new file mode 100644
@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/* Highlights:
+ * 1. The major difference between this bpf program and tcp_cubic.c
+ * is that this bpf program relies on `cong_control` rather than
+ * `cong_avoid` in the struct tcp_congestion_ops.
+ * 2. Logic such as tcp_cwnd_reduction, tcp_cong_avoid, and
+ * tcp_update_pacing_rate is bypassed when `cong_control` is
+ * defined, so moving these logic to `cong_control`.
+ * 3. WARNING: This bpf program is NOT the same as tcp_cubic.c.
+ * The main purpose is to show use cases of the arguments in
+ * `cong_control`. For simplicity's sake, it reuses tcp cubic's
+ * kernel functions.
+ */
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_tracing_net.h"
+
+#define BPF_STRUCT_OPS(name, args...) \
+SEC("struct_ops/"#name) \
+BPF_PROG(name, args)
+
+
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#define max(a, b) ((a) > (b) ? (a) : (b))
+
+static __always_inline struct inet_connection_sock *inet_csk(const struct sock *sk)
+{
+ return (struct inet_connection_sock *)sk;
+}
+
+static __always_inline struct tcp_sock *tcp_sk(const struct sock *sk)
+{
+ return (struct tcp_sock *)sk;
+}
+
+static __always_inline bool before(__u32 seq1, __u32 seq2)
+{
+ return (__s32)(seq1-seq2) < 0;
+}
+#define after(seq2, seq1) before(seq1, seq2)
+
+char _license[] SEC("license") = "GPL";
+
+extern void cubictcp_init(struct sock *sk) __ksym;
+extern void cubictcp_cwnd_event(struct sock *sk, enum tcp_ca_event event) __ksym;
+extern __u32 cubictcp_recalc_ssthresh(struct sock *sk) __ksym;
+extern void cubictcp_state(struct sock *sk, __u8 new_state) __ksym;
+extern __u32 tcp_reno_undo_cwnd(struct sock *sk) __ksym;
+extern void cubictcp_acked(struct sock *sk, const struct ack_sample *sample) __ksym;
+extern void cubictcp_cong_avoid(struct sock *sk, __u32 ack, __u32 acked) __ksym;
+
+
+void BPF_STRUCT_OPS(bpf_cubic_init, struct sock *sk)
+{
+ cubictcp_init(sk);
+}
+
+void BPF_STRUCT_OPS(bpf_cubic_cwnd_event, struct sock *sk, enum tcp_ca_event event)
+{
+ cubictcp_cwnd_event(sk, event);
+}
+
+#define USEC_PER_SEC 1000000UL
+#define TCP_PACING_SS_RATIO (200)
+#define TCP_PACING_CA_RATIO (120)
+#define TCP_REORDERING (12)
+#define likely(x) (__builtin_expect(!!(x), 1))
+
+static __always_inline __u64 div64_u64(__u64 dividend, __u64 divisor)
+{
+ return dividend / divisor;
+}
+
+static __always_inline void tcp_update_pacing_rate(struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ __u64 rate;
+
+ /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
+ rate = (__u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3);
+
+ /* current rate is (cwnd * mss) / srtt
+ * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
+ * In Congestion Avoidance phase, set it to 120 % the current rate.
+ *
+ * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
+ * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
+ * end of slow start and should slow down.
+ */
+ if (tp->snd_cwnd < tp->snd_ssthresh / 2)
+ rate *= TCP_PACING_SS_RATIO;
+ else
+ rate *= TCP_PACING_CA_RATIO;
+
+ rate *= max(tp->snd_cwnd, tp->packets_out);
+
+ if (likely(tp->srtt_us))
+ rate = div64_u64(rate, (__u64)tp->srtt_us);
+
+ sk->sk_pacing_rate = min(rate, sk->sk_max_pacing_rate);
+}
+
+static __always_inline void tcp_cwnd_reduction(
+ struct sock *sk,
+ int newly_acked_sacked,
+ int newly_lost,
+ int flag) {
+ struct tcp_sock *tp = tcp_sk(sk);
+ int sndcnt = 0;
+ __u32 pkts_in_flight = tp->packets_out - (tp->sacked_out + tp->lost_out) + tp->retrans_out;
+ int delta = tp->snd_ssthresh - pkts_in_flight;
+
+ if (newly_acked_sacked <= 0 || !tp->prior_cwnd)
+ return;
+
+ __u32 prr_delivered = tp->prr_delivered + newly_acked_sacked;
+
+ if (delta < 0) {
+ __u64 dividend =
+ (__u64)tp->snd_ssthresh * prr_delivered + tp->prior_cwnd - 1;
+ sndcnt = (__u32)div64_u64(dividend, (__u64)tp->prior_cwnd) - tp->prr_out;
+ } else {
+ sndcnt = max(prr_delivered - tp->prr_out, newly_acked_sacked);
+ if (flag & FLAG_SND_UNA_ADVANCED && !newly_lost)
+ sndcnt++;
+ sndcnt = min(delta, sndcnt);
+ }
+ /* Force a fast retransmit upon entering fast recovery */
+ sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1));
+ tp->snd_cwnd = pkts_in_flight + sndcnt;
+}
+
+/* Decide wheather to run the increase function of congestion control. */
+static __always_inline bool tcp_may_raise_cwnd(
+ const struct sock *sk,
+ const int flag) {
+ if (tcp_sk(sk)->reordering > TCP_REORDERING)
+ return flag & FLAG_FORWARD_PROGRESS;
+
+ return flag & FLAG_DATA_ACKED;
+}
+
+void BPF_STRUCT_OPS(bpf_cubic_cong_control, struct sock *sk, __u32 ack, int flag,
+ const struct rate_sample *rs)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (((1<<TCP_CA_CWR) | (1<<TCP_CA_Recovery)) &
+ (1 << inet_csk(sk)->icsk_ca_state)) {
+ /* Reduce cwnd if state mandates */
+ tcp_cwnd_reduction(sk, rs->acked_sacked, rs->losses, flag);
+
+ if (!before(tp->snd_una, tp->high_seq)) {
+ /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
+ if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH &&
+ inet_csk(sk)->icsk_ca_state == TCP_CA_CWR) {
+ tp->snd_cwnd = tp->snd_ssthresh;
+ tp->snd_cwnd_stamp = tcp_jiffies32;
+ }
+ // __cwnd_event(sk, CA_EVENT_COMPLETE_CWR);
+ }
+ } else if (tcp_may_raise_cwnd(sk, flag)) {
+ /* Advance cwnd if state allows */
+ cubictcp_cong_avoid(sk, ack, rs->acked_sacked);
+ tp->snd_cwnd_stamp = tcp_jiffies32;
+ }
+
+ tcp_update_pacing_rate(sk);
+}
+
+__u32 BPF_STRUCT_OPS(bpf_cubic_recalc_ssthresh, struct sock *sk)
+{
+ return cubictcp_recalc_ssthresh(sk);
+}
+
+void BPF_STRUCT_OPS(bpf_cubic_state, struct sock *sk, __u8 new_state)
+{
+ cubictcp_state(sk, new_state);
+}
+
+void BPF_STRUCT_OPS(bpf_cubic_acked, struct sock *sk,
+ const struct ack_sample *sample)
+{
+ cubictcp_acked(sk, sample);
+}
+
+__u32 BPF_STRUCT_OPS(bpf_cubic_undo_cwnd, struct sock *sk)
+{
+ return tcp_reno_undo_cwnd(sk);
+}
+
+
+SEC(".struct_ops")
+struct tcp_congestion_ops cubic = {
+ .init = (void *)bpf_cubic_init,
+ .ssthresh = (void *)bpf_cubic_recalc_ssthresh,
+ .cong_control = (void *)bpf_cubic_cong_control,
+ .set_state = (void *)bpf_cubic_state,
+ .undo_cwnd = (void *)bpf_cubic_undo_cwnd,
+ .cwnd_event = (void *)bpf_cubic_cwnd_event,
+ .pkts_acked = (void *)bpf_cubic_acked,
+ .name = "bpf_cubic",
+};
@@ -80,6 +80,14 @@
#define TCP_INFINITE_SSTHRESH 0x7fffffff
#define TCP_PINGPONG_THRESH 3
+#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
+#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
+#define FLAG_DATA_SACKED 0x20 /* New SACK. */
+#define FLAG_SND_UNA_ADVANCED \
+ 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
+#define FLAG_ACKED (FLAG_DATA_ACKED | FLAG_SYN_ACKED)
+#define FLAG_FORWARD_PROGRESS (FLAG_ACKED | FLAG_DATA_SACKED)
+
#define fib_nh_dev nh_common.nhc_dev
#define fib_nh_gw_family nh_common.nhc_gw_family
#define fib_nh_gw6 nh_common.nhc_gw.ipv6
@@ -119,4 +127,6 @@
#define tw_v6_daddr __tw_common.skc_v6_daddr
#define tw_v6_rcv_saddr __tw_common.skc_v6_rcv_saddr
+#define tcp_jiffies32 ((__u32)bpf_jiffies64())
+
#endif
This patch adds a selftest to show the usage of the new arguments in cong_control. For simplicity's sake, the testing example reuses cubic's kernel functions. -- Changes in v2: * Added highlights to explain major differences between the bpf program and tcp_cubic.c. * bpf_tcp_helpers.h should not be further extended, so remove the dependency on this file. Use vmlinux.h instead. * Minor changes such as indentation. Signed-off-by: Miao Xu <miaxu@meta.com> --- .../bpf/progs/bpf_cubic_cong_control.c | 207 ++++++++++++++++++ .../selftests/bpf/progs/bpf_tracing_net.h | 10 + 2 files changed, 217 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/bpf_cubic_cong_control.c