[ovs-dev] [PATCH] uuid: Use current time to compute sha.

[Ben Pfaff]

On Mon, Mar 10, 2014 at 10:56:38AM -0700, Gurucharan Shetty wrote:
> Windows does not have the getppid(), getuid(), getgid() functions.
> We do get a random seed from CryptGenRandom(). That seed along with
> process id and current time hopefully is good enough.
> 
> Signed-off-by: Gurucharan Shetty <gshetty at nicira.com>

I see that there was a bug that 'now' wasn't getting folded in.  Let's
fix that for all systems, not just for Windows.

I think that this could be a little nicer by adding a function like
this:

static void
sha1_update_int(struct sha1 *sha1_ctx, uintmax_t x)
{
   sha1_update(sha1_ctx, &x, sizeof x);
}

and then we can delete the variables and the assignments and the
changes to windefs.h and just write:

    sha1_update_int(&sha1_ctx, getpid());
#ifndef _WIN32
    sha1_update_int(&sha1_ctx, getppid());
    sha1_update_int(&sha1_ctx, getuid());
    sha1_update_int(&sha1_ctx, getgid());
#endif

> ---
>  include/windows/windefs.h |    4 ++++
>  lib/uuid.c                |    6 ++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/include/windows/windefs.h b/include/windows/windefs.h
> index 6d36adc..6fde1ea 100644
> --- a/include/windows/windefs.h
> +++ b/include/windows/windefs.h
> @@ -32,4 +32,8 @@
>  #define u_int32_t uint32_t
>  #define u_int64_t uint64_t
>  
> +typedef int pid_t;
> +typedef int uid_t;
> +typedef int gid_t;
> +
>  #endif /* windefs.h */
> diff --git a/lib/uuid.c b/lib/uuid.c
> index 315c851..9ac5b55 100644
> --- a/lib/uuid.c
> +++ b/lib/uuid.c
> @@ -220,17 +220,23 @@ do_init(void)
>      get_entropy_or_die(random_seed, sizeof random_seed);
>      xgettimeofday(&now);
>      pid = getpid();
> +#ifndef _WIN32
>      ppid = getppid();
>      uid = getuid();
>      gid = getgid();
> +#endif
>  
>      /* Convert seed into key. */
>      sha1_init(&sha1_ctx);
>      sha1_update(&sha1_ctx, random_seed, sizeof random_seed);
>      sha1_update(&sha1_ctx, &pid, sizeof pid);
> +#ifndef _WIN32
>      sha1_update(&sha1_ctx, &ppid, sizeof ppid);
>      sha1_update(&sha1_ctx, &uid, sizeof uid);
>      sha1_update(&sha1_ctx, &gid, sizeof gid);
> +#else
> +    sha1_update(&sha1_ctx, &now, sizeof now);
> +#endif
>      sha1_final(&sha1_ctx, sha1);
>  
>      /* Generate key. */