samples/bpf: sample application and documentation for AF_XDP sockets

This is a sample application for AF_XDP sockets. The application
supports three different modes of operation: rxdrop, txonly and l2fwd.

To show-case a simple round-robin load-balancing between a set of
sockets in an xskmap, set the RR_LB compile time define option to 1 in
"xdpsock.h".

v2: The entries variable was calculated twice in {umem,xq}_nb_avail.
Co-authored-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Documentation/networking/af_xdp.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+======
+AF_XDP
+======
+
+Overview
+========
+
+AF_XDP is an address family that is optimized for high performance
+packet processing.
+
+This document assumes that the reader is familiar with BPF and XDP. If
+not, the Cilium project has an excellent reference guide at
+http://cilium.readthedocs.io/en/doc-1.0/bpf/.
+
+Using the XDP_REDIRECT action from an XDP program, the program can
+redirect ingress frames to other XDP enabled netdevs, using the
+bpf_redirect_map() function. AF_XDP sockets enable the possibility for
+XDP programs to redirect frames to a memory buffer in a user-space
+application.
+
+An AF_XDP socket (XSK) is created with the normal socket()
+syscall. Associated with each XSK are two rings: the RX ring and the
+TX ring. A socket can receive packets on the RX ring and it can send
+packets on the TX ring. These rings are registered and sized with the
+setsockopts XDP_RX_RING and XDP_TX_RING, respectively. It is mandatory
+to have at least one of these rings for each socket. An RX or TX
+descriptor ring points to a data buffer in a memory area called a
+UMEM. RX and TX can share the same UMEM so that a packet does not have
+to be copied between RX and TX. Moreover, if a packet needs to be kept
+for a while due to a possible retransmit, the descriptor that points
+to that packet can be changed to point to another and reused right
+away. This again avoids copying data.
+
+The UMEM consists of a number of equally size frames and each frame
+has a unique frame id. A descriptor in one of the rings references a
+frame by referencing its frame id. The user space allocates memory for
+this UMEM using whatever means it feels is most appropriate (malloc,
+mmap, huge pages, etc). This memory area is then registered with the
+kernel using the new setsockopt XDP_UMEM_REG. The UMEM also has two
+rings: the FILL ring and the COMPLETION ring. The fill ring is used by
+the application to send down frame ids for the kernel to fill in with
+RX packet data. References to these frames will then appear in the RX
+ring once each packet has been received. The completion ring, on the
+other hand, contains frame ids that the kernel has transmitted
+completely and can now be used again by user space, for either TX or
+RX. Thus, the frame ids appearing in the completion ring are ids that
+were previously transmitted using the TX ring. In summary, the RX and
+FILL rings are used for the RX path and the TX and COMPLETION rings
+are used for the TX path.
+
+The socket is then finally bound with a bind() call to a device and a
+specific queue id on that device, and it is not until bind is
+completed that traffic starts to flow.
+
+The UMEM can be shared between processes, if desired. If a process
+wants to do this, it simply skips the registration of the UMEM and its
+corresponding two rings, sets the XDP_SHARED_UMEM flag in the bind
+call and submits the XSK of the process it would like to share UMEM
+with as well as its own newly created XSK socket. The new process will
+then receive frame id references in its own RX ring that point to this
+shared UMEM. Note that since the ring structures are single-consumer /
+single-producer (for performance reasons), the new process has to
+create its own socket with associated RX and TX rings, since it cannot
+share this with the other process. This is also the reason that there
+is only one set of FILL and COMPLETION rings per UMEM. It is the
+responsibility of a single process to handle the UMEM.
+
+How is then packets distributed from an XDP program to the XSKs? There
+is a BPF map called XSKMAP (or BPF_MAP_TYPE_XSKMAP in full). The
+user-space application can place an XSK at an arbitrary place in this
+map. The XDP program can then redirect a packet to a specific index in
+this map and at this point XDP validates that the XSK in that map was
+indeed bound to that device and ring number. If not, the packet is
+dropped. If the map is empty at that index, the packet is also
+dropped. This also means that it is currently mandatory to have an XDP
+program loaded (and one XSK in the XSKMAP) to be able to get any
+traffic to user space through the XSK.
+
+AF_XDP can operate in two different modes: XDP_SKB and XDP_DRV. If the
+driver does not have support for XDP, or XDP_SKB is explicitly chosen
+when loading the XDP program, XDP_SKB mode is employed that uses SKBs
+together with the generic XDP support and copies out the data to user
+space. A fallback mode that works for any network device. On the other
+hand, if the driver has support for XDP, it will be used by the AF_XDP
+code to provide better performance, but there is still a copy of the
+data into user space.
+
+Concepts
+========
+
+In order to use an AF_XDP socket, a number of associated objects need
+to be setup.
+
+Jonathan Corbet has also written an excellent article on LWN,
+"Accelerating networking with AF_XDP". It can be found at
+https://lwn.net/Articles/750845/.
+
+UMEM
+----
+
+UMEM is a region of virtual contiguous memory, divided into
+equal-sized frames. An UMEM is associated to a netdev and a specific
+queue id of that netdev. It is created and configured (frame size,
+frame headroom, start address and size) by using the XDP_UMEM_REG
+setsockopt system call. A UMEM is bound to a netdev and queue id, via
+the bind() system call.
+
+An AF_XDP is socket linked to a single UMEM, but one UMEM can have
+multiple AF_XDP sockets. To share an UMEM created via one socket A,
+the next socket B can do this by setting the XDP_SHARED_UMEM flag in
+struct sockaddr_xdp member sxdp_flags, and passing the file descriptor
+of A to struct sockaddr_xdp member sxdp_shared_umem_fd.
+
+The UMEM has two single-producer/single-consumer rings, that are used
+to transfer ownership of UMEM frames between the kernel and the
+user-space application.
+
+Rings
+-----
+
+There are a four different kind of rings: Fill, Completion, RX and
+TX. All rings are single-producer/single-consumer, so the user-space
+application need explicit synchronization of multiple
+processes/threads are reading/writing to them.
+
+The UMEM uses two rings: Fill and Completion. Each socket associated
+with the UMEM must have an RX queue, TX queue or both. Say, that there
+is a setup with four sockets (all doing TX and RX). Then there will be
+one Fill ring, one Completion ring, four TX rings and four RX rings.
+
+The rings are head(producer)/tail(consumer) based rings. A producer
+writes the data ring at the index pointed out by struct xdp_ring
+producer member, and increasing the producer index. A consumer reads
+the data ring at the index pointed out by struct xdp_ring consumer
+member, and increasing the consumer index.
+
+The rings are configured and created via the _RING setsockopt system
+calls and mmapped to user-space using the appropriate offset to mmap()
+(XDP_PGOFF_RX_RING, XDP_PGOFF_TX_RING, XDP_UMEM_PGOFF_FILL_RING and
+XDP_UMEM_PGOFF_COMPLETION_RING).
+
+The size of the rings need to be of size power of two.
+
+UMEM Fill Ring
+~~~~~~~~~~~~~~
+
+The Fill ring is used to transfer ownership of UMEM frames from
+user-space to kernel-space. The UMEM indicies are passed in the
+ring. As an example, if the UMEM is 64k and each frame is 4k, then the
+UMEM has 16 frames and can pass indicies between 0 and 15.
+
+Frames passed to the kernel are used for the ingress path (RX rings).
+
+The user application produces UMEM indicies to this ring.
+
+UMEM Completetion Ring
+~~~~~~~~~~~~~~~~~~~~~~
+
+The Completion Ring is used transfer ownership of UMEM frames from
+kernel-space to user-space. Just like the Fill ring, UMEM indicies are
+used.
+
+Frames passed from the kernel to user-space are frames that has been
+sent (TX ring) and can be used by user-space again.
+
+The user application consumes UMEM indicies from this ring.
+
+
+RX Ring
+~~~~~~~
+
+The RX ring is the receiving side of a socket. Each entry in the ring
+is a struct xdp_desc descriptor. The descriptor contains UMEM index
+(idx), the length of the data (len), the offset into the frame
+(offset).
+
+If no frames have been passed to kernel via the Fill ring, no
+descriptors will (or can) appear on the RX ring.
+
+The user application consumes struct xdp_desc descriptors from this
+ring.
+
+TX Ring
+~~~~~~~
+
+The TX ring is used to send frames. The struct xdp_desc descriptor is
+filled (index, length and offset) and passed into the ring.
+
+To start the transfer a sendmsg() system call is required. This might
+be relaxed in the future.
+
+The user application produces struct xdp_desc descriptors to this
+ring.
+
+XSKMAP / BPF_MAP_TYPE_XSKMAP
+----------------------------
+
+On XDP side there is a BPF map type BPF_MAP_TYPE_XSKMAP (XSKMAP) that
+is used in conjunction with bpf_redirect_map() to pass the ingress
+frame to a socket.
+
+The user application inserts the socket into the map, via the bpf()
+system call.
+
+Note that if an XDP program tries to redirect to a socket that does
+not match the queue configuration and netdev, the frame will be
+dropped. E.g. an AF_XDP socket is bound to netdev eth0 and
+queue 17. Only the XDP program executing for eth0 and queue 17 will
+successfully pass data to the socket. Please refer to the sample
+application (samples/bpf/) in for an example.
+
+Usage
+=====
+
+In order to use AF_XDP sockets there are two parts needed. The
+user-space application and the XDP program. For a complete setup and
+usage example, please refer to the sample application. The user-space
+side is xdpsock_user.c and the XDP side xdpsock_kern.c.
+
+Naive ring dequeue and enqueue could look like this::
+
+    // typedef struct xdp_rxtx_ring RING;
+    // typedef struct xdp_umem_ring RING;
+
+    // typedef struct xdp_desc RING_TYPE;
+    // typedef __u32 RING_TYPE;
+
+    int dequeue_one(RING *ring, RING_TYPE *item)
+    {
+        __u32 entries = ring->ptrs.producer - ring->ptrs.consumer;
+
+        if (entries == 0)
+            return -1;
+
+        // read-barrier!
+
+        *item = ring->desc[ring->ptrs.consumer & (RING_SIZE - 1)];
+        ring->ptrs.consumer++;
+        return 0;
+    }
+
+    int enqueue_one(RING *ring, const RING_TYPE *item)
+    {
+        u32 free_entries = RING_SIZE - (ring->ptrs.producer - ring->ptrs.consumer);
+
+        if (free_entries == 0)
+            return -1;
+
+        ring->desc[ring->ptrs.producer & (RING_SIZE - 1)] = *item;
+
+        // write-barrier!
+
+        ring->ptrs.producer++;
+        return 0;
+    }
+
+
+For a more optimized version, please refer to the sample application.
+
+Sample application
+==================
+
+There is a xdpsock benchmarking/test application included that
+demonstrates how to use AF_XDP sockets with both private and shared
+UMEMs. Say that you would like your UDP traffic from port 4242 to end
+up in queue 16, that we will enable AF_XDP on. Here, we use ethtool
+for this::
+
+      ethtool -N p3p2 rx-flow-hash udp4 fn
+      ethtool -N p3p2 flow-type udp4 src-port 4242 dst-port 4242 \
+          action 16
+
+Running the rxdrop benchmark in XDP_DRV mode can then be done
+using::
+
+      samples/bpf/xdpsock -i p3p2 -q 16 -r -N
+
+For XDP_SKB mode, use the switch "-S" instead of "-N" and all options
+can be displayed with "-h", as usual.
+
+Credits
+=======
+
+- Björn Töpel (AF_XDP core)
+- Magnus Karlsson (AF_XDP core)
+- Alexander Duyck
+- Alexei Starovoitov
+- Daniel Borkmann
+- Jesper Dangaard Brouer
+- John Fastabend
+- Jonathan Corbet (LWN coverage)
+- Michael S. Tsirkin
+- Qi Z Zhang
+- Willem de Bruijn
+

Documentation/networking/index.rst

@@ -6,6 +6,7 @@ Contents:
 .. toctree::
    :maxdepth: 2
 
+   af_xdp
    batman-adv
    can
    dpaa2/index

samples/bpf/Makefile

@@ -45,6 +45,7 @@ hostprogs-y += xdp_rxq_info
 hostprogs-y += syscall_tp
 hostprogs-y += cpustat
 hostprogs-y += xdp_adjust_tail
+hostprogs-y += xdpsock
 
 # Libbpf dependencies
 LIBBPF := ../../tools/lib/bpf/bpf.o ../../tools/lib/bpf/nlattr.o
@@ -98,6 +99,7 @@ xdp_rxq_info-objs := bpf_load.o $(LIBBPF) xdp_rxq_info_user.o
 syscall_tp-objs := bpf_load.o $(LIBBPF) syscall_tp_user.o
 cpustat-objs := bpf_load.o $(LIBBPF) cpustat_user.o
 xdp_adjust_tail-objs := bpf_load.o $(LIBBPF) xdp_adjust_tail_user.o
+xdpsock-objs := bpf_load.o $(LIBBPF) xdpsock_user.o
 
 # Tell kbuild to always build the programs
 always := $(hostprogs-y)
@@ -151,6 +153,7 @@ always += xdp2skb_meta_kern.o
 always += syscall_tp_kern.o
 always += cpustat_kern.o
 always += xdp_adjust_tail_kern.o
+always += xdpsock_kern.o
 
 HOSTCFLAGS += -I$(objtree)/usr/include
 HOSTCFLAGS += -I$(srctree)/tools/lib/
@@ -197,6 +200,7 @@ HOSTLOADLIBES_xdp_rxq_info += -lelf
 HOSTLOADLIBES_syscall_tp += -lelf
 HOSTLOADLIBES_cpustat += -lelf
 HOSTLOADLIBES_xdp_adjust_tail += -lelf
+HOSTLOADLIBES_xdpsock += -lelf -pthread
 
 # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
 #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang

samples/bpf/xdpsock.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef XDPSOCK_H_
+#define XDPSOCK_H_
+
+/* Power-of-2 number of sockets */
+#define MAX_SOCKS 4
+
+/* Round-robin receive */
+#define RR_LB 0
+
+#endif /* XDPSOCK_H_ */

samples/bpf/xdpsock_kern.c

+// SPDX-License-Identifier: GPL-2.0
+#define KBUILD_MODNAME "foo"
+#include <uapi/linux/bpf.h>
+#include "bpf_helpers.h"
+
+#include "xdpsock.h"
+
+struct bpf_map_def SEC("maps") qidconf_map = {
+	.type		= BPF_MAP_TYPE_ARRAY,
+	.key_size	= sizeof(int),
+	.value_size	= sizeof(int),
+	.max_entries	= 1,
+};
+
+struct bpf_map_def SEC("maps") xsks_map = {
+	.type = BPF_MAP_TYPE_XSKMAP,
+	.key_size = sizeof(int),
+	.value_size = sizeof(int),
+	.max_entries = 4,
+};
+
+struct bpf_map_def SEC("maps") rr_map = {
+	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size = sizeof(int),
+	.value_size = sizeof(unsigned int),
+	.max_entries = 1,
+};
+
+SEC("xdp_sock")
+int xdp_sock_prog(struct xdp_md *ctx)
+{
+	int *qidconf, key = 0, idx;
+	unsigned int *rr;
+
+	qidconf = bpf_map_lookup_elem(&qidconf_map, &key);
+	if (!qidconf)
+		return XDP_ABORTED;
+
+	if (*qidconf != ctx->rx_queue_index)
+		return XDP_PASS;
+
+#if RR_LB /* NB! RR_LB is configured in xdpsock.h */
+	rr = bpf_map_lookup_elem(&rr_map, &key);
+	if (!rr)
+		return XDP_ABORTED;
+
+	*rr = (*rr + 1) & (MAX_SOCKS - 1);
+	idx = *rr;
+#else
+	idx = 0;
+#endif
+
+	return bpf_redirect_map(&xsks_map, idx, 0);
+}
+
+char _license[] SEC("license") = "GPL";

samples/bpf/xdpsock_user.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2017 - 2018 Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <getopt.h>
+#include <libgen.h>
+#include <linux/bpf.h>
+#include <linux/if_link.h>
+#include <linux/if_xdp.h>
+#include <linux/if_ether.h>
+#include <net/if.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <net/ethernet.h>
+#include <sys/resource.h>
+#include <sys/socket.h>
+#include <sys/mman.h>
+#include <time.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <locale.h>
+#include <sys/types.h>
+#include <poll.h>
+
+#include "bpf_load.h"
+#include "bpf_util.h"
+#include "libbpf.h"
+
+#include "xdpsock.h"
+
+#ifndef SOL_XDP
+#define SOL_XDP 283
+#endif
+
+#ifndef AF_XDP
+#define AF_XDP 44
+#endif
+
+#ifndef PF_XDP
+#define PF_XDP AF_XDP
+#endif
+
+#define NUM_FRAMES 131072
+#define FRAME_HEADROOM 0
+#define FRAME_SIZE 2048
+#define NUM_DESCS 1024
+#define BATCH_SIZE 16
+
+#define FQ_NUM_DESCS 1024
+#define CQ_NUM_DESCS 1024
+
+#define DEBUG_HEXDUMP 0
+
+typedef __u32 u32;
+
+static unsigned long prev_time;
+
+enum benchmark_type {
+	BENCH_RXDROP = 0,
+	BENCH_TXONLY = 1,
+	BENCH_L2FWD = 2,
+};
+
+static enum benchmark_type opt_bench = BENCH_RXDROP;
+static u32 opt_xdp_flags;
+static const char *opt_if = "";
+static int opt_ifindex;
+static int opt_queue;
+static int opt_poll;
+static int opt_shared_packet_buffer;
+static int opt_interval = 1;
+
+struct xdp_umem_uqueue {
+	u32 cached_prod;
+	u32 cached_cons;
+	u32 mask;
+	u32 size;
+	struct xdp_umem_ring *ring;
+};
+
+struct xdp_umem {
+	char (*frames)[FRAME_SIZE];
+	struct xdp_umem_uqueue fq;
+	struct xdp_umem_uqueue cq;
+	int fd;
+};
+
+struct xdp_uqueue {
+	u32 cached_prod;
+	u32 cached_cons;
+	u32 mask;
+	u32 size;
+	struct xdp_rxtx_ring *ring;
+};
+
+struct xdpsock {
+	struct xdp_uqueue rx;
+	struct xdp_uqueue tx;
+	int sfd;
+	struct xdp_umem *umem;
+	u32 outstanding_tx;
+	unsigned long rx_npkts;
+	unsigned long tx_npkts;
+	unsigned long prev_rx_npkts;
+	unsigned long prev_tx_npkts;
+};
+
+#define MAX_SOCKS 4
+static int num_socks;
+struct xdpsock *xsks[MAX_SOCKS];
+
+static unsigned long get_nsecs(void)
+{
+	struct timespec ts;
+
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return ts.tv_sec * 1000000000UL + ts.tv_nsec;
+}
+
+static void dump_stats(void);
+
+#define lassert(expr)							\
+	do {								\
+		if (!(expr)) {						\
+			fprintf(stderr, "%s:%s:%i: Assertion failed: "	\
+				#expr ": errno: %d/\"%s\"\n",		\
+				__FILE__, __func__, __LINE__,		\
+				errno, strerror(errno));		\
+			dump_stats();					\
+			exit(EXIT_FAILURE);				\
+		}							\
+	} while (0)
+
+#define barrier() __asm__ __volatile__("": : :"memory")
+#define u_smp_rmb() barrier()
+#define u_smp_wmb() barrier()
+#define likely(x) __builtin_expect(!!(x), 1)
+#define unlikely(x) __builtin_expect(!!(x), 0)
+
+static const char pkt_data[] =
+	"\x3c\xfd\xfe\x9e\x7f\x71\xec\xb1\xd7\x98\x3a\xc0\x08\x00\x45\x00"
+	"\x00\x2e\x00\x00\x00\x00\x40\x11\x88\x97\x05\x08\x07\x08\xc8\x14"
+	"\x1e\x04\x10\x92\x10\x92\x00\x1a\x6d\xa3\x34\x33\x1f\x69\x40\x6b"
+	"\x54\x59\xb6\x14\x2d\x11\x44\xbf\xaf\xd9\xbe\xaa";
+
+static inline u32 umem_nb_free(struct xdp_umem_uqueue *q, u32 nb)
+{
+	u32 free_entries = q->size - (q->cached_prod - q->cached_cons);
+
+	if (free_entries >= nb)
+		return free_entries;
+
+	/* Refresh the local tail pointer */
+	q->cached_cons = q->ring->ptrs.consumer;
+
+	return q->size - (q->cached_prod - q->cached_cons);
+}
+
+static inline u32 xq_nb_free(struct xdp_uqueue *q, u32 ndescs)
+{
+	u32 free_entries = q->cached_cons - q->cached_prod;
+
+	if (free_entries >= ndescs)
+		return free_entries;
+
+	/* Refresh the local tail pointer */
+	q->cached_cons = q->ring->ptrs.consumer + q->size;
+	return q->cached_cons - q->cached_prod;
+}
+
+static inline u32 umem_nb_avail(struct xdp_umem_uqueue *q, u32 nb)
+{
+	u32 entries = q->cached_prod - q->cached_cons;
+
+	if (entries == 0) {
+		q->cached_prod = q->ring->ptrs.producer;
+		entries = q->cached_prod - q->cached_cons;
+	}
+
+	return (entries > nb) ? nb : entries;
+}
+
+static inline u32 xq_nb_avail(struct xdp_uqueue *q, u32 ndescs)
+{
+	u32 entries = q->cached_prod - q->cached_cons;
+
+	if (entries == 0) {
+		q->cached_prod = q->ring->ptrs.producer;
+		entries = q->cached_prod - q->cached_cons;
+	}
+
+	return (entries > ndescs) ? ndescs : entries;
+}
+
+static inline int umem_fill_to_kernel_ex(struct xdp_umem_uqueue *fq,
+					 struct xdp_desc *d,
+					 size_t nb)
+{
+	u32 i;
+
+	if (umem_nb_free(fq, nb) < nb)
+		return -ENOSPC;
+
+	for (i = 0; i < nb; i++) {
+		u32 idx = fq->cached_prod++ & fq->mask;
+
+		fq->ring->desc[idx] = d[i].idx;
+	}
+
+	u_smp_wmb();
+
+	fq->ring->ptrs.producer = fq->cached_prod;
+
+	return 0;
+}
+
+static inline int umem_fill_to_kernel(struct xdp_umem_uqueue *fq, u32 *d,
+				      size_t nb)
+{
+	u32 i;
+
+	if (umem_nb_free(fq, nb) < nb)
+		return -ENOSPC;
+
+	for (i = 0; i < nb; i++) {
+		u32 idx = fq->cached_prod++ & fq->mask;
+
+		fq->ring->desc[idx] = d[i];
+	}
+
+	u_smp_wmb();
+
+	fq->ring->ptrs.producer = fq->cached_prod;
+
+	return 0;
+}
+
+static inline size_t umem_complete_from_kernel(struct xdp_umem_uqueue *cq,
+					       u32 *d, size_t nb)
+{
+	u32 idx, i, entries = umem_nb_avail(cq, nb);
+
+	u_smp_rmb();
+
+	for (i = 0; i < entries; i++) {
+		idx = cq->cached_cons++ & cq->mask;
+		d[i] = cq->ring->desc[idx];
+	}
+
+	if (entries > 0) {
+		u_smp_wmb();
+
+		cq->ring->ptrs.consumer = cq->cached_cons;
+	}
+
+	return entries;
+}
+
+static inline void *xq_get_data(struct xdpsock *xsk, __u32 idx, __u32 off)
+{
+	lassert(idx < NUM_FRAMES);
+	return &xsk->umem->frames[idx][off];
+}
+
+static inline int xq_enq(struct xdp_uqueue *uq,
+			 const struct xdp_desc *descs,
+			 unsigned int ndescs)
+{
+	struct xdp_rxtx_ring *r = uq->ring;
+	unsigned int i;
+
+	if (xq_nb_free(uq, ndescs) < ndescs)
+		return -ENOSPC;
+
+	for (i = 0; i < ndescs; i++) {
+		u32 idx = uq->cached_prod++ & uq->mask;
+
+		r->desc[idx].idx = descs[i].idx;
+		r->desc[idx].len = descs[i].len;
+		r->desc[idx].offset = descs[i].offset;
+	}
+
+	u_smp_wmb();
+
+	r->ptrs.producer = uq->cached_prod;
+	return 0;
+}
+
+static inline int xq_enq_tx_only(struct xdp_uqueue *uq,
+				 __u32 idx, unsigned int ndescs)
+{
+	struct xdp_rxtx_ring *q = uq->ring;
+	unsigned int i;
+
+	if (xq_nb_free(uq, ndescs) < ndescs)
+		return -ENOSPC;
+
+	for (i = 0; i < ndescs; i++) {
+		u32 idx = uq->cached_prod++ & uq->mask;
+
+		q->desc[idx].idx	= idx + i;
+		q->desc[idx].len	= sizeof(pkt_data) - 1;
+		q->desc[idx].offset	= 0;
+	}
+
+	u_smp_wmb();
+
+	q->ptrs.producer = uq->cached_prod;
+	return 0;
+}
+
+static inline int xq_deq(struct xdp_uqueue *uq,
+			 struct xdp_desc *descs,
+			 int ndescs)
+{
+	struct xdp_rxtx_ring *r = uq->ring;
+	unsigned int idx;
+	int i, entries;
+
+	entries = xq_nb_avail(uq, ndescs);
+
+	u_smp_rmb();
+
+	for (i = 0; i < entries; i++) {
+		idx = uq->cached_cons++ & uq->mask;
+		descs[i] = r->desc[idx];
+	}
+
+	if (entries > 0) {
+		u_smp_wmb();
+
+		r->ptrs.consumer = uq->cached_cons;
+	}
+
+	return entries;
+}
+
+static void swap_mac_addresses(void *data)
+{
+	struct ether_header *eth = (struct ether_header *)data;
+	struct ether_addr *src_addr = (struct ether_addr *)&eth->ether_shost;
+	struct ether_addr *dst_addr = (struct ether_addr *)&eth->ether_dhost;
+	struct ether_addr tmp;
+
+	tmp = *src_addr;
+	*src_addr = *dst_addr;
+	*dst_addr = tmp;
+}
+
+#if DEBUG_HEXDUMP
+static void hex_dump(void *pkt, size_t length, const char *prefix)
+{
+	int i = 0;
+	const unsigned char *address = (unsigned char *)pkt;
+	const unsigned char *line = address;
+	size_t line_size = 32;
+	unsigned char c;
+
+	printf("length = %zu\n", length);
+	printf("%s | ", prefix);
+	while (length-- > 0) {
+		printf("%02X ", *address++);
+		if (!(++i % line_size) || (length == 0 && i % line_size)) {
+			if (length == 0) {
+				while (i++ % line_size)
+					printf("__ ");
+			}
+			printf(" | ");	/* right close */
+			while (line < address) {
+				c = *line++;
+				printf("%c", (c < 33 || c == 255) ? 0x2E : c);
+			}
+			printf("\n");
+			if (length > 0)
+				printf("%s | ", prefix);
+		}
+	}
+	printf("\n");
+}
+#endif
+
+static size_t gen_eth_frame(char *frame)
+{
+	memcpy(frame, pkt_data, sizeof(pkt_data) - 1);
+	return sizeof(pkt_data) - 1;
+}
+
+static struct xdp_umem *xdp_umem_configure(int sfd)
+{
+	int fq_size = FQ_NUM_DESCS, cq_size = CQ_NUM_DESCS;
+	struct xdp_umem_reg mr;
+	struct xdp_umem *umem;
+	void *bufs;
+
+	umem = calloc(1, sizeof(*umem));
+	lassert(umem);
+
+	lassert(posix_memalign(&bufs, getpagesize(), /* PAGE_SIZE aligned */
+			       NUM_FRAMES * FRAME_SIZE) == 0);
+
+	mr.addr = (__u64)bufs;
+	mr.len = NUM_FRAMES * FRAME_SIZE;
+	mr.frame_size = FRAME_SIZE;
+	mr.frame_headroom = FRAME_HEADROOM;
+
+	lassert(setsockopt(sfd, SOL_XDP, XDP_UMEM_REG, &mr, sizeof(mr)) == 0);
+	lassert(setsockopt(sfd, SOL_XDP, XDP_UMEM_FILL_RING, &fq_size,
+			   sizeof(int)) == 0);
+	lassert(setsockopt(sfd, SOL_XDP, XDP_UMEM_COMPLETION_RING, &cq_size,
+			   sizeof(int)) == 0);
+
+	umem->fq.ring = mmap(0, sizeof(struct xdp_umem_ring) +
+			     FQ_NUM_DESCS * sizeof(u32),
+			     PROT_READ | PROT_WRITE,
+			     MAP_SHARED | MAP_POPULATE, sfd,
+			     XDP_UMEM_PGOFF_FILL_RING);
+	lassert(umem->fq.ring != MAP_FAILED);
+
+	umem->fq.mask = FQ_NUM_DESCS - 1;
+	umem->fq.size = FQ_NUM_DESCS;
+
+	umem->cq.ring = mmap(0, sizeof(struct xdp_umem_ring) +
+			     CQ_NUM_DESCS * sizeof(u32),
+			     PROT_READ | PROT_WRITE,
+			     MAP_SHARED | MAP_POPULATE, sfd,
+			     XDP_UMEM_PGOFF_COMPLETION_RING);
+	lassert(umem->cq.ring != MAP_FAILED);
+
+	umem->cq.mask = CQ_NUM_DESCS - 1;
+	umem->cq.size = CQ_NUM_DESCS;
+
+	umem->frames = (char (*)[FRAME_SIZE])bufs;
+	umem->fd = sfd;
+
+	if (opt_bench == BENCH_TXONLY) {
+		int i;
+
+		for (i = 0; i < NUM_FRAMES; i++)
+			(void)gen_eth_frame(&umem->frames[i][0]);
+	}
+
+	return umem;
+}
+
+static struct xdpsock *xsk_configure(struct xdp_umem *umem)
+{
+	struct sockaddr_xdp sxdp = {};
+	int sfd, ndescs = NUM_DESCS;
+	struct xdpsock *xsk;
+	bool shared = true;
+	u32 i;
+
+	sfd = socket(PF_XDP, SOCK_RAW, 0);
+	lassert(sfd >= 0);
+
+	xsk = calloc(1, sizeof(*xsk));
+	lassert(xsk);
+
+	xsk->sfd = sfd;
+	xsk->outstanding_tx = 0;
+
+	if (!umem) {
+		shared = false;
+		xsk->umem = xdp_umem_configure(sfd);
+	} else {
+		xsk->umem = umem;
+	}
+
+	lassert(setsockopt(sfd, SOL_XDP, XDP_RX_RING,
+			   &ndescs, sizeof(int)) == 0);
+	lassert(setsockopt(sfd, SOL_XDP, XDP_TX_RING,
+			   &ndescs, sizeof(int)) == 0);
+
+	/* Rx */
+	xsk->rx.ring = mmap(NULL,
+			    sizeof(struct xdp_ring) +
+			    NUM_DESCS * sizeof(struct xdp_desc),
+			    PROT_READ | PROT_WRITE,
+			    MAP_SHARED | MAP_POPULATE, sfd,
+			    XDP_PGOFF_RX_RING);
+	lassert(xsk->rx.ring != MAP_FAILED);
+
+	if (!shared) {
+		for (i = 0; i < NUM_DESCS / 2; i++)
+			lassert(umem_fill_to_kernel(&xsk->umem->fq, &i, 1)
+				== 0);
+	}
+
+	/* Tx */
+	xsk->tx.ring = mmap(NULL,
+			 sizeof(struct xdp_ring) +
+			 NUM_DESCS * sizeof(struct xdp_desc),
+			 PROT_READ | PROT_WRITE,
+			 MAP_SHARED | MAP_POPULATE, sfd,
+			 XDP_PGOFF_TX_RING);
+	lassert(xsk->tx.ring != MAP_FAILED);
+
+	xsk->rx.mask = NUM_DESCS - 1;
+	xsk->rx.size = NUM_DESCS;
+
+	xsk->tx.mask = NUM_DESCS - 1;
+	xsk->tx.size = NUM_DESCS;
+
+	sxdp.sxdp_family = PF_XDP;
+	sxdp.sxdp_ifindex = opt_ifindex;
+	sxdp.sxdp_queue_id = opt_queue;
+	if (shared) {
+		sxdp.sxdp_flags = XDP_SHARED_UMEM;
+		sxdp.sxdp_shared_umem_fd = umem->fd;
+	}
+
+	lassert(bind(sfd, (struct sockaddr *)&sxdp, sizeof(sxdp)) == 0);
+
+	return xsk;
+}
+
+static void print_benchmark(bool running)
+{
+	const char *bench_str = "INVALID";
+
+	if (opt_bench == BENCH_RXDROP)
+		bench_str = "rxdrop";
+	else if (opt_bench == BENCH_TXONLY)
+		bench_str = "txonly";
+	else if (opt_bench == BENCH_L2FWD)
+		bench_str = "l2fwd";
+
+	printf("%s:%d %s ", opt_if, opt_queue, bench_str);
+	if (opt_xdp_flags & XDP_FLAGS_SKB_MODE)
+		printf("xdp-skb ");
+	else if (opt_xdp_flags & XDP_FLAGS_DRV_MODE)
+		printf("xdp-drv ");
+	else
+		printf("	");
+
+	if (opt_poll)
+		printf("poll() ");
+
+	if (running) {
+		printf("running...");
+		fflush(stdout);
+	}
+}
+
+static void dump_stats(void)
+{
+	unsigned long now = get_nsecs();
+	long dt = now - prev_time;
+	int i;
+
+	prev_time = now;
+
+	for (i = 0; i < num_socks; i++) {
+		char *fmt = "%-15s %'-11.0f %'-11lu\n";
+		double rx_pps, tx_pps;
+
+		rx_pps = (xsks[i]->rx_npkts - xsks[i]->prev_rx_npkts) *
+			 1000000000. / dt;
+		tx_pps = (xsks[i]->tx_npkts - xsks[i]->prev_tx_npkts) *
+			 1000000000. / dt;
+
+		printf("\n sock%d@", i);
+		print_benchmark(false);
+		printf("\n");
+
+		printf("%-15s %-11s %-11s %-11.2f\n", "", "pps", "pkts",
+		       dt / 1000000000.);
+		printf(fmt, "rx", rx_pps, xsks[i]->rx_npkts);
+		printf(fmt, "tx", tx_pps, xsks[i]->tx_npkts);
+
+		xsks[i]->prev_rx_npkts = xsks[i]->rx_npkts;
+		xsks[i]->prev_tx_npkts = xsks[i]->tx_npkts;
+	}
+}
+
+static void *poller(void *arg)
+{
+	(void)arg;
+	for (;;) {
+		sleep(opt_interval);
+		dump_stats();
+	}
+
+	return NULL;
+}
+
+static void int_exit(int sig)
+{
+	(void)sig;
+	dump_stats();
+	bpf_set_link_xdp_fd(opt_ifindex, -1, opt_xdp_flags);
+	exit(EXIT_SUCCESS);
+}
+
+static struct option long_options[] = {
+	{"rxdrop", no_argument, 0, 'r'},
+	{"txonly", no_argument, 0, 't'},
+	{"l2fwd", no_argument, 0, 'l'},
+	{"interface", required_argument, 0, 'i'},
+	{"queue", required_argument, 0, 'q'},
+	{"poll", no_argument, 0, 'p'},
+	{"shared-buffer", no_argument, 0, 's'},
+	{"xdp-skb", no_argument, 0, 'S'},
+	{"xdp-native", no_argument, 0, 'N'},
+	{"interval", required_argument, 0, 'n'},
+	{0, 0, 0, 0}
+};
+
+static void usage(const char *prog)
+{
+	const char *str =
+		"  Usage: %s [OPTIONS]\n"
+		"  Options:\n"
+		"  -r, --rxdrop		Discard all incoming packets (default)\n"
+		"  -t, --txonly		Only send packets\n"
+		"  -l, --l2fwd		MAC swap L2 forwarding\n"
+		"  -i, --interface=n	Run on interface n\n"
+		"  -q, --queue=n	Use queue n (default 0)\n"
+		"  -p, --poll		Use poll syscall\n"
+		"  -s, --shared-buffer	Use shared packet buffer\n"
+		"  -S, --xdp-skb=n	Use XDP skb-mod\n"
+		"  -N, --xdp-native=n	Enfore XDP native mode\n"
+		"  -n, --interval=n	Specify statistics update interval (default 1 sec).\n"
+		"\n";
+	fprintf(stderr, str, prog);
+	exit(EXIT_FAILURE);
+}
+
+static void parse_command_line(int argc, char **argv)
+{
+	int option_index, c;
+
+	opterr = 0;
+
+	for (;;) {
+		c = getopt_long(argc, argv, "rtli:q:psSNn:", long_options,
+				&option_index);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'r':
+			opt_bench = BENCH_RXDROP;
+			break;
+		case 't':
+			opt_bench = BENCH_TXONLY;
+			break;
+		case 'l':
+			opt_bench = BENCH_L2FWD;
+			break;
+		case 'i':
+			opt_if = optarg;
+			break;
+		case 'q':
+			opt_queue = atoi(optarg);
+			break;
+		case 's':
+			opt_shared_packet_buffer = 1;
+			break;
+		case 'p':
+			opt_poll = 1;
+			break;
+		case 'S':
+			opt_xdp_flags |= XDP_FLAGS_SKB_MODE;
+			break;
+		case 'N':
+			opt_xdp_flags |= XDP_FLAGS_DRV_MODE;
+			break;
+		case 'n':
+			opt_interval = atoi(optarg);
+			break;
+		default:
+			usage(basename(argv[0]));
+		}
+	}
+
+	opt_ifindex = if_nametoindex(opt_if);
+	if (!opt_ifindex) {
+		fprintf(stderr, "ERROR: interface \"%s\" does not exist\n",
+			opt_if);
+		usage(basename(argv[0]));
+	}
+}
+
+static void kick_tx(int fd)
+{
+	int ret;
+
+	ret = sendto(fd, NULL, 0, MSG_DONTWAIT, NULL, 0);
+	if (ret >= 0 || errno == ENOBUFS || errno == EAGAIN)
+		return;
+	lassert(0);
+}
+
+static inline void complete_tx_l2fwd(struct xdpsock *xsk)
+{
+	u32 descs[BATCH_SIZE];
+	unsigned int rcvd;
+	size_t ndescs;
+
+	if (!xsk->outstanding_tx)
+		return;
+
+	kick_tx(xsk->sfd);
+	ndescs = (xsk->outstanding_tx > BATCH_SIZE) ? BATCH_SIZE :
+		 xsk->outstanding_tx;
+
+	/* re-add completed Tx buffers */
+	rcvd = umem_complete_from_kernel(&xsk->umem->cq, descs, ndescs);
+	if (rcvd > 0) {
+		umem_fill_to_kernel(&xsk->umem->fq, descs, rcvd);
+		xsk->outstanding_tx -= rcvd;
+		xsk->tx_npkts += rcvd;
+	}
+}
+
+static inline void complete_tx_only(struct xdpsock *xsk)
+{
+	u32 descs[BATCH_SIZE];
+	unsigned int rcvd;
+
+	if (!xsk->outstanding_tx)
+		return;
+
+	kick_tx(xsk->sfd);
+
+	rcvd = umem_complete_from_kernel(&xsk->umem->cq, descs, BATCH_SIZE);
+	if (rcvd > 0) {
+		xsk->outstanding_tx -= rcvd;
+		xsk->tx_npkts += rcvd;
+	}
+}
+
+static void rx_drop(struct xdpsock *xsk)
+{
+	struct xdp_desc descs[BATCH_SIZE];
+	unsigned int rcvd, i;
+
+	rcvd = xq_deq(&xsk->rx, descs, BATCH_SIZE);
+	if (!rcvd)
+		return;
+
+	for (i = 0; i < rcvd; i++) {
+		u32 idx = descs[i].idx;
+
+		lassert(idx < NUM_FRAMES);
+#if DEBUG_HEXDUMP
+		char *pkt;
+		char buf[32];
+
+		pkt = xq_get_data(xsk, idx, descs[i].offset);
+		sprintf(buf, "idx=%d", idx);
+		hex_dump(pkt, descs[i].len, buf);
+#endif
+	}
+
+	xsk->rx_npkts += rcvd;
+
+	umem_fill_to_kernel_ex(&xsk->umem->fq, descs, rcvd);
+}
+
+static void rx_drop_all(void)
+{
+	struct pollfd fds[MAX_SOCKS + 1];
+	int i, ret, timeout, nfds = 1;
+
+	memset(fds, 0, sizeof(fds));
+
+	for (i = 0; i < num_socks; i++) {
+		fds[i].fd = xsks[i]->sfd;
+		fds[i].events = POLLIN;
+		timeout = 1000; /* 1sn */
+	}
+
+	for (;;) {
+		if (opt_poll) {
+			ret = poll(fds, nfds, timeout);
+			if (ret <= 0)
+				continue;
+		}
+
+		for (i = 0; i < num_socks; i++)
+			rx_drop(xsks[i]);
+	}
+}
+
+static void tx_only(struct xdpsock *xsk)
+{
+	int timeout, ret, nfds = 1;
+	struct pollfd fds[nfds + 1];
+	unsigned int idx = 0;
+
+	memset(fds, 0, sizeof(fds));
+	fds[0].fd = xsk->sfd;
+	fds[0].events = POLLOUT;
+	timeout = 1000; /* 1sn */
+
+	for (;;) {
+		if (opt_poll) {
+			ret = poll(fds, nfds, timeout);
+			if (ret <= 0)
+				continue;
+
+			if (fds[0].fd != xsk->sfd ||
+			    !(fds[0].revents & POLLOUT))
+				continue;
+		}
+
+		if (xq_nb_free(&xsk->tx, BATCH_SIZE) >= BATCH_SIZE) {
+			lassert(xq_enq_tx_only(&xsk->tx, idx, BATCH_SIZE) == 0);
+
+			xsk->outstanding_tx += BATCH_SIZE;
+			idx += BATCH_SIZE;
+			idx %= NUM_FRAMES;
+		}
+
+		complete_tx_only(xsk);
+	}
+}
+
+static void l2fwd(struct xdpsock *xsk)
+{
+	for (;;) {
+		struct xdp_desc descs[BATCH_SIZE];
+		unsigned int rcvd, i;
+		int ret;
+
+		for (;;) {
+			complete_tx_l2fwd(xsk);
+
+			rcvd = xq_deq(&xsk->rx, descs, BATCH_SIZE);
+			if (rcvd > 0)
+				break;
+		}
+
+		for (i = 0; i < rcvd; i++) {
+			char *pkt = xq_get_data(xsk, descs[i].idx,
+						descs[i].offset);
+
+			swap_mac_addresses(pkt);
+#if DEBUG_HEXDUMP
+			char buf[32];
+			u32 idx = descs[i].idx;
+
+			sprintf(buf, "idx=%d", idx);
+			hex_dump(pkt, descs[i].len, buf);
+#endif
+		}
+
+		xsk->rx_npkts += rcvd;
+
+		ret = xq_enq(&xsk->tx, descs, rcvd);
+		lassert(ret == 0);
+		xsk->outstanding_tx += rcvd;
+	}
+}
+
+int main(int argc, char **argv)
+{
+	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
+	char xdp_filename[256];
+	int i, ret, key = 0;
+	pthread_t pt;
+
+	parse_command_line(argc, argv);
+
+	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
+		fprintf(stderr, "ERROR: setrlimit(RLIMIT_MEMLOCK) \"%s\"\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	snprintf(xdp_filename, sizeof(xdp_filename), "%s_kern.o", argv[0]);
+
+	if (load_bpf_file(xdp_filename)) {
+		fprintf(stderr, "ERROR: load_bpf_file %s\n", bpf_log_buf);
+		exit(EXIT_FAILURE);
+	}
+
+	if (!prog_fd[0]) {
+		fprintf(stderr, "ERROR: load_bpf_file: \"%s\"\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	if (bpf_set_link_xdp_fd(opt_ifindex, prog_fd[0], opt_xdp_flags) < 0) {
+		fprintf(stderr, "ERROR: link set xdp fd failed\n");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = bpf_map_update_elem(map_fd[0], &key, &opt_queue, 0);
+	if (ret) {
+		fprintf(stderr, "ERROR: bpf_map_update_elem qidconf\n");
+		exit(EXIT_FAILURE);
+	}
+
+	/* Create sockets... */
+	xsks[num_socks++] = xsk_configure(NULL);
+
+#if RR_LB
+	for (i = 0; i < MAX_SOCKS - 1; i++)
+		xsks[num_socks++] = xsk_configure(xsks[0]->umem);
+#endif
+
+	/* ...and insert them into the map. */
+	for (i = 0; i < num_socks; i++) {
+		key = i;
+		ret = bpf_map_update_elem(map_fd[1], &key, &xsks[i]->sfd, 0);
+		if (ret) {
+			fprintf(stderr, "ERROR: bpf_map_update_elem %d\n", i);
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	signal(SIGINT, int_exit);
+	signal(SIGTERM, int_exit);
+	signal(SIGABRT, int_exit);
+
+	setlocale(LC_ALL, "");
+
+	ret = pthread_create(&pt, NULL, poller, NULL);
+	lassert(ret == 0);
+
+	prev_time = get_nsecs();
+
+	if (opt_bench == BENCH_RXDROP)
+		rx_drop_all();
+	else if (opt_bench == BENCH_TXONLY)
+		tx_only(xsks[0]);
+	else
+		l2fwd(xsks[0]);
+
+	return 0;
+}