Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/samples/bpf/hbm_out_kern.c b/samples/bpf/hbm_out_kern.c
new file mode 100644
index 0000000..829934b
--- /dev/null
+++ b/samples/bpf/hbm_out_kern.c
@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * Sample Host Bandwidth Manager (HBM) BPF program.
+ *
+ * A cgroup skb BPF egress program to limit cgroup output bandwidth.
+ * It uses a modified virtual token bucket queue to limit average
+ * egress bandwidth. The implementation uses credits instead of tokens.
+ * Negative credits imply that queueing would have happened (this is
+ * a virtual queue, so no queueing is done by it. However, queueing may
+ * occur at the actual qdisc (which is not used for rate limiting).
+ *
+ * This implementation uses 3 thresholds, one to start marking packets and
+ * the other two to drop packets:
+ * CREDIT
+ * - <--------------------------|------------------------> +
+ * | | | 0
+ * | Large pkt |
+ * | drop thresh |
+ * Small pkt drop Mark threshold
+ * thresh
+ *
+ * The effect of marking depends on the type of packet:
+ * a) If the packet is ECN enabled and it is a TCP packet, then the packet
+ * is ECN marked.
+ * b) If the packet is a TCP packet, then we probabilistically call tcp_cwr
+ * to reduce the congestion window. The current implementation uses a linear
+ * distribution (0% probability at marking threshold, 100% probability
+ * at drop threshold).
+ * c) If the packet is not a TCP packet, then it is dropped.
+ *
+ * If the credit is below the drop threshold, the packet is dropped. If it
+ * is a TCP packet, then it also calls tcp_cwr since packets dropped by
+ * by a cgroup skb BPF program do not automatically trigger a call to
+ * tcp_cwr in the current kernel code.
+ *
+ * This BPF program actually uses 2 drop thresholds, one threshold
+ * for larger packets (>= 120 bytes) and another for smaller packets. This
+ * protects smaller packets such as SYNs, ACKs, etc.
+ *
+ * The default bandwidth limit is set at 1Gbps but this can be changed by
+ * a user program through a shared BPF map. In addition, by default this BPF
+ * program does not limit connections using loopback. This behavior can be
+ * overwritten by the user program. There is also an option to calculate
+ * some statistics, such as percent of packets marked or dropped, which
+ * the user program can access.
+ *
+ * A latter patch provides such a program (hbm.c)
+ */
+
+#include "hbm_kern.h"
+
+SEC("cgroup_skb/egress")
+int _hbm_out_cg(struct __sk_buff *skb)
+{
+ struct hbm_pkt_info pkti;
+ int len = skb->len;
+ unsigned int queue_index = 0;
+ unsigned long long curtime;
+ int credit;
+ signed long long delta = 0, new_credit;
+ int max_credit = MAX_CREDIT;
+ bool congestion_flag = false;
+ bool drop_flag = false;
+ bool cwr_flag = false;
+ bool ecn_ce_flag = false;
+ struct hbm_vqueue *qdp;
+ struct hbm_queue_stats *qsp = NULL;
+ int rv = ALLOW_PKT;
+
+ qsp = bpf_map_lookup_elem(&queue_stats, &queue_index);
+ if (qsp != NULL && !qsp->loopback && (skb->ifindex == 1))
+ return ALLOW_PKT;
+
+ hbm_get_pkt_info(skb, &pkti);
+
+ // We may want to account for the length of headers in len
+ // calculation, like ETH header + overhead, specially if it
+ // is a gso packet. But I am not doing it right now.
+
+ qdp = bpf_get_local_storage(&queue_state, 0);
+ if (!qdp)
+ return ALLOW_PKT;
+ else if (qdp->lasttime == 0)
+ hbm_init_vqueue(qdp, 1024);
+
+ curtime = bpf_ktime_get_ns();
+
+ // Begin critical section
+ bpf_spin_lock(&qdp->lock);
+ credit = qdp->credit;
+ delta = curtime - qdp->lasttime;
+ /* delta < 0 implies that another process with a curtime greater
+ * than ours beat us to the critical section and already added
+ * the new credit, so we should not add it ourselves
+ */
+ if (delta > 0) {
+ qdp->lasttime = curtime;
+ new_credit = credit + CREDIT_PER_NS(delta, qdp->rate);
+ if (new_credit > MAX_CREDIT)
+ credit = MAX_CREDIT;
+ else
+ credit = new_credit;
+ }
+ credit -= len;
+ qdp->credit = credit;
+ bpf_spin_unlock(&qdp->lock);
+ // End critical section
+
+ // Check if we should update rate
+ if (qsp != NULL && (qsp->rate * 128) != qdp->rate) {
+ qdp->rate = qsp->rate * 128;
+ bpf_printk("Updating rate: %d (1sec:%llu bits)\n",
+ (int)qdp->rate,
+ CREDIT_PER_NS(1000000000, qdp->rate) * 8);
+ }
+
+ // Set flags (drop, congestion, cwr)
+ // Dropping => we are congested, so ignore congestion flag
+ if (credit < -DROP_THRESH ||
+ (len > LARGE_PKT_THRESH && credit < -LARGE_PKT_DROP_THRESH)) {
+ // Very congested, set drop packet
+ drop_flag = true;
+ if (pkti.ecn)
+ congestion_flag = true;
+ else if (pkti.is_tcp)
+ cwr_flag = true;
+ } else if (credit < 0) {
+ // Congested, set congestion flag
+ if (pkti.ecn || pkti.is_tcp) {
+ if (credit < -MARK_THRESH)
+ congestion_flag = true;
+ else
+ congestion_flag = false;
+ } else {
+ congestion_flag = true;
+ }
+ }
+
+ if (congestion_flag) {
+ if (bpf_skb_ecn_set_ce(skb)) {
+ ecn_ce_flag = true;
+ } else {
+ if (pkti.is_tcp) {
+ unsigned int rand = bpf_get_prandom_u32();
+
+ if (-credit >= MARK_THRESH +
+ (rand % MARK_REGION_SIZE)) {
+ // Do congestion control
+ cwr_flag = true;
+ }
+ } else if (len > LARGE_PKT_THRESH) {
+ // Problem if too many small packets?
+ drop_flag = true;
+ }
+ }
+ }
+
+ if (qsp != NULL)
+ if (qsp->no_cn)
+ cwr_flag = false;
+
+ hbm_update_stats(qsp, len, curtime, congestion_flag, drop_flag,
+ cwr_flag, ecn_ce_flag, &pkti, credit);
+
+ if (drop_flag) {
+ __sync_add_and_fetch(&(qdp->credit), len);
+ rv = DROP_PKT;
+ }
+
+ if (cwr_flag)
+ rv |= 2;
+ return rv;
+}
+char _license[] SEC("license") = "GPL";