selftests/bpf: do not hardcode target rate in test_tc_edt BPF program

test_tc_edt currently defines the target rate in both the userspace and
BPF parts. This value could be defined once in the userspace part if we
make it able to configure the BPF program before starting the test.

Add a target_rate variable in the BPF part, and make the userspace part
set it to the desired rate before attaching the shaping program.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <[email protected]>

Author: Tropicao

tools/testing/selftests/bpf/prog_tests/test_tc_edt.c

@@ -175,6 +175,7 @@ static int setup(struct test_tc_edt *skel)
 	SYS(fail_close_client_ns, "ip -4 addr add " IP4_ADDR_VETH1 "/24 dev veth1");
 	SYS(fail_close_client_ns, "ip link set veth1 up");
 	SYS(fail_close_client_ns, "tc qdisc add dev veth1 root fq");
+	skel->bss->target_rate = TARGET_RATE_MBPS * 1000 * 1000;
 	ret = tc_prog_attach("veth1", -1, bpf_program__fd(skel->progs.tc_prog));
 	if (!ASSERT_OK(ret, "attach bpf prog"))
 		goto fail_close_client_ns;

tools/testing/selftests/bpf/progs/test_tc_edt.c

@@ -14,7 +14,6 @@
 #define TIME_HORIZON_NS (2000 * 1000 * 1000)
 #define NS_PER_SEC 1000000000
 #define ECN_HORIZON_NS 5000000
-#define THROTTLE_RATE_BPS (5 * 1000 * 1000)
 
 /* flow_key => last_tstamp timestamp used */
 struct {
@@ -24,12 +23,13 @@ struct {
 	__uint(max_entries, 1);
 } flow_map SEC(".maps");
 
+__uint64_t target_rate;
+
 static inline int throttle_flow(struct __sk_buff *skb)
 {
 	int key = 0;
 	uint64_t *last_tstamp = bpf_map_lookup_elem(&flow_map, &key);
-	uint64_t delay_ns = ((uint64_t)skb->len) * NS_PER_SEC /
-			THROTTLE_RATE_BPS;
+	uint64_t delay_ns = ((uint64_t)skb->len) * NS_PER_SEC / target_rate;
 	uint64_t now = bpf_ktime_get_ns();
 	uint64_t tstamp, next_tstamp = 0;