[PATCH bpf-next v10 5/5] selftests/bpf: add bpf_icmp_send no route test

[Mahe Tardy <mahe.tardy@gmail.com>]

For normal live cgroup_skb paths, the skb should already be routed. The
exception is for test run via BPF_PROG_TEST_RUN with packets created
via bpf_prog_test_run_skb. Those lack dst route and thus the icmp_send
would quietly fail by returning early.

This test exercises this and makes sure the kfunc returns -ENETUNREACH.

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Jordan Rife <jordan@jrife.io>
Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
---
 .../bpf/prog_tests/icmp_send_kfunc.c          | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
index bb532aa0d158..ffaf0fe1880b 100644
--- a/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
+++ b/tools/testing/selftests/bpf/prog_tests/icmp_send_kfunc.c
@@ -169,6 +169,29 @@ static void run_icmp_test(struct icmp_send *skel, int af, const char *ip,
 	}
 }

+static void run_icmp_no_route_test(struct icmp_send *skel)
+{
+	struct ipv4_packet pkt = pkt_v4;
+	LIBBPF_OPTS(bpf_test_run_opts, opts,
+		.data_in = &pkt,
+		.data_size_in = sizeof(pkt),
+	);
+	int err;
+
+	pkt.iph.version = 4;
+	pkt.iph.daddr = inet_addr("127.0.0.1");
+	pkt.tcp.dest = htons(80);
+	skel->bss->server_port = 80;
+	skel->bss->unreach_type = ICMP_DEST_UNREACH;
+	skel->bss->unreach_code = ICMP_HOST_UNREACH;
+	skel->data->kfunc_ret = KFUNC_RET_UNSET;
+
+	err = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.egress), &opts);
+	if (!ASSERT_OK(err, "test_run"))
+		return;
+	ASSERT_EQ(skel->data->kfunc_ret, -ENETUNREACH, "kfunc_ret_no_route");
+}
+
 void test_icmp_send_unreach_cgroup(void)
 {
 	struct icmp_send *skel;
@@ -193,6 +216,9 @@ void test_icmp_send_unreach_cgroup(void)
 	if (test__start_subtest("ipv6"))
 		run_icmp_test(skel, AF_INET6, "::1", ICMPV6_REJECT_ROUTE);

+	if (test__start_subtest("no_route"))
+		run_icmp_no_route_test(skel);
+
 cleanup:
 	icmp_send__destroy(skel);
 	if (cgroup_fd >= 0)
--
2.34.1