selftests/bpf: Add tests for cgroup unix socket address hooks

These selftests are written in prog_tests style instead of adding
them to the existing test_sock_addr tests. Migrating the existing
sock addr tests to prog_tests style is left for future work. This
commit adds support for testing bind() sockaddr hooks, even though
there's no unix socket sockaddr hook for bind(). We leave this code
intact for when the INET and INET6 tests are migrated in the future
which do support intercepting bind().

Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
Link: https://lore.kernel.org/r/20231011185113.140426-10-daan.j.demeyer@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/sendmsg_unix_prog.c b/tools/testing/selftests/bpf/progs/sendmsg_unix_prog.c
new file mode 100644
index 000000000000..1f67e832666e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/sendmsg_unix_prog.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+
+#include <string.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_kfuncs.h"
+
+__u8 SERVUN_REWRITE_ADDRESS[] = "\0bpf_cgroup_unix_test_rewrite";
+
+SEC("cgroup/sendmsg_unix")
+int sendmsg_unix_prog(struct bpf_sock_addr *ctx)
+{
+	struct bpf_sock_addr_kern *sa_kern = bpf_cast_to_kern_ctx(ctx);
+	struct sockaddr_un *sa_kern_unaddr;
+	__u32 unaddrlen = offsetof(struct sockaddr_un, sun_path) +
+			  sizeof(SERVUN_REWRITE_ADDRESS) - 1;
+	int ret;
+
+	/* Rewrite destination. */
+	ret = bpf_sock_addr_set_sun_path(sa_kern, SERVUN_REWRITE_ADDRESS,
+					 sizeof(SERVUN_REWRITE_ADDRESS) - 1);
+	if (ret)
+		return 0;
+
+	if (sa_kern->uaddrlen != unaddrlen)
+		return 0;
+
+	sa_kern_unaddr = bpf_rdonly_cast(sa_kern->uaddr,
+						bpf_core_type_id_kernel(struct sockaddr_un));
+	if (memcmp(sa_kern_unaddr->sun_path, SERVUN_REWRITE_ADDRESS,
+			sizeof(SERVUN_REWRITE_ADDRESS) - 1) != 0)
+		return 0;
+
+	return 1;
+}
+
+char _license[] SEC("license") = "GPL";