linux-kernel - [PATCH bpf-next 2/2] bpf: Add a selftest for the tracing bpf_get_socket

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Date:   Thu, 26 Nov 2020 18:02:12 +0100
From:   Florent Revest <revest@...omium.org>
To:     bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kpsingh@...omium.org, revest@...gle.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next 2/2] bpf: Add a selftest for the tracing bpf_get_socket_cookie

This builds up on the existing socket cookie test which checks whether
the bpf_get_socket_cookie helpers provide the same value in
cgroup/connect6 and sockops programs for a socket created by the
userspace part of the test.

Adding a tracing program to the existing objects requires a different
attachment strategy and different headers.

Signed-off-by: Florent Revest <revest@...gle.com>
---
 .../selftests/bpf/progs/socket_cookie_prog.c  | 41 ++++++++++++++++---
 .../selftests/bpf/test_socket_cookie.c        | 18 +++++---
 2 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/socket_cookie_prog.c b/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
index 0cb5656a22b0..a11026aeaaf1 100644
--- a/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
+++ b/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
@@ -1,11 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (c) 2018 Facebook
 
-#include <linux/bpf.h>
-#include <sys/socket.h>
+#include "vmlinux.h"
 
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_endian.h>
+#include <bpf/bpf_tracing.h>
+
+#define AF_INET6 10
 
 struct socket_cookie {
 	__u64 cookie_key;
@@ -19,6 +21,14 @@ struct {
 	__type(value, struct socket_cookie);
 } socket_cookies SEC(".maps");
 
+/*
+ * These three programs get executed in a row on connect() syscalls. The
+ * userspace side of the test creates a client socket, issues a connect() on it
+ * and then checks that the local storage associated with this socket has:
+ * cookie_value == local_port << 8 | 0xFF
+ * The different parts of this cookie_value are appended by those hooks if they
+ * all agree on the output of bpf_get_socket_cookie().
+ */
 SEC("cgroup/connect6")
 int set_cookie(struct bpf_sock_addr *ctx)
 {
@@ -32,14 +42,14 @@ int set_cookie(struct bpf_sock_addr *ctx)
 	if (!p)
 		return 1;
 
-	p->cookie_value = 0xFF;
+	p->cookie_value = 0xF;
 	p->cookie_key = bpf_get_socket_cookie(ctx);
 
 	return 1;
 }
 
 SEC("sockops")
-int update_cookie(struct bpf_sock_ops *ctx)
+int update_cookie_sockops(struct bpf_sock_ops *ctx)
 {
 	struct bpf_sock *sk;
 	struct socket_cookie *p;
@@ -60,11 +70,32 @@ int update_cookie(struct bpf_sock_ops *ctx)
 	if (p->cookie_key != bpf_get_socket_cookie(ctx))
 		return 1;
 
-	p->cookie_value = (ctx->local_port << 8) | p->cookie_value;
+	p->cookie_value |= (ctx->local_port << 8);
 
 	return 1;
 }
 
+SEC("fexit/inet_stream_connect")
+int BPF_PROG(update_cookie_tracing, struct socket *sock,
+	     struct sockaddr *uaddr, int addr_len, int flags)
+{
+	struct socket_cookie *p;
+
+	if (uaddr->sa_family != AF_INET6)
+		return 0;
+
+	p = bpf_sk_storage_get(&socket_cookies, sock->sk, 0, 0);
+	if (!p)
+		return 0;
+
+	if (p->cookie_key != bpf_get_socket_cookie(sock->sk))
+		return 0;
+
+	p->cookie_value |= 0xF0;
+
+	return 0;
+}
+
 int _version SEC("version") = 1;
 
 char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/test_socket_cookie.c b/tools/testing/selftests/bpf/test_socket_cookie.c
index ca7ca87e91aa..0d955c65a4f8 100644
--- a/tools/testing/selftests/bpf/test_socket_cookie.c
+++ b/tools/testing/selftests/bpf/test_socket_cookie.c
@@ -133,6 +133,7 @@ static int run_test(int cgfd)
 	struct bpf_prog_load_attr attr;
 	struct bpf_program *prog;
 	struct bpf_object *pobj;
+	struct bpf_link *link;
 	const char *prog_name;
 	int server_fd = -1;
 	int client_fd = -1;
@@ -153,11 +154,18 @@ static int run_test(int cgfd)
 	bpf_object__for_each_program(prog, pobj) {
 		prog_name = bpf_program__section_name(prog);
 
-		if (libbpf_attach_type_by_name(prog_name, &attach_type))
-			goto err;
-
-		err = bpf_prog_attach(bpf_program__fd(prog), cgfd, attach_type,
-				      BPF_F_ALLOW_OVERRIDE);
+		if (bpf_program__is_tracing(prog)) {
+			link = bpf_program__attach(prog);
+			err = !link;
+			continue;
+		} else {
+			if (libbpf_attach_type_by_name(prog_name, &attach_type))
+				goto err;
+
+			err = bpf_prog_attach(bpf_program__fd(prog), cgfd,
+					      attach_type,
+					      BPF_F_ALLOW_OVERRIDE);
+		}
 		if (err) {
 			log_err("Failed to attach prog %s", prog_name);
 			goto out;
-- 
2.29.2.454.gaff20da3a2-goog