tools/lib/bpf/netlink.c - linux - Git at Google

 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
 /* Copyright (c) 2018 Facebook */

 #include <stdlib.h>
 #include <memory.h>
 #include <unistd.h>
 #include <linux/bpf.h>
 #include <linux/rtnetlink.h>
 #include <sys/socket.h>
 #include <errno.h>
 #include <time.h>

 #include "bpf.h"
 #include "libbpf.h"
 #include "libbpf_internal.h"
 #include "nlattr.h"

 #ifndef SOL_NETLINK
 #define SOL_NETLINK 270
 #endif

 typedef int (*libbpf_dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);

 typedef int (*__dump_nlmsg_t)(struct nlmsghdr *nlmsg, libbpf_dump_nlmsg_t,
 			      void *cookie);

 struct xdp_id_md {
 	int ifindex;
 	__u32 flags;
 	struct xdp_link_info info;
 };

 static int libbpf_netlink_open(__u32 *nl_pid)
 {
 	struct sockaddr_nl sa;
 	socklen_t addrlen;
 	int one = 1, ret;
 	int sock;

 	memset(&sa, 0, sizeof(sa));
 	sa.nl_family = AF_NETLINK;

 	sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 	if (sock < 0)
 		return -errno;

 	if (setsockopt(sock, SOL_NETLINK, NETLINK_EXT_ACK,
 		       &one, sizeof(one)) < 0) {
 		pr_warn("Netlink error reporting not supported\n");
 	}

 	if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
 		ret = -errno;
 		goto cleanup;
 	}

 	addrlen = sizeof(sa);
 	if (getsockname(sock, (struct sockaddr *)&sa, &addrlen) < 0) {
 		ret = -errno;
 		goto cleanup;
 	}

 	if (addrlen != sizeof(sa)) {
 		ret = -LIBBPF_ERRNO__INTERNAL;
 		goto cleanup;
 	}

 	*nl_pid = sa.nl_pid;
 	return sock;

 cleanup:
 	close(sock);
 	return ret;
 }

 static int bpf_netlink_recv(int sock, __u32 nl_pid, int seq,
 			    __dump_nlmsg_t _fn, libbpf_dump_nlmsg_t fn,
 			    void *cookie)
 {
 	bool multipart = true;
 	struct nlmsgerr *err;
 	struct nlmsghdr *nh;
 	char buf[4096];
 	int len, ret;

 	while (multipart) {
 		multipart = false;
 		len = recv(sock, buf, sizeof(buf), 0);
 		if (len < 0) {
 			ret = -errno;
 			goto done;
 		}

 		if (len == 0)
 			break;

 		for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
 		     nh = NLMSG_NEXT(nh, len)) {
 			if (nh->nlmsg_pid != nl_pid) {
 				ret = -LIBBPF_ERRNO__WRNGPID;
 				goto done;
 			}
 			if (nh->nlmsg_seq != seq) {
 				ret = -LIBBPF_ERRNO__INVSEQ;
 				goto done;
 			}
 			if (nh->nlmsg_flags & NLM_F_MULTI)
 				multipart = true;
 			switch (nh->nlmsg_type) {
 			case NLMSG_ERROR:
 				err = (struct nlmsgerr *)NLMSG_DATA(nh);
 				if (!err->error)
 					continue;
 				ret = err->error;
 				libbpf_nla_dump_errormsg(nh);
 				goto done;
 			case NLMSG_DONE:
 				return 0;
 			default:
 				break;
 			}
 			if (_fn) {
 				ret = _fn(nh, fn, cookie);
 				if (ret)
 					return ret;
 			}
 		}
 	}
 	ret = 0;
 done:
 	return ret;
 }

 static int __bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd,
 					 __u32 flags)
 {
 	int sock, seq = 0, ret;
 	struct nlattr *nla, *nla_xdp;
 	struct {
 		struct nlmsghdr  nh;
 		struct ifinfomsg ifinfo;
 		char             attrbuf[64];
 	} req;
 	__u32 nl_pid = 0;

 	sock = libbpf_netlink_open(&nl_pid);
 	if (sock < 0)
 		return sock;

 	memset(&req, 0, sizeof(req));
 	req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
 	req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
 	req.nh.nlmsg_type = RTM_SETLINK;
 	req.nh.nlmsg_pid = 0;
 	req.nh.nlmsg_seq = ++seq;
 	req.ifinfo.ifi_family = AF_UNSPEC;
 	req.ifinfo.ifi_index = ifindex;

 	/* started nested attribute for XDP */
 	nla = (struct nlattr *)(((char *)&req)
 				+ NLMSG_ALIGN(req.nh.nlmsg_len));
 	nla->nla_type = NLA_F_NESTED | IFLA_XDP;
 	nla->nla_len = NLA_HDRLEN;

 	/* add XDP fd */
 	nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
 	nla_xdp->nla_type = IFLA_XDP_FD;
 	nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
 	memcpy((char *)nla_xdp + NLA_HDRLEN, &fd, sizeof(fd));
 	nla->nla_len += nla_xdp->nla_len;

 	/* if user passed in any flags, add those too */
 	if (flags) {
 		nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
 		nla_xdp->nla_type = IFLA_XDP_FLAGS;
 		nla_xdp->nla_len = NLA_HDRLEN + sizeof(flags);
 		memcpy((char *)nla_xdp + NLA_HDRLEN, &flags, sizeof(flags));
 		nla->nla_len += nla_xdp->nla_len;
 	}

 	if (flags & XDP_FLAGS_REPLACE) {
 		nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
 		nla_xdp->nla_type = IFLA_XDP_EXPECTED_FD;
 		nla_xdp->nla_len = NLA_HDRLEN + sizeof(old_fd);
 		memcpy((char *)nla_xdp + NLA_HDRLEN, &old_fd, sizeof(old_fd));
 		nla->nla_len += nla_xdp->nla_len;
 	}

 	req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);

 	if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
 		ret = -errno;
 		goto cleanup;
 	}
 	ret = bpf_netlink_recv(sock, nl_pid, seq, NULL, NULL, NULL);

 cleanup:
 	close(sock);
 	return ret;
 }

 int bpf_set_link_xdp_fd_opts(int ifindex, int fd, __u32 flags,
 			     const struct bpf_xdp_set_link_opts *opts)
 {
 	int old_fd = -1;

 	if (!OPTS_VALID(opts, bpf_xdp_set_link_opts))
 		return -EINVAL;

 	if (OPTS_HAS(opts, old_fd)) {
 		old_fd = OPTS_GET(opts, old_fd, -1);
 		flags |= XDP_FLAGS_REPLACE;
 	}

 	return __bpf_set_link_xdp_fd_replace(ifindex, fd,
 					     old_fd,
 					     flags);
 }

 int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
 {
 	return __bpf_set_link_xdp_fd_replace(ifindex, fd, 0, flags);
 }

 static int __dump_link_nlmsg(struct nlmsghdr *nlh,
 			     libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
 {
 	struct nlattr *tb[IFLA_MAX + 1], *attr;
 	struct ifinfomsg *ifi = NLMSG_DATA(nlh);
 	int len;

 	len = nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
 	attr = (struct nlattr *) ((void *) ifi + NLMSG_ALIGN(sizeof(*ifi)));
 	if (libbpf_nla_parse(tb, IFLA_MAX, attr, len, NULL) != 0)
 		return -LIBBPF_ERRNO__NLPARSE;

 	return dump_link_nlmsg(cookie, ifi, tb);
 }

 static int get_xdp_info(void *cookie, void *msg, struct nlattr **tb)
 {
 	struct nlattr *xdp_tb[IFLA_XDP_MAX + 1];
 	struct xdp_id_md *xdp_id = cookie;
 	struct ifinfomsg *ifinfo = msg;
 	int ret;

 	if (xdp_id->ifindex && xdp_id->ifindex != ifinfo->ifi_index)
 		return 0;

 	if (!tb[IFLA_XDP])
 		return 0;

 	ret = libbpf_nla_parse_nested(xdp_tb, IFLA_XDP_MAX, tb[IFLA_XDP], NULL);
 	if (ret)
 		return ret;

 	if (!xdp_tb[IFLA_XDP_ATTACHED])
 		return 0;

 	xdp_id->info.attach_mode = libbpf_nla_getattr_u8(
 		xdp_tb[IFLA_XDP_ATTACHED]);

 	if (xdp_id->info.attach_mode == XDP_ATTACHED_NONE)
 		return 0;

 	if (xdp_tb[IFLA_XDP_PROG_ID])
 		xdp_id->info.prog_id = libbpf_nla_getattr_u32(
 			xdp_tb[IFLA_XDP_PROG_ID]);

 	if (xdp_tb[IFLA_XDP_SKB_PROG_ID])
 		xdp_id->info.skb_prog_id = libbpf_nla_getattr_u32(
 			xdp_tb[IFLA_XDP_SKB_PROG_ID]);

 	if (xdp_tb[IFLA_XDP_DRV_PROG_ID])
 		xdp_id->info.drv_prog_id = libbpf_nla_getattr_u32(
 			xdp_tb[IFLA_XDP_DRV_PROG_ID]);

 	if (xdp_tb[IFLA_XDP_HW_PROG_ID])
 		xdp_id->info.hw_prog_id = libbpf_nla_getattr_u32(
 			xdp_tb[IFLA_XDP_HW_PROG_ID]);

 	return 0;
 }

 static int libbpf_nl_get_link(int sock, unsigned int nl_pid,
 			      libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie);

 int bpf_get_link_xdp_info(int ifindex, struct xdp_link_info *info,
 			  size_t info_size, __u32 flags)
 {
 	struct xdp_id_md xdp_id = {};
 	int sock, ret;
 	__u32 nl_pid = 0;
 	__u32 mask;

 	if (flags & ~XDP_FLAGS_MASK || !info_size)
 		return -EINVAL;

 	/* Check whether the single {HW,DRV,SKB} mode is set */
 	flags &= (XDP_FLAGS_SKB_MODE | XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE);
 	mask = flags - 1;
 	if (flags && flags & mask)
 		return -EINVAL;

 	sock = libbpf_netlink_open(&nl_pid);
 	if (sock < 0)
 		return sock;

 	xdp_id.ifindex = ifindex;
 	xdp_id.flags = flags;

 	ret = libbpf_nl_get_link(sock, nl_pid, get_xdp_info, &xdp_id);
 	if (!ret) {
 		size_t sz = min(info_size, sizeof(xdp_id.info));

 		memcpy(info, &xdp_id.info, sz);
 		memset((void *) info + sz, 0, info_size - sz);
 	}

 	close(sock);
 	return ret;
 }

 static __u32 get_xdp_id(struct xdp_link_info *info, __u32 flags)
 {
 	flags &= XDP_FLAGS_MODES;

 	if (info->attach_mode != XDP_ATTACHED_MULTI && !flags)
 		return info->prog_id;
 	if (flags & XDP_FLAGS_DRV_MODE)
 		return info->drv_prog_id;
 	if (flags & XDP_FLAGS_HW_MODE)
 		return info->hw_prog_id;
 	if (flags & XDP_FLAGS_SKB_MODE)
 		return info->skb_prog_id;

 	return 0;
 }

 int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
 {
 	struct xdp_link_info info;
 	int ret;

 	ret = bpf_get_link_xdp_info(ifindex, &info, sizeof(info), flags);
 	if (!ret)
 		*prog_id = get_xdp_id(&info, flags);

 	return ret;
 }

 int libbpf_nl_get_link(int sock, unsigned int nl_pid,
 		       libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
 {
 	struct {
 		struct nlmsghdr nlh;
 		struct ifinfomsg ifm;
 	} req = {
 		.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
 		.nlh.nlmsg_type = RTM_GETLINK,
 		.nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
 		.ifm.ifi_family = AF_PACKET,
 	};
 	int seq = time(NULL);

 	req.nlh.nlmsg_seq = seq;
 	if (send(sock, &req, req.nlh.nlmsg_len, 0) < 0)
 		return -errno;

 	return bpf_netlink_recv(sock, nl_pid, seq, __dump_link_nlmsg,
 				dump_link_nlmsg, cookie);
 }
	// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
	/* Copyright (c) 2018 Facebook */

	#include <stdlib.h>
	#include <memory.h>
	#include <unistd.h>
	#include <linux/bpf.h>
	#include <linux/rtnetlink.h>
	#include <sys/socket.h>
	#include <errno.h>
	#include <time.h>

	#include "bpf.h"
	#include "libbpf.h"
	#include "libbpf_internal.h"
	#include "nlattr.h"

	#ifndef SOL_NETLINK
	#define SOL_NETLINK 270
	#endif

	typedef int (libbpf_dump_nlmsg_t)(void cookie, void msg, struct nlattr *tb);

	typedef int (__dump_nlmsg_t)(struct nlmsghdr nlmsg, libbpf_dump_nlmsg_t,
	void *cookie);

	struct xdp_id_md {
	int ifindex;
	__u32 flags;
	struct xdp_link_info info;
	};

	static int libbpf_netlink_open(__u32 *nl_pid)
	{
	struct sockaddr_nl sa;
	socklen_t addrlen;
	int one = 1, ret;
	int sock;

	memset(&sa, 0, sizeof(sa));
	sa.nl_family = AF_NETLINK;

	sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
	if (sock < 0)
	return -errno;

	if (setsockopt(sock, SOL_NETLINK, NETLINK_EXT_ACK,
	&one, sizeof(one)) < 0) {
	pr_warn("Netlink error reporting not supported\n");
	}

	if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
	ret = -errno;
	goto cleanup;
	}

	addrlen = sizeof(sa);
	if (getsockname(sock, (struct sockaddr *)&sa, &addrlen) < 0) {
	ret = -errno;
	goto cleanup;
	}

	if (addrlen != sizeof(sa)) {
	ret = -LIBBPF_ERRNO__INTERNAL;
	goto cleanup;
	}

	*nl_pid = sa.nl_pid;
	return sock;

	cleanup:
	close(sock);
	return ret;
	}

	static int bpf_netlink_recv(int sock, __u32 nl_pid, int seq,
	__dump_nlmsg_t _fn, libbpf_dump_nlmsg_t fn,
	void *cookie)
	{
	bool multipart = true;
	struct nlmsgerr *err;
	struct nlmsghdr *nh;
	char buf[4096];
	int len, ret;

	while (multipart) {
	multipart = false;
	len = recv(sock, buf, sizeof(buf), 0);
	if (len < 0) {
	ret = -errno;
	goto done;
	}

	if (len == 0)
	break;

	for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
	nh = NLMSG_NEXT(nh, len)) {
	if (nh->nlmsg_pid != nl_pid) {
	ret = -LIBBPF_ERRNO__WRNGPID;
	goto done;
	}
	if (nh->nlmsg_seq != seq) {
	ret = -LIBBPF_ERRNO__INVSEQ;
	goto done;
	}
	if (nh->nlmsg_flags & NLM_F_MULTI)
	multipart = true;
	switch (nh->nlmsg_type) {
	case NLMSG_ERROR:
	err = (struct nlmsgerr *)NLMSG_DATA(nh);
	if (!err->error)
	continue;
	ret = err->error;
	libbpf_nla_dump_errormsg(nh);
	goto done;
	case NLMSG_DONE:
	return 0;
	default:
	break;
	}
	if (_fn) {
	ret = _fn(nh, fn, cookie);
	if (ret)
	return ret;
	}
	}
	}
	ret = 0;
	done:
	return ret;
	}

	static int __bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd,
	__u32 flags)
	{
	int sock, seq = 0, ret;
	struct nlattr nla, nla_xdp;
	struct {
	struct nlmsghdr nh;
	struct ifinfomsg ifinfo;
	char attrbuf[64];
	} req;
	__u32 nl_pid = 0;

	sock = libbpf_netlink_open(&nl_pid);
	if (sock < 0)
	return sock;

	memset(&req, 0, sizeof(req));
	req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
	req.nh.nlmsg_flags = NLM_F_REQUEST \| NLM_F_ACK;
	req.nh.nlmsg_type = RTM_SETLINK;
	req.nh.nlmsg_pid = 0;
	req.nh.nlmsg_seq = ++seq;
	req.ifinfo.ifi_family = AF_UNSPEC;
	req.ifinfo.ifi_index = ifindex;

	/* started nested attribute for XDP */
	nla = (struct nlattr )(((char )&req)
	+ NLMSG_ALIGN(req.nh.nlmsg_len));
	nla->nla_type = NLA_F_NESTED \| IFLA_XDP;
	nla->nla_len = NLA_HDRLEN;

	/* add XDP fd */
	nla_xdp = (struct nlattr )((char )nla + nla->nla_len);
	nla_xdp->nla_type = IFLA_XDP_FD;
	nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
	memcpy((char *)nla_xdp + NLA_HDRLEN, &fd, sizeof(fd));
	nla->nla_len += nla_xdp->nla_len;

	/* if user passed in any flags, add those too */
	if (flags) {
	nla_xdp = (struct nlattr )((char )nla + nla->nla_len);
	nla_xdp->nla_type = IFLA_XDP_FLAGS;
	nla_xdp->nla_len = NLA_HDRLEN + sizeof(flags);
	memcpy((char *)nla_xdp + NLA_HDRLEN, &flags, sizeof(flags));
	nla->nla_len += nla_xdp->nla_len;
	}

	if (flags & XDP_FLAGS_REPLACE) {
	nla_xdp = (struct nlattr )((char )nla + nla->nla_len);
	nla_xdp->nla_type = IFLA_XDP_EXPECTED_FD;
	nla_xdp->nla_len = NLA_HDRLEN + sizeof(old_fd);
	memcpy((char *)nla_xdp + NLA_HDRLEN, &old_fd, sizeof(old_fd));
	nla->nla_len += nla_xdp->nla_len;
	}

	req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);

	if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
	ret = -errno;
	goto cleanup;
	}
	ret = bpf_netlink_recv(sock, nl_pid, seq, NULL, NULL, NULL);

	cleanup:
	close(sock);
	return ret;
	}

	int bpf_set_link_xdp_fd_opts(int ifindex, int fd, __u32 flags,
	const struct bpf_xdp_set_link_opts *opts)
	{
	int old_fd = -1;

	if (!OPTS_VALID(opts, bpf_xdp_set_link_opts))
	return -EINVAL;

	if (OPTS_HAS(opts, old_fd)) {
	old_fd = OPTS_GET(opts, old_fd, -1);
	flags \|= XDP_FLAGS_REPLACE;
	}

	return __bpf_set_link_xdp_fd_replace(ifindex, fd,
	old_fd,
	flags);
	}

	int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
	{
	return __bpf_set_link_xdp_fd_replace(ifindex, fd, 0, flags);
	}

	static int __dump_link_nlmsg(struct nlmsghdr *nlh,
	libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
	{
	struct nlattr tb[IFLA_MAX + 1], attr;
	struct ifinfomsg *ifi = NLMSG_DATA(nlh);
	int len;

	len = nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
	attr = (struct nlattr ) ((void ) ifi + NLMSG_ALIGN(sizeof(*ifi)));
	if (libbpf_nla_parse(tb, IFLA_MAX, attr, len, NULL) != 0)
	return -LIBBPF_ERRNO__NLPARSE;

	return dump_link_nlmsg(cookie, ifi, tb);
	}

	static int get_xdp_info(void cookie, void msg, struct nlattr **tb)
	{
	struct nlattr *xdp_tb[IFLA_XDP_MAX + 1];
	struct xdp_id_md *xdp_id = cookie;
	struct ifinfomsg *ifinfo = msg;
	int ret;

	if (xdp_id->ifindex && xdp_id->ifindex != ifinfo->ifi_index)
	return 0;

	if (!tb[IFLA_XDP])
	return 0;

	ret = libbpf_nla_parse_nested(xdp_tb, IFLA_XDP_MAX, tb[IFLA_XDP], NULL);
	if (ret)
	return ret;

	if (!xdp_tb[IFLA_XDP_ATTACHED])
	return 0;

	xdp_id->info.attach_mode = libbpf_nla_getattr_u8(
	xdp_tb[IFLA_XDP_ATTACHED]);

	if (xdp_id->info.attach_mode == XDP_ATTACHED_NONE)
	return 0;

	if (xdp_tb[IFLA_XDP_PROG_ID])
	xdp_id->info.prog_id = libbpf_nla_getattr_u32(
	xdp_tb[IFLA_XDP_PROG_ID]);

	if (xdp_tb[IFLA_XDP_SKB_PROG_ID])
	xdp_id->info.skb_prog_id = libbpf_nla_getattr_u32(
	xdp_tb[IFLA_XDP_SKB_PROG_ID]);

	if (xdp_tb[IFLA_XDP_DRV_PROG_ID])
	xdp_id->info.drv_prog_id = libbpf_nla_getattr_u32(
	xdp_tb[IFLA_XDP_DRV_PROG_ID]);

	if (xdp_tb[IFLA_XDP_HW_PROG_ID])
	xdp_id->info.hw_prog_id = libbpf_nla_getattr_u32(
	xdp_tb[IFLA_XDP_HW_PROG_ID]);

	return 0;
	}

	static int libbpf_nl_get_link(int sock, unsigned int nl_pid,
	libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie);

	int bpf_get_link_xdp_info(int ifindex, struct xdp_link_info *info,
	size_t info_size, __u32 flags)
	{
	struct xdp_id_md xdp_id = {};
	int sock, ret;
	__u32 nl_pid = 0;
	__u32 mask;

	if (flags & ~XDP_FLAGS_MASK \|\| !info_size)
	return -EINVAL;

	/* Check whether the single {HW,DRV,SKB} mode is set */
	flags &= (XDP_FLAGS_SKB_MODE \| XDP_FLAGS_DRV_MODE \| XDP_FLAGS_HW_MODE);
	mask = flags - 1;
	if (flags && flags & mask)
	return -EINVAL;

	sock = libbpf_netlink_open(&nl_pid);
	if (sock < 0)
	return sock;

	xdp_id.ifindex = ifindex;
	xdp_id.flags = flags;

	ret = libbpf_nl_get_link(sock, nl_pid, get_xdp_info, &xdp_id);
	if (!ret) {
	size_t sz = min(info_size, sizeof(xdp_id.info));

	memcpy(info, &xdp_id.info, sz);
	memset((void *) info + sz, 0, info_size - sz);
	}

	close(sock);
	return ret;
	}

	static __u32 get_xdp_id(struct xdp_link_info *info, __u32 flags)
	{
	flags &= XDP_FLAGS_MODES;

	if (info->attach_mode != XDP_ATTACHED_MULTI && !flags)
	return info->prog_id;
	if (flags & XDP_FLAGS_DRV_MODE)
	return info->drv_prog_id;
	if (flags & XDP_FLAGS_HW_MODE)
	return info->hw_prog_id;
	if (flags & XDP_FLAGS_SKB_MODE)
	return info->skb_prog_id;

	return 0;
	}

	int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
	{
	struct xdp_link_info info;
	int ret;

	ret = bpf_get_link_xdp_info(ifindex, &info, sizeof(info), flags);
	if (!ret)
	*prog_id = get_xdp_id(&info, flags);

	return ret;
	}

	int libbpf_nl_get_link(int sock, unsigned int nl_pid,
	libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
	{
	struct {
	struct nlmsghdr nlh;
	struct ifinfomsg ifm;
	} req = {
	.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
	.nlh.nlmsg_type = RTM_GETLINK,
	.nlh.nlmsg_flags = NLM_F_DUMP \| NLM_F_REQUEST,
	.ifm.ifi_family = AF_PACKET,
	};
	int seq = time(NULL);

	req.nlh.nlmsg_seq = seq;
	if (send(sock, &req, req.nlh.nlmsg_len, 0) < 0)
	return -errno;

	return bpf_netlink_recv(sock, nl_pid, seq, __dump_link_nlmsg,
	dump_link_nlmsg, cookie);
	}