Linux通过c语言函数管理网络(1)-----获取/修改IP和MAC地址

原创

NoName51C_T_O 2022-01-18 10:46:04 ©著作权

文章标签 linux linux网络管理 Linux网卡配置接口 #include ip地址 文章分类 代码人生

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在Linux下编写程序经常遇到需要对网卡进行管理，但是在glic库中或者其他函数库中却发现没有境界能用的API。有的人在程序中通过system()执行ifconfig命令进行配置,但是获取参数却很麻烦，也有的人通过int getifaddrs(struct ifaddrs **ifap);去获取ip地址等信息，但是只能获取，却不能配置。

还有是通过ioctl()接口进行控制，ioctl接口算是比较常用的

但是处理原始的netlink消息非常麻烦，且容易出错。但是netlink的功能相比于上面的方法要强大，比如现在ioctl()接口是不能处理ipv6的。netlink还可以轻松的获取路由信息。

我这里不直接使用netlink进行配置，其实早就已经有大牛帮我们写好了netlink相关的库即libnl-3.0

Linux通过c语言函数管理网络(1)-----获取/修改IP和MAC地址_Linux网卡配置接口

编译下面函数需要：

-lnl-route-3
-lnl-3
-Ilibnl3

/*
 * Copyright (C) 2021, 2021  huohongpeng
 * Author: huohongpeng <1045338804@qq.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Change logs:
 * Date        Author       Notes
 * 2021-10-19  huohongpeng   首次添加
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/route.h>
#include <errno.h>
#include <netlink/route/link.h>
#include <netlink/route/route.h>
#include <netlink/route/addr.h>
#include <netlink/netlink.h>
#include <linux/if_arp.h>
#include <ifaddrs.h>
#include <net/ethernet.h>
#include <sys/socket.h>
#include <netdb.h>


/*
 * 启动/停用 网卡状态 (类似 ifconfig ethx up或ifconfig ethx down)
 * @eth_name: 网卡名, 如:eth0, wlan0..
 * @state: "up": 启动网卡, "down": 停用网卡
 * @ret: 0: 成功, -1: 失败
 */
int rtnetlink_eth_state(char *eth_name, char *state)
{
  int ret;
  struct rtnl_link *link, *link_conf;
  struct nl_sock *sk = nl_socket_alloc();
  nl_connect(sk, NETLINK_ROUTE);

  ret = rtnl_link_get_kernel(sk, 0, eth_name, &link);

  if (ret < 0) {
    printf("Err: %s not found!!!\n", eth_name);
    ret = -1;
    goto ERROR1;
  }

  link_conf = rtnl_link_alloc();

  if (strcmp("up", state) == 0) {
    rtnl_link_set_flags(link_conf, IFF_UP);
  } else if (strcmp("down", state) == 0) {
    rtnl_link_unset_flags(link_conf, IFF_UP);
  } else {
    ret = -1;
    printf("Err: %s para error!!!\n", state);
    goto ERROR2;
  }

  ret = rtnl_link_change(sk, link, link_conf, 0);

  if (ret < 0) {
    printf("Err: rtnetlink_eth_state: %d\n", ret);
  }

ERROR2:
  rtnl_link_put(link);
  rtnl_link_put(link_conf);

ERROR1:
  nl_close(sk);
  nl_socket_free(sk);
  return ret;
}

/*
 * 修改网卡的MAC地址
 * @eth_name: 网卡名, 如:eth0, wlan0..
 * @mac: 6字节mac地址, 如unsigned char mac[6] = {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB};
 *       类似于 ifconfig ethx hw ether 12:34:56:78:90:AB
 * @ret: 0: 成功, -1: 失败
 */
int rtnetlink_eth_set_mac(char *eth_name, unsigned char *mac)
{
  int ret;
  struct rtnl_link *link, *link_conf;
  struct nl_addr *hw_addr;
  struct nl_sock *sk = nl_socket_alloc();
  nl_connect(sk, NETLINK_ROUTE);

  ret = rtnl_link_get_kernel(sk, 0, eth_name, &link);

  if (ret < 0) {
    printf("Err: %s not found!!!\n", eth_name);
    ret = -1;
    goto ERROR1;
  }

  unsigned int if_flag = rtnl_link_get_flags(link);

  /*
   * 只有在网卡不启用的时候才能设置MAC地址,所以如果网卡已经启用,
   * 首先停用网卡,然后设置MAC地址,设置完成后，再次启动网卡
   */
  if (if_flag & IFF_UP) {
    rtnetlink_eth_state(eth_name, "down");
  }

  link_conf = rtnl_link_alloc();

  /*
   * AF_LLC: 地址簇是MAC地址
   */
  hw_addr = nl_addr_build(AF_LLC, mac, 6);
  rtnl_link_set_addr(link_conf, hw_addr);

  ret = rtnl_link_change(sk, link, link_conf, 0);

  if (ret < 0) {
    printf("Err: rtnetlink_eth_change_mac: %d\n", ret);
  }

  if (if_flag & IFF_UP) {
    rtnetlink_eth_state(eth_name, "up");
  }

  nl_addr_put(hw_addr);
  rtnl_link_put(link);
  rtnl_link_put(link_conf);

ERROR1:
  nl_close(sk);
  nl_socket_free(sk);
  return ret;
}

/*
 * 获取网卡的MAC地址
 * @eth_name: 网卡名, 如:eth0, wlan0..
 * @mac: 返回6字节mac地址, 如unsigned char mac[6] = {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB};
 * @ret: 0: 成功, -1: 失败
 */
int rtnetlink_eth_get_mac(char *eth_name, unsigned char *mac)
{
  int ret;
  struct rtnl_link *link;
  struct nl_addr *hw_addr;
  struct nl_sock *sk = nl_socket_alloc();
  nl_connect(sk, NETLINK_ROUTE);

  ret = rtnl_link_get_kernel(sk, 0, eth_name, &link);

  if (ret < 0) {
    printf("Err: %s not found!!!", eth_name);
    ret = -1;
    goto ERROR1;
  }

  hw_addr = rtnl_link_get_addr(link);

  if (nl_addr_get_len(hw_addr) != 6 || nl_addr_get_family(hw_addr) != AF_LLC) {
    ret = -1;
    printf("Err: hw_addr len or family error!!!\n");
    goto ERROR2;
  }

  unsigned char *pmac = (unsigned char *)nl_addr_get_binary_addr(hw_addr);
  memcpy(mac, pmac, 6);

ERROR2:
  rtnl_link_put(link);

ERROR1:
  nl_close(sk);
  nl_socket_free(sk);
  return ret;
}


static int ipv4_netmask2prefixlen(unsigned char *netmask)
{
  int count  = 0;
  for (int i = 0; i < 4; i++) {
    for (int j = 0; j < 8; j++) {
      if ((netmask[i] & (0x01<<j)) != 0) {
        count++;
      }
    }
  }
  return count;
}


static void ipv4_prefixlen2netmask(int prefixlen, unsigned char *netmask)
{
  int i;

  memset(netmask, 0x00, 4);

  int byte = prefixlen / 8;
  int bit = prefixlen % 8;

  for (i = 0; i < byte; i++) {
    netmask[i] = 0xff;
  }

  netmask[byte] = 0;

  for (i = 0; i < bit; i++) {
    netmask[byte] |= (0x01<<(7 - i));
  }
}


struct get_ipv4_addr_ctx_t {
  struct nl_sock *sk;
  int flag; /* 是否找到ip */
  int index; /* 网卡索引 */
  unsigned char *ip;
  unsigned char *netmask;
};


static void get_ipv4_addr_cache_cb(struct nl_object *obj, void *arg)
{
  struct get_ipv4_addr_ctx_t *ctx = (struct get_ipv4_addr_ctx_t *)arg;
  struct rtnl_addr *rtnl_addr = (struct rtnl_addr *)obj;

  if (rtnl_addr_get_ifindex(rtnl_addr) == ctx->index) {
    struct nl_addr *nl_addr = rtnl_addr_get_local(rtnl_addr);

    if (nl_addr_get_family(nl_addr) == AF_INET && nl_addr_get_len(nl_addr) == 4) {
      ctx->flag = 0x01;
      int netmask_prefixlen = rtnl_addr_get_prefixlen(rtnl_addr);
      char *ip = (char *)nl_addr_get_binary_addr(nl_addr);
      memcpy(ctx->ip, ip, 4);
      if (netmask_prefixlen <= 32) {
        ipv4_prefixlen2netmask(netmask_prefixlen, ctx->netmask);
      }
    }
  }
}


/*
 * 获取网卡ip地址
 * @eth_name: 网卡名, 如:eth0, wlan0..
 * @ip: 返回4字节ip地址, 如char ip[4] = {10, 10, 10, 3};即: 10.10.10.3
 * @netmask: 返回4字节netmask地址, 如char netmask[4] = {0xff, 0xff, 0xff, 0};即: 255.255.255.0
 * @ret: 0: 成功, -1: 不能获取ip地址
 */
int rtnetlink_eth_get_ipv4_addr(char *eth_name, unsigned char *ip, unsigned char *netmask)
{
  int ret = 0;
  struct nl_cache *addr_cache;
  struct rtnl_link *link;
  struct nl_sock *sk = nl_socket_alloc();
  nl_connect(sk, NETLINK_ROUTE);

  ret = rtnl_link_get_kernel(sk, 0, eth_name, &link);

  if (ret < 0) {
    printf("Err: %s not found!!!\n", eth_name);
    ret = -1;
    goto ERROR1;
  }

  struct get_ipv4_addr_ctx_t ctx;
  memset(&ctx, 0x00, sizeof(struct get_ipv4_addr_ctx_t));

  ctx.index = rtnl_link_get_ifindex(link);
  ctx.ip = ip;
  ctx.netmask = netmask;

  rtnl_addr_alloc_cache(sk, &addr_cache);
  nl_cache_foreach(addr_cache, get_ipv4_addr_cache_cb, &ctx);

  if (ctx.flag == 0) {
    ret = -1;
    printf("Err: %s not find ip!!!\n", eth_name);
  } 

  nl_cache_put(addr_cache);
  rtnl_link_put(link);

ERROR1:
  nl_close(sk);
  nl_socket_free(sk);
  return ret;
}

static void del_ipv4_addr_cache_cb(struct nl_object *obj, void *arg)
{
  struct get_ipv4_addr_ctx_t *ctx = (struct get_ipv4_addr_ctx_t *)arg;
  struct rtnl_addr *rtnl_addr = (struct rtnl_addr *)obj;

  if (rtnl_addr_get_ifindex(rtnl_addr) == ctx->index) {
    struct nl_addr *nl_addr = rtnl_addr_get_local(rtnl_addr);

    if (nl_addr_get_family(nl_addr) == AF_INET && nl_addr_get_len(nl_addr) == 4) {
      int ret = rtnl_addr_delete(ctx->sk, rtnl_addr, 0);
      if (ret < 0) {
        printf("Err: rtnl_addr_delete:%d!!!\n", ret);
      }
    }
  }
}


/*
 * 删除网卡ip地址
 * @eth_name: 网卡名, 如:eth0, wlan0..
 * @ip: 返回4字节ip地址, 如char ip[4] = {10, 10, 10, 3};即: 10.10.10.3
 * @netmask: 返回4字节netmask地址, 如char netmask[4] = {0xff, 0xff, 0xff, 0};即: 255.255.255.0
 * @ret: 0: 成功, -1: 不能获取ip地址
 */
int rtnetlink_eth_del_ipv4_addr(char *eth_name)
{
  int ret = 0;
  struct nl_cache *addr_cache;
  struct rtnl_link *link;
  struct nl_sock *sk = nl_socket_alloc();
  nl_connect(sk, NETLINK_ROUTE);

  ret = rtnl_link_get_kernel(sk, 0, eth_name, &link);

  if (ret < 0) {
    printf("Err: %s not found!!!\n", eth_name);
    ret = -1;
    goto ERROR1;
  }

  struct get_ipv4_addr_ctx_t ctx;
  memset(&ctx, 0x00, sizeof(struct get_ipv4_addr_ctx_t));

  ctx.index = rtnl_link_get_ifindex(link);
  ctx.sk = sk;

  rtnl_addr_alloc_cache(sk, &addr_cache);
  nl_cache_foreach(addr_cache, del_ipv4_addr_cache_cb, &ctx);

  nl_cache_put(addr_cache);
  rtnl_link_put(link);

ERROR1:
  nl_close(sk);
  nl_socket_free(sk);
  return ret;
}


/*
 * 设置网卡ip地址
 * @eth_name: 网卡名, 如:eth0, wlan0..
 * @ip: 返回4字节ip地址, 如char ip[4] = {10, 10, 10, 3};即: 10.10.10.3
 * @netmask: 返回4字节netmask地址, 如char netmask[4] = {0xff, 0xff, 0xff, 0};即: 255.255.255.0
 * @ret: 0: 成功, -1: 不能获取ip地址
 * 注意: 一般情况下网卡可以设置多个IP地址，这个函数只设置1个IP地址,设置过程是首先删除原来的IP地址,然后在添加新的IP地址
 */
int rtnetlink_eth_set_ipv4_addr(char *eth_name, unsigned char *ip, unsigned char *netmask)
{
  int ret = 0;
  struct rtnl_link *link;
  struct nl_sock *sk = nl_socket_alloc();
  nl_connect(sk, NETLINK_ROUTE);

  ret = rtnl_link_get_kernel(sk, 0, eth_name, &link);

  if (ret < 0) {
    printf("Err: %s not found!!!\n", eth_name);
    ret = -1;
    goto ERROR1;
  }

  struct rtnl_addr *new_rtnl_addr = rtnl_addr_alloc();

  int if_index = rtnl_link_get_ifindex(link);
  /*
   * 在rtnl_addr中,netmask用ip地址有效长度表示,
   * 如: 255.225.0.0有效长度为16
   */
  int netmask_prefixlen = ipv4_netmask2prefixlen(netmask);

  rtnl_addr_set_ifindex(new_rtnl_addr, if_index);
  rtnl_addr_set_family(new_rtnl_addr, AF_INET);

  struct nl_addr *ip_addr = nl_addr_build(AF_INET, ip, 4);
  rtnl_addr_set_local(new_rtnl_addr, ip_addr);
  nl_addr_put(ip_addr);

  rtnl_addr_set_prefixlen(new_rtnl_addr, netmask_prefixlen);

  unsigned char broadcast[4];

  for (int i = 0; i< 4; i++) {
    broadcast[i] = (netmask[i] & ip[i]);
    broadcast[i] |= ~netmask[i];
  }

  struct nl_addr *broadcast_addr = nl_addr_build(AF_INET, broadcast, 4);
  rtnl_addr_set_broadcast(new_rtnl_addr, broadcast_addr);
  nl_addr_put(broadcast_addr);

  /*
   * 添加地址之前首先删除原来的地址
   */
  rtnetlink_eth_del_ipv4_addr(eth_name);

  ret = rtnl_addr_add(sk, new_rtnl_addr, 0);

  if (ret < 0) {
    printf("Err: rtnl_addr_add: %d\n", ret);
  }

  rtnl_addr_put(new_rtnl_addr);
  rtnl_link_put(link);

ERROR1:
  nl_close(sk);
  nl_socket_free(sk);
  return ret;
}



void test_rtnetlink_manage(void)
{

  unsigned char ip[4] = {192, 168, 60, 85};
  unsigned char netmask[] = {255, 255, 255, 0};
  //rtnetlink_eth_del_ipv4_addr("wlan0");
  rtnetlink_eth_set_ipv4_addr("eth0", ip, netmask);


  return;
  //getifaddrs()
}