This test implements a simple network emulator qdisc that simulates
packet drop, loss and delay. The qdisc uses Gilbert-Elliott model to
simulate packet drops. When used with mq qdisc, the bpf netem qdiscs
on different tx queues maintain a global state machine using a bpf map.
Signed-off-by: Amery Hung <amery.hung@xxxxxxxxxxxxx>
---
.../selftests/bpf/prog_tests/bpf_qdisc.c | 30 ++
.../selftests/bpf/progs/bpf_qdisc_netem.c | 258 ++++++++++++++++++
2 files changed, 288 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/bpf_qdisc_netem.c
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
index 394bf5a4adae..ec9c0d166e89 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
@@ -6,6 +6,13 @@
#include "bpf_qdisc_fifo.skel.h"
#include "bpf_qdisc_fq.skel.h"
+struct crndstate {
+ u32 last;
+ u32 rho;
+};
+
+#include "bpf_qdisc_netem.skel.h"
+
#ifndef ENOTSUPP
#define ENOTSUPP 524
#endif
@@ -176,10 +183,33 @@ static void test_fq(void)
bpf_qdisc_fq__destroy(fq_skel);
}
+static void test_netem(void)
+{
+ struct bpf_qdisc_netem *netem_skel;
+ struct bpf_link *link;
+
+ netem_skel = bpf_qdisc_netem__open_and_load();
+ if (!ASSERT_OK_PTR(netem_skel, "bpf_qdisc_netem__open_and_load"))
+ return;
+
+ link = bpf_map__attach_struct_ops(netem_skel->maps.netem);
+ if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops")) {
+ bpf_qdisc_netem__destroy(netem_skel);
+ return;
+ }
+
+ do_test("bpf_netem");
+
+ bpf_link__destroy(link);
+ bpf_qdisc_netem__destroy(netem_skel);
+}
+
void test_bpf_qdisc(void)
{
if (test__start_subtest("fifo"))
test_fifo();
if (test__start_subtest("fq"))
test_fq();
+ if (test__start_subtest("netem"))
+ test_netem();
}
diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_netem.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_netem.c
new file mode 100644
index 000000000000..39be88a5f16a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_netem.c
@@ -0,0 +1,258 @@
+#include <vmlinux.h>
+#include "bpf_experimental.h"
+#include "bpf_qdisc_common.h"
+
+char _license[] SEC("license") = "GPL";
+
+int q_loss_model = CLG_GILB_ELL;
+unsigned int q_limit = 1000;
+signed long q_latency = 0;
+signed long q_jitter = 0;
+unsigned int q_loss = 1;
+unsigned int q_qlen = 0;
+
+struct crndstate q_loss_cor = {.last = 0, .rho = 0,};
+struct crndstate q_delay_cor = {.last = 0, .rho = 0,};
+
+struct skb_node {
+ u64 tstamp;
+ struct sk_buff __kptr *skb;
+ struct bpf_rb_node node;
+};
+
+struct clg_state {
+ u64 state;
+ u32 a1;
+ u32 a2;
+ u32 a3;
+ u32 a4;
+ u32 a5;
+};
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __type(key, __u32);
+ __type(value, struct clg_state);
+ __uint(max_entries, 1);
+} g_clg_state SEC(".maps");
+
+#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
+
+private(A) struct bpf_spin_lock t_root_lock;
+private(A) struct bpf_rb_root t_root __contains(skb_node, node);
+
+static bool skb_tstamp_less(struct bpf_rb_node *a, const struct bpf_rb_node *b)
+{
+ struct skb_node *skbn_a;
+ struct skb_node *skbn_b;
+
+ skbn_a = container_of(a, struct skb_node, node);
+ skbn_b = container_of(b, struct skb_node, node);
+
+ return skbn_a->tstamp < skbn_b->tstamp;
+}
+
+static u32 get_crandom(struct crndstate *state)
+{
+ u64 value, rho;
+ unsigned long answer;
+
+ if (!state || state->rho == 0) /* no correlation */
+ return bpf_get_prandom_u32();
+
+ value = bpf_get_prandom_u32();
+ rho = (u64)state->rho + 1;
+ answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
+ state->last = answer;
+ return answer;
+}
+
+static s64 tabledist(s64 mu, s32 sigma, struct crndstate *state)
+{
+ u32 rnd;
+
+ if (sigma == 0)
+ return mu;
+
+ rnd = get_crandom(state);
+
+ /* default uniform distribution */
+ return ((rnd % (2 * (u32)sigma)) + mu) - sigma;
+}
+
+static bool loss_gilb_ell(void)
+{
+ struct clg_state *clg;
+ u32 r1, r2, key = 0;
+ bool ret = false;
+
+ clg = bpf_map_lookup_elem(&g_clg_state, &key);
+ if (!clg)
+ return false;
+
+ r1 = bpf_get_prandom_u32();
+ r2 = bpf_get_prandom_u32();
+
+ switch (clg->state) {
+ case GOOD_STATE:
+ if (r1 < clg->a1)
+ __sync_val_compare_and_swap(&clg->state,
+ GOOD_STATE, BAD_STATE);
+ if (r2 < clg->a4)
+ ret = true;
+ break;
+ case BAD_STATE:
+ if (r1 < clg->a2)
+ __sync_val_compare_and_swap(&clg->state,
+ BAD_STATE, GOOD_STATE);
+ if (r2 > clg->a3)
+ ret = true;
+ }
+
+ return ret;
+}
+
+static bool loss_event(void)
+{
+ switch (q_loss_model) {
+ case CLG_RANDOM:
+ return q_loss && q_loss >= get_crandom(&q_loss_cor);
+ case CLG_GILB_ELL:
+ return loss_gilb_ell();
+ }
+
+ return false;
+}
+
+SEC("struct_ops/bpf_netem_enqueue")
+int BPF_PROG(bpf_netem_enqueue, struct sk_buff *skb, struct Qdisc *sch,
+ struct bpf_sk_buff_ptr *to_free)
+{
+ struct skb_node *skbn;
+ int count = 1;
+ s64 delay = 0;
+ u64 now;
+
+ if (loss_event())
+ --count;
+
+ if (count == 0) {
+ bpf_qdisc_skb_drop(skb, to_free);
+ return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
+ }
+
+ q_qlen++;
+ if (q_qlen > q_limit) {
+ bpf_qdisc_skb_drop(skb, to_free);
+ return NET_XMIT_DROP;
+ }
+
+ skbn = bpf_obj_new(typeof(*skbn));
+ if (!skbn) {
+ bpf_qdisc_skb_drop(skb, to_free);
+ return NET_XMIT_DROP;
+ }
+
+ skb = bpf_kptr_xchg(&skbn->skb, skb);
+ if (skb)
+ bpf_qdisc_skb_drop(skb, to_free);
+
+ delay = tabledist(q_latency, q_jitter, &q_delay_cor);
+ now = bpf_ktime_get_ns();
+ skbn->tstamp = now + delay;
+
+ bpf_spin_lock(&t_root_lock);
+ bpf_rbtree_add(&t_root, &skbn->node, skb_tstamp_less);
+ bpf_spin_unlock(&t_root_lock);
+
+ return NET_XMIT_SUCCESS;
+}
+
+SEC("struct_ops/bpf_netem_dequeue")
+struct sk_buff *BPF_PROG(bpf_netem_dequeue, struct Qdisc *sch)
+{
+ struct sk_buff *skb = NULL;
+ struct bpf_rb_node *node;
+ struct skb_node *skbn;
+ u64 now, tstamp;
+
+ now = bpf_ktime_get_ns();
+
+ bpf_spin_lock(&t_root_lock);
+ node = bpf_rbtree_first(&t_root);
+ if (!node) {
+ bpf_spin_unlock(&t_root_lock);
+ return NULL;
+ }
+
+ skbn = container_of(node, struct skb_node, node);
+ tstamp = skbn->tstamp;
+ if (tstamp <= now) {
+ node = bpf_rbtree_remove(&t_root, node);
+ bpf_spin_unlock(&t_root_lock);
+
+ if (!node)
+ return NULL;
+
+ skbn = container_of(node, struct skb_node, node);
+ skb = bpf_kptr_xchg(&skbn->skb, skb);
+ bpf_obj_drop(skbn);
+
+ q_qlen--;
+ return skb;
+ }
+
+ bpf_spin_unlock(&t_root_lock);
+ bpf_qdisc_watchdog_schedule(sch, tstamp, 0);
+ return NULL;
+}
+
+SEC("struct_ops/bpf_netem_init")
+int BPF_PROG(bpf_netem_init, struct Qdisc *sch, struct nlattr *opt,
+ struct netlink_ext_ack *extack)
+{
+ return 0;
+}
+
+SEC("struct_ops/bpf_netem_reset")
+void BPF_PROG(bpf_netem_reset, struct Qdisc *sch)
+{
+ struct bpf_rb_node *node;
+ struct skb_node *skbn;
+ int i;
+
+ bpf_for(i, 0, q_limit) {
+ struct sk_buff *skb = NULL;
+
+ bpf_spin_lock(&t_root_lock);
+ node = bpf_rbtree_first(&t_root);
+ if (!node) {
+ bpf_spin_unlock(&t_root_lock);
+ break;
+ }
+
+ skbn = container_of(node, struct skb_node, node);
+ node = bpf_rbtree_remove(&t_root, node);
+ bpf_spin_unlock(&t_root_lock);
+
+ if (!node)
+ continue;
+
+ skbn = container_of(node, struct skb_node, node);
+ skb = bpf_kptr_xchg(&skbn->skb, skb);
+ if (skb)
+ bpf_skb_release(skb);
+ bpf_obj_drop(skbn);
+ }
+ q_qlen = 0;
+}
+
+SEC(".struct_ops")
+struct Qdisc_ops netem = {
+ .enqueue = (void *)bpf_netem_enqueue,
+ .dequeue = (void *)bpf_netem_dequeue,
+ .init = (void *)bpf_netem_init,
+ .reset = (void *)bpf_netem_reset,
+ .id = "bpf_netem",
+};
+
--
2.20.1
