samples/bpf: add userspace example for prohibiting sockets

Add examples preventing a process in a cgroup from opening a socket
based family, protocol and type.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 66 insertions, 0 deletions

diff --git a/samples/bpf/test_cgrp2_sock2.c b/samples/bpf/test_cgrp2_sock2.c
new file mode 100644
index 000000000000..455ef0d06e93
--- /dev/null
+++ b/samples/bpf/test_cgrp2_sock2.c
@@ -0,0 +1,66 @@
+/* eBPF example program:
+ *
+ * - Loads eBPF program
+ *
+ *   The eBPF program loads a filter from file and attaches the
+ *   program to a cgroup using BPF_PROG_ATTACH
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <unistd.h>
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <net/if.h>
+#include <linux/bpf.h>
+
+#include "libbpf.h"
+#include "bpf_load.h"
+
+static int usage(const char *argv0)
+{
+	printf("Usage: %s cg-path filter-path [filter-id]\n", argv0);
+	return EXIT_FAILURE;
+}
+
+int main(int argc, char **argv)
+{
+	int cg_fd, ret, filter_id = 0;
+
+	if (argc < 3)
+		return usage(argv[0]);
+
+	cg_fd = open(argv[1], O_DIRECTORY | O_RDONLY);
+	if (cg_fd < 0) {
+		printf("Failed to open cgroup path: '%s'\n", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	if (load_bpf_file(argv[2]))
+		return EXIT_FAILURE;
+
+	printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
+
+	if (argc > 3)
+		filter_id = atoi(argv[3]);
+
+	if (filter_id > prog_cnt) {
+		printf("Invalid program id; program not found in file\n");
+		return EXIT_FAILURE;
+	}
+
+	ret = bpf_prog_attach(prog_fd[filter_id], cg_fd,
+			      BPF_CGROUP_INET_SOCK_CREATE);
+	if (ret < 0) {
+		printf("Failed to attach prog to cgroup: '%s'\n",
+		       strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	return EXIT_SUCCESS;
+}