selftests/bpf: Check bpf_cubic_acked() is called via struct_ops

Test bpf_tcp_ca (in test_progs) checks multiple tcp_congestion_ops.
However, there isn't a test that verifies functions in the
tcp_congestion_ops is actually called. Add a check to verify that
bpf_cubic_acked is actually called during the test.

Suggested-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230919060258.3237176-3-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Update selftests to always provide "struct_ops" SEC

Update struct_ops selftests to always specify "struct_ops" section
prefix. Libbpf will require a proper BPF program type set in the next
patch, so this prevents tests breaking.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210914014733.2768-2-andrii@kernel.org

bpf: selftests: Bpf_cubic and bpf_dctcp calling kernel functions

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 <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015246.1551062-1-kafai@fb.com

bpf: selftests: Rename bictcp to bpf_cubic

As a similar chanage in the kernel, this patch gives the proper
name to the bpf cubic.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015240.1550074-1-kafai@fb.com

bpf: selftest: Remove enum tcp_ca_state from bpf_tcp_helpers.h

The enum tcp_ca_state is available in <linux/tcp.h>.
Remove it from the bpf_tcp_helpers.h to avoid conflict when the bpf prog
needs to include both both <linux/tcp.h> and bpf_tcp_helpers.h.

Modify the bpf_cubic.c and bpf_dctcp.c to use <linux/tcp.h> instead.
The <linux/stddef.h> is needed by <linux/tcp.h>.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200925000452.3859313-1-kafai@fb.com

bpf: tcp: bpf_cubic: fix spurious HYSTART_DELAY exit upon drop in min RTT

Apply the fix from:
"tcp_cubic: fix spurious HYSTART_DELAY exit upon drop in min RTT"
to the BPF implementation of TCP CUBIC congestion control.

Repeating the commit description here for completeness:

Mirja Kuehlewind reported a bug in Linux TCP CUBIC Hystart, where
Hystart HYSTART_DELAY mechanism can exit Slow Start spuriously on an
ACK when the minimum rtt of a connection goes down. From inspection it
is clear from the existing code that this could happen in an example
like the following:

o The first 8 RTT samples in a round trip are 150ms, resulting in a
curr_rtt of 150ms and a delay_min of 150ms.

o The 9th RTT sample is 100ms. The curr_rtt does not change after the
first 8 samples, so curr_rtt remains 150ms. But delay_min can be
lowered at any time, so delay_min falls to 100ms. The code executes
the HYSTART_DELAY comparison between curr_rtt of 150ms and delay_min
of 100ms, and the curr_rtt is declared far enough above delay_min to
force a (spurious) exit of Slow start.

The fix here is simple: allow every RTT sample in a round trip to
lower the curr_rtt.

Fixes: 6de4a9c430b5 ("bpf: tcp: Add bpf_cubic example")
Reported-by: Mirja Kuehlewind <mirja.kuehlewind@ericsson.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

bpf: tcp: Add bpf_cubic example

This patch adds a bpf_cubic example. Some highlights:
1. CONFIG_HZ .kconfig map is used.
2. In bictcp_update(), calculation is changed to use usec
resolution (i.e. USEC_PER_JIFFY) instead of using jiffies.
Thus, usecs_to_jiffies() is not used in the bpf_cubic.c.
3. In bitctcp_update() [under tcp_friendliness], the original
"while (ca->ack_cnt > delta)" loop is changed to the equivalent
"ca->ack_cnt / delta" operation.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200122233658.903774-1-kafai@fb.com