From 562dc56a88983421a6c5a46e0feb891873d118a1 Mon Sep 17 00:00:00 2001 From: Yixin Shen Date: Wed, 29 Mar 2023 07:35:57 +0000 Subject: [PATCH 1/2] bpf: allow a TCP CC to write app_limited A CC that implements tcp_congestion_ops.cong_control() should be able to write app_limited. A built-in CC or one from a kernel module is already able to write to this member of struct tcp_sock. For a BPF program, write access has not been allowed, yet. Signed-off-by: Yixin Shen Link: https://lore.kernel.org/r/20230329073558.8136-2-bobankhshen@gmail.com Signed-off-by: Martin KaFai Lau --- net/ipv4/bpf_tcp_ca.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c index e8b27826283ea..ea21c96c03aa1 100644 --- a/net/ipv4/bpf_tcp_ca.c +++ b/net/ipv4/bpf_tcp_ca.c @@ -113,6 +113,9 @@ static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log, case offsetof(struct tcp_sock, ecn_flags): end = offsetofend(struct tcp_sock, ecn_flags); break; + case offsetof(struct tcp_sock, app_limited): + end = offsetofend(struct tcp_sock, app_limited); + break; default: bpf_log(log, "no write support to tcp_sock at off %d\n", off); return -EACCES; From 4239561b69feb94e52e43d93685cc46fb9dbcae5 Mon Sep 17 00:00:00 2001 From: Yixin Shen Date: Wed, 29 Mar 2023 07:35:58 +0000 Subject: [PATCH 2/2] selftests/bpf: test a BPF CC writing app_limited Test whether a TCP CC implemented in BPF is allowed to write app_limited in struct tcp_sock. This is already allowed for the built-in TCP CC. Signed-off-by: Yixin Shen Link: https://lore.kernel.org/r/20230329073558.8136-3-bobankhshen@gmail.com Signed-off-by: Martin KaFai Lau --- .../selftests/bpf/progs/tcp_ca_write_sk_pacing.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/progs/tcp_ca_write_sk_pacing.c b/tools/testing/selftests/bpf/progs/tcp_ca_write_sk_pacing.c index 43447704cf0e6..0724a79cec786 100644 --- a/tools/testing/selftests/bpf/progs/tcp_ca_write_sk_pacing.c +++ b/tools/testing/selftests/bpf/progs/tcp_ca_write_sk_pacing.c @@ -16,6 +16,16 @@ static inline struct tcp_sock *tcp_sk(const struct sock *sk) return (struct tcp_sock *)sk; } +static inline unsigned int tcp_left_out(const struct tcp_sock *tp) +{ + return tp->sacked_out + tp->lost_out; +} + +static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp) +{ + return tp->packets_out - tcp_left_out(tp) + tp->retrans_out; +} + SEC("struct_ops/write_sk_pacing_init") void BPF_PROG(write_sk_pacing_init, struct sock *sk) { @@ -31,11 +41,12 @@ SEC("struct_ops/write_sk_pacing_cong_control") void BPF_PROG(write_sk_pacing_cong_control, struct sock *sk, const struct rate_sample *rs) { - const struct tcp_sock *tp = tcp_sk(sk); + struct tcp_sock *tp = tcp_sk(sk); unsigned long rate = ((tp->snd_cwnd * tp->mss_cache * USEC_PER_SEC) << 3) / (tp->srtt_us ?: 1U << 3); sk->sk_pacing_rate = min(rate, sk->sk_max_pacing_rate); + tp->app_limited = (tp->delivered + tcp_packets_in_flight(tp)) ?: 1; } SEC("struct_ops/write_sk_pacing_ssthresh")