[lxc-devel] [PATCH 1/2] command socket: use hash if needed

[S.Çağlar Onur]

Hey Serge,

On Fri, Aug 8, 2014 at 8:28 PM, Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> The container command socket is an abstract unix socket containing
> the lxcpath and container name.  Those can be too long.  In that case,
> use the hash of the lxcpath and lxcname.  Continue to use the path and
> name if possible to avoid any back compat issues.

Last time I tried this [1] I ended up breaking list_active_containers
as it parses /proc/unix/net, do we still have that problem?

[1] https://lists.linuxcontainers.org/pipermail/lxc-devel/2014-February/008145.html

Cheers,

> Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
> ---
>  src/lxc/commands.c | 32 +++++++++++++++++++++++++++-----
>  1 file changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/src/lxc/commands.c b/src/lxc/commands.c
> index 458d41e..f46efc5 100644
> --- a/src/lxc/commands.c
> +++ b/src/lxc/commands.c
> @@ -28,6 +28,7 @@
>  #include <fcntl.h>
>  #include <poll.h>
>  #include <sys/socket.h>
> +#include <inttypes.h>
>  #include <sys/un.h>
>  #include <sys/param.h>
>  #include <malloc.h>
> @@ -74,24 +75,45 @@
>  lxc_log_define(lxc_commands, lxc);
>
>  static int fill_sock_name(char *path, int len, const char *name,
> -                         const char *inpath)
> +                         const char *lxcpath)
>  {
> -       const char *lxcpath = NULL;
> +       char *tmppath;
> +       size_t tmplen;
> +       uint64_t hash;
>         int ret;
>
> -       if (!inpath) {
> +       if (!lxcpath) {
>                 lxcpath = lxc_global_config_value("lxc.lxcpath");
>                 if (!lxcpath) {
>                         ERROR("Out of memory getting lxcpath");
>                         return -1;
>                 }
>         }
> -       ret = snprintf(path, len, "%s/%s/command", lxcpath ? lxcpath : inpath, name);
> +
> +       ret = snprintf(path, len, "%s/%s/command", lxcpath, name);
>
> +       if (ret < 0) {
> +               ERROR("Error writing to command sock path");
> +               return -1;
> +       }
> +       if (ret < len)
> +               return 0;
> +
> +       /* ret >= len; lxcpath or name is too long.  hash both */
> +       tmplen = strlen(name) + strlen(lxcpath) + 2;
> +       tmppath = alloca(tmplen);
> +       ret = snprintf(tmppath, tmplen, "%s/%s", lxcpath, name);
> +       if (ret < 0 || ret >= tmplen) {
> +               ERROR("memory error");
> +               return -1;
> +       }
> +       hash = fnv_64a_buf(tmppath, ret, FNV1A_64_INIT);
> +       ret = snprintf(path, len, "lxc/%016" PRIx64 "/cmd_sock", hash);
>         if (ret < 0 || ret >= len) {
> -               ERROR("Name too long");
> +               ERROR("Command socket name too long");
>                 return -1;
>         }
> +
>         return 0;
>  }
>
> --
> 2.1.0.rc1
>
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> lxc-devel at lists.linuxcontainers.org
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-- 
S.Çağlar Onur <caglar at 10ur.org>