selftests/bpf: Test loading bpf-tcp-cc prog calling the kernel tcp-cc kfuncs

This patch adds a test to ensure all static tcp-cc kfuncs is visible to
the struct_ops bpf programs. It is checked by successfully loading
the struct_ops programs calling these tcp-cc kfuncs.

This patch needs to enable the CONFIG_TCP_CONG_DCTCP and
the CONFIG_TCP_CONG_BBR.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20240322191433.4133280-2-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/config

@@ -88,3 +88,5 @@ CONFIG_VSOCKETS=y
 CONFIG_VXLAN=y
 CONFIG_XDP_SOCKETS=y
 CONFIG_XFRM_INTERFACE=y
+CONFIG_TCP_CONG_DCTCP=y
+CONFIG_TCP_CONG_BBR=y

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

@@ -13,6 +13,7 @@
 #include "tcp_ca_write_sk_pacing.skel.h"
 #include "tcp_ca_incompl_cong_ops.skel.h"
 #include "tcp_ca_unsupp_cong_op.skel.h"
+#include "tcp_ca_kfunc.skel.h"
 
 #ifndef ENOTSUPP
 #define ENOTSUPP 524
@@ -518,6 +519,15 @@ static void test_link_replace(void)
 	tcp_ca_update__destroy(skel);
 }
 
+static void test_tcp_ca_kfunc(void)
+{
+	struct tcp_ca_kfunc *skel;
+
+	skel = tcp_ca_kfunc__open_and_load();
+	ASSERT_OK_PTR(skel, "tcp_ca_kfunc__open_and_load");
+	tcp_ca_kfunc__destroy(skel);
+}
+
 void test_bpf_tcp_ca(void)
 {
 	if (test__start_subtest("dctcp"))
@@ -546,4 +556,6 @@ void test_bpf_tcp_ca(void)
 		test_multi_links();
 	if (test__start_subtest("link_replace"))
 		test_link_replace();
+	if (test__start_subtest("tcp_ca_kfunc"))
+		test_tcp_ca_kfunc();
 }

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

@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_tracing.h>
+
+extern void bbr_init(struct sock *sk) __ksym;
+extern void bbr_main(struct sock *sk, const struct rate_sample *rs) __ksym;
+extern u32 bbr_sndbuf_expand(struct sock *sk) __ksym;
+extern u32 bbr_undo_cwnd(struct sock *sk) __ksym;
+extern void bbr_cwnd_event(struct sock *sk, enum tcp_ca_event event) __ksym;
+extern u32 bbr_ssthresh(struct sock *sk) __ksym;
+extern u32 bbr_min_tso_segs(struct sock *sk) __ksym;
+extern void bbr_set_state(struct sock *sk, u8 new_state) __ksym;
+
+extern void dctcp_init(struct sock *sk) __ksym;
+extern void dctcp_update_alpha(struct sock *sk, u32 flags) __ksym;
+extern void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev) __ksym;
+extern u32 dctcp_ssthresh(struct sock *sk) __ksym;
+extern u32 dctcp_cwnd_undo(struct sock *sk) __ksym;
+extern void dctcp_state(struct sock *sk, u8 new_state) __ksym;
+
+extern void cubictcp_init(struct sock *sk) __ksym;
+extern u32 cubictcp_recalc_ssthresh(struct sock *sk) __ksym;
+extern void cubictcp_cong_avoid(struct sock *sk, u32 ack, u32 acked) __ksym;
+extern void cubictcp_state(struct sock *sk, u8 new_state) __ksym;
+extern void cubictcp_cwnd_event(struct sock *sk, enum tcp_ca_event event) __ksym;
+extern void cubictcp_acked(struct sock *sk, const struct ack_sample *sample) __ksym;
+
+SEC("struct_ops/init")
+void BPF_PROG(init, struct sock *sk)
+{
+	bbr_init(sk);
+	dctcp_init(sk);
+	cubictcp_init(sk);
+}
+
+SEC("struct_ops/in_ack_event")
+void BPF_PROG(in_ack_event, struct sock *sk, u32 flags)
+{
+	dctcp_update_alpha(sk, flags);
+}
+
+SEC("struct_ops/cong_control")
+void BPF_PROG(cong_control, struct sock *sk, const struct rate_sample *rs)
+{
+	bbr_main(sk, rs);
+}
+
+SEC("struct_ops/cong_avoid")
+void BPF_PROG(cong_avoid, struct sock *sk, u32 ack, u32 acked)
+{
+	cubictcp_cong_avoid(sk, ack, acked);
+}
+
+SEC("struct_ops/sndbuf_expand")
+u32 BPF_PROG(sndbuf_expand, struct sock *sk)
+{
+	return bbr_sndbuf_expand(sk);
+}
+
+SEC("struct_ops/undo_cwnd")
+u32 BPF_PROG(undo_cwnd, struct sock *sk)
+{
+	bbr_undo_cwnd(sk);
+	return dctcp_cwnd_undo(sk);
+}
+
+SEC("struct_ops/cwnd_event")
+void BPF_PROG(cwnd_event, struct sock *sk, enum tcp_ca_event event)
+{
+	bbr_cwnd_event(sk, event);
+	dctcp_cwnd_event(sk, event);
+	cubictcp_cwnd_event(sk, event);
+}
+
+SEC("struct_ops/ssthresh")
+u32 BPF_PROG(ssthresh, struct sock *sk)
+{
+	bbr_ssthresh(sk);
+	dctcp_ssthresh(sk);
+	return cubictcp_recalc_ssthresh(sk);
+}
+
+SEC("struct_ops/min_tso_segs")
+u32 BPF_PROG(min_tso_segs, struct sock *sk)
+{
+	return bbr_min_tso_segs(sk);
+}
+
+SEC("struct_ops/set_state")
+void BPF_PROG(set_state, struct sock *sk, u8 new_state)
+{
+	bbr_set_state(sk, new_state);
+	dctcp_state(sk, new_state);
+	cubictcp_state(sk, new_state);
+}
+
+SEC("struct_ops/pkts_acked")
+void BPF_PROG(pkts_acked, struct sock *sk, const struct ack_sample *sample)
+{
+	cubictcp_acked(sk, sample);
+}
+
+SEC(".struct_ops")
+struct tcp_congestion_ops tcp_ca_kfunc = {
+	.init		= (void *)init,
+	.in_ack_event	= (void *)in_ack_event,
+	.cong_control	= (void *)cong_control,
+	.cong_avoid	= (void *)cong_avoid,
+	.sndbuf_expand	= (void *)sndbuf_expand,
+	.undo_cwnd	= (void *)undo_cwnd,
+	.cwnd_event	= (void *)cwnd_event,
+	.ssthresh	= (void *)ssthresh,
+	.min_tso_segs	= (void *)min_tso_segs,
+	.set_state	= (void *)set_state,
+	.pkts_acked     = (void *)pkts_acked,
+	.name		= "tcp_ca_kfunc",
+};
+
+char _license[] SEC("license") = "GPL";