcpd (Redhat-ish systems) grows fairly long.

As far as I can tell, this is just a minor annoyance but I thought
I would report it for posterity or in case anyone else sees
this turn into a real problem.

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx]On Behalf Of Dan
> Magenheimer
> Sent: Wednesday, January 23, 2008 4:29 PM
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] [PATCH] get dhcp working for network-nat (Take 2)
> 
> 
> I fixed up the previous patch to resolve a couple of problems and
> make a couple of things more automatic. The patch now works on
> RHEL5, SLES10, and Ubuntu7.04, and applies to xen-unstable.  With
> this patch, it is now (relatively) easy to use dom0 as a DHCP
> server for all domU's running on the machine.
> 
> Please apply.
> 
> Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
> 
> Thanks,
> Dan
> 
> P.S. Here's the manual steps required to to get it to work.
> 
> 1) Install the dhcp package on dom0 using your distro's tools
> 2) Modify /etc/dhcpd.conf to look like this:
>       ddns-update-style interim;
>       deny client-updates;
>       authoritative;
>       option domain-name-servers dnsip1 dnsip2;
>       option ntp-servers ntpip1 ntpip2 ntpip3;
>       default-lease-time 14400;
>       max-lease-time 172800;
>    where dnsip1 etc are of course all real IPv4 addresses.
>    The ntp-servers line can be removed if desired.  A subnet
>    line for 10.0.0.0/8 is added automagically by the tools.
> 3) Modify /etc/xen/xend-config.sxp
>    - comment the line (network-script network-bridge)
>    - comment the line (vif-script vif-bridge)
>    - uncomment (network-script network-nat)
>    - uncomment (vif-script vif-nat)
> 4) Reboot or restart xend
> 5) Launch a domain for which the primary interface
>    is configured for dhcp
>    - change name= in your config file to something
>      useful first as this will be the machine name
>      given to it by dhcp
> 6) Try out networking in your VM!
> 
> > -----Original Message-----
> > From: Dan Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx]
> > Sent: Wednesday, January 16, 2008 3:49 PM
> > To: 'xen-devel@xxxxxxxxxxxxxxxxxxx'
> > Subject: [PATCH] get dhcp working for network-nat
> > 
> > 
> > Has anybody successfully used the network-nat script, with 
> or without
> > dhcp?  The existing documentation around this is fairly poor, so if
> > youâve seen it âjust workâ (or with only some minor tweaks),
> > please reply.  Iâm not much of a networking expert so I hope my
> > time on this wasnât wasted.
> > 
> > Assuming not (and supported by google search), perhaps 
> network-nat has
> > been broken for a long time?  It certainly has not received 
> much love
> > recently and many mailing list queries about it have gone 
> unanswered.
> > 
> > That said, here's my situation:
> > 
> > Due to limited IP availability in my office, I wanted to configure a
> > setup where dom0 works like an inexpensive home router 
> (e.g. Linksys,
> > Dlink,Belkin), which does NAT and DHCP for multiple attached (or
> > wireless) machines.  So I need dom0 to both provide network address
> > translation and to serve dhcp addresses to any VM's launched on it.
> > 
> > It appears that this should work.  Or maybe once upon a time it did
> > work.  But I had to muck around with it quite a bit and spin a patch
> > to get it work with 3.1 bits.  And since the key files haven't been
> > changed in over a year, though untested as of yet, I think the same
> > patch and process is necessary on xen-unstable.
> > 
> > Also, this is tested on a RHEL5-based dom0.  I don't know much about
> > dhcp implementations on other distros and haven't tried this recipe
> > on other distros, so your mileage may vary but please do provide
> > feedback if this patch will fail on your favorite distro.
> > 
> > Here's the process I used:
> > 1) Install the dhcp package using your distro's tools
> > 2) Modify /etc/dhcpd.conf to look like this:
> >     ddns-update-style interim;
> >     deny client-updates;
> >     authoratitive;
> >     option domain-name-servers dnsip1 dnsip2;
> >     option ntp-servers ntpip1 ntpip2 ntpip3;
> >     default-lease-time 14400;
> >     max-lease-time 172800;
> >     subnet 10.0.0.0 netmask 255.0.0.0 {}
> >    where dnsip1 etc are of course all real IPv4 addresses.
> >    The ntp-servers line can be removed if desired.
> > 3) Apply the attached patch.  The patch applies to
> >    xen-3.1-testing.hg and you will need to apply
> >    it to the same files in /etc/xen/scripts.
> > 4) Modify /etc/xen/xend-config.sxp
> >    - comment the line (network-script network-bridge)
> >    - comment the line (vif-script vif-bridge)
> >    - uncomment (network-script network-nat)
> >    - uncomment (vif-script vif-nat)
> > 5) Modify /etc/xen/scripts/network-nat
> >    - change dhcp=${dhcp:-no} from no to yes
> > 6) Modify /etc/xen/scripts/vif-nat
> >    - change dhcp=${dhcp:-no} from no to yes
> > 7) Restart xend (probably "service xend restart")
> > 8) Launch a domain for which the primary interface
> >    is configured for dhcp (pv and pvhvm tested so
> >    far; don't know if hvm works yet)
> >    - change name= in your config file to something
> >      useful first as this will be the machine name
> >      given to it by dhcp
> > 9) Try out networking in your VM!
> > 
> > This patch could use some tweaking... the code to add
> > and remove vifâs from /etc/sysconfig/dhcpd needs some
> > work.  But I thought it would be good to get others
> > trying this version out.  If the patch doesnât work
> > on your distro, this is a good place to tweak.
> > 
> > Finally, Iâm not sure if nat without dhcp is used much.
> > Iâd like to propose that the default for dhcp (see steps
> > 5 and 6) be changed from no to yes.
> > 
> > Thanks for any feedback!
> > Dan
> > 
>

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