[lxc-devel] [PATCH 11/17] Use srand/rand instead of initstate/random

[Stéphane Graber]

On Fri, Aug 16, 2013 at 10:36:58AM -0500, Serge Hallyn wrote:
> Quoting Stéphane Graber (stgraber at ubuntu.com):
> > initstate/random doesn't work on bionic, srand/rand works on everything,
> > so let's use that.
> 
> Is rand_r available on bionic?
> 
> rand() isn't thread-safe.

Unfortunately no, I actually don't think Bionic has any of the _r
functions.

Is it actually a problem in this case? It looks like the worst that
could happen is that the random number generator gets re-seeded from
urandom between two calls, which would just make it even more random,
no?

> 
> > Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>
> > ---
> >  src/lxc/conf.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> > index 867a150..3d99469 100644
> > --- a/src/lxc/conf.c
> > +++ b/src/lxc/conf.c
> > @@ -288,7 +288,6 @@ static char *mkifname(char *template)
> >  	int i = 0;
> >  	FILE *urandom;
> >  	unsigned int seed;
> > -	char randstate[2048];
> >  	struct ifaddrs *ifaddr, *ifa;
> >  	int ifexists = 0;
> >  
> > @@ -304,7 +303,7 @@ static char *mkifname(char *template)
> >  	}
> >  	else
> >  		seed = time(0);
> > -	initstate(seed, randstate, 256);
> > +	srand(seed);
> >  
> >  	/* Generate random names until we find one that doesn't exist */
> >  	while(1) {
> > @@ -316,7 +315,7 @@ static char *mkifname(char *template)
> >  
> >  		for (i = 0; i < strlen(name); i++) {
> >  			if (name[i] == 'X') {
> > -				name[i] = padchar[random() % (strlen(padchar) - 1)];
> > +				name[i] = padchar[rand() % (strlen(padchar) - 1)];
> >  			}
> >  		}
> >  
> > -- 
> > 1.8.3.2
> > 
> > 
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-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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