samples/bpf: add cpumap sample program xdp_redirect_cpu

This sample program show how to use cpumap and the associated
tracepoints.

It provides command line stats, which shows how the XDP-RX process,
cpumap-enqueue and cpumap kthread dequeue is cooperating on a per CPU
basis.  It also utilize the xdp_exception and xdp_redirect_err
transpoints to allow users quickly to identify setup issues.

One issue with ixgbe driver is that the driver reset the link when
loading XDP.  This reset the procfs smp_affinity settings.  Thus,
after loading the program, these must be reconfigured.  The easiest
workaround it to reduce the RX-queue to e.g. two via:

 # ethtool --set-channels ixgbe1 combined 2

And then add CPUs above 0 and 1, like:

 # xdp_redirect_cpu --dev ixgbe1 --prog 2 --cpu 2 --cpu 3 --cpu 4

Another issue with ixgbe is that the page recycle mechanism is tied to
the RX-ring size.  And the default setting of 512 elements is too
small.  This is the same issue with regular devmap XDP_REDIRECT.
To overcome this I've been using 1024 rx-ring size:

 # ethtool -G ixgbe1 rx 1024 tx 1024

V3:
 - whitespace cleanups
 - bpf tracepoint cannot access top part of struct

V4:
 - report on kthread sched events, according to tracepoint change
 - report average bulk enqueue size

V5:
 - bpf_map_lookup_elem on cpumap not allowed from bpf_prog
   use separate map to mark CPUs not available

V6:
 - correct kthread sched summary output

V7:
 - Added a --stress-mode for concurrently changing underlying cpumap
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

samples/bpf/Makefile

@@ -39,6 +39,7 @@ hostprogs-y += per_socket_stats_example
 hostprogs-y += load_sock_ops
 hostprogs-y += xdp_redirect
 hostprogs-y += xdp_redirect_map
+hostprogs-y += xdp_redirect_cpu
 hostprogs-y += xdp_monitor
 hostprogs-y += syscall_tp
 
@@ -84,6 +85,7 @@ test_map_in_map-objs := bpf_load.o $(LIBBPF) test_map_in_map_user.o
 per_socket_stats_example-objs := $(LIBBPF) cookie_uid_helper_example.o
 xdp_redirect-objs := bpf_load.o $(LIBBPF) xdp_redirect_user.o
 xdp_redirect_map-objs := bpf_load.o $(LIBBPF) xdp_redirect_map_user.o
+xdp_redirect_cpu-objs := bpf_load.o $(LIBBPF) xdp_redirect_cpu_user.o
 xdp_monitor-objs := bpf_load.o $(LIBBPF) xdp_monitor_user.o
 syscall_tp-objs := bpf_load.o $(LIBBPF) syscall_tp_user.o
 
@@ -129,6 +131,7 @@ always += tcp_iw_kern.o
 always += tcp_clamp_kern.o
 always += xdp_redirect_kern.o
 always += xdp_redirect_map_kern.o
+always += xdp_redirect_cpu_kern.o
 always += xdp_monitor_kern.o
 always += syscall_tp_kern.o
 
@@ -169,6 +172,7 @@ HOSTLOADLIBES_xdp_tx_iptunnel += -lelf
 HOSTLOADLIBES_test_map_in_map += -lelf
 HOSTLOADLIBES_xdp_redirect += -lelf
 HOSTLOADLIBES_xdp_redirect_map += -lelf
+HOSTLOADLIBES_xdp_redirect_cpu += -lelf
 HOSTLOADLIBES_xdp_monitor += -lelf
 HOSTLOADLIBES_syscall_tp += -lelf
 

samples/bpf/xdp_redirect_cpu_kern.c

+/*  XDP redirect to CPUs via cpumap (BPF_MAP_TYPE_CPUMAP)
+ *
+ *  GPLv2, Copyright(c) 2017 Jesper Dangaard Brouer, Red Hat, Inc.
+ */
+#include <uapi/linux/if_ether.h>
+#include <uapi/linux/if_packet.h>
+#include <uapi/linux/if_vlan.h>
+#include <uapi/linux/ip.h>
+#include <uapi/linux/ipv6.h>
+#include <uapi/linux/in.h>
+#include <uapi/linux/tcp.h>
+#include <uapi/linux/udp.h>
+
+#include <uapi/linux/bpf.h>
+#include "bpf_helpers.h"
+
+#define MAX_CPUS 12 /* WARNING - sync with _user.c */
+
+/* Special map type that can XDP_REDIRECT frames to another CPU */
+struct bpf_map_def SEC("maps") cpu_map = {
+	.type		= BPF_MAP_TYPE_CPUMAP,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(u32),
+	.max_entries	= MAX_CPUS,
+};
+
+/* Common stats data record to keep userspace more simple */
+struct datarec {
+	__u64 processed;
+	__u64 dropped;
+	__u64 issue;
+};
+
+/* Count RX packets, as XDP bpf_prog doesn't get direct TX-success
+ * feedback.  Redirect TX errors can be caught via a tracepoint.
+ */
+struct bpf_map_def SEC("maps") rx_cnt = {
+	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(struct datarec),
+	.max_entries	= 1,
+};
+
+/* Used by trace point */
+struct bpf_map_def SEC("maps") redirect_err_cnt = {
+	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(struct datarec),
+	.max_entries	= 2,
+	/* TODO: have entries for all possible errno's */
+};
+
+/* Used by trace point */
+struct bpf_map_def SEC("maps") cpumap_enqueue_cnt = {
+	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(struct datarec),
+	.max_entries	= MAX_CPUS,
+};
+
+/* Used by trace point */
+struct bpf_map_def SEC("maps") cpumap_kthread_cnt = {
+	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(struct datarec),
+	.max_entries	= 1,
+};
+
+/* Set of maps controlling available CPU, and for iterating through
+ * selectable redirect CPUs.
+ */
+struct bpf_map_def SEC("maps") cpus_available = {
+	.type		= BPF_MAP_TYPE_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(u32),
+	.max_entries	= MAX_CPUS,
+};
+struct bpf_map_def SEC("maps") cpus_count = {
+	.type		= BPF_MAP_TYPE_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(u32),
+	.max_entries	= 1,
+};
+struct bpf_map_def SEC("maps") cpus_iterator = {
+	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(u32),
+	.max_entries	= 1,
+};
+
+/* Used by trace point */
+struct bpf_map_def SEC("maps") exception_cnt = {
+	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(struct datarec),
+	.max_entries	= 1,
+};
+
+/* Helper parse functions */
+
+/* Parse Ethernet layer 2, extract network layer 3 offset and protocol
+ *
+ * Returns false on error and non-supported ether-type
+ */
+struct vlan_hdr {
+	__be16 h_vlan_TCI;
+	__be16 h_vlan_encapsulated_proto;
+};
+
+static __always_inline
+bool parse_eth(struct ethhdr *eth, void *data_end,
+	       u16 *eth_proto, u64 *l3_offset)
+{
+	u16 eth_type;
+	u64 offset;
+
+	offset = sizeof(*eth);
+	if ((void *)eth + offset > data_end)
+		return false;
+
+	eth_type = eth->h_proto;
+
+	/* Skip non 802.3 Ethertypes */
+	if (unlikely(ntohs(eth_type) < ETH_P_802_3_MIN))
+		return false;
+
+	/* Handle VLAN tagged packet */
+	if (eth_type == htons(ETH_P_8021Q) || eth_type == htons(ETH_P_8021AD)) {
+		struct vlan_hdr *vlan_hdr;
+
+		vlan_hdr = (void *)eth + offset;
+		offset += sizeof(*vlan_hdr);
+		if ((void *)eth + offset > data_end)
+			return false;
+		eth_type = vlan_hdr->h_vlan_encapsulated_proto;
+	}
+	/* TODO: Handle double VLAN tagged packet */
+
+	*eth_proto = ntohs(eth_type);
+	*l3_offset = offset;
+	return true;
+}
+
+static __always_inline
+u16 get_dest_port_ipv4_udp(struct xdp_md *ctx, u64 nh_off)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+	struct iphdr *iph = data + nh_off;
+	struct udphdr *udph;
+	u16 dport;
+
+	if (iph + 1 > data_end)
+		return 0;
+	if (!(iph->protocol == IPPROTO_UDP))
+		return 0;
+
+	udph = (void *)(iph + 1);
+	if (udph + 1 > data_end)
+		return 0;
+
+	dport = ntohs(udph->dest);
+	return dport;
+}
+
+static __always_inline
+int get_proto_ipv4(struct xdp_md *ctx, u64 nh_off)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+	struct iphdr *iph = data + nh_off;
+
+	if (iph + 1 > data_end)
+		return 0;
+	return iph->protocol;
+}
+
+static __always_inline
+int get_proto_ipv6(struct xdp_md *ctx, u64 nh_off)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+	struct ipv6hdr *ip6h = data + nh_off;
+
+	if (ip6h + 1 > data_end)
+		return 0;
+	return ip6h->nexthdr;
+}
+
+SEC("xdp_cpu_map0")
+int  xdp_prognum0_no_touch(struct xdp_md *ctx)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+	struct datarec *rec;
+	u32 *cpu_selected;
+	u32 cpu_dest;
+	u32 key = 0;
+
+	/* Only use first entry in cpus_available */
+	cpu_selected = bpf_map_lookup_elem(&cpus_available, &key);
+	if (!cpu_selected)
+		return XDP_ABORTED;
+	cpu_dest = *cpu_selected;
+
+	/* Count RX packet in map */
+	rec = bpf_map_lookup_elem(&rx_cnt, &key);
+	if (!rec)
+		return XDP_ABORTED;
+	rec->processed++;
+
+	if (cpu_dest >= MAX_CPUS) {
+		rec->issue++;
+		return XDP_ABORTED;
+	}
+
+	return bpf_redirect_map(&cpu_map, cpu_dest, 0);
+}
+
+SEC("xdp_cpu_map1_touch_data")
+int  xdp_prognum1_touch_data(struct xdp_md *ctx)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+	struct ethhdr *eth = data;
+	struct datarec *rec;
+	u32 *cpu_selected;
+	u32 cpu_dest;
+	u16 eth_type;
+	u32 key = 0;
+
+	/* Only use first entry in cpus_available */
+	cpu_selected = bpf_map_lookup_elem(&cpus_available, &key);
+	if (!cpu_selected)
+		return XDP_ABORTED;
+	cpu_dest = *cpu_selected;
+
+	/* Validate packet length is minimum Eth header size */
+	if (eth + 1 > data_end)
+		return XDP_ABORTED;
+
+	/* Count RX packet in map */
+	rec = bpf_map_lookup_elem(&rx_cnt, &key);
+	if (!rec)
+		return XDP_ABORTED;
+	rec->processed++;
+
+	/* Read packet data, and use it (drop non 802.3 Ethertypes) */
+	eth_type = eth->h_proto;
+	if (ntohs(eth_type) < ETH_P_802_3_MIN) {
+		rec->dropped++;
+		return XDP_DROP;
+	}
+
+	if (cpu_dest >= MAX_CPUS) {
+		rec->issue++;
+		return XDP_ABORTED;
+	}
+
+	return bpf_redirect_map(&cpu_map, cpu_dest, 0);
+}
+
+SEC("xdp_cpu_map2_round_robin")
+int  xdp_prognum2_round_robin(struct xdp_md *ctx)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+	struct ethhdr *eth = data;
+	struct datarec *rec;
+	u32 cpu_dest;
+	u32 *cpu_lookup;
+	u32 key0 = 0;
+
+	u32 *cpu_selected;
+	u32 *cpu_iterator;
+	u32 *cpu_max;
+	u32 cpu_idx;
+
+	cpu_max = bpf_map_lookup_elem(&cpus_count, &key0);
+	if (!cpu_max)
+		return XDP_ABORTED;
+
+	cpu_iterator = bpf_map_lookup_elem(&cpus_iterator, &key0);
+	if (!cpu_iterator)
+		return XDP_ABORTED;
+	cpu_idx = *cpu_iterator;
+
+	*cpu_iterator += 1;
+	if (*cpu_iterator == *cpu_max)
+		*cpu_iterator = 0;
+
+	cpu_selected = bpf_map_lookup_elem(&cpus_available, &cpu_idx);
+	if (!cpu_selected)
+		return XDP_ABORTED;
+	cpu_dest = *cpu_selected;
+
+	/* Count RX packet in map */
+	rec = bpf_map_lookup_elem(&rx_cnt, &key0);
+	if (!rec)
+		return XDP_ABORTED;
+	rec->processed++;
+
+	if (cpu_dest >= MAX_CPUS) {
+		rec->issue++;
+		return XDP_ABORTED;
+	}
+
+	return bpf_redirect_map(&cpu_map, cpu_dest, 0);
+}
+
+SEC("xdp_cpu_map3_proto_separate")
+int  xdp_prognum3_proto_separate(struct xdp_md *ctx)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+	struct ethhdr *eth = data;
+	u8 ip_proto = IPPROTO_UDP;
+	struct datarec *rec;
+	u16 eth_proto = 0;
+	u64 l3_offset = 0;
+	u32 cpu_dest = 0;
+	u32 cpu_idx = 0;
+	u32 *cpu_lookup;
+	u32 key = 0;
+
+	/* Count RX packet in map */
+	rec = bpf_map_lookup_elem(&rx_cnt, &key);
+	if (!rec)
+		return XDP_ABORTED;
+	rec->processed++;
+
+	if (!(parse_eth(eth, data_end, &eth_proto, &l3_offset)))
+		return XDP_PASS; /* Just skip */
+
+	/* Extract L4 protocol */
+	switch (eth_proto) {
+	case ETH_P_IP:
+		ip_proto = get_proto_ipv4(ctx, l3_offset);
+		break;
+	case ETH_P_IPV6:
+		ip_proto = get_proto_ipv6(ctx, l3_offset);
+		break;
+	case ETH_P_ARP:
+		cpu_idx = 0; /* ARP packet handled on separate CPU */
+		break;
+	default:
+		cpu_idx = 0;
+	}
+
+	/* Choose CPU based on L4 protocol */
+	switch (ip_proto) {
+	case IPPROTO_ICMP:
+	case IPPROTO_ICMPV6:
+		cpu_idx = 2;
+		break;
+	case IPPROTO_TCP:
+		cpu_idx = 0;
+		break;
+	case IPPROTO_UDP:
+		cpu_idx = 1;
+		break;
+	default:
+		cpu_idx = 0;
+	}
+
+	cpu_lookup = bpf_map_lookup_elem(&cpus_available, &cpu_idx);
+	if (!cpu_lookup)
+		return XDP_ABORTED;
+	cpu_dest = *cpu_lookup;
+
+	if (cpu_dest >= MAX_CPUS) {
+		rec->issue++;
+		return XDP_ABORTED;
+	}
+
+	return bpf_redirect_map(&cpu_map, cpu_dest, 0);
+}
+
+SEC("xdp_cpu_map4_ddos_filter_pktgen")
+int  xdp_prognum4_ddos_filter_pktgen(struct xdp_md *ctx)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data     = (void *)(long)ctx->data;
+	struct ethhdr *eth = data;
+	u8 ip_proto = IPPROTO_UDP;
+	struct datarec *rec;
+	u16 eth_proto = 0;
+	u64 l3_offset = 0;
+	u32 cpu_dest = 0;
+	u32 cpu_idx = 0;
+	u16 dest_port;
+	u32 *cpu_lookup;
+	u32 key = 0;
+
+	/* Count RX packet in map */
+	rec = bpf_map_lookup_elem(&rx_cnt, &key);
+	if (!rec)
+		return XDP_ABORTED;
+	rec->processed++;
+
+	if (!(parse_eth(eth, data_end, &eth_proto, &l3_offset)))
+		return XDP_PASS; /* Just skip */
+
+	/* Extract L4 protocol */
+	switch (eth_proto) {
+	case ETH_P_IP:
+		ip_proto = get_proto_ipv4(ctx, l3_offset);
+		break;
+	case ETH_P_IPV6:
+		ip_proto = get_proto_ipv6(ctx, l3_offset);
+		break;
+	case ETH_P_ARP:
+		cpu_idx = 0; /* ARP packet handled on separate CPU */
+		break;
+	default:
+		cpu_idx = 0;
+	}
+
+	/* Choose CPU based on L4 protocol */
+	switch (ip_proto) {
+	case IPPROTO_ICMP:
+	case IPPROTO_ICMPV6:
+		cpu_idx = 2;
+		break;
+	case IPPROTO_TCP:
+		cpu_idx = 0;
+		break;
+	case IPPROTO_UDP:
+		cpu_idx = 1;
+		/* DDoS filter UDP port 9 (pktgen) */
+		dest_port = get_dest_port_ipv4_udp(ctx, l3_offset);
+		if (dest_port == 9) {
+			if (rec)
+				rec->dropped++;
+			return XDP_DROP;
+		}
+		break;
+	default:
+		cpu_idx = 0;
+	}
+
+	cpu_lookup = bpf_map_lookup_elem(&cpus_available, &cpu_idx);
+	if (!cpu_lookup)
+		return XDP_ABORTED;
+	cpu_dest = *cpu_lookup;
+
+	if (cpu_dest >= MAX_CPUS) {
+		rec->issue++;
+		return XDP_ABORTED;
+	}
+
+	return bpf_redirect_map(&cpu_map, cpu_dest, 0);
+}
+
+
+char _license[] SEC("license") = "GPL";
+
+/*** Trace point code ***/
+
+/* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_redirect/format
+ * Code in:                kernel/include/trace/events/xdp.h
+ */
+struct xdp_redirect_ctx {
+	u64 __pad;	// First 8 bytes are not accessible by bpf code
+	int prog_id;	//	offset:8;  size:4; signed:1;
+	u32 act;	//	offset:12  size:4; signed:0;
+	int ifindex;	//	offset:16  size:4; signed:1;
+	int err;	//	offset:20  size:4; signed:1;
+	int to_ifindex;	//	offset:24  size:4; signed:1;
+	u32 map_id;	//	offset:28  size:4; signed:0;
+	int map_index;	//	offset:32  size:4; signed:1;
+};			//	offset:36
+
+enum {
+	XDP_REDIRECT_SUCCESS = 0,
+	XDP_REDIRECT_ERROR = 1
+};
+
+static __always_inline
+int xdp_redirect_collect_stat(struct xdp_redirect_ctx *ctx)
+{
+	u32 key = XDP_REDIRECT_ERROR;
+	struct datarec *rec;
+	int err = ctx->err;
+
+	if (!err)
+		key = XDP_REDIRECT_SUCCESS;
+
+	rec = bpf_map_lookup_elem(&redirect_err_cnt, &key);
+	if (!rec)
+		return 0;
+	rec->dropped += 1;
+
+	return 0; /* Indicate event was filtered (no further processing)*/
+	/*
+	 * Returning 1 here would allow e.g. a perf-record tracepoint
+	 * to see and record these events, but it doesn't work well
+	 * in-practice as stopping perf-record also unload this
+	 * bpf_prog.  Plus, there is additional overhead of doing so.
+	 */
+}
+
+SEC("tracepoint/xdp/xdp_redirect_err")
+int trace_xdp_redirect_err(struct xdp_redirect_ctx *ctx)
+{
+	return xdp_redirect_collect_stat(ctx);
+}
+
+SEC("tracepoint/xdp/xdp_redirect_map_err")
+int trace_xdp_redirect_map_err(struct xdp_redirect_ctx *ctx)
+{
+	return xdp_redirect_collect_stat(ctx);
+}
+
+/* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_exception/format
+ * Code in:                kernel/include/trace/events/xdp.h
+ */
+struct xdp_exception_ctx {
+	u64 __pad;	// First 8 bytes are not accessible by bpf code
+	int prog_id;	//	offset:8;  size:4; signed:1;
+	u32 act;	//	offset:12; size:4; signed:0;
+	int ifindex;	//	offset:16; size:4; signed:1;
+};
+
+SEC("tracepoint/xdp/xdp_exception")
+int trace_xdp_exception(struct xdp_exception_ctx *ctx)
+{
+	struct datarec *rec;
+	u32 key = 0;
+
+	rec = bpf_map_lookup_elem(&exception_cnt, &key);
+	if (!rec)
+		return 1;
+	rec->dropped += 1;
+
+	return 0;
+}
+
+/* Tracepoint: /sys/kernel/debug/tracing/events/xdp/xdp_cpumap_enqueue/format
+ * Code in:         kernel/include/trace/events/xdp.h
+ */
+struct cpumap_enqueue_ctx {
+	u64 __pad;		// First 8 bytes are not accessible by bpf code
+	int map_id;		//	offset:8;  size:4; signed:1;
+	u32 act;		//	offset:12; size:4; signed:0;
+	int cpu;		//	offset:16; size:4; signed:1;
+	unsigned int drops;	//	offset:20; size:4; signed:0;
+	unsigned int processed;	//	offset:24; size:4; signed:0;
+	int to_cpu;		//	offset:28; size:4; signed:1;
+};
+
+SEC("tracepoint/xdp/xdp_cpumap_enqueue")
+int trace_xdp_cpumap_enqueue(struct cpumap_enqueue_ctx *ctx)
+{
+	u32 to_cpu = ctx->to_cpu;
+	struct datarec *rec;
+
+	if (to_cpu >= MAX_CPUS)
+		return 1;
+
+	rec = bpf_map_lookup_elem(&cpumap_enqueue_cnt, &to_cpu);
+	if (!rec)
+		return 0;
+	rec->processed += ctx->processed;
+	rec->dropped   += ctx->drops;
+
+	/* Record bulk events, then userspace can calc average bulk size */
+	if (ctx->processed > 0)
+		rec->issue += 1;
+
+	/* Inception: It's possible to detect overload situations, via
+	 * this tracepoint.  This can be used for creating a feedback
+	 * loop to XDP, which can take appropriate actions to mitigate
+	 * this overload situation.
+	 */
+	return 0;
+}
+
+/* Tracepoint: /sys/kernel/debug/tracing/events/xdp/xdp_cpumap_kthread/format
+ * Code in:         kernel/include/trace/events/xdp.h
+ */
+struct cpumap_kthread_ctx {
+	u64 __pad;		// First 8 bytes are not accessible by bpf code
+	int map_id;		//	offset:8;  size:4; signed:1;
+	u32 act;		//	offset:12; size:4; signed:0;
+	int cpu;		//	offset:16; size:4; signed:1;
+	unsigned int drops;	//	offset:20; size:4; signed:0;
+	unsigned int processed;	//	offset:24; size:4; signed:0;
+	int sched;		//	offset:28; size:4; signed:1;
+};
+
+SEC("tracepoint/xdp/xdp_cpumap_kthread")
+int trace_xdp_cpumap_kthread(struct cpumap_kthread_ctx *ctx)
+{
+	struct datarec *rec;
+	u32 key = 0;
+
+	rec = bpf_map_lookup_elem(&cpumap_kthread_cnt, &key);
+	if (!rec)
+		return 0;
+	rec->processed += ctx->processed;
+	rec->dropped   += ctx->drops;
+
+	/* Count times kthread yielded CPU via schedule call */
+	if (ctx->sched)
+		rec->issue++;
+
+	return 0;
+}

samples/bpf/xdp_redirect_cpu_user.c

+/* GPLv2 Copyright(c) 2017 Jesper Dangaard Brouer, Red Hat, Inc.
+ */
+static const char *__doc__ =
+	" XDP redirect with a CPU-map type \"BPF_MAP_TYPE_CPUMAP\"";
+
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+#include <locale.h>
+#include <sys/resource.h>
+#include <getopt.h>
+#include <net/if.h>
+#include <time.h>
+
+#include <arpa/inet.h>
+#include <linux/if_link.h>
+
+#define MAX_CPUS 12 /* WARNING - sync with _kern.c */
+
+/* How many xdp_progs are defined in _kern.c */
+#define MAX_PROG 5
+
+/* Wanted to get rid of bpf_load.h and fake-"libbpf.h" (and instead
+ * use bpf/libbpf.h), but cannot as (currently) needed for XDP
+ * attaching to a device via set_link_xdp_fd()
+ */
+#include "libbpf.h"
+#include "bpf_load.h"
+
+#include "bpf_util.h"
+
+static int ifindex = -1;
+static char ifname_buf[IF_NAMESIZE];
+static char *ifname;
+
+static __u32 xdp_flags;
+
+/* Exit return codes */
+#define EXIT_OK		0
+#define EXIT_FAIL		1
+#define EXIT_FAIL_OPTION	2
+#define EXIT_FAIL_XDP		3
+#define EXIT_FAIL_BPF		4
+#define EXIT_FAIL_MEM		5
+
+static const struct option long_options[] = {
+	{"help",	no_argument,		NULL, 'h' },
+	{"dev",		required_argument,	NULL, 'd' },
+	{"skb-mode",	no_argument,		NULL, 'S' },
+	{"debug",	no_argument,		NULL, 'D' },
+	{"sec",		required_argument,	NULL, 's' },
+	{"prognum",	required_argument,	NULL, 'p' },
+	{"qsize",	required_argument,	NULL, 'q' },
+	{"cpu",		required_argument,	NULL, 'c' },
+	{"stress-mode", no_argument,		NULL, 'x' },
+	{"no-separators", no_argument,		NULL, 'z' },
+	{0, 0, NULL,  0 }
+};
+
+static void int_exit(int sig)
+{
+	fprintf(stderr,
+		"Interrupted: Removing XDP program on ifindex:%d device:%s\n",
+		ifindex, ifname);
+	if (ifindex > -1)
+		set_link_xdp_fd(ifindex, -1, xdp_flags);
+	exit(EXIT_OK);
+}
+
+static void usage(char *argv[])
+{
+	int i;
+
+	printf("\nDOCUMENTATION:\n%s\n", __doc__);
+	printf("\n");
+	printf(" Usage: %s (options-see-below)\n", argv[0]);
+	printf(" Listing options:\n");
+	for (i = 0; long_options[i].name != 0; i++) {
+		printf(" --%-12s", long_options[i].name);
+		if (long_options[i].flag != NULL)
+			printf(" flag (internal value:%d)",
+				*long_options[i].flag);
+		else
+			printf(" short-option: -%c",
+				long_options[i].val);
+		printf("\n");
+	}
+	printf("\n");
+}
+
+/* gettime returns the current time of day in nanoseconds.
+ * Cost: clock_gettime (ns) => 26ns (CLOCK_MONOTONIC)
+ *       clock_gettime (ns) =>  9ns (CLOCK_MONOTONIC_COARSE)
+ */
+#define NANOSEC_PER_SEC 1000000000 /* 10^9 */
+static __u64 gettime(void)
+{
+	struct timespec t;
+	int res;
+
+	res = clock_gettime(CLOCK_MONOTONIC, &t);
+	if (res < 0) {
+		fprintf(stderr, "Error with gettimeofday! (%i)\n", res);
+		exit(EXIT_FAIL);
+	}
+	return (__u64) t.tv_sec * NANOSEC_PER_SEC + t.tv_nsec;
+}
+
+/* Common stats data record shared with _kern.c */
+struct datarec {
+	__u64 processed;
+	__u64 dropped;
+	__u64 issue;
+};
+struct record {
+	__u64 timestamp;
+	struct datarec total;
+	struct datarec *cpu;
+};
+struct stats_record {
+	struct record rx_cnt;
+	struct record redir_err;
+	struct record kthread;
+	struct record exception;
+	struct record enq[MAX_CPUS];
+};
+
+static bool map_collect_percpu(int fd, __u32 key, struct record *rec)
+{
+	/* For percpu maps, userspace gets a value per possible CPU */
+	unsigned int nr_cpus = bpf_num_possible_cpus();
+	struct datarec values[nr_cpus];
+	__u64 sum_processed = 0;
+	__u64 sum_dropped = 0;
+	__u64 sum_issue = 0;
+	int i;
+
+	if ((bpf_map_lookup_elem(fd, &key, values)) != 0) {
+		fprintf(stderr,
+			"ERR: bpf_map_lookup_elem failed key:0x%X\n", key);
+		return false;
+	}
+	/* Get time as close as possible to reading map contents */
+	rec->timestamp = gettime();
+
+	/* Record and sum values from each CPU */
+	for (i = 0; i < nr_cpus; i++) {
+		rec->cpu[i].processed = values[i].processed;
+		sum_processed        += values[i].processed;
+		rec->cpu[i].dropped = values[i].dropped;
+		sum_dropped        += values[i].dropped;
+		rec->cpu[i].issue = values[i].issue;
+		sum_issue        += values[i].issue;
+	}
+	rec->total.processed = sum_processed;
+	rec->total.dropped   = sum_dropped;
+	rec->total.issue     = sum_issue;
+	return true;
+}
+
+static struct datarec *alloc_record_per_cpu(void)
+{
+	unsigned int nr_cpus = bpf_num_possible_cpus();
+	struct datarec *array;
+	size_t size;
+
+	size = sizeof(struct datarec) * nr_cpus;
+	array = malloc(size);
+	memset(array, 0, size);
+	if (!array) {
+		fprintf(stderr, "Mem alloc error (nr_cpus:%u)\n", nr_cpus);
+		exit(EXIT_FAIL_MEM);
+	}
+	return array;
+}
+
+static struct stats_record *alloc_stats_record(void)
+{
+	struct stats_record *rec;
+	int i;
+
+	rec = malloc(sizeof(*rec));
+	memset(rec, 0, sizeof(*rec));
+	if (!rec) {
+		fprintf(stderr, "Mem alloc error\n");
+		exit(EXIT_FAIL_MEM);
+	}
+	rec->rx_cnt.cpu    = alloc_record_per_cpu();
+	rec->redir_err.cpu = alloc_record_per_cpu();
+	rec->kthread.cpu   = alloc_record_per_cpu();
+	rec->exception.cpu = alloc_record_per_cpu();
+	for (i = 0; i < MAX_CPUS; i++)
+		rec->enq[i].cpu = alloc_record_per_cpu();
+
+	return rec;
+}
+
+static void free_stats_record(struct stats_record *r)
+{
+	int i;
+
+	for (i = 0; i < MAX_CPUS; i++)
+		free(r->enq[i].cpu);
+	free(r->exception.cpu);
+	free(r->kthread.cpu);
+	free(r->redir_err.cpu);
+	free(r->rx_cnt.cpu);
+	free(r);
+}
+
+static double calc_period(struct record *r, struct record *p)
+{
+	double period_ = 0;
+	__u64 period = 0;
+
+	period = r->timestamp - p->timestamp;
+	if (period > 0)
+		period_ = ((double) period / NANOSEC_PER_SEC);
+
+	return period_;
+}
+
+static __u64 calc_pps(struct datarec *r, struct datarec *p, double period_)
+{
+	__u64 packets = 0;
+	__u64 pps = 0;
+
+	if (period_ > 0) {
+		packets = r->processed - p->processed;
+		pps = packets / period_;
+	}
+	return pps;
+}
+
+static __u64 calc_drop_pps(struct datarec *r, struct datarec *p, double period_)
+{
+	__u64 packets = 0;
+	__u64 pps = 0;
+
+	if (period_ > 0) {
+		packets = r->dropped - p->dropped;
+		pps = packets / period_;
+	}
+	return pps;
+}
+
+static __u64 calc_errs_pps(struct datarec *r,
+			    struct datarec *p, double period_)
+{
+	__u64 packets = 0;
+	__u64 pps = 0;
+
+	if (period_ > 0) {
+		packets = r->issue - p->issue;
+		pps = packets / period_;
+	}
+	return pps;
+}
+
+static void stats_print(struct stats_record *stats_rec,
+			struct stats_record *stats_prev,
+			int prog_num)
+{
+	unsigned int nr_cpus = bpf_num_possible_cpus();
+	double pps = 0, drop = 0, err = 0;
+	struct record *rec, *prev;
+	int to_cpu;
+	double t;
+	int i;
+
+	/* Header */
+	printf("Running XDP/eBPF prog_num:%d\n", prog_num);
+	printf("%-15s %-7s %-14s %-11s %-9s\n",
+	       "XDP-cpumap", "CPU:to", "pps", "drop-pps", "extra-info");
+
+	/* XDP rx_cnt */
+	{
+		char *fmt_rx = "%-15s %-7d %'-14.0f %'-11.0f %'-10.0f %s\n";
+		char *fm2_rx = "%-15s %-7s %'-14.0f %'-11.0f\n";
+		char *errstr = "";
+
+		rec  = &stats_rec->rx_cnt;
+		prev = &stats_prev->rx_cnt;
+		t = calc_period(rec, prev);
+		for (i = 0; i < nr_cpus; i++) {
+			struct datarec *r = &rec->cpu[i];
+			struct datarec *p = &prev->cpu[i];
+
+			pps = calc_pps(r, p, t);
+			drop = calc_drop_pps(r, p, t);
+			err  = calc_errs_pps(r, p, t);
+			if (err > 0)
+				errstr = "cpu-dest/err";
+			if (pps > 0)
+				printf(fmt_rx, "XDP-RX",
+					i, pps, drop, err, errstr);
+		}
+		pps  = calc_pps(&rec->total, &prev->total, t);
+		drop = calc_drop_pps(&rec->total, &prev->total, t);
+		err  = calc_errs_pps(&rec->total, &prev->total, t);
+		printf(fm2_rx, "XDP-RX", "total", pps, drop);
+	}
+
+	/* cpumap enqueue stats */
+	for (to_cpu = 0; to_cpu < MAX_CPUS; to_cpu++) {
+		char *fmt = "%-15s %3d:%-3d %'-14.0f %'-11.0f %'-10.2f %s\n";
+		char *fm2 = "%-15s %3s:%-3d %'-14.0f %'-11.0f %'-10.2f %s\n";
+		char *errstr = "";
+
+		rec  =  &stats_rec->enq[to_cpu];
+		prev = &stats_prev->enq[to_cpu];
+		t = calc_period(rec, prev);
+		for (i = 0; i < nr_cpus; i++) {
+			struct datarec *r = &rec->cpu[i];
+			struct datarec *p = &prev->cpu[i];
+
+			pps  = calc_pps(r, p, t);
+			drop = calc_drop_pps(r, p, t);
+			err  = calc_errs_pps(r, p, t);
+			if (err > 0) {
+				errstr = "bulk-average";
+				err = pps / err; /* calc average bulk size */
+			}
+			if (pps > 0)
+				printf(fmt, "cpumap-enqueue",
+				       i, to_cpu, pps, drop, err, errstr);
+		}
+		pps = calc_pps(&rec->total, &prev->total, t);
+		if (pps > 0) {
+			drop = calc_drop_pps(&rec->total, &prev->total, t);
+			err  = calc_errs_pps(&rec->total, &prev->total, t);
+			if (err > 0) {
+				errstr = "bulk-average";
+				err = pps / err; /* calc average bulk size */
+			}
+			printf(fm2, "cpumap-enqueue",
+			       "sum", to_cpu, pps, drop, err, errstr);
+		}
+	}
+
+	/* cpumap kthread stats */
+	{
+		char *fmt_k = "%-15s %-7d %'-14.0f %'-11.0f %'-10.0f %s\n";
+		char *fm2_k = "%-15s %-7s %'-14.0f %'-11.0f %'-10.0f %s\n";
+		char *e_str = "";
+
+		rec  = &stats_rec->kthread;
+		prev = &stats_prev->kthread;
+		t = calc_period(rec, prev);
+		for (i = 0; i < nr_cpus; i++) {
+			struct datarec *r = &rec->cpu[i];
+			struct datarec *p = &prev->cpu[i];
+
+			pps  = calc_pps(r, p, t);
+			drop = calc_drop_pps(r, p, t);
+			err  = calc_errs_pps(r, p, t);
+			if (err > 0)
+				e_str = "sched";
+			if (pps > 0)
+				printf(fmt_k, "cpumap_kthread",
+				       i, pps, drop, err, e_str);
+		}
+		pps = calc_pps(&rec->total, &prev->total, t);
+		drop = calc_drop_pps(&rec->total, &prev->total, t);
+		err  = calc_errs_pps(&rec->total, &prev->total, t);
+		if (err > 0)
+			e_str = "sched-sum";
+		printf(fm2_k, "cpumap_kthread", "total", pps, drop, err, e_str);
+	}
+
+	/* XDP redirect err tracepoints (very unlikely) */
+	{
+		char *fmt_err = "%-15s %-7d %'-14.0f %'-11.0f\n";
+		char *fm2_err = "%-15s %-7s %'-14.0f %'-11.0f\n";
+
+		rec  = &stats_rec->redir_err;
+		prev = &stats_prev->redir_err;
+		t = calc_period(rec, prev);
+		for (i = 0; i < nr_cpus; i++) {
+			struct datarec *r = &rec->cpu[i];
+			struct datarec *p = &prev->cpu[i];
+
+			pps  = calc_pps(r, p, t);
+			drop = calc_drop_pps(r, p, t);
+			if (pps > 0)
+				printf(fmt_err, "redirect_err", i, pps, drop);
+		}
+		pps = calc_pps(&rec->total, &prev->total, t);
+		drop = calc_drop_pps(&rec->total, &prev->total, t);
+		printf(fm2_err, "redirect_err", "total", pps, drop);
+	}
+
+	/* XDP general exception tracepoints */
+	{
+		char *fmt_err = "%-15s %-7d %'-14.0f %'-11.0f\n";
+		char *fm2_err = "%-15s %-7s %'-14.0f %'-11.0f\n";
+
+		rec  = &stats_rec->exception;
+		prev = &stats_prev->exception;
+		t = calc_period(rec, prev);
+		for (i = 0; i < nr_cpus; i++) {
+			struct datarec *r = &rec->cpu[i];
+			struct datarec *p = &prev->cpu[i];
+
+			pps  = calc_pps(r, p, t);
+			drop = calc_drop_pps(r, p, t);
+			if (pps > 0)
+				printf(fmt_err, "xdp_exception", i, pps, drop);
+		}
+		pps = calc_pps(&rec->total, &prev->total, t);
+		drop = calc_drop_pps(&rec->total, &prev->total, t);
+		printf(fm2_err, "xdp_exception", "total", pps, drop);
+	}
+
+	printf("\n");
+	fflush(stdout);
+}
+
+static void stats_collect(struct stats_record *rec)
+{
+	int fd, i;
+
+	fd = map_fd[1]; /* map: rx_cnt */
+	map_collect_percpu(fd, 0, &rec->rx_cnt);
+
+	fd = map_fd[2]; /* map: redirect_err_cnt */
+	map_collect_percpu(fd, 1, &rec->redir_err);
+
+	fd = map_fd[3]; /* map: cpumap_enqueue_cnt */
+	for (i = 0; i < MAX_CPUS; i++)
+		map_collect_percpu(fd, i, &rec->enq[i]);
+
+	fd = map_fd[4]; /* map: cpumap_kthread_cnt */
+	map_collect_percpu(fd, 0, &rec->kthread);
+
+	fd = map_fd[8]; /* map: exception_cnt */
+	map_collect_percpu(fd, 0, &rec->exception);
+}
+
+
+/* Pointer swap trick */
+static inline void swap(struct stats_record **a, struct stats_record **b)
+{
+	struct stats_record *tmp;
+
+	tmp = *a;
+	*a = *b;
+	*b = tmp;
+}
+
+static int create_cpu_entry(__u32 cpu, __u32 queue_size,
+			    __u32 avail_idx, bool new)
+{
+	__u32 curr_cpus_count = 0;
+	__u32 key = 0;
+	int ret;
+
+	/* Add a CPU entry to cpumap, as this allocate a cpu entry in
+	 * the kernel for the cpu.
+	 */
+	ret = bpf_map_update_elem(map_fd[0], &cpu, &queue_size, 0);
+	if (ret) {
+		fprintf(stderr, "Create CPU entry failed (err:%d)\n", ret);
+		exit(EXIT_FAIL_BPF);
+	}
+
+	/* Inform bpf_prog's that a new CPU is available to select
+	 * from via some control maps.
+	 */
+	/* map_fd[5] = cpus_available */
+	ret = bpf_map_update_elem(map_fd[5], &avail_idx, &cpu, 0);
+	if (ret) {
+		fprintf(stderr, "Add to avail CPUs failed\n");
+		exit(EXIT_FAIL_BPF);
+	}
+
+	/* When not replacing/updating existing entry, bump the count */
+	/* map_fd[6] = cpus_count */
+	ret = bpf_map_lookup_elem(map_fd[6], &key, &curr_cpus_count);
+	if (ret) {
+		fprintf(stderr, "Failed reading curr cpus_count\n");
+		exit(EXIT_FAIL_BPF);
+	}
+	if (new) {
+		curr_cpus_count++;
+		ret = bpf_map_update_elem(map_fd[6], &key, &curr_cpus_count, 0);
+		if (ret) {
+			fprintf(stderr, "Failed write curr cpus_count\n");
+			exit(EXIT_FAIL_BPF);
+		}
+	}
+	/* map_fd[7] = cpus_iterator */
+	printf("%s CPU:%u as idx:%u queue_size:%d (total cpus_count:%u)\n",
+	       new ? "Add-new":"Replace", cpu, avail_idx,
+	       queue_size, curr_cpus_count);
+
+	return 0;
+}
+
+/* CPUs are zero-indexed. Thus, add a special sentinel default value
+ * in map cpus_available to mark CPU index'es not configured
+ */
+static void mark_cpus_unavailable(void)
+{
+	__u32 invalid_cpu = MAX_CPUS;
+	int ret, i;
+
+	for (i = 0; i < MAX_CPUS; i++) {
+		/* map_fd[5] = cpus_available */
+		ret = bpf_map_update_elem(map_fd[5], &i, &invalid_cpu, 0);
+		if (ret) {
+			fprintf(stderr, "Failed marking CPU unavailable\n");
+			exit(EXIT_FAIL_BPF);
+		}
+	}
+}
+
+/* Stress cpumap management code by concurrently changing underlying cpumap */
+static void stress_cpumap(void)
+{
+	/* Changing qsize will cause kernel to free and alloc a new
+	 * bpf_cpu_map_entry, with an associated/complicated tear-down
+	 * procedure.
+	 */
+	create_cpu_entry(1,  1024, 0, false);
+	create_cpu_entry(1,   128, 0, false);
+	create_cpu_entry(1, 16000, 0, false);
+}
+
+static void stats_poll(int interval, bool use_separators, int prog_num,
+		       bool stress_mode)
+{
+	struct stats_record *record, *prev;
+
+	record = alloc_stats_record();
+	prev   = alloc_stats_record();
+	stats_collect(record);
+
+	/* Trick to pretty printf with thousands separators use %' */
+	if (use_separators)
+		setlocale(LC_NUMERIC, "en_US");
+
+	while (1) {
+		swap(&prev, &record);
+		stats_collect(record);
+		stats_print(record, prev, prog_num);
+		sleep(interval);
+		if (stress_mode)
+			stress_cpumap();
+	}
+
+	free_stats_record(record);
+	free_stats_record(prev);
+}
+
+int main(int argc, char **argv)
+{
+	struct rlimit r = {10 * 1024 * 1024, RLIM_INFINITY};
+	bool use_separators = true;
+	bool stress_mode = false;
+	char filename[256];
+	bool debug = false;
+	int added_cpus = 0;
+	int longindex = 0;
+	int interval = 2;
+	int prog_num = 0;
+	int add_cpu = -1;
+	__u32 qsize;
+	int opt;
+
+	/* Notice: choosing he queue size is very important with the
+	 * ixgbe driver, because it's driver page recycling trick is
+	 * dependend on pages being returned quickly.  The number of
+	 * out-standing packets in the system must be less-than 2x
+	 * RX-ring size.
+	 */
+	qsize = 128+64;
+
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
+		perror("setrlimit(RLIMIT_MEMLOCK)");
+		return 1;
+	}
+
+	if (load_bpf_file(filename)) {
+		fprintf(stderr, "ERR in load_bpf_file(): %s", bpf_log_buf);
+		return EXIT_FAIL;
+	}
+
+	if (!prog_fd[0]) {
+		fprintf(stderr, "ERR: load_bpf_file: %s\n", strerror(errno));
+		return EXIT_FAIL;
+	}
+
+	mark_cpus_unavailable();
+
+	/* Parse commands line args */
+	while ((opt = getopt_long(argc, argv, "hSd:",
+				  long_options, &longindex)) != -1) {
+		switch (opt) {
+		case 'd':
+			if (strlen(optarg) >= IF_NAMESIZE) {
+				fprintf(stderr, "ERR: --dev name too long\n");
+				goto error;
+			}
+			ifname = (char *)&ifname_buf;
+			strncpy(ifname, optarg, IF_NAMESIZE);
+			ifindex = if_nametoindex(ifname);
+			if (ifindex == 0) {
+				fprintf(stderr,
+					"ERR: --dev name unknown err(%d):%s\n",
+					errno, strerror(errno));
+				goto error;
+			}
+			break;
+		case 's':
+			interval = atoi(optarg);
+			break;
+		case 'S':
+			xdp_flags |= XDP_FLAGS_SKB_MODE;
+			break;
+		case 'D':
+			debug = true;
+			break;
+		case 'x':
+			stress_mode = true;
+			break;
+		case 'z':
+			use_separators = false;
+			break;
+		case 'p':
+			/* Selecting eBPF prog to load */
+			prog_num = atoi(optarg);
+			if (prog_num < 0 || prog_num >= MAX_PROG) {
+				fprintf(stderr,
+					"--prognum too large err(%d):%s\n",
+					errno, strerror(errno));
+				goto error;
+			}
+			break;
+		case 'c':
+			/* Add multiple CPUs */
+			add_cpu = strtoul(optarg, NULL, 0);
+			if (add_cpu >= MAX_CPUS) {
+				fprintf(stderr,
+				"--cpu nr too large for cpumap err(%d):%s\n",
+					errno, strerror(errno));
+				goto error;
+			}
+			create_cpu_entry(add_cpu, qsize, added_cpus, true);
+			added_cpus++;
+			break;
+		case 'q':
+			qsize = atoi(optarg);
+			break;
+		case 'h':
+		error:
+		default:
+			usage(argv);
+			return EXIT_FAIL_OPTION;
+		}
+	}
+	/* Required option */
+	if (ifindex == -1) {
+		fprintf(stderr, "ERR: required option --dev missing\n");
+		usage(argv);
+		return EXIT_FAIL_OPTION;
+	}
+	/* Required option */
+	if (add_cpu == -1) {
+		fprintf(stderr, "ERR: required option --cpu missing\n");
+		fprintf(stderr, " Specify multiple --cpu option to add more\n");
+		usage(argv);
+		return EXIT_FAIL_OPTION;
+	}
+
+	/* Remove XDP program when program is interrupted */
+	signal(SIGINT, int_exit);
+
+	if (set_link_xdp_fd(ifindex, prog_fd[prog_num], xdp_flags) < 0) {
+		fprintf(stderr, "link set xdp fd failed\n");
+		return EXIT_FAIL_XDP;
+	}
+
+	if (debug) {
+		printf("Debug-mode reading trace pipe (fix #define DEBUG)\n");
+		read_trace_pipe();
+	}
+
+	stats_poll(interval, use_separators, prog_num, stress_mode);
+	return EXIT_OK;
+}