Subject: Re: [PATCH bpf-next 2/5] samples/bpf: add XDP_SHARED_UMEM support to xdpsock

From: William Tu <[email-masked]>
Date: Fri, 8 Nov 2019 10:13:30 -0800

On Thu, Nov 07, 2019 at 06:47:37PM +0100, Magnus Karlsson wrote:
> Add support for the XDP_SHARED_UMEM mode to the xdpsock sample
> application. As libbpf does not have a built in XDP program for this
> mode, we use an explicitly loaded XDP program. This also serves as an
> example on how to write your own XDP program that can route to an
> AF_XDP socket.
> 
> Signed-off-by: Magnus Karlsson <[email-masked]>
> ---
>  samples/bpf/Makefile       |   1 +
>  samples/bpf/xdpsock.h      |  11 ++++
>  samples/bpf/xdpsock_kern.c |  24 ++++++++
>  samples/bpf/xdpsock_user.c | 141 +++++++++++++++++++++++++++++++--------------
>  4 files changed, 135 insertions(+), 42 deletions(-)
>  create mode 100644 samples/bpf/xdpsock.h
>  create mode 100644 samples/bpf/xdpsock_kern.c
> 
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 4df11dd..8a9af3a 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -167,6 +167,7 @@ always += xdp_sample_pkts_kern.o
>  always += ibumad_kern.o
>  always += hbm_out_kern.o
>  always += hbm_edt_kern.o
> +always += xdpsock_kern.o
>  
>  ifeq ($(ARCH), arm)
>  # Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
> diff --git a/samples/bpf/xdpsock.h b/samples/bpf/xdpsock.h
> new file mode 100644
> index 0000000..b7eca15
> --- /dev/null
> +++ b/samples/bpf/xdpsock.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * Copyright(c) 2019 Intel Corporation.
> + */
> +
> +#ifndef XDPSOCK_H_
> +#define XDPSOCK_H_
> +
> +#define MAX_SOCKS 4
> +
> +#endif /* XDPSOCK_H */
> diff --git a/samples/bpf/xdpsock_kern.c b/samples/bpf/xdpsock_kern.c
> new file mode 100644
> index 0000000..a06177c
> --- /dev/null
> +++ b/samples/bpf/xdpsock_kern.c
> @@ -0,0 +1,24 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/bpf.h>
> +#include "bpf_helpers.h"
> +#include "xdpsock.h"
> +
> +/* This XDP program is only needed for the XDP_SHARED_UMEM mode.
> + * If you do not use this mode, libbpf can supply an XDP program for you.
> + */
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_XSKMAP);
> +	__uint(max_entries, MAX_SOCKS);
> +	__uint(key_size, sizeof(int));
> +	__uint(value_size, sizeof(int));
> +} xsks_map SEC(".maps");
> +
> +static unsigned int rr;
> +
> +SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx)
> +{
> +	rr = (rr + 1) & (MAX_SOCKS - 1);
> +
> +	return bpf_redirect_map(&xsks_map, rr, XDP_DROP);
> +}
> diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
> index 405c4e0..d3dba93 100644
> --- a/samples/bpf/xdpsock_user.c
> +++ b/samples/bpf/xdpsock_user.c
> @@ -29,6 +29,7 @@
>  
>  #include "libbpf.h"
>  #include "xsk.h"
> +#include "xdpsock.h"
>  #include <bpf/bpf.h>
>  
>  #ifndef SOL_XDP
> @@ -47,7 +48,6 @@
>  #define BATCH_SIZE 64
>  
>  #define DEBUG_HEXDUMP 0
> -#define MAX_SOCKS 8
>  
>  typedef __u64 u64;
>  typedef __u32 u32;
> @@ -75,7 +75,8 @@ static u32 opt_xdp_bind_flags;
>  static int opt_xsk_frame_size = XSK_UMEM__DEFAULT_FRAME_SIZE;
>  static int opt_timeout = 1000;
>  static bool opt_need_wakeup = true;
> -static __u32 prog_id;
> +static u32 opt_num_xsks = 1;
> +static u32 prog_id;
>  
>  struct xsk_umem_info {
>  	struct xsk_ring_prod fq;
> @@ -179,7 +180,7 @@ static void *poller(void *arg)
>  
>  static void remove_xdp_program(void)
>  {
> -	__u32 curr_prog_id = 0;
> +	u32 curr_prog_id = 0;
>  
>  	if (bpf_get_link_xdp_id(opt_ifindex, &curr_prog_id, opt_xdp_flags)) {
>  		printf("bpf_get_link_xdp_id failed\n");
> @@ -196,11 +197,11 @@ static void remove_xdp_program(void)
>  static void int_exit(int sig)
>  {
>  	struct xsk_umem *umem = xsks[0]->umem->umem;
> -
> -	(void)sig;
> +	int i;
>  
>  	dump_stats();
> -	xsk_socket__delete(xsks[0]->xsk);
> +	for (i = 0; i < num_socks; i++)
> +		xsk_socket__delete(xsks[i]->xsk);
>  	(void)xsk_umem__delete(umem);
>  	remove_xdp_program();
>  
> @@ -290,8 +291,8 @@ static struct xsk_umem_info *xsk_configure_umem(void *buffer, u64 size)
>  		.frame_headroom = XSK_UMEM__DEFAULT_FRAME_HEADROOM,
>  		.flags = opt_umem_flags
>  	};
> -
> -	int ret;
> +	int ret, i;
> +	u32 idx;
>  
>  	umem = calloc(1, sizeof(*umem));
>  	if (!umem)
> @@ -303,6 +304,15 @@ static struct xsk_umem_info *xsk_configure_umem(void *buffer, u64 size)
>  	if (ret)
>  		exit_with_error(-ret);
>  
> +	ret = xsk_ring_prod__reserve(&umem->fq,
> +				     XSK_RING_PROD__DEFAULT_NUM_DESCS, &idx);
> +	if (ret != XSK_RING_PROD__DEFAULT_NUM_DESCS)
> +		exit_with_error(-ret);
> +	for (i = 0; i < XSK_RING_PROD__DEFAULT_NUM_DESCS; i++)
> +		*xsk_ring_prod__fill_addr(&umem->fq, idx++) =
> +			i * opt_xsk_frame_size;
> +	xsk_ring_prod__submit(&umem->fq, XSK_RING_PROD__DEFAULT_NUM_DESCS);
> +
>  	umem->buffer = buffer;
>  	return umem;
>  }
> @@ -312,8 +322,6 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)
>  	struct xsk_socket_config cfg;
>  	struct xsk_socket_info *xsk;
>  	int ret;
> -	u32 idx;
> -	int i;
>  
>  	xsk = calloc(1, sizeof(*xsk));
>  	if (!xsk)
> @@ -322,11 +330,15 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)
>  	xsk->umem = umem;
>  	cfg.rx_size = XSK_RING_CONS__DEFAULT_NUM_DESCS;
>  	cfg.tx_size = XSK_RING_PROD__DEFAULT_NUM_DESCS;
> -	cfg.libbpf_flags = 0;
> +	if (opt_num_xsks > 1)
> +		cfg.libbpf_flags = XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD;

I think we can still load our own XDP program, and don't set
XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD.
So the xsk_setup_xdp_prog() will find the the loaded XDP program
and sets the xsk map.

> +	else
> +		cfg.libbpf_flags = 0;
>  	cfg.xdp_flags = opt_xdp_flags;
>  	cfg.bind_flags = opt_xdp_bind_flags;

Do we need to 
cfg.bind_flags |= XDP_SHARED_UMEM?

Thanks
William

> -	ret = xsk_socket__create(&xsk->xsk, opt_if, opt_queue, umem->umem,
> -				 &xsk->rx, &xsk->tx, &cfg);
> +
> +	ret = xsk_socket__create(&xsk->xsk, opt_if, opt_queue,
> +				 umem->umem, &xsk->rx, &xsk->tx, &cfg);
>  	if (ret)
>  		exit_with_error(-ret);
>  
> @@ -334,17 +346,6 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)
>  	if (ret)
>  		exit_with_error(-ret);
>  
> -	ret = xsk_ring_prod__reserve(&xsk->umem->fq,
> -				     XSK_RING_PROD__DEFAULT_NUM_DESCS,
> -				     &idx);
> -	if (ret != XSK_RING_PROD__DEFAULT_NUM_DESCS)
> -		exit_with_error(-ret);
> -	for (i = 0; i < XSK_RING_PROD__DEFAULT_NUM_DESCS; i++)
> -		*xsk_ring_prod__fill_addr(&xsk->umem->fq, idx++) =
> -			i * opt_xsk_frame_size;
> -	xsk_ring_prod__submit(&xsk->umem->fq,
> -			      XSK_RING_PROD__DEFAULT_NUM_DESCS);
> -
>  	return xsk;
>  }
>  
> @@ -363,6 +364,7 @@ static struct option long_options[] = {
>  	{"frame-size", required_argument, 0, 'f'},
>  	{"no-need-wakeup", no_argument, 0, 'm'},
>  	{"unaligned", no_argument, 0, 'u'},
> +	{"shared-umem", no_argument, 0, 'M'},
>  	{0, 0, 0, 0}
>  };
>  
> @@ -386,6 +388,7 @@ static void usage(const char *prog)
>  		"  -m, --no-need-wakeup Turn off use of driver need wakeup flag.\n"
>  		"  -f, --frame-size=n   Set the frame size (must be a power of two in aligned mode, default is %d).\n"
>  		"  -u, --unaligned	Enable unaligned chunk placement\n"
> +		"  -M, --shared-umem	Enable XDP_SHARED_UMEM\n"
>  		"\n";
>  	fprintf(stderr, str, prog, XSK_UMEM__DEFAULT_FRAME_SIZE);
>  	exit(EXIT_FAILURE);
> @@ -398,7 +401,7 @@ static void parse_command_line(int argc, char **argv)
>  	opterr = 0;
>  
>  	for (;;) {
> -		c = getopt_long(argc, argv, "Frtli:q:psSNn:czf:mu",
> +		c = getopt_long(argc, argv, "Frtli:q:psSNn:czf:muM",
>  				long_options, &option_index);
>  		if (c == -1)
>  			break;
> @@ -448,11 +451,14 @@ static void parse_command_line(int argc, char **argv)
>  			break;
>  		case 'f':
>  			opt_xsk_frame_size = atoi(optarg);
> +			break;
>  		case 'm':
>  			opt_need_wakeup = false;
>  			opt_xdp_bind_flags &= ~XDP_USE_NEED_WAKEUP;
>  			break;
> -
> +		case 'M':
> +			opt_num_xsks = MAX_SOCKS;
> +			break;
>  		default:
>  			usage(basename(argv[0]));
>  		}
> @@ -586,11 +592,9 @@ static void rx_drop(struct xsk_socket_info *xsk, struct pollfd *fds)
>  
>  static void rx_drop_all(void)
>  {
> -	struct pollfd fds[MAX_SOCKS + 1];
> +	struct pollfd fds[MAX_SOCKS] = {};
>  	int i, ret;
>  
> -	memset(fds, 0, sizeof(fds));
> -
>  	for (i = 0; i < num_socks; i++) {
>  		fds[i].fd = xsk_socket__fd(xsks[i]->xsk);
>  		fds[i].events = POLLIN;
> @@ -633,11 +637,10 @@ static void tx_only(struct xsk_socket_info *xsk, u32 frame_nb)
>  
>  static void tx_only_all(void)
>  {
> -	struct pollfd fds[MAX_SOCKS];
> +	struct pollfd fds[MAX_SOCKS] = {};
>  	u32 frame_nb[MAX_SOCKS] = {};
>  	int i, ret;
>  
> -	memset(fds, 0, sizeof(fds));
>  	for (i = 0; i < num_socks; i++) {
>  		fds[0].fd = xsk_socket__fd(xsks[i]->xsk);
>  		fds[0].events = POLLOUT;
> @@ -706,11 +709,9 @@ static void l2fwd(struct xsk_socket_info *xsk, struct pollfd *fds)
>  
>  static void l2fwd_all(void)
>  {
> -	struct pollfd fds[MAX_SOCKS];
> +	struct pollfd fds[MAX_SOCKS] = {};
>  	int i, ret;
>  
> -	memset(fds, 0, sizeof(fds));
> -
>  	for (i = 0; i < num_socks; i++) {
>  		fds[i].fd = xsk_socket__fd(xsks[i]->xsk);
>  		fds[i].events = POLLOUT | POLLIN;
> @@ -728,13 +729,65 @@ static void l2fwd_all(void)
>  	}
>  }
>  
> +static void load_xdp_program(char **argv, struct bpf_object **obj)
> +{
> +	struct bpf_prog_load_attr prog_load_attr = {
> +		.prog_type      = BPF_PROG_TYPE_XDP,
> +	};
> +	char xdp_filename[256];
> +	int prog_fd;
> +
> +	snprintf(xdp_filename, sizeof(xdp_filename), "%s_kern.o", argv[0]);
> +	prog_load_attr.file = xdp_filename;
> +
> +	if (bpf_prog_load_xattr(&prog_load_attr, obj, &prog_fd))
> +		exit(EXIT_FAILURE);
> +	if (prog_fd < 0) {
> +		fprintf(stderr, "ERROR: no program found: %s\n",
> +			strerror(prog_fd));
> +		exit(EXIT_FAILURE);
> +	}
> +
> +	if (bpf_set_link_xdp_fd(opt_ifindex, prog_fd, opt_xdp_flags) < 0) {
> +		fprintf(stderr, "ERROR: link set xdp fd failed\n");
> +		exit(EXIT_FAILURE);
> +	}
> +}
> +
> +static void enter_xsks_into_map(struct bpf_object *obj)
> +{
> +	struct bpf_map *map;
> +	int i, xsks_map;
> +
> +	map = bpf_object__find_map_by_name(obj, "xsks_map");
> +	xsks_map = bpf_map__fd(map);
> +	if (xsks_map < 0) {
> +		fprintf(stderr, "ERROR: no xsks map found: %s\n",
> +			strerror(xsks_map));
> +			exit(EXIT_FAILURE);
> +	}
> +
> +	for (i = 0; i < num_socks; i++) {
> +		int fd = xsk_socket__fd(xsks[i]->xsk);
> +		int key, ret;
> +
> +		key = i;
> +		ret = bpf_map_update_elem(xsks_map, &key, &fd, 0);
> +		if (ret) {
> +			fprintf(stderr, "ERROR: bpf_map_update_elem %d\n", i);
> +			exit(EXIT_FAILURE);
> +		}
> +	}
> +}
> +
>  int main(int argc, char **argv)
>  {
>  	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
>  	struct xsk_umem_info *umem;
> +	struct bpf_object *obj;
>  	pthread_t pt;
> +	int i, ret;
>  	void *bufs;
> -	int ret;
>  
>  	parse_command_line(argc, argv);
>  
> @@ -744,6 +797,9 @@ int main(int argc, char **argv)
>  		exit(EXIT_FAILURE);
>  	}
>  
> +	if (opt_num_xsks > 1)
> +		load_xdp_program(argv, &obj);
> +
>  	/* Reserve memory for the umem. Use hugepages if unaligned chunk mode */
>  	bufs = mmap(NULL, NUM_FRAMES * opt_xsk_frame_size,
>  		    PROT_READ | PROT_WRITE,
> @@ -752,16 +808,17 @@ int main(int argc, char **argv)
>  		printf("ERROR: mmap failed\n");
>  		exit(EXIT_FAILURE);
>  	}
> -       /* Create sockets... */
> +
> +	/* Create sockets... */
>  	umem = xsk_configure_umem(bufs, NUM_FRAMES * opt_xsk_frame_size);
> -	xsks[num_socks++] = xsk_configure_socket(umem);
> +	for (i = 0; i < opt_num_xsks; i++)
> +		xsks[num_socks++] = xsk_configure_socket(umem);
>  
> -	if (opt_bench == BENCH_TXONLY) {
> -		int i;
> +	for (i = 0; i < NUM_FRAMES; i++)
> +		gen_eth_frame(umem, i * opt_xsk_frame_size);
>  
> -		for (i = 0; i < NUM_FRAMES; i++)
> -			(void)gen_eth_frame(umem, i * opt_xsk_frame_size);
> -	}
> +	if (opt_num_xsks > 1 && opt_bench != BENCH_TXONLY)
> +		enter_xsks_into_map(obj);
>  
>  	signal(SIGINT, int_exit);
>  	signal(SIGTERM, int_exit);
> -- 
> 2.7.4
>