Re: [PATCH bpf-next v4 12/14] libbpf: support shared umems between queues and devices

["Björn Töpel" <bjorn.topel@intel.com>]

On 2020-07-21 07:04, Magnus Karlsson wrote:
> Add support for shared umems between hardware queues and devices to
> the AF_XDP part of libbpf. This so that zero-copy can be achieved in
> applications that want to send and receive packets between HW queues
> on one device or between different devices/netdevs.
> 
> In order to create sockets that share a umem between hardware queues
> and devices, a new function has been added called
> xsk_socket__create_shared(). It takes the same arguments as
> xsk_socket_create() plus references to a fill ring and a completion
> ring. So for every socket that share a umem, you need to have one more
> set of fill and completion rings. This in order to maintain the
> single-producer single-consumer semantics of the rings.
> 
> You can create all the sockets via the new xsk_socket__create_shared()
> call, or create the first one with xsk_socket__create() and the rest
> with xsk_socket__create_shared(). Both methods work.
> 
> Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>

Acked-by: Björn Töpel <bjorn.topel@intel.com>


> ---
>   tools/lib/bpf/libbpf.map |   1 +
>   tools/lib/bpf/xsk.c      | 376 ++++++++++++++++++++++++++++++-----------------
>   tools/lib/bpf/xsk.h      |   9 ++
>   3 files changed, 254 insertions(+), 132 deletions(-)
> 
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 6f0856a..bc06b67 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -291,4 +291,5 @@ LIBBPF_0.1.0 {
>   		bpf_program__set_autoload;
>   		bpf_program__set_sk_lookup;
>   		btf__set_fd;
> +		xsk_socket__create_shared;
>   } LIBBPF_0.0.9;
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index f7f4efb..86ad4f7 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -20,6 +20,7 @@
>   #include <linux/if_ether.h>
>   #include <linux/if_packet.h>
>   #include <linux/if_xdp.h>
> +#include <linux/list.h>
>   #include <linux/sockios.h>
>   #include <net/if.h>
>   #include <sys/ioctl.h>
> @@ -48,26 +49,35 @@
>   #endif
>   
>   struct xsk_umem {
> -	struct xsk_ring_prod *fill;
> -	struct xsk_ring_cons *comp;
> +	struct xsk_ring_prod *fill_save;
> +	struct xsk_ring_cons *comp_save;
>   	char *umem_area;
>   	struct xsk_umem_config config;
>   	int fd;
>   	int refcount;
> +	struct list_head ctx_list;
> +};
> +
> +struct xsk_ctx {
> +	struct xsk_ring_prod *fill;
> +	struct xsk_ring_cons *comp;
> +	__u32 queue_id;
> +	struct xsk_umem *umem;
> +	int refcount;
> +	int ifindex;
> +	struct list_head list;
> +	int prog_fd;
> +	int xsks_map_fd;
> +	char ifname[IFNAMSIZ];
>   };
>   
>   struct xsk_socket {
>   	struct xsk_ring_cons *rx;
>   	struct xsk_ring_prod *tx;
>   	__u64 outstanding_tx;
> -	struct xsk_umem *umem;
> +	struct xsk_ctx *ctx;
>   	struct xsk_socket_config config;
>   	int fd;
> -	int ifindex;
> -	int prog_fd;
> -	int xsks_map_fd;
> -	__u32 queue_id;
> -	char ifname[IFNAMSIZ];
>   };
>   
>   struct xsk_nl_info {
> @@ -203,15 +213,73 @@ static int xsk_get_mmap_offsets(int fd, struct xdp_mmap_offsets *off)
>   	return -EINVAL;
>   }
>   
> +static int xsk_create_umem_rings(struct xsk_umem *umem, int fd,
> +				 struct xsk_ring_prod *fill,
> +				 struct xsk_ring_cons *comp)
> +{
> +	struct xdp_mmap_offsets off;
> +	void *map;
> +	int err;
> +
> +	err = setsockopt(fd, SOL_XDP, XDP_UMEM_FILL_RING,
> +			 &umem->config.fill_size,
> +			 sizeof(umem->config.fill_size));
> +	if (err)
> +		return -errno;
> +
> +	err = setsockopt(fd, SOL_XDP, XDP_UMEM_COMPLETION_RING,
> +			 &umem->config.comp_size,
> +			 sizeof(umem->config.comp_size));
> +	if (err)
> +		return -errno;
> +
> +	err = xsk_get_mmap_offsets(fd, &off);
> +	if (err)
> +		return -errno;
> +
> +	map = mmap(NULL, off.fr.desc + umem->config.fill_size * sizeof(__u64),
> +		   PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, fd,
> +		   XDP_UMEM_PGOFF_FILL_RING);
> +	if (map == MAP_FAILED)
> +		return -errno;
> +
> +	fill->mask = umem->config.fill_size - 1;
> +	fill->size = umem->config.fill_size;
> +	fill->producer = map + off.fr.producer;
> +	fill->consumer = map + off.fr.consumer;
> +	fill->flags = map + off.fr.flags;
> +	fill->ring = map + off.fr.desc;
> +	fill->cached_cons = umem->config.fill_size;
> +
> +	map = mmap(NULL, off.cr.desc + umem->config.comp_size * sizeof(__u64),
> +		   PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, fd,
> +		   XDP_UMEM_PGOFF_COMPLETION_RING);
> +	if (map == MAP_FAILED) {
> +		err = -errno;
> +		goto out_mmap;
> +	}
> +
> +	comp->mask = umem->config.comp_size - 1;
> +	comp->size = umem->config.comp_size;
> +	comp->producer = map + off.cr.producer;
> +	comp->consumer = map + off.cr.consumer;
> +	comp->flags = map + off.cr.flags;
> +	comp->ring = map + off.cr.desc;
> +
> +	return 0;
> +
> +out_mmap:
> +	munmap(map, off.fr.desc + umem->config.fill_size * sizeof(__u64));
> +	return err;
> +}
> +
>   int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
>   			    __u64 size, struct xsk_ring_prod *fill,
>   			    struct xsk_ring_cons *comp,
>   			    const struct xsk_umem_config *usr_config)
>   {
> -	struct xdp_mmap_offsets off;
>   	struct xdp_umem_reg mr;
>   	struct xsk_umem *umem;
> -	void *map;
>   	int err;
>   
>   	if (!umem_area || !umem_ptr || !fill || !comp)
> @@ -230,6 +298,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
>   	}
>   
>   	umem->umem_area = umem_area;
> +	INIT_LIST_HEAD(&umem->ctx_list);
>   	xsk_set_umem_config(&umem->config, usr_config);
>   
>   	memset(&mr, 0, sizeof(mr));
> @@ -244,71 +313,16 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
>   		err = -errno;
>   		goto out_socket;
>   	}
> -	err = setsockopt(umem->fd, SOL_XDP, XDP_UMEM_FILL_RING,
> -			 &umem->config.fill_size,
> -			 sizeof(umem->config.fill_size));
> -	if (err) {
> -		err = -errno;
> -		goto out_socket;
> -	}
> -	err = setsockopt(umem->fd, SOL_XDP, XDP_UMEM_COMPLETION_RING,
> -			 &umem->config.comp_size,
> -			 sizeof(umem->config.comp_size));
> -	if (err) {
> -		err = -errno;
> -		goto out_socket;
> -	}
>   
> -	err = xsk_get_mmap_offsets(umem->fd, &off);
> -	if (err) {
> -		err = -errno;
> -		goto out_socket;
> -	}
> -
> -	map = mmap(NULL, off.fr.desc + umem->config.fill_size * sizeof(__u64),
> -		   PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, umem->fd,
> -		   XDP_UMEM_PGOFF_FILL_RING);
> -	if (map == MAP_FAILED) {
> -		err = -errno;
> +	err = xsk_create_umem_rings(umem, umem->fd, fill, comp);
> +	if (err)
>   		goto out_socket;
> -	}
> -
> -	umem->fill = fill;
> -	fill->mask = umem->config.fill_size - 1;
> -	fill->size = umem->config.fill_size;
> -	fill->producer = map + off.fr.producer;
> -	fill->consumer = map + off.fr.consumer;
> -	fill->flags = map + off.fr.flags;
> -	fill->ring = map + off.fr.desc;
> -	fill->cached_prod = *fill->producer;
> -	/* cached_cons is "size" bigger than the real consumer pointer
> -	 * See xsk_prod_nb_free
> -	 */
> -	fill->cached_cons = *fill->consumer + umem->config.fill_size;
> -
> -	map = mmap(NULL, off.cr.desc + umem->config.comp_size * sizeof(__u64),
> -		   PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, umem->fd,
> -		   XDP_UMEM_PGOFF_COMPLETION_RING);
> -	if (map == MAP_FAILED) {
> -		err = -errno;
> -		goto out_mmap;
> -	}
> -
> -	umem->comp = comp;
> -	comp->mask = umem->config.comp_size - 1;
> -	comp->size = umem->config.comp_size;
> -	comp->producer = map + off.cr.producer;
> -	comp->consumer = map + off.cr.consumer;
> -	comp->flags = map + off.cr.flags;
> -	comp->ring = map + off.cr.desc;
> -	comp->cached_prod = *comp->producer;
> -	comp->cached_cons = *comp->consumer;
>   
> +	umem->fill_save = fill;
> +	umem->comp_save = comp;
>   	*umem_ptr = umem;
>   	return 0;
>   
> -out_mmap:
> -	munmap(map, off.fr.desc + umem->config.fill_size * sizeof(__u64));
>   out_socket:
>   	close(umem->fd);
>   out_umem_alloc:
> @@ -342,6 +356,7 @@ DEFAULT_VERSION(xsk_umem__create_v0_0_4, xsk_umem__create, LIBBPF_0.0.4)
>   static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>   {
>   	static const int log_buf_size = 16 * 1024;
> +	struct xsk_ctx *ctx = xsk->ctx;
>   	char log_buf[log_buf_size];
>   	int err, prog_fd;
>   
> @@ -369,7 +384,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>   		/* *(u32 *)(r10 - 4) = r2 */
>   		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -4),
>   		/* r1 = xskmap[] */
> -		BPF_LD_MAP_FD(BPF_REG_1, xsk->xsks_map_fd),
> +		BPF_LD_MAP_FD(BPF_REG_1, ctx->xsks_map_fd),
>   		/* r3 = XDP_PASS */
>   		BPF_MOV64_IMM(BPF_REG_3, 2),
>   		/* call bpf_redirect_map */
> @@ -381,7 +396,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>   		/* r2 += -4 */
>   		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
>   		/* r1 = xskmap[] */
> -		BPF_LD_MAP_FD(BPF_REG_1, xsk->xsks_map_fd),
> +		BPF_LD_MAP_FD(BPF_REG_1, ctx->xsks_map_fd),
>   		/* call bpf_map_lookup_elem */
>   		BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
>   		/* r1 = r0 */
> @@ -393,7 +408,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>   		/* r2 = *(u32 *)(r10 - 4) */
>   		BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_10, -4),
>   		/* r1 = xskmap[] */
> -		BPF_LD_MAP_FD(BPF_REG_1, xsk->xsks_map_fd),
> +		BPF_LD_MAP_FD(BPF_REG_1, ctx->xsks_map_fd),
>   		/* r3 = 0 */
>   		BPF_MOV64_IMM(BPF_REG_3, 0),
>   		/* call bpf_redirect_map */
> @@ -411,19 +426,21 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>   		return prog_fd;
>   	}
>   
> -	err = bpf_set_link_xdp_fd(xsk->ifindex, prog_fd, xsk->config.xdp_flags);
> +	err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, prog_fd,
> +				  xsk->config.xdp_flags);
>   	if (err) {
>   		close(prog_fd);
>   		return err;
>   	}
>   
> -	xsk->prog_fd = prog_fd;
> +	ctx->prog_fd = prog_fd;
>   	return 0;
>   }
>   
>   static int xsk_get_max_queues(struct xsk_socket *xsk)
>   {
>   	struct ethtool_channels channels = { .cmd = ETHTOOL_GCHANNELS };
> +	struct xsk_ctx *ctx = xsk->ctx;
>   	struct ifreq ifr = {};
>   	int fd, err, ret;
>   
> @@ -432,7 +449,7 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
>   		return -errno;
>   
>   	ifr.ifr_data = (void *)&channels;
> -	memcpy(ifr.ifr_name, xsk->ifname, IFNAMSIZ - 1);
> +	memcpy(ifr.ifr_name, ctx->ifname, IFNAMSIZ - 1);
>   	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
>   	err = ioctl(fd, SIOCETHTOOL, &ifr);
>   	if (err && errno != EOPNOTSUPP) {
> @@ -460,6 +477,7 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
>   
>   static int xsk_create_bpf_maps(struct xsk_socket *xsk)
>   {
> +	struct xsk_ctx *ctx = xsk->ctx;
>   	int max_queues;
>   	int fd;
>   
> @@ -472,15 +490,17 @@ static int xsk_create_bpf_maps(struct xsk_socket *xsk)
>   	if (fd < 0)
>   		return fd;
>   
> -	xsk->xsks_map_fd = fd;
> +	ctx->xsks_map_fd = fd;
>   
>   	return 0;
>   }
>   
>   static void xsk_delete_bpf_maps(struct xsk_socket *xsk)
>   {
> -	bpf_map_delete_elem(xsk->xsks_map_fd, &xsk->queue_id);
> -	close(xsk->xsks_map_fd);
> +	struct xsk_ctx *ctx = xsk->ctx;
> +
> +	bpf_map_delete_elem(ctx->xsks_map_fd, &ctx->queue_id);
> +	close(ctx->xsks_map_fd);
>   }
>   
>   static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
> @@ -488,10 +508,11 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
>   	__u32 i, *map_ids, num_maps, prog_len = sizeof(struct bpf_prog_info);
>   	__u32 map_len = sizeof(struct bpf_map_info);
>   	struct bpf_prog_info prog_info = {};
> +	struct xsk_ctx *ctx = xsk->ctx;
>   	struct bpf_map_info map_info;
>   	int fd, err;
>   
> -	err = bpf_obj_get_info_by_fd(xsk->prog_fd, &prog_info, &prog_len);
> +	err = bpf_obj_get_info_by_fd(ctx->prog_fd, &prog_info, &prog_len);
>   	if (err)
>   		return err;
>   
> @@ -505,11 +526,11 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
>   	prog_info.nr_map_ids = num_maps;
>   	prog_info.map_ids = (__u64)(unsigned long)map_ids;
>   
> -	err = bpf_obj_get_info_by_fd(xsk->prog_fd, &prog_info, &prog_len);
> +	err = bpf_obj_get_info_by_fd(ctx->prog_fd, &prog_info, &prog_len);
>   	if (err)
>   		goto out_map_ids;
>   
> -	xsk->xsks_map_fd = -1;
> +	ctx->xsks_map_fd = -1;
>   
>   	for (i = 0; i < prog_info.nr_map_ids; i++) {
>   		fd = bpf_map_get_fd_by_id(map_ids[i]);
> @@ -523,7 +544,7 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
>   		}
>   
>   		if (!strcmp(map_info.name, "xsks_map")) {
> -			xsk->xsks_map_fd = fd;
> +			ctx->xsks_map_fd = fd;
>   			continue;
>   		}
>   
> @@ -531,7 +552,7 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
>   	}
>   
>   	err = 0;
> -	if (xsk->xsks_map_fd == -1)
> +	if (ctx->xsks_map_fd == -1)
>   		err = -ENOENT;
>   
>   out_map_ids:
> @@ -541,16 +562,19 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
>   
>   static int xsk_set_bpf_maps(struct xsk_socket *xsk)
>   {
> -	return bpf_map_update_elem(xsk->xsks_map_fd, &xsk->queue_id,
> +	struct xsk_ctx *ctx = xsk->ctx;
> +
> +	return bpf_map_update_elem(ctx->xsks_map_fd, &ctx->queue_id,
>   				   &xsk->fd, 0);
>   }
>   
>   static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
>   {
> +	struct xsk_ctx *ctx = xsk->ctx;
>   	__u32 prog_id = 0;
>   	int err;
>   
> -	err = bpf_get_link_xdp_id(xsk->ifindex, &prog_id,
> +	err = bpf_get_link_xdp_id(ctx->ifindex, &prog_id,
>   				  xsk->config.xdp_flags);
>   	if (err)
>   		return err;
> @@ -566,12 +590,12 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
>   			return err;
>   		}
>   	} else {
> -		xsk->prog_fd = bpf_prog_get_fd_by_id(prog_id);
> -		if (xsk->prog_fd < 0)
> +		ctx->prog_fd = bpf_prog_get_fd_by_id(prog_id);
> +		if (ctx->prog_fd < 0)
>   			return -errno;
>   		err = xsk_lookup_bpf_maps(xsk);
>   		if (err) {
> -			close(xsk->prog_fd);
> +			close(ctx->prog_fd);
>   			return err;
>   		}
>   	}
> @@ -580,25 +604,110 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
>   		err = xsk_set_bpf_maps(xsk);
>   	if (err) {
>   		xsk_delete_bpf_maps(xsk);
> -		close(xsk->prog_fd);
> +		close(ctx->prog_fd);
>   		return err;
>   	}
>   
>   	return 0;
>   }
>   
> -int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
> -		       __u32 queue_id, struct xsk_umem *umem,
> -		       struct xsk_ring_cons *rx, struct xsk_ring_prod *tx,
> -		       const struct xsk_socket_config *usr_config)
> +static struct xsk_ctx *xsk_get_ctx(struct xsk_umem *umem, int ifindex,
> +				   __u32 queue_id)
> +{
> +	struct xsk_ctx *ctx;
> +
> +	if (list_empty(&umem->ctx_list))
> +		return NULL;
> +
> +	list_for_each_entry(ctx, &umem->ctx_list, list) {
> +		if (ctx->ifindex == ifindex && ctx->queue_id == queue_id) {
> +			ctx->refcount++;
> +			return ctx;
> +		}
> +	}
> +
> +	return NULL;
> +}
> +
> +static void xsk_put_ctx(struct xsk_ctx *ctx)
> +{
> +	struct xsk_umem *umem = ctx->umem;
> +	struct xdp_mmap_offsets off;
> +	int err;
> +
> +	if (--ctx->refcount == 0) {
> +		err = xsk_get_mmap_offsets(umem->fd, &off);
> +		if (!err) {
> +			munmap(ctx->fill->ring - off.fr.desc,
> +			       off.fr.desc + umem->config.fill_size *
> +			       sizeof(__u64));
> +			munmap(ctx->comp->ring - off.cr.desc,
> +			       off.cr.desc + umem->config.comp_size *
> +			       sizeof(__u64));
> +		}
> +
> +		list_del(&ctx->list);
> +		free(ctx);
> +	}
> +}
> +
> +static struct xsk_ctx *xsk_create_ctx(struct xsk_socket *xsk,
> +				      struct xsk_umem *umem, int ifindex,
> +				      const char *ifname, __u32 queue_id,
> +				      struct xsk_ring_prod *fill,
> +				      struct xsk_ring_cons *comp)
> +{
> +	struct xsk_ctx *ctx;
> +	int err;
> +
> +	ctx = calloc(1, sizeof(*ctx));
> +	if (!ctx)
> +		return NULL;
> +
> +	if (!umem->fill_save) {
> +		err = xsk_create_umem_rings(umem, xsk->fd, fill, comp);
> +		if (err) {
> +			free(ctx);
> +			return NULL;
> +		}
> +	} else if (umem->fill_save != fill || umem->comp_save != comp) {
> +		/* Copy over rings to new structs. */
> +		memcpy(fill, umem->fill_save, sizeof(*fill));
> +		memcpy(comp, umem->comp_save, sizeof(*comp));
> +	}
> +
> +	ctx->ifindex = ifindex;
> +	ctx->refcount = 1;
> +	ctx->umem = umem;
> +	ctx->queue_id = queue_id;
> +	memcpy(ctx->ifname, ifname, IFNAMSIZ - 1);
> +	ctx->ifname[IFNAMSIZ - 1] = '\0';
> +
> +	umem->fill_save = NULL;
> +	umem->comp_save = NULL;
> +	ctx->fill = fill;
> +	ctx->comp = comp;
> +	list_add(&ctx->list, &umem->ctx_list);
> +	return ctx;
> +}
> +
> +int xsk_socket__create_shared(struct xsk_socket **xsk_ptr,
> +			      const char *ifname,
> +			      __u32 queue_id, struct xsk_umem *umem,
> +			      struct xsk_ring_cons *rx,
> +			      struct xsk_ring_prod *tx,
> +			      struct xsk_ring_prod *fill,
> +			      struct xsk_ring_cons *comp,
> +			      const struct xsk_socket_config *usr_config)
>   {
>   	void *rx_map = NULL, *tx_map = NULL;
>   	struct sockaddr_xdp sxdp = {};
>   	struct xdp_mmap_offsets off;
>   	struct xsk_socket *xsk;
> -	int err;
> +	struct xsk_ctx *ctx;
> +	int err, ifindex;
>   
> -	if (!umem || !xsk_ptr || !(rx || tx))
> +	if (!umem || !xsk_ptr || !(rx || tx) || !fill || !comp)
>   		return -EFAULT;
>   
>   	xsk = calloc(1, sizeof(*xsk));
> @@ -609,10 +718,10 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   	if (err)
>   		goto out_xsk_alloc;
>   
> -	if (umem->refcount &&
> -	    !(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
> -		pr_warn("Error: shared umems not supported by libbpf supplied XDP program.\n");
> -		err = -EBUSY;
> +	xsk->outstanding_tx = 0;
> +	ifindex = if_nametoindex(ifname);
> +	if (!ifindex) {
> +		err = -errno;
>   		goto out_xsk_alloc;
>   	}
>   
> @@ -626,16 +735,16 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   		xsk->fd = umem->fd;
>   	}
>   
> -	xsk->outstanding_tx = 0;
> -	xsk->queue_id = queue_id;
> -	xsk->umem = umem;
> -	xsk->ifindex = if_nametoindex(ifname);
> -	if (!xsk->ifindex) {
> -		err = -errno;
> -		goto out_socket;
> +	ctx = xsk_get_ctx(umem, ifindex, queue_id);
> +	if (!ctx) {
> +		ctx = xsk_create_ctx(xsk, umem, ifindex, ifname, queue_id,
> +				     fill, comp);
> +		if (!ctx) {
> +			err = -ENOMEM;
> +			goto out_socket;
> +		}
>   	}
> -	memcpy(xsk->ifname, ifname, IFNAMSIZ - 1);
> -	xsk->ifname[IFNAMSIZ - 1] = '\0';
> +	xsk->ctx = ctx;
>   
>   	if (rx) {
>   		err = setsockopt(xsk->fd, SOL_XDP, XDP_RX_RING,
> @@ -643,7 +752,7 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   				 sizeof(xsk->config.rx_size));
>   		if (err) {
>   			err = -errno;
> -			goto out_socket;
> +			goto out_put_ctx;
>   		}
>   	}
>   	if (tx) {
> @@ -652,14 +761,14 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   				 sizeof(xsk->config.tx_size));
>   		if (err) {
>   			err = -errno;
> -			goto out_socket;
> +			goto out_put_ctx;
>   		}
>   	}
>   
>   	err = xsk_get_mmap_offsets(xsk->fd, &off);
>   	if (err) {
>   		err = -errno;
> -		goto out_socket;
> +		goto out_put_ctx;
>   	}
>   
>   	if (rx) {
> @@ -669,7 +778,7 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   			      xsk->fd, XDP_PGOFF_RX_RING);
>   		if (rx_map == MAP_FAILED) {
>   			err = -errno;
> -			goto out_socket;
> +			goto out_put_ctx;
>   		}
>   
>   		rx->mask = xsk->config.rx_size - 1;
> @@ -708,10 +817,10 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   	xsk->tx = tx;
>   
>   	sxdp.sxdp_family = PF_XDP;
> -	sxdp.sxdp_ifindex = xsk->ifindex;
> -	sxdp.sxdp_queue_id = xsk->queue_id;
> +	sxdp.sxdp_ifindex = ctx->ifindex;
> +	sxdp.sxdp_queue_id = ctx->queue_id;
>   	if (umem->refcount > 1) {
> -		sxdp.sxdp_flags = XDP_SHARED_UMEM;
> +		sxdp.sxdp_flags |= XDP_SHARED_UMEM;
>   		sxdp.sxdp_shared_umem_fd = umem->fd;
>   	} else {
>   		sxdp.sxdp_flags = xsk->config.bind_flags;
> @@ -723,7 +832,7 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   		goto out_mmap_tx;
>   	}
>   
> -	xsk->prog_fd = -1;
> +	ctx->prog_fd = -1;
>   
>   	if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
>   		err = xsk_setup_xdp_prog(xsk);
> @@ -742,6 +851,8 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   	if (rx)
>   		munmap(rx_map, off.rx.desc +
>   		       xsk->config.rx_size * sizeof(struct xdp_desc));
> +out_put_ctx:
> +	xsk_put_ctx(ctx);
>   out_socket:
>   	if (--umem->refcount)
>   		close(xsk->fd);
> @@ -750,25 +861,24 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   	return err;
>   }
>   
> -int xsk_umem__delete(struct xsk_umem *umem)
> +int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
> +		       __u32 queue_id, struct xsk_umem *umem,
> +		       struct xsk_ring_cons *rx, struct xsk_ring_prod *tx,
> +		       const struct xsk_socket_config *usr_config)
>   {
> -	struct xdp_mmap_offsets off;
> -	int err;
> +	return xsk_socket__create_shared(xsk_ptr, ifname, queue_id, umem,
> +					 rx, tx, umem->fill_save,
> +					 umem->comp_save, usr_config);
> +}
>   
> +int xsk_umem__delete(struct xsk_umem *umem)
> +{
>   	if (!umem)
>   		return 0;
>   
>   	if (umem->refcount)
>   		return -EBUSY;
>   
> -	err = xsk_get_mmap_offsets(umem->fd, &off);
> -	if (!err) {
> -		munmap(umem->fill->ring - off.fr.desc,
> -		       off.fr.desc + umem->config.fill_size * sizeof(__u64));
> -		munmap(umem->comp->ring - off.cr.desc,
> -		       off.cr.desc + umem->config.comp_size * sizeof(__u64));
> -	}
> -
>   	close(umem->fd);
>   	free(umem);
>   
> @@ -778,15 +888,16 @@ int xsk_umem__delete(struct xsk_umem *umem)
>   void xsk_socket__delete(struct xsk_socket *xsk)
>   {
>   	size_t desc_sz = sizeof(struct xdp_desc);
> +	struct xsk_ctx *ctx = xsk->ctx;
>   	struct xdp_mmap_offsets off;
>   	int err;
>   
>   	if (!xsk)
>   		return;
>   
> -	if (xsk->prog_fd != -1) {
> +	if (ctx->prog_fd != -1) {
>   		xsk_delete_bpf_maps(xsk);
> -		close(xsk->prog_fd);
> +		close(ctx->prog_fd);
>   	}
>   
>   	err = xsk_get_mmap_offsets(xsk->fd, &off);
> @@ -799,14 +910,15 @@ void xsk_socket__delete(struct xsk_socket *xsk)
>   			munmap(xsk->tx->ring - off.tx.desc,
>   			       off.tx.desc + xsk->config.tx_size * desc_sz);
>   		}
> -
>   	}
>   
> -	xsk->umem->refcount--;
> +	xsk_put_ctx(ctx);
> +
> +	ctx->umem->refcount--;
>   	/* Do not close an fd that also has an associated umem connected
>   	 * to it.
>   	 */
> -	if (xsk->fd != xsk->umem->fd)
> +	if (xsk->fd != ctx->umem->fd)
>   		close(xsk->fd);
>   	free(xsk);
>   }
> diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> index 584f682..1069c46 100644
> --- a/tools/lib/bpf/xsk.h
> +++ b/tools/lib/bpf/xsk.h
> @@ -234,6 +234,15 @@ LIBBPF_API int xsk_socket__create(struct xsk_socket **xsk,
>   				  struct xsk_ring_cons *rx,
>   				  struct xsk_ring_prod *tx,
>   				  const struct xsk_socket_config *config);
> +LIBBPF_API int
> +xsk_socket__create_shared(struct xsk_socket **xsk_ptr,
> +			  const char *ifname,
> +			  __u32 queue_id, struct xsk_umem *umem,
> +			  struct xsk_ring_cons *rx,
> +			  struct xsk_ring_prod *tx,
> +			  struct xsk_ring_prod *fill,
> +			  struct xsk_ring_cons *comp,
> +			  const struct xsk_socket_config *config);
>   
>   /* Returns 0 for success and -EBUSY if the umem is still in use. */
>   LIBBPF_API int xsk_umem__delete(struct xsk_umem *umem);
>