selftests/bpf: Remove the "/sys" mount and umount dance in {open,close}_netns

The previous patches have removed the need to do the mount and umount
dance when switching netns. In particular:
* Avoid remounting /sys/fs/bpf to have a clean start
* Avoid remounting /sys to get a ifindex of a particular netns

This patch can finally remove the mount and umount dance in
{open,close}_netns which is unnecessarily complicated and
error-prone.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20221129070900.3142427-6-martin.lau@linux.dev

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index 1f37adf..01de331 100644 (file)
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -390,49 +390,6 @@ struct nstoken {
        int orig_netns_fd;
 };
 
-static int setns_by_fd(int nsfd)
-{
-       int err;
-
-       err = setns(nsfd, CLONE_NEWNET);
-       close(nsfd);
-
-       if (!ASSERT_OK(err, "setns"))
-               return err;
-
-       /* Switch /sys to the new namespace so that e.g. /sys/class/net
-        * reflects the devices in the new namespace.
-        */
-       err = unshare(CLONE_NEWNS);
-       if (!ASSERT_OK(err, "unshare"))
-               return err;
-
-       /* Make our /sys mount private, so the following umount won't
-        * trigger the global umount in case it's shared.
-        */
-       err = mount("none", "/sys", NULL, MS_PRIVATE, NULL);
-       if (!ASSERT_OK(err, "remount private /sys"))
-               return err;
-
-       err = umount2("/sys", MNT_DETACH);
-       if (!ASSERT_OK(err, "umount2 /sys"))
-               return err;
-
-       err = mount("sysfs", "/sys", "sysfs", 0, NULL);
-       if (!ASSERT_OK(err, "mount /sys"))
-               return err;
-
-       err = mount("bpffs", "/sys/fs/bpf", "bpf", 0, NULL);
-       if (!ASSERT_OK(err, "mount /sys/fs/bpf"))
-               return err;
-
-       err = mount("debugfs", "/sys/kernel/debug", "debugfs", 0, NULL);
-       if (!ASSERT_OK(err, "mount /sys/kernel/debug"))
-               return err;
-
-       return 0;
-}
-
 struct nstoken *open_netns(const char *name)
 {
        int nsfd;
@@ -453,8 +410,9 @@ struct nstoken *open_netns(const char *name)
        if (!ASSERT_GE(nsfd, 0, "open netns fd"))
                goto fail;
 
-       err = setns_by_fd(nsfd);
-       if (!ASSERT_OK(err, "setns_by_fd"))
+       err = setns(nsfd, CLONE_NEWNET);
+       close(nsfd);
+       if (!ASSERT_OK(err, "setns"))
                goto fail;
 
        return token;
@@ -465,6 +423,7 @@ fail:
 
 void close_netns(struct nstoken *token)
 {
-       ASSERT_OK(setns_by_fd(token->orig_netns_fd), "setns_by_fd");
+       ASSERT_OK(setns(token->orig_netns_fd, CLONE_NEWNET), "setns");
+       close(token->orig_netns_fd);
        free(token);
 }