Re: [PATCH bpf-next v2 2/3] selftests/bpf: Test for IPv6 ext header parsing

This test creates a client and a server exchanging a single byte
with a Segment Routing Header and the eBPF program saves
the inner segment in a sk_storage. The test program checks that
the segment is correct.

Signed-off-by: Mathieu Jadin <redacted>
---
 .../bpf/prog_tests/tcp_ipv6_exthdr_srh.c      | 171 ++++++++++++++++++
 .../selftests/bpf/progs/tcp_ipv6_exthdr_srh.c |  78 ++++++++
 2 files changed, 249 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/tcp_ipv6_exthdr_srh.c
 create mode 100644 tools/testing/selftests/bpf/progs/tcp_ipv6_exthdr_srh.c

diff --git a/tools/testing/selftests/bpf/prog_tests/tcp_ipv6_exthdr_srh.c b/tools/testing/selftests/bpf/prog_tests/tcp_ipv6_exthdr_srh.c
new file mode 100644
index 000000000000..70f7ee230975
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/tcp_ipv6_exthdr_srh.c

@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <linux/seg6.h>
+#include "cgroup_helpers.h"
+#include "network_helpers.h"
+
+struct tcp_srh_storage {
+       struct in6_addr inner_segment;
+};
+
+static void send_byte(int fd)
+{
+       char b = 0x55;
+
+       if (CHECK_FAIL(send(fd, &b, sizeof(b), 0) != 1))
+               perror("Failed to send single byte");
+}
+
+static int verify_srh(int map_fd, int server_fd, struct ipv6_sr_hdr *client_srh)
+{
+       int err = 0;
+       struct tcp_srh_storage val;
+
+       if (CHECK_FAIL(bpf_map_lookup_elem(map_fd, &server_fd, &val) < 0)) {

+               perror("Failed to read socket storage");
+               return -1;
+       }
+
+       if (memcmp(&val.inner_segment, &client_srh->segments[1],
+                  sizeof(struct in6_addr))) {
+               log_err("The inner segment of the received SRH differs from the sent one");
+               err++;
+       }
+
+       return err;
+}
+
+static int run_test(int cgroup_fd, int listen_fd)
+{
+       struct bpf_prog_load_attr attr = {
+               .prog_type = BPF_PROG_TYPE_SOCK_OPS,
+               .file = "./tcp_ipv6_exthdr_srh.o",
+               .expected_attach_type = BPF_CGROUP_SOCK_OPS,
+       };
+       size_t srh_size = sizeof(struct ipv6_sr_hdr) +
+               2 * sizeof(struct in6_addr);
+       struct ipv6_sr_hdr *client_srh;
+       struct bpf_object *obj;
+       struct bpf_map *map;
+       struct timeval tv;
+       int client_fd;
+       int server_fd;
+       int prog_fd;
+       int map_fd;
+       char byte;
+       int err;
+
+       err = bpf_prog_load_xattr(&attr, &obj, &prog_fd);

+       if (err) {
+               log_err("Failed to load BPF object");
+               return -1;
+       }
+
+       map = bpf_object__next_map(obj, NULL);
+       map_fd = bpf_map__fd(map);
+

+
+void test_tcp_ipv6_exthdr_srh(void)
+{
+       int server_fd, cgroup_fd;
+
+       cgroup_fd = test__join_cgroup("/tcp_ipv6_exthdr_srh");
+       if (CHECK_FAIL(cgroup_fd < 0))
+               return;
+
+       server_fd = start_server(AF_INET6, SOCK_STREAM, "::1", 0, 0);
+       if (CHECK_FAIL(server_fd < 0))
+               goto close_cgroup_fd;
+
+       if (CHECK_FAIL(system("sysctl net.ipv6.conf.all.seg6_enabled=1")))
+               goto close_server;
+
+       if (CHECK_FAIL(system("sysctl net.ipv6.conf.lo.seg6_enabled=1")))
+               goto reset_sysctl;
+
+       CHECK_FAIL(run_test(cgroup_fd, server_fd));
+
+       if (CHECK_FAIL(system("sysctl net.ipv6.conf.lo.seg6_enabled=0")))
+               log_err("Cannot reset sysctl net.ipv6.conf.lo.seg6_enabled to 0");
+
+reset_sysctl:
+       if (CHECK_FAIL(system("sysctl net.ipv6.conf.all.seg6_enabled=0")))
+               log_err("Cannot reset sysctl net.ipv6.conf.all.seg6_enabled to 0");
+

+close_server:
+       close(server_fd);
+close_cgroup_fd:
+       close(cgroup_fd);
+}