리눅스 ip, gateway, netmask, mac 찾는 코드

인터넷에 돌아다니는 코드 막 붙여 넣었음. 코드 정리가 필요함;;;

 

출처: https://kldp.org/node/42683

        http://www.qnx.com/developers/docs/6.5.0/index.jsp?topic=%2Fcom.qnx.doc.neutrino_lib_ref%2Fi%2Fifaddrs.html

        http://pencil1031.tistory.com/69

        http://stackoverflow.com/questions/1779715/how-to-get-mac-address-of-your-machine-using-a-c-program

 

 

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <netdb.h>
#include <netinet/in.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>

#define dpt()        printf( "[dmsg] [file:%s, line:%d] \n", __FILE__, __LINE__ )

#include <stdlib.h>
#include <arpa/inet.h>

#include <sys/ioctl.h>

#define BUFSIZE 8192

struct route_info
{
  struct in_addr dstAddr;
  struct in_addr srcAddr;
  struct in_addr gateWay;
  char ifName[IF_NAMESIZE];
};

int readNlSock(int sockFd, char *bufPtr, size_t buf_size, int seqNum, int pId)
{
  struct nlmsghdr *nlHdr;
  int readLen = 0, msgLen = 0;

  do
  {
    /* Recieve response from the kernel */
    if((readLen = recv(sockFd, bufPtr, buf_size - msgLen, 0)) < 0)
    {
      perror("SOCK READ: ");
      return -1;
    }

    nlHdr = (struct nlmsghdr *)bufPtr;

    /* Check if the header is valid */
    if((NLMSG_OK(nlHdr, readLen) == 0) || (nlHdr->nlmsg_type == NLMSG_ERROR))
    {
      perror("Error in recieved packet");
      return -1;
    }

    /* Check if the its the last message */
    if(nlHdr->nlmsg_type == NLMSG_DONE)
    {
      break;
    }
    else
    {
      /* Else move the pointer to buffer appropriately */
      bufPtr += readLen;
      msgLen += readLen;
    }

    /* Check if its a multi part message */
    if((nlHdr->nlmsg_flags & NLM_F_MULTI) == 0)
    {
      /* return if its not */
      break;
    }
  }
  while((nlHdr->nlmsg_seq != seqNum) || (nlHdr->nlmsg_pid != pId));

  return msgLen;
}

/* parse the route info returned */
int parseRoutes(struct nlmsghdr *nlHdr, struct route_info *rtInfo)
{
  struct rtmsg *rtMsg;
  struct rtattr *rtAttr;
  int rtLen;

  rtMsg = (struct rtmsg *)NLMSG_DATA(nlHdr);

  /* If the route is not for AF_INET or does not belong to main routing table then return. */
  if((rtMsg->rtm_family != AF_INET) || (rtMsg->rtm_table != RT_TABLE_MAIN))
    return -1;

  /* get the rtattr field */
  rtAttr = (struct rtattr *)RTM_RTA(rtMsg);
  rtLen = RTM_PAYLOAD(nlHdr);

  for(; RTA_OK(rtAttr,rtLen); rtAttr = RTA_NEXT(rtAttr,rtLen))
  {
    switch(rtAttr->rta_type)
    {
    case RTA_OIF:
      if_indextoname(*(int *)RTA_DATA(rtAttr), rtInfo->ifName);
      break;

    case RTA_GATEWAY:
      memcpy(&rtInfo->gateWay, RTA_DATA(rtAttr), sizeof(rtInfo->gateWay));
      break;

    case RTA_PREFSRC:
      memcpy(&rtInfo->srcAddr, RTA_DATA(rtAttr), sizeof(rtInfo->srcAddr));
      break;

    case RTA_DST:
      memcpy(&rtInfo->dstAddr, RTA_DATA(rtAttr), sizeof(rtInfo->dstAddr));
      break;
    }
  }

  return 0;
}

// meat
int get_gatewayip(char *gatewayip, socklen_t size)
{
  int found_gatewayip = 0;

  struct nlmsghdr *nlMsg;
  struct rtmsg *rtMsg;
  struct route_info route_info;
  char msgBuf[BUFSIZE]; // pretty large buffer

  int sock, len, msgSeq = 0;

  /* Create Socket */
  if((sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0)
  {
    perror("Socket Creation: ");
    return(-1);
  }

  /* Initialize the buffer */
  memset(msgBuf, 0, sizeof(msgBuf));

  /* point the header and the msg structure pointers into the buffer */
  nlMsg = (struct nlmsghdr *)msgBuf;
  rtMsg = (struct rtmsg *)NLMSG_DATA(nlMsg);

  /* Fill in the nlmsg header*/
  nlMsg->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)); // Length of message.
  nlMsg->nlmsg_type = RTM_GETROUTE; // Get the routes from kernel routing table .

  nlMsg->nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST; // The message is a request for dump.
  nlMsg->nlmsg_seq = msgSeq++; // Sequence of the message packet.
  nlMsg->nlmsg_pid = getpid(); // PID of process sending the request.

  /* Send the request */
  if(send(sock, nlMsg, nlMsg->nlmsg_len, 0) < 0)
  {
    printf("Write To Socket Failed...\n");
    return -1;
  }

  /* Read the response */
  if((len = readNlSock(sock, msgBuf, sizeof(msgBuf), msgSeq, getpid())) < 0)
  {
    printf("Read From Socket Failed...\n");
    return -1;
  }

  /* Parse and print the response */
  for(; NLMSG_OK(nlMsg,len); nlMsg = NLMSG_NEXT(nlMsg,len))
  {
    memset(&route_info, 0, sizeof(route_info));
    if ( parseRoutes(nlMsg, &route_info) < 0 )
      continue;  // don't check route_info if it has not been set up

    // Check if default gateway
    if (strstr((char *)inet_ntoa(route_info.dstAddr), "0.0.0.0"))
    {
      // copy it over
      inet_ntop(AF_INET, &route_info.gateWay, gatewayip, size);
      found_gatewayip = 1;
      break;
    }
  }

  close(sock);

  return found_gatewayip;
}

static int
create_sock (const char *nic)
{
  struct sockaddr_nl addr;
  int                sock;

  memset (&addr, 0, sizeof (addr));
  addr.nl_family = AF_NETLINK;
  addr.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR;

  sock = socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
  if (sock < 0)
    {
      printf ("failed to open NETLINK_ROUTE socket for %s - %s(%d)",
               nic, strerror (errno), errno);
      return -1;
    }

  if (bind (sock, (struct sockaddr *)&addr, sizeof(addr)) < 0)
    {
      printf ( "failed to bind NETLINK_ROUTE socket for %s - %s(%d)",
                 nic, strerror (errno), errno);
      close (sock);
      return -1;
    }

  return sock;
}

static int
ip_changed (int         sock,
            const char *nic)
{
  struct nlmsghdr   *nlh;
  char               buffer[4096];
  int                len;
  int                idx;
  int                found;

  len = recv (sock, buffer, sizeof (buffer), 0);
  if (len <= 0)
    {
      printf ( "NETLINK_ROUTE socket recv() failedn");
      return -1;
    }

  found = 0;
  idx = if_nametoindex (nic);

  for (nlh = (struct nlmsghdr *)buffer;
       NLMSG_OK (nlh, len);
       nlh = NLMSG_NEXT (nlh, len))
    {
      if (nlh->nlmsg_type == NLMSG_DONE)
        break;
      if (nlh->nlmsg_type == NLMSG_ERROR)
        continue;
      if (!(NLMSG_OK (nlh, len)))
        continue;

      switch (nlh->nlmsg_type)
        {
        case RTM_NEWADDR:
          {
            struct ifaddrmsg *ifa = (struct ifaddrmsg *)NLMSG_DATA (nlh);

            if (ifa->ifa_index == idx)
              found = 1;
          }
          break;
        case RTM_NEWLINK:
          {
            struct ifinfomsg *ifi = (struct ifinfomsg *)NLMSG_DATA (nlh);

            if (ifi->ifi_index == idx)
              found = 1;
          }
          break;
        default:
          break;
        }
    }

  return found;
}

static int
get_nic_addr (const char     *nic,
              struct ifaddrs *ifaddr,
              int             wanted_family,
              char           *host,
              int             host_len,
              int            *active)
{
  struct ifaddrs *ifa;

  char test[100];

  for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next)
    {
      int family;
      int s;

      if (ifa->ifa_addr == NULL)
        continue;

      if (strcmp (ifa->ifa_name, nic))
        continue;

      /* Skip unwanted families. */
      family = ifa->ifa_addr->sa_family;
      if (family != wanted_family)
        continue;

      *active = (ifa->ifa_flags & IFF_RUNNING) ? 1 : 0;

      s = getnameinfo (ifa->ifa_addr,
                       family == AF_INET ? sizeof (struct sockaddr_in) :
                                           sizeof (struct sockaddr_in6),
                       host,
                       host_len,
                       NULL,
                       0,
                       NI_NUMERICHOST);
      if (s != 0)
        {
          printf ( "failed to getnameinfo() for '%s - %s(%d)",
                   ifa->ifa_name, strerror (errno), errno);
          continue;
        }

  memset(test, 0, 100);
      s = getnameinfo (ifa->ifa_netmask,
                       family == AF_INET ? sizeof (struct sockaddr_in) :
                                           sizeof (struct sockaddr_in6),
                       test,
                       100,
                       NULL,
                       0,
                       NI_NUMERICHOST);
  printf("netmask:%s\n",test);

  memset(test, 0, 100);
      s = getnameinfo (ifa->ifa_dstaddr,
                       family == AF_INET ? sizeof (struct sockaddr_in) :
                                           sizeof (struct sockaddr_in6),
                       test,
                       100,
                       NULL,
                       0,
                       NI_NUMERICHOST);
  printf("ifa_dstaddr:%s\n",test);

      /* Get the address of only the first network interface card. */
      return 1;
    }

  return 0;
}

static void
print_ip (const char *nic)
{
  struct ifaddrs *ifaddr;
  char            addr[NI_MAXHOST];
  int             active;

  if (getifaddrs (&ifaddr) == -1)
    {
      printf ( "failed to getifaddrs() - %s(%d)", strerror (errno), errno);
      return;
    }

  if (!get_nic_addr (nic, ifaddr, AF_INET, addr, sizeof (addr), &active))
    if (!get_nic_addr (nic, ifaddr, AF_INET6, addr, sizeof (addr), &active))
      {
        strcpy (addr, "127.0.0.1");
        active = 0;
      }

  freeifaddrs (ifaddr);

  printf ( "%s is %s (link %s)n", nic, addr, active ? "active" : "inactive");
}

 

int
main (void)
{
  char *nic = "eth0";
  int   sock;
 char gw[100];

    struct ifreq ifr;
    struct ifconf ifc;
    char buf[1024];
    int success = 0;

    sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
    if (sock == -1) { /* handle error*/ };

    ifc.ifc_len = sizeof(buf);
    ifc.ifc_buf = buf;
    if (ioctl(sock, SIOCGIFCONF, &ifc) == -1) { /* handle error */ }

    struct ifreq* it = ifc.ifc_req;
    const struct ifreq* const end = it + (ifc.ifc_len / sizeof(struct ifreq));

    for (; it != end; ++it) {
        strcpy(ifr.ifr_name, it->ifr_name);
        if (ioctl(sock, SIOCGIFFLAGS, &ifr) == 0) {
            if (! (ifr.ifr_flags & IFF_LOOPBACK)) { // don't count loopback
                if (ioctl(sock, SIOCGIFHWADDR, &ifr) == 0) {
                    success = 1;
                    break;
                }
            }
        }
        else { /* handle error */ }
    }

    unsigned char mac_address[6];

    if (success) memcpy(mac_address, ifr.ifr_hwaddr.sa_data, 6);
 printf("mac_address:%02x\n",mac_address[0]);
 printf("mac_address:%02x\n",mac_address[1]);
 printf("mac_address:%02x\n",mac_address[2]);
 printf("mac_address:%02x\n",mac_address[3]);
 printf("mac_address:%02x\n",mac_address[4]);
 printf("mac_address:%02x\n",mac_address[5]);
 

 
  print_ip (nic);

dpt();
  sock = create_sock (nic);
  if (sock < 0)
    return -1;

  memset(gw, 0, 100);

 get_gatewayip(gw,100);
 printf("gw:%s\n",gw);

dpt();
  while (1)
    {
      int ret;

      ret = ip_changed (sock, nic);
      if (ret < 0)
        return -1;

      if (ret)
        print_ip (nic);
    }

  close (sock);

  return 0;
}