selftests/bpf: Selftest for sys_bind post-hooks.

Add selftest for attach types `BPF_CGROUP_INET4_POST_BIND` and
`BPF_CGROUP_INET6_POST_BIND`.

The main things tested are:
* prog load behaves as expected (valid/invalid accesses in prog);
* prog attach behaves as expected (load- vs attach-time attach types);
* `BPF_CGROUP_INET_SOCK_CREATE` can be attached in a backward compatible
  way;
* post-hooks return expected result and errno.

Example:
  # ./test_sock
  Test case: bind4 load with invalid access: src_ip6 .. [PASS]
  Test case: bind4 load with invalid access: mark .. [PASS]
  Test case: bind6 load with invalid access: src_ip4 .. [PASS]
  Test case: sock_create load with invalid access: src_port .. [PASS]
  Test case: sock_create load w/o expected_attach_type (compat mode) ..
  [PASS]
  Test case: sock_create load w/ expected_attach_type .. [PASS]
  Test case: attach type mismatch bind4 vs bind6 .. [PASS]
  Test case: attach type mismatch bind6 vs bind4 .. [PASS]
  Test case: attach type mismatch default vs bind4 .. [PASS]
  Test case: attach type mismatch bind6 vs sock_create .. [PASS]
  Test case: bind4 reject all .. [PASS]
  Test case: bind6 reject all .. [PASS]
  Test case: bind6 deny specific IP & port .. [PASS]
  Test case: bind4 allow specific IP & port .. [PASS]
  Test case: bind4 allow all .. [PASS]
  Test case: bind6 allow all .. [PASS]
  Summary: 16 PASSED, 0 FAILED

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 11 insertions, 0 deletions

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 71051d01e8dd..9d07465023a2 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -152,6 +152,8 @@ enum bpf_attach_type {
 	BPF_CGROUP_INET6_BIND,
 	BPF_CGROUP_INET4_CONNECT,
 	BPF_CGROUP_INET6_CONNECT,
+	BPF_CGROUP_INET4_POST_BIND,
+	BPF_CGROUP_INET6_POST_BIND,
 	__MAX_BPF_ATTACH_TYPE
 };
 
@@ -947,6 +949,15 @@ struct bpf_sock {
 	__u32 protocol;
 	__u32 mark;
 	__u32 priority;
+	__u32 src_ip4;		/* Allows 1,2,4-byte read.
+				 * Stored in network byte order.
+				 */
+	__u32 src_ip6[4];	/* Allows 1,2,4-byte read.
+				 * Stored in network byte order.
+				 */
+	__u32 src_port;		/* Allows 4-byte read.
+				 * Stored in host byte order
+				 */
 };
 
 #define XDP_PACKET_HEADROOM 256