Re: [PATCH bpf-next v1 2/2] selftests: bpf: read netns from struct bpf_sock_ops

[Song Liu <liu.song.a23@gmail.com>]

On Fri, Apr 12, 2019 at 3:02 AM Alban Crequy <alban.crequy@gmail.com> wrote:
>
> From: Alban Crequy <alban@kinvolk.io>
>
> This shows how a sockops program could be restricted to a specific
> network namespace. The sockops program looks at the current netns via
> (struct bpf_sock_ops)->netns and checks if the value matches the
> configuration in the new BPF map "sock_netns".
>
> The test program ./test_sockmap accepts a new parameter "--netns"; the
> default value is the current netns found by stat() on /proc/self/ns/net,
> so the previous tests still pass:
>
> sudo ./test_sockmap
> ...
> Summary: 412 PASSED 0 FAILED
> ...
> Summary: 824 PASSED 0 FAILED
>
> I run my additional test in the following way:
>
> NETNS=$(readlink /proc/self/ns/net | sed 's/^net:\[\(.*\)\]$/\1/')
> CGR=/sys/fs/cgroup/unified/user.slice/user-1000.slice/session-5.scope/
> sudo ./test_sockmap --cgroup $CGR --netns $NETNS &
>
> cat /sys/kernel/debug/tracing/trace_pipe
>
> echo foo | nc -l 127.0.0.1 8080 &
> echo bar | nc 127.0.0.1 8080
>
> => the connection goes through the sockmap
>
> When testing with a wrong $NETNS, I get the trace_pipe log:
> > not binding connection on netns 4026531992
>
> Signed-off-by: Alban Crequy <alban@kinvolk.io>

Acked-by: Song Liu <songliubraving@fb.com>

I think we should also add verifier tests for this?

Thanks,
Song

> ---
>  tools/include/uapi/linux/bpf.h                |  1 +
>  tools/testing/selftests/bpf/test_sockmap.c    | 38 +++++++++++++++++--
>  .../testing/selftests/bpf/test_sockmap_kern.h | 19 ++++++++++
>  3 files changed, 55 insertions(+), 3 deletions(-)
>
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 31a27dd337dc..5afaab25f205 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -3069,6 +3069,7 @@ struct bpf_sock_ops {
>         __u32 sk_txhash;
>         __u64 bytes_received;
>         __u64 bytes_acked;
> +       __u64 netns;
>  };
>
>  /* Definitions for bpf_sock_ops_cb_flags */
> diff --git a/tools/testing/selftests/bpf/test_sockmap.c b/tools/testing/selftests/bpf/test_sockmap.c
> index 3845144e2c91..5a1b9c96fca1 100644
> --- a/tools/testing/selftests/bpf/test_sockmap.c
> +++ b/tools/testing/selftests/bpf/test_sockmap.c
> @@ -2,6 +2,7 @@
>  // Copyright (c) 2017-2018 Covalent IO, Inc. http://covalent.io
>  #include <stdio.h>
>  #include <stdlib.h>
> +#include <stdint.h>
>  #include <sys/socket.h>
>  #include <sys/ioctl.h>
>  #include <sys/select.h>
> @@ -21,6 +22,7 @@
>  #include <sys/resource.h>
>  #include <sys/types.h>
>  #include <sys/sendfile.h>
> +#include <sys/stat.h>
>
>  #include <linux/netlink.h>
>  #include <linux/socket.h>
> @@ -63,8 +65,8 @@ int s1, s2, c1, c2, p1, p2;
>  int test_cnt;
>  int passed;
>  int failed;
> -int map_fd[8];
> -struct bpf_map *maps[8];
> +int map_fd[9];
> +struct bpf_map *maps[9];
>  int prog_fd[11];
>
>  int txmsg_pass;
> @@ -84,6 +86,7 @@ int txmsg_ingress;
>  int txmsg_skb;
>  int ktls;
>  int peek_flag;
> +uint64_t netns_opt;
>
>  static const struct option long_options[] = {
>         {"help",        no_argument,            NULL, 'h' },
> @@ -111,6 +114,7 @@ static const struct option long_options[] = {
>         {"txmsg_skb", no_argument,              &txmsg_skb, 1 },
>         {"ktls", no_argument,                   &ktls, 1 },
>         {"peek", no_argument,                   &peek_flag, 1 },
> +       {"netns",       required_argument,      NULL, 'n'},
>         {0, 0, NULL, 0 }
>  };
>
> @@ -1585,6 +1589,7 @@ char *map_names[] = {
>         "sock_bytes",
>         "sock_redir_flags",
>         "sock_skb_opts",
> +       "sock_netns",
>  };
>
>  int prog_attach_type[] = {
> @@ -1619,6 +1624,8 @@ static int populate_progs(char *bpf_file)
>         struct bpf_object *obj;
>         int i = 0;
>         long err;
> +       struct stat netns_sb;
> +       uint64_t netns_ino;
>
>         obj = bpf_object__open(bpf_file);
>         err = libbpf_get_error(obj);
> @@ -1655,6 +1662,28 @@ static int populate_progs(char *bpf_file)
>                 }
>         }
>
> +       if (netns_opt == 0) {
> +               err = stat("/proc/self/ns/net", &netns_sb);
> +               if (err) {
> +                       fprintf(stderr,
> +                               "ERROR: cannot stat network namespace: %ld (%s)\n",
> +                               err, strerror(errno));
> +                       return -1;
> +               }
> +               netns_ino = netns_sb.st_ino;
> +       } else {
> +               netns_ino = netns_opt;
> +       }
> +       i = 1;
> +       err = bpf_map_update_elem(map_fd[8], &netns_ino, &i, BPF_ANY);
> +       if (err) {
> +               fprintf(stderr,
> +                       "ERROR: bpf_map_update_elem (netns):  %ld (%s)\n",
> +                       err, strerror(errno));
> +               return -1;
> +       }
> +
> +
>         return 0;
>  }
>
> @@ -1738,7 +1767,7 @@ int main(int argc, char **argv)
>         if (argc < 2)
>                 return test_suite(-1);
>
> -       while ((opt = getopt_long(argc, argv, ":dhvc:r:i:l:t:p:q:",
> +       while ((opt = getopt_long(argc, argv, ":dhvc:r:i:l:t:p:q:n:",
>                                   long_options, &longindex)) != -1) {
>                 switch (opt) {
>                 case 's':
> @@ -1805,6 +1834,9 @@ int main(int argc, char **argv)
>                                 return -1;
>                         }
>                         break;
> +               case 'n':
> +                       netns_opt = strtoull(optarg, NULL, 10);
> +                       break;
>                 case 0:
>                         break;
>                 case 'h':
> diff --git a/tools/testing/selftests/bpf/test_sockmap_kern.h b/tools/testing/selftests/bpf/test_sockmap_kern.h
> index e7639f66a941..3bad9c70376b 100644
> --- a/tools/testing/selftests/bpf/test_sockmap_kern.h
> +++ b/tools/testing/selftests/bpf/test_sockmap_kern.h
> @@ -91,6 +91,13 @@ struct bpf_map_def SEC("maps") sock_skb_opts = {
>         .max_entries = 1
>  };
>
> +struct bpf_map_def SEC("maps") sock_netns = {
> +       .type = BPF_MAP_TYPE_HASH,
> +       .key_size = sizeof(__u64),
> +       .value_size = sizeof(int),
> +       .max_entries = 16
> +};
> +
>  SEC("sk_skb1")
>  int bpf_prog1(struct __sk_buff *skb)
>  {
> @@ -132,9 +139,21 @@ int bpf_sockmap(struct bpf_sock_ops *skops)
>  {
>         __u32 lport, rport;
>         int op, err = 0, index, key, ret;
> +       int i = 0;
> +       __u64 netns;
> +       int *allowed;
>
>
>         op = (int) skops->op;
> +       netns = skops->netns;
> +       bpf_printk("bpf_sockmap: netns = %lu\n", netns);
> +
> +       // Only allow sockmap connection on the configured network namespace
> +       allowed = bpf_map_lookup_elem(&sock_netns, &netns);
> +       if (allowed == NULL || *allowed == 0) {
> +               bpf_printk("not binding connection on netns %lu\n", netns);
> +               return 0;
> +       }
>
>         switch (op) {
>         case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
> --
> 2.20.1
>