[lxc-devel] [PATCH] hwaddr templating

[Serge Hallyn]

Quoting Serge Hallyn (serge.hallyn at ubuntu.com):
> Quoting Guillaume ZITTA (lxc at zitta.fr):
> > This change introduce mac address templating.
> > 
> > By setting lxc.network.hwaddr to something like fe:xx:xx:xx:xx:xx
> > each "x" will be replaced by a random value.
> > If less significant bit of first byte is "templated", it will be
> > set to 0.
> > 
> > This chage introduce also a common randinit() function that could be
> > used to initialize random generator.
> > 
> > Signed-off-by: gza <lxc at zitta.fr>
> > ---
> >  doc/lxc.conf.sgml.in |  4 +++-
> >  src/lxc/confile.c    | 36 ++++++++++++++++++++++++++++++++++--
> >  src/lxc/utils.c      | 22 ++++++++++++++++++++++
> >  src/lxc/utils.h      |  2 ++
> >  4 files changed, 61 insertions(+), 3 deletions(-)
> > 
> > diff --git a/doc/lxc.conf.sgml.in b/doc/lxc.conf.sgml.in
> > index e6d9689..4bbeeeb 100644
> > --- a/doc/lxc.conf.sgml.in
> > +++ b/doc/lxc.conf.sgml.in
> > @@ -326,7 +326,9 @@ Foundation, Inc., 51 Franklin Street, Fifth
> > Floor, Boston, MA 02110-1301 USA
> >  	      the interface mac address is dynamically allocated by
> >  	      default to the virtual interface, but in some cases,
> >  	      this is needed to resolve a mac address conflict or to
> > -	      always have the same link-local ipv6 address
> > +	      always have the same link-local ipv6 address.
> > +	      Any "x" in address will be replaced by random value,
> > +	      this allows setting hwaddr templates.
> >  	    </para>
> >  	  </listitem>
> >  	</varlistentry>
> > diff --git a/src/lxc/confile.c b/src/lxc/confile.c
> > index 0982b3e..3d7554a 100644
> > --- a/src/lxc/confile.c
> > +++ b/src/lxc/confile.c
> > @@ -508,6 +508,28 @@ static int macvlan_mode(int *valuep, const char
> > *value)
> >  	return -1;
> >  }
> > 
> > +static int rand_complete_hwaddr(char *hwaddr)
> > +{
> > +	const char hex[] = "0123456789abcdef";
> > +	char *curs = hwaddr;
> > +
> > +	randinit();
> > +
> > +	while (*curs != '\0')
> > +	{
> > +		if ( *curs == 'x' || *curs == 'X' ) {
> > +			if (curs - hwaddr == 1) {
> > +				//ensure address is unicast
> > +				*curs = hex[(rand() & 0x0E)];
> > +			} else {
> > +				*curs = hex[rand() & 0x0F];
> > +			}
> > +		}
> > +		curs++;
> > +	}
> > +	return 0;
> > +}
> > +
> >  static int config_network_flags(const char *key, const char *value,
> >  				struct lxc_conf *lxc_conf)
> >  {
> > @@ -575,11 +597,21 @@ static int config_network_hwaddr(const char
> > *key, const char *value,
> >  {
> >  	struct lxc_netdev *netdev;
> > 
> > -	netdev = network_netdev(key, value, &lxc_conf->network);
> > +	char *newval = strdup(value);
> 
> Since this is strdup'd,
> 
> > +
> > +	rand_complete_hwaddr(newval);
> > +
> > +	netdev = network_netdev(key, newval, &lxc_conf->network);
> >  	if (!netdev)
> 
> this error path needs to free it,
> 
> >  		return -1;
> > 
> > -	return config_string_item(&netdev->hwaddr, value);
> > +	if (!newval || strlen(newval) == 0) {
> > +		netdev->hwaddr = NULL;
> 
> as does this one in the case where newval != NULL.

To be less terse: once you add this, it looks good, thanks.