[PATCH bpf-next 14/15] bpf: selftest: bpf_cubic and bpf_dctcp calling kernel functions

[Martin KaFai Lau]

This patch removes the bpf implementation of tcp_slow_start()
and tcp_cong_avoid_ai().  Instead, it directly uses the kernel
implementation.

It also replaces the bpf_cubic_undo_cwnd implementation by directly
calling tcp_reno_undo_cwnd().  bpf_dctcp also directly calls
tcp_reno_cong_avoid() instead.

Signed-off-by: Martin KaFai Lau <ka...@fb.com>
---
 tools/testing/selftests/bpf/bpf_tcp_helpers.h | 29 ++-----------------
 tools/testing/selftests/bpf/progs/bpf_cubic.c |  6 ++--
 tools/testing/selftests/bpf/progs/bpf_dctcp.c | 22 ++++----------
 3 files changed, 11 insertions(+), 46 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpf_tcp_helpers.h 
b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
index 91f0fac632f4..029589c008c9 100644
--- a/tools/testing/selftests/bpf/bpf_tcp_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
@@ -187,16 +187,6 @@ struct tcp_congestion_ops {
        typeof(y) __y = (y);                    \
        __x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); })
 
-static __always_inline __u32 tcp_slow_start(struct tcp_sock *tp, __u32 acked)
-{
-       __u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh);
-
-       acked -= cwnd - tp->snd_cwnd;
-       tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);
-
-       return acked;
-}
-
 static __always_inline bool tcp_in_slow_start(const struct tcp_sock *tp)
 {
        return tp->snd_cwnd < tp->snd_ssthresh;
@@ -213,22 +203,7 @@ static __always_inline bool tcp_is_cwnd_limited(const 
struct sock *sk)
        return !!BPF_CORE_READ_BITFIELD(tp, is_cwnd_limited);
 }
 
-static __always_inline void tcp_cong_avoid_ai(struct tcp_sock *tp, __u32 w, 
__u32 acked)
-{
-       /* If credits accumulated at a higher w, apply them gently now. */
-       if (tp->snd_cwnd_cnt >= w) {
-               tp->snd_cwnd_cnt = 0;
-               tp->snd_cwnd++;
-       }
-
-       tp->snd_cwnd_cnt += acked;
-       if (tp->snd_cwnd_cnt >= w) {
-               __u32 delta = tp->snd_cwnd_cnt / w;
-
-               tp->snd_cwnd_cnt -= delta * w;
-               tp->snd_cwnd += delta;
-       }
-       tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_cwnd_clamp);
-}
+extern __u32 tcp_slow_start(struct tcp_sock *tp, __u32 acked) __ksym;
+extern void tcp_cong_avoid_ai(struct tcp_sock *tp, __u32 w, __u32 acked) 
__ksym;
 
 #endif
diff --git a/tools/testing/selftests/bpf/progs/bpf_cubic.c 
b/tools/testing/selftests/bpf/progs/bpf_cubic.c
index 33c4d2bded64..f62df4d023f9 100644
--- a/tools/testing/selftests/bpf/progs/bpf_cubic.c
+++ b/tools/testing/selftests/bpf/progs/bpf_cubic.c
@@ -525,11 +525,11 @@ void BPF_STRUCT_OPS(bpf_cubic_acked, struct sock *sk,
                hystart_update(sk, delay);
 }
 
+extern __u32 tcp_reno_undo_cwnd(struct sock *sk) __ksym;
+
 __u32 BPF_STRUCT_OPS(bpf_cubic_undo_cwnd, struct sock *sk)
 {
-       const struct tcp_sock *tp = tcp_sk(sk);
-
-       return max(tp->snd_cwnd, tp->prior_cwnd);
+       return tcp_reno_undo_cwnd(sk);
 }
 
 SEC(".struct_ops")
diff --git a/tools/testing/selftests/bpf/progs/bpf_dctcp.c 
b/tools/testing/selftests/bpf/progs/bpf_dctcp.c
index 4dc1a967776a..fd42247da8b4 100644
--- a/tools/testing/selftests/bpf/progs/bpf_dctcp.c
+++ b/tools/testing/selftests/bpf/progs/bpf_dctcp.c
@@ -194,22 +194,12 @@ __u32 BPF_PROG(dctcp_cwnd_undo, struct sock *sk)
        return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
 }
 
-SEC("struct_ops/tcp_reno_cong_avoid")
-void BPF_PROG(tcp_reno_cong_avoid, struct sock *sk, __u32 ack, __u32 acked)
-{
-       struct tcp_sock *tp = tcp_sk(sk);
-
-       if (!tcp_is_cwnd_limited(sk))
-               return;
+extern void tcp_reno_cong_avoid(struct sock *sk, __u32 ack, __u32 acked) 
__ksym;
 
-       /* In "safe" area, increase. */
-       if (tcp_in_slow_start(tp)) {
-               acked = tcp_slow_start(tp, acked);
-               if (!acked)
-                       return;
-       }
-       /* In dangerous area, increase slowly. */
-       tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
+SEC("struct_ops/dctcp_reno_cong_avoid")
+void BPF_PROG(dctcp_cong_avoid, struct sock *sk, __u32 ack, __u32 acked)
+{
+       tcp_reno_cong_avoid(sk, ack, acked);
 }
 
 SEC(".struct_ops")
@@ -226,7 +216,7 @@ struct tcp_congestion_ops dctcp = {
        .in_ack_event   = (void *)dctcp_update_alpha,
        .cwnd_event     = (void *)dctcp_cwnd_event,
        .ssthresh       = (void *)dctcp_ssthresh,
-       .cong_avoid     = (void *)tcp_reno_cong_avoid,
+       .cong_avoid     = (void *)dctcp_cong_avoid,
        .undo_cwnd      = (void *)dctcp_cwnd_undo,
        .set_state      = (void *)dctcp_state,
        .flags          = TCP_CONG_NEEDS_ECN,
-- 
2.30.2