Re: [PATCH bpf-next v4 1/2] libbpf: add support for using AF_XDP sockets
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2019-02-15 17:03:58
On 02/08/2019 02:05 PM, Magnus Karlsson wrote:
This commit adds AF_XDP support to libbpf. The main reason for this is to facilitate writing applications that use AF_XDP by offering higher-level APIs that hide many of the details of the AF_XDP uapi. This is in the same vein as libbpf facilitates XDP adoption by offering easy-to-use higher level interfaces of XDP functionality. Hopefully this will facilitate adoption of AF_XDP, make applications using it simpler and smaller, and finally also make it possible for applications to benefit from optimizations in the AF_XDP user space access code. Previously, people just copied and pasted the code from the sample application into their application, which is not desirable. The interface is composed of two parts: * Low-level access interface to the four rings and the packet * High-level control plane interface for creating and setting up umems and af_xdp sockets as well as a simple XDP program. Tested-by: Björn Töpel <redacted> Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
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quoted hunk ↗ jump to hunk
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c new file mode 100644 index 0000000..a982a76 --- /dev/null +++ b/tools/lib/bpf/xsk.c@@ -0,0 +1,742 @@ +// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) + +/* + * AF_XDP user-space access library. + * + * Copyright(c) 2018 - 2019 Intel Corporation. + * + * Author(s): Magnus Karlsson <magnus.karlsson@intel.com> + */ + +#include <errno.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <arpa/inet.h> +#include <asm/barrier.h> +#include <linux/compiler.h> +#include <linux/filter.h> +#include <linux/if_ether.h> +#include <linux/if_link.h> +#include <linux/if_packet.h> +#include <linux/if_xdp.h> +#include <linux/rtnetlink.h> +#include <net/if.h> +#include <sys/mman.h> +#include <sys/socket.h> +#include <sys/types.h> + +#include "bpf.h" +#include "libbpf.h" +#include "libbpf_util.h" +#include "nlattr.h" +#include "xsk.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 + +struct xsk_umem { + struct xsk_ring_prod *fill; + struct xsk_ring_cons *comp; + char *umem_area; + struct xsk_umem_config config; + int fd; + int refcount; +}; + +struct xsk_socket { + struct xsk_ring_cons *rx; + struct xsk_ring_prod *tx; + __u64 outstanding_tx; + struct xsk_umem *umem; + struct xsk_socket_config config; + int fd; + int xsks_map; + int ifindex; + int prog_fd; + int qidconf_map_fd; + int xsks_map_fd; + __u32 queue_id; +}; + +struct xsk_nl_info { + bool xdp_prog_attached; + int ifindex; + int fd; +}; + +#define MAX_QUEUES 128
Why is this a fixed constant here, shouldn't this be dynamic due to being NIC specific anyway? [...]
+void *xsk_umem__get_data(struct xsk_umem *umem, __u64 addr)
+{
+ return &((char *)(umem->umem_area))[addr];
+}There's also a xsk_umem__get_data_raw() doing the same. Why having both, resp. when to choose which? ;)
+int xsk_umem__fd(const struct xsk_umem *umem)
+{
+ return umem ? umem->fd : -EINVAL;
+}
+
+int xsk_socket__fd(const struct xsk_socket *xsk)
+{
+ return xsk ? xsk->fd : -EINVAL;
+}
+
+static bool xsk_page_aligned(void *buffer)
+{
+ unsigned long addr = (unsigned long)buffer;
+
+ return !(addr & (getpagesize() - 1));
+}
+
+static void xsk_set_umem_config(struct xsk_umem_config *cfg,
+ const struct xsk_umem_config *usr_cfg)
+{
+ if (!usr_cfg) {
+ cfg->fill_size = XSK_RING_PROD__DEFAULT_NUM_DESCS;
+ cfg->comp_size = XSK_RING_CONS__DEFAULT_NUM_DESCS;
+ cfg->frame_size = XSK_UMEM__DEFAULT_FRAME_SIZE;
+ cfg->frame_headroom = XSK_UMEM__DEFAULT_FRAME_HEADROOM;
+ return;
+ }
+
+ cfg->fill_size = usr_cfg->fill_size;
+ cfg->comp_size = usr_cfg->comp_size;
+ cfg->frame_size = usr_cfg->frame_size;
+ cfg->frame_headroom = usr_cfg->frame_headroom;Just optional nit, might be a bit nicer to have it in this form: cfg->fill_size = usr_cfg ? usr_cfg->fill_size : XSK_RING_PROD__DEFAULT_NUM_DESCS;
+}
+
+static void xsk_set_xdp_socket_config(struct xsk_socket_config *cfg,
+ const struct xsk_socket_config *usr_cfg)
+{
+ if (!usr_cfg) {
+ cfg->rx_size = XSK_RING_CONS__DEFAULT_NUM_DESCS;
+ cfg->tx_size = XSK_RING_PROD__DEFAULT_NUM_DESCS;
+ cfg->libbpf_flags = 0;
+ cfg->xdp_flags = 0;
+ cfg->bind_flags = 0;
+ return;
+ }
+
+ cfg->rx_size = usr_cfg->rx_size;
+ cfg->tx_size = usr_cfg->tx_size;
+ cfg->libbpf_flags = usr_cfg->libbpf_flags;
+ cfg->xdp_flags = usr_cfg->xdp_flags;
+ cfg->bind_flags = usr_cfg->bind_flags;(Ditto)
+}
+
+int xsk_umem__create(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;
+ socklen_t optlen;
+ void *map;
+ int err;
+
+ if (!umem_area || !umem_ptr || !fill || !comp)
+ return -EFAULT;
+ if (!size && !xsk_page_aligned(umem_area))
+ return -EINVAL;
+
+ umem = calloc(1, sizeof(*umem));
+ if (!umem)
+ return -ENOMEM;
+
+ umem->fd = socket(AF_XDP, SOCK_RAW, 0);
+ if (umem->fd < 0) {
+ err = -errno;
+ goto out_umem_alloc;
+ }
+
+ umem->umem_area = umem_area;
+ xsk_set_umem_config(&umem->config, usr_config);
+
+ mr.addr = (uintptr_t)umem_area;
+ mr.len = size;
+ mr.chunk_size = umem->config.frame_size;
+ mr.headroom = umem->config.frame_headroom;
+
+ err = setsockopt(umem->fd, SOL_XDP, XDP_UMEM_REG, &mr, sizeof(mr));
+ if (err) {
+ 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;
+ }
+
+ optlen = sizeof(off);
+ err = getsockopt(umem->fd, SOL_XDP, XDP_MMAP_OFFSETS, &off, &optlen);
+ if (err) {
+ err = -errno;
+ goto out_socket;
+ }
+
+ map = xsk_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;
+ 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->ring = map + off.fr.desc;
+ fill->cached_cons = umem->config.fill_size;
+
+ map = xsk_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->ring = map + off.cr.desc;
+
+ *umem_ptr = umem;
+ return 0;
+
+out_mmap:
+ munmap(umem->fill,
+ off.fr.desc + umem->config.fill_size * sizeof(__u64));
+out_socket:
+ close(umem->fd);
+out_umem_alloc:
+ free(umem);
+ return err;
+}
+
+static int xsk_parse_nl(void *cookie, void *msg, struct nlattr **tb)
+{
+ struct nlattr *tb_parsed[IFLA_XDP_MAX + 1];
+ struct xsk_nl_info *nl_info = cookie;
+ struct ifinfomsg *ifinfo = msg;
+ unsigned char mode;
+ int err;
+
+ if (nl_info->ifindex && nl_info->ifindex != ifinfo->ifi_index)
+ return 0;
+
+ if (!tb[IFLA_XDP])
+ return 0;
+
+ err = libbpf_nla_parse_nested(tb_parsed, IFLA_XDP_MAX, tb[IFLA_XDP],
+ NULL);
+ if (err)
+ return err;
+
+ if (!tb_parsed[IFLA_XDP_ATTACHED] || !tb_parsed[IFLA_XDP_FD])
+ return 0;
+
+ mode = libbpf_nla_getattr_u8(tb_parsed[IFLA_XDP_ATTACHED]);
+ if (mode == XDP_ATTACHED_NONE)
+ return 0;
+
+ nl_info->xdp_prog_attached = true;
+ nl_info->fd = libbpf_nla_getattr_u32(tb_parsed[IFLA_XDP_FD]);Hm, I don't think this works if I read the intention of this helper correctly. IFLA_XDP_FD is never set for retrieving the prog from the kernel. So the above is a bug. We also have bpf_get_link_xdp_id(). This should probably just be reused in this context here.
+ return 0;
+}
+
+static bool xsk_xdp_prog_attached(struct xsk_socket *xsk)
+{
+ struct xsk_nl_info nl_info;
+ unsigned int nl_pid;
+ char err_buf[256];
+ int sock, err;
+
+ sock = libbpf_netlink_open(&nl_pid);
+ if (sock < 0)
+ return false;
+
+ nl_info.xdp_prog_attached = false;
+ nl_info.ifindex = xsk->ifindex;
+ nl_info.fd = -1;
+
+ err = libbpf_nl_get_link(sock, nl_pid, xsk_parse_nl, &nl_info);
+ if (err) {
+ libbpf_strerror(err, err_buf, sizeof(err_buf));
+ pr_warning("Error:\n%s\n", err_buf);
+ close(sock);
+ return false;
+ }
+
+ close(sock);
+ xsk->prog_fd = nl_info.fd;
+ return nl_info.xdp_prog_attached;
+}(See bpf_get_link_xdp_id().)
+
+static int xsk_load_xdp_prog(struct xsk_socket *xsk)
+{
+ char bpf_log_buf[BPF_LOG_BUF_SIZE];
+ int err, prog_fd;
+
+ /* This is the C-program:
+ * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx)
+ * {
+ * int *qidconf, index = ctx->rx_queue_index;[...]
+
+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 sockaddr_xdp sxdp = {};
+ struct xdp_mmap_offsets off;
+ struct xsk_socket *xsk;
+ socklen_t optlen;
+ void *map;
+ int err;
+
+ if (!umem || !xsk_ptr || !rx || !tx)
+ return -EFAULT;
+
+ if (umem->refcount) {
+ pr_warning("Error: shared umems not supported by libbpf.\n");
+ return -EBUSY;
+ }
+
+ xsk = calloc(1, sizeof(*xsk));
+ if (!xsk)
+ return -ENOMEM;
+
+ if (umem->refcount++ > 0) {Should this refcount rather be atomic actually?
+ xsk->fd = socket(AF_XDP, SOCK_RAW, 0);
+ if (xsk->fd < 0) {
+ err = -errno;
+ goto out_xsk_alloc;
+ }
+ } else {
+ 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;
+ }
+
+ xsk_set_xdp_socket_config(&xsk->config, usr_config);[...]