c/c++ 网络编程 UDP 主机网络信息取得

网络编程 udp 主机网络信息取得

1，if_nametoindex 通过网卡名字取得网卡编号

2，if_indextoname 通过网卡编号取得网卡名字

#include <stdio.h>
#include <string.h>
#include <net/if.h>

int main(){
  int index;
  char buf[128];

  //根据名字取得编号
  index = if_nametoindex("enp0s3");
  if(index == 0){
    perror("if_nametoindex");
    return 1;
  }
  printf("index:%d\n", index);

  memset(buf, 0, sizeof(buf));

  //根据编号取得名字
  if(if_indextoname(index, buf) == null){
    perror("if_indextoname");
    return 1;
  }
  printf("name:%s\n", buf);
  return 0;
}

3，getifaddrs 取得网卡的名字，取得网卡的flags，取得ip地址，取得netmask

#include <stdio.h>
#include <string.h>
#include <ifaddrs.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main(){
  ifaddrs *ifa_list;
  ifaddrs *ifa;
  int n;
  char addrstr[256], netmaskstr[256];

  n = getifaddrs(&ifa_list);
  if(n != 0){
    return 1;
  }

  for(ifa = ifa_list; ifa != null; ifa = ifa->ifa_next){
    printf("ifa_name:%s\n", ifa->ifa_name);
    printf("ifa_flags:  0x%.8x\n", ifa->ifa_flags);

    memset(addrstr, 0, sizeof(addrstr));
    memset(netmaskstr, 0, sizeof(netmaskstr));

    //ipv4
    if(ifa->ifa_addr->sa_family == af_inet){
      //ip
      inet_ntop(af_inet,
        &((sockaddr_in*)ifa->ifa_addr)->sin_addr,
        addrstr, sizeof(addrstr));
      //mask
      inet_ntop(af_inet,
        &((sockaddr_in*)ifa->ifa_netmask)->sin_addr,
        netmaskstr, sizeof(netmaskstr));

      printf("   ipv4: %s netmask : %s\n", addrstr, netmaskstr);
    }
    //ipv6
    else if(ifa->ifa_addr->sa_family == af_inet6){
      //ip
      inet_ntop(af_inet6,
        &((sockaddr_in6*)ifa->ifa_addr)->sin6_addr,
        addrstr, sizeof(addrstr));
      //mask
      inet_ntop(af_inet6,
        &((sockaddr_in6*)ifa->ifa_netmask)->sin6_addr,
        netmaskstr, sizeof(netmaskstr));

      printf("   ipv6: %s netmask : %s\n", addrstr, netmaskstr);
    }
    else if(ifa->ifa_addr->sa_family == af_packet){
      printf("  af_packet:%d\n", ifa->ifa_addr->sa_family);
    }
    else{
      printf("  else:%d\n", ifa->ifa_addr->sa_family);
    }
    printf("\n");
  }
  freeifaddrs(ifa_list);

  return 0;
}

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