selftests/bpf: Add tests for {set|get} socket option from setsockopt BPF

Adding selftests for the newly added functionality to call bpf_setsockopt()
and bpf_getsockopt() from setsockopt BPF programs.

Test Details:

1. BPF Program

   Checks for changes in IPV6_TCLASS(SOL_IPV6) via setsockopt
   If the cca for the socket is not cubic do nothing
   If the newly set value for IPV6_TCLASS is 45 (0x2d) (as per our use-case)
   then change the cc from cubic to reno

2. User Space Program

   Creates an AF_INET6 socket and set the cca for that to be "cubic"
   Attach the program and set the IPV6_TCLASS to 0x2d using setsockopt
   Verify the cca for the socket changed to reno

Signed-off-by: Prankur Gupta <prankgup@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210817224221.3257826-3-prankgup@fb.com

1 files changed, 70 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/sockopt_qos_to_cc.c b/tools/testing/selftests/bpf/prog_tests/sockopt_qos_to_cc.c
new file mode 100644
index 000000000000..6b53b3cb8dad
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/sockopt_qos_to_cc.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <test_progs.h>
+#include <netinet/tcp.h>
+#include "sockopt_qos_to_cc.skel.h"
+
+static void run_setsockopt_test(int cg_fd, int sock_fd)
+{
+	socklen_t optlen;
+	char cc[16]; /* TCP_CA_NAME_MAX */
+	int buf;
+	int err = -1;
+
+	buf = 0x2D;
+	err = setsockopt(sock_fd, SOL_IPV6, IPV6_TCLASS, &buf, sizeof(buf));
+	if (!ASSERT_OK(err, "setsockopt(sock_fd, IPV6_TCLASS)"))
+		return;
+
+	/* Verify the setsockopt cc change */
+	optlen = sizeof(cc);
+	err = getsockopt(sock_fd, SOL_TCP, TCP_CONGESTION, cc, &optlen);
+	if (!ASSERT_OK(err, "getsockopt(sock_fd, TCP_CONGESTION)"))
+		return;
+
+	if (!ASSERT_STREQ(cc, "reno", "getsockopt(sock_fd, TCP_CONGESTION)"))
+		return;
+}
+
+void test_sockopt_qos_to_cc(void)
+{
+	struct sockopt_qos_to_cc *skel;
+	char cc_cubic[16] = "cubic"; /* TCP_CA_NAME_MAX */
+	int cg_fd = -1;
+	int sock_fd = -1;
+	int err;
+
+	cg_fd = test__join_cgroup("/sockopt_qos_to_cc");
+	if (!ASSERT_GE(cg_fd, 0, "cg-join(sockopt_qos_to_cc)"))
+		return;
+
+	skel = sockopt_qos_to_cc__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel"))
+		goto done;
+
+	sock_fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (!ASSERT_GE(sock_fd, 0, "v6 socket open"))
+		goto done;
+
+	err = setsockopt(sock_fd, SOL_TCP, TCP_CONGESTION, &cc_cubic,
+			 sizeof(cc_cubic));
+	if (!ASSERT_OK(err, "setsockopt(sock_fd, TCP_CONGESTION)"))
+		goto done;
+
+	skel->links.sockopt_qos_to_cc =
+		bpf_program__attach_cgroup(skel->progs.sockopt_qos_to_cc,
+					   cg_fd);
+	if (!ASSERT_OK_PTR(skel->links.sockopt_qos_to_cc,
+			   "prog_attach(sockopt_qos_to_cc)"))
+		goto done;
+
+	run_setsockopt_test(cg_fd, sock_fd);
+
+done:
+	if (sock_fd != -1)
+		close(sock_fd);
+	if (cg_fd != -1)
+		close(cg_fd);
+	/* destroy can take null and error pointer */
+	sockopt_qos_to_cc__destroy(skel);
+}