netdev - Re: [PATCH bpf-next 2/2] samples: bpf: get ifindex from ifname

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Date:   Thu, 18 Oct 2018 22:34:51 -0700
From:   Y Song <ys114321@...il.com>
To:     mcroce@...hat.com
Cc:     netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next 2/2] samples: bpf: get ifindex from ifname

On Thu, Oct 18, 2018 at 1:48 PM Matteo Croce <mcroce@...hat.com> wrote:
>
> Find the ifindex via ioctl(SIOCGIFINDEX) instead of requiring the
> numeric ifindex.

Maybe use if_nametoindex which is simpler?

>
> Signed-off-by: Matteo Croce <mcroce@...hat.com>
> ---
>  samples/bpf/xdp1_user.c | 26 ++++++++++++++++++++++++--
>  1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/samples/bpf/xdp1_user.c b/samples/bpf/xdp1_user.c
> index 4f3d824fc044..a1d0c5dcee9c 100644
> --- a/samples/bpf/xdp1_user.c
> +++ b/samples/bpf/xdp1_user.c
> @@ -15,6 +15,9 @@
>  #include <unistd.h>
>  #include <libgen.h>
>  #include <sys/resource.h>
> +#include <sys/ioctl.h>
> +#include <sys/socket.h>
> +#include <linux/if.h>
>
>  #include "bpf_util.h"
>  #include "bpf/bpf.h"
> @@ -59,7 +62,7 @@ static void poll_stats(int map_fd, int interval)
>  static void usage(const char *prog)
>  {
>         fprintf(stderr,
> -               "usage: %s [OPTS] IFINDEX\n\n"
> +               "usage: %s [OPTS] IFACE\n\n"
>                 "OPTS:\n"
>                 "    -S    use skb-mode\n"
>                 "    -N    enforce native mode\n",
> @@ -74,9 +77,11 @@ int main(int argc, char **argv)
>         };
>         const char *optstr = "SN";
>         int prog_fd, map_fd, opt;
> +       struct ifreq ifr = { 0 };
>         struct bpf_object *obj;
>         struct bpf_map *map;
>         char filename[256];
> +       int sock;
>
>         while ((opt = getopt(argc, argv, optstr)) != -1) {
>                 switch (opt) {
> @@ -102,7 +107,24 @@ int main(int argc, char **argv)
>                 return 1;
>         }
>
> -       ifindex = strtoul(argv[optind], NULL, 0);
> +       sock = socket(AF_UNIX, SOCK_DGRAM, 0);
> +       if (sock == -1) {
> +               perror("socket");
> +               return 1;
> +       }
> +
> +       if (strlen(argv[optind]) >= IFNAMSIZ) {
> +               printf("invalid ifname '%s'\n", argv[optind]);
> +               return 1;
> +       }
> +
> +       strcpy(ifr.ifr_name, argv[optind]);
> +       if (ioctl(sock, SIOCGIFINDEX, &ifr) < 0) {
> +               perror("SIOCGIFINDEX");
> +               return 1;
> +       }
> +       close(sock);
> +       ifindex = ifr.ifr_ifindex;
>
>         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
>         prog_load_attr.file = filename;
> --
> 2.19.1
>