WSL2-Linux-Kernel/tools/lib/bpf/netlink.c

// SPDX-License-Identifier: LGPL-2.1
/* 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 "nlattr.h"

#ifndef SOL_NETLINK
#define SOL_NETLINK 270
#endif

static int bpf_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) {
		fprintf(stderr, "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)
{
	struct nlmsgerr *err;
	struct nlmsghdr *nh;
	char buf[4096];
	int len, ret;

	while (1) {
		len = recv(sock, buf, sizeof(buf), 0);
		if (len < 0) {
			ret = -errno;
			goto done;
		}

		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;
			}
			switch (nh->nlmsg_type) {
			case NLMSG_ERROR:
				err = (struct nlmsgerr *)NLMSG_DATA(nh);
				if (!err->error)
					continue;
				ret = err->error;
				nla_dump_errormsg(nh);
				goto done;
			case NLMSG_DONE:
				return 0;
			default:
				break;
			}
		}
	}
	ret = 0;
done:
	return ret;
}

int bpf_set_link_xdp_fd(int ifindex, int 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;

	sock = bpf_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;
	}

	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);

cleanup:
	close(sock);
	return ret;
}