libbpf/src/netlink.c

// 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 | SOCK_CLOEXEC, 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 void libbpf_netlink_close(int sock)
{
	close(sock);
}

static int libbpf_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 libbpf_netlink_send_recv(struct nlmsghdr *nh,
				    __dump_nlmsg_t parse_msg,
				    libbpf_dump_nlmsg_t parse_attr,
				    void *cookie)
{
	__u32 nl_pid = 0;
	int sock, ret;

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

	nh->nlmsg_pid = 0;
	nh->nlmsg_seq = time(NULL);

	if (send(sock, nh, nh->nlmsg_len, 0) < 0) {
		ret = -errno;
		goto out;
	}

	ret = libbpf_netlink_recv(sock, nl_pid, nh->nlmsg_seq,
				  parse_msg, parse_attr, cookie);
out:
	libbpf_netlink_close(sock);
	return ret;
}

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

	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.ifinfo.ifi_family = AF_UNSPEC;
	req.ifinfo.ifi_index  = ifindex;

	nla = nlattr_begin_nested(&req.nh, sizeof(req), IFLA_XDP);
	if (!nla)
		return -EMSGSIZE;
	ret = nlattr_add(&req.nh, sizeof(req), IFLA_XDP_FD, &fd, sizeof(fd));
	if (ret < 0)
		return ret;
	if (flags) {
		ret = nlattr_add(&req.nh, sizeof(req), IFLA_XDP_FLAGS, &flags,
				 sizeof(flags));
		if (ret < 0)
			return ret;
	}
	if (flags & XDP_FLAGS_REPLACE) {
		ret = nlattr_add(&req.nh, sizeof(req), IFLA_XDP_EXPECTED_FD,
				 &old_fd, sizeof(old_fd));
		if (ret < 0)
			return ret;
	}
	nlattr_end_nested(&req.nh, nla);

	return libbpf_netlink_send_recv(&req.nh, NULL, NULL, NULL);
}

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;
}

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 = {};
	__u32 mask;
	int ret;
	struct {
		struct nlmsghdr  nh;
		struct ifinfomsg ifm;
	} req = {
		.nh.nlmsg_len   = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
		.nh.nlmsg_type  = RTM_GETLINK,
		.nh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
		.ifm.ifi_family = AF_PACKET,
	};

	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;

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

	ret = libbpf_netlink_send_recv(&req.nh, __dump_link_nlmsg,
				       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);
	}

	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;
}