Netlink 获取网卡接口信息

#include <linux/types.h>  #include <asm/types.h>  #include <inttypes.h>  #include <sys/file.h>  #include <sys/user.h>  #include <sys/socket.h>  #include <linux/netlink.h>  #include <linux/rtnetlink.h>  #include <linux/if.h>  #include <unistd.h>  #include <stdlib.h>  #include <string.h>  #include <stdio.h>  #include <stdbool.h>  #include <errno.h>  #include <arpa/inet.h>typedef uint32_t u32;  typedef uint16_t u16;    struct nlsock {      int sock;      int seq;      struct sockaddr_nl snl;      char *name;  } nl_cmd = { -1, 0, {0}, "netlink-cmd" };    static int index_oif = 0;  struct nl_if_info {      u32 addr;      char *name;  };  static int nl_socket ( struct nlsock *nl, unsigned long groups )  {      int ret;      struct sockaddr_nl snl;      int sock;      int namelen;    /*创建netlink套接字*/    sock = socket ( AF_NETLINK, SOCK_RAW, NETLINK_ROUTE );      if ( sock < 0 ) {          fprintf ( stderr,  "Can't open %s socket: %s", nl->name,                  strerror ( errno ) );          return -1;      }        ret = fcntl ( sock, F_SETFL, O_NONBLOCK );      if ( ret < 0 ) {          fprintf ( stderr,  "Can't set %s socket flags: %s", nl->name,                  strerror ( errno ) );          close ( sock );          return -1;      }    /*设置地址信息*/    memset ( &snl, 0, sizeof snl );      snl.nl_family = AF_NETLINK;      snl.nl_groups = groups;        /* Bind the socket to the netlink structure for anything. */      ret = bind ( sock, ( struct sockaddr * ) &snl, sizeof snl );      if ( ret < 0 ) {          fprintf ( stderr,  "Can't bind %s socket to group 0x%x: %s",                  nl->name, snl.nl_groups, strerror ( errno ) );          close ( sock );          return -1;      }        /* multiple netlink sockets will have different nl_pid */      namelen = sizeof snl;      ret = getsockname ( sock, ( struct sockaddr * ) &snl, &namelen );      if ( ret < 0 || namelen != sizeof snl ) {          fprintf ( stderr,  "Can't get %s socket name: %s", nl->name,                  strerror ( errno ) );          close ( sock );          return -1;      }        nl->snl = snl;      nl->sock = sock;      return ret;  }  /**发送请求*/static int nl_request ( int family, int type, struct nlsock *nl )  {      int ret;      struct sockaddr_nl snl;        struct {          struct nlmsghdr nlh;          struct rtgenmsg g;      } req;          /* Check netlink socket. */      if ( nl->sock < 0 ) {          fprintf ( stderr, "%s socket isn't active.", nl->name );          return -1;      }        memset ( &snl, 0, sizeof snl );      snl.nl_family = AF_NETLINK;        req.nlh.nlmsg_len = sizeof req;  //        req.nlh.nlmsg_type = type;  //设置自定义消息类型        req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;  //消息的附加选项        req.nlh.nlmsg_pid = 0;  //设置发送者的pid        req.nlh.nlmsg_seq = ++nl->seq;  //        req.g.rtgen_family = family;  //      ret = sendto ( nl->sock, ( void* ) &req, sizeof req, 0,              ( struct sockaddr* ) &snl, sizeof snl );      if ( ret < 0 ) {          fprintf ( stderr, "%s sendto failed: %s", nl->name, strerror ( errno ) );          return -1;      }      return 0;  }    /* Receive message from netlink interface and pass those information    to the given function. */  static int  nl_parse_info ( int ( *filter ) ( struct sockaddr_nl *, struct nlmsghdr *, void * ),          struct nlsock *nl, void *arg )  {      int status;      int ret = 0;      int error;    /*接受队列里的所有信息，每次接受4096，并解析*/    while ( 1 ) {          char buf[4096];          struct iovec iov = { buf, sizeof buf };  //netlink消息头        struct sockaddr_nl snl;          struct msghdr msg = { ( void* ) &snl, sizeof snl, &iov, 1, NULL, 0, 0};  //设置消息头        struct nlmsghdr *h;  //netlink消息头          status = recvmsg ( nl->sock, &msg, 0 );            if ( status < 0 ) {              if ( errno == EINTR )                  continue;              if ( errno == EWOULDBLOCK || errno == EAGAIN )                  break;              fprintf ( stderr, "%s recvmsg overrun", nl->name );              continue;          }    /*如果不是内核的消息，忽略*/        if ( snl.nl_pid != 0 ) {              fprintf ( stderr, "Ignoring non kernel message from pid %u",                      snl.nl_pid );              continue;          }    /*转出错处理*/        if ( status == 0 ) {              fprintf ( stderr, "%s EOF", nl->name );              return -1;          }    /*如果socket地址长度不对，转出错处理*/        if ( msg.msg_namelen != sizeof snl ) {              fprintf ( stderr, "%s sender address length error: length %d",                      nl->name, msg.msg_namelen );              return -1;          }            for ( h = ( struct nlmsghdr * ) buf; NLMSG_OK ( h, status );  //枚举缓冲中的netlink消息                h = NLMSG_NEXT ( h, status ) ) {              /* Finish of reading. */              if ( h->nlmsg_type == NLMSG_DONE )  //消息已读取完毕                return ret;                /* Error handling. */              if ( h->nlmsg_type == NLMSG_ERROR ) {  //消息读取出错                struct nlmsgerr *err = ( struct nlmsgerr * ) NLMSG_DATA ( h );                    /* If the error field is zero, then this is an ACK */                  if ( err->error == 0 ) {                      /* return if not a multipart message, otherwise continue */                      if ( ! ( h->nlmsg_flags & NLM_F_MULTI ) ) {                          return 0;                      }                      continue;                  }                    if ( h->nlmsg_len < NLMSG_LENGTH ( sizeof ( struct nlmsgerr ) ) ) {                      fprintf ( stderr, "%s error: message truncated",                              nl->name );                      return -1;                  }                  fprintf ( stderr, "%s error: %s, type=%u, seq=%u, pid=%d",                          nl->name, strerror ( -err->error ),                          err->msg.nlmsg_type, err->msg.nlmsg_seq,                          err->msg.nlmsg_pid );                  /*                 ret = -1;                 continue;                 */                  return -1;              }                  /* skip unsolicited messages originating from command socket */              if ( nl != &nl_cmd && h->nlmsg_pid == nl_cmd.snl.nl_pid ) {                  continue;              }    /*读取一条netlink消息，就解析得到的消息*/            error = ( *filter ) ( &snl, h, arg );              if ( error < 0 ) {                  fprintf ( stderr, "%s filter function error/n", nl->name );                  ret = error;              }          }            /* After error care. */          if ( msg.msg_flags & MSG_TRUNC ) {              fprintf ( stderr, "%s error: message truncated", nl->name );              continue;          }          if ( status ) {              fprintf ( stderr, "%s error: data remnant size %d", nl->name,                      status );              return -1;          }      }      return ret;  }    static void nl_parse_rtattr ( struct rtattr **tb, int max, struct rtattr *rta, int len )  {      while ( RTA_OK ( rta, len ) ) {          if ( rta->rta_type <= max )              tb[rta->rta_type] = rta;          rta = RTA_NEXT ( rta,len );      }  }    static int nl_get_oif ( struct sockaddr_nl *snl, struct nlmsghdr *h, void *arg )  {      int len;      struct rtmsg *rtm;      struct rtattr *tb [RTA_MAX + 1];      u_char flags = 0;        char anyaddr[16] = {0};        int index;      int table;      void *dest;      void *gate;        rtm = NLMSG_DATA ( h );   //得到消息数据部分      if ( h->nlmsg_type != RTM_NEWROUTE )          return 0;      if ( rtm->rtm_type != RTN_UNICAST )          return 0;        table = rtm->rtm_table;        len = h->nlmsg_len - NLMSG_LENGTH ( sizeof ( struct rtmsg ) );      if ( len < 0 )          return -1;        memset ( tb, 0, sizeof tb );      nl_parse_rtattr ( tb, RTA_MAX, RTM_RTA ( rtm ), len );        if ( rtm->rtm_flags & RTM_F_CLONED )          return 0;      if ( rtm->rtm_protocol == RTPROT_REDIRECT )          return 0;      if ( rtm->rtm_protocol == RTPROT_KERNEL )          return 0;        if ( rtm->rtm_src_len != 0 )          return 0;             // 这里可以对所有路由进行识别           // 取得out interface index        if ( tb[RTA_OIF] ) {          index = * ( int * ) RTA_DATA ( tb[RTA_OIF] );      }        if ( tb[RTA_DST] )          dest = RTA_DATA ( tb[RTA_DST] );      else          dest = anyaddr;        /* Multipath treatment is needed. */      if ( tb[RTA_GATEWAY] )          gate = RTA_DATA ( tb[RTA_GATEWAY] );             // 判断是否为默认路由      if ( dest == anyaddr && gate ) {          if ( arg != NULL ) {              * ( int * ) arg = index;              return 0;          }      }      return 0;  }    static int nl_get_if_addr ( struct sockaddr_nl *snl, struct nlmsghdr *h, void *arg )  {      int len;      struct ifaddrmsg *ifa;      struct rtattr *tb [IFA_MAX + 1];      void *addr = NULL;      void *broad = NULL;      u_char flags = 0;      char *label = NULL;      struct in_addr ifa_addr, ifa_local;      char ifa_label[IFNAMSIZ + 1];         ifa = NLMSG_DATA ( h );  //得到消息数据部分    if ( ifa->ifa_family != AF_INET )       return 0;             if ( h->nlmsg_type != RTM_NEWADDR && h->nlmsg_type != RTM_DELADDR )          return 0;        len = h->nlmsg_len - NLMSG_LENGTH ( sizeof ( struct ifaddrmsg ) );      if ( len < 0 )          return -1;        memset ( tb, 0, sizeof tb );        nl_parse_rtattr ( tb, IFA_MAX, IFA_RTA ( ifa ), len );            if (tb[IFA_ADDRESS] == NULL)      tb[IFA_ADDRESS] = tb[IFA_LOCAL];  /*网卡地址*/    if ( tb[IFA_ADDRESS] )       ifa_addr = *(struct in_addr*) RTA_DATA ( tb[IFA_ADDRESS] );             if ( tb[IFA_LOCAL] )       ifa_local = *(struct in_addr *) RTA_DATA ( tb[IFA_LOCAL] );   /*网卡名*/    if ( tb[IFA_LABEL] )       strncpy( ifa_label, RTA_DATA ( tb[IFA_LABEL] ), IFNAMSIZ );                // 打印所有地址信息    printf( "addr=%sloal=%sname=%s\n",        inet_ntoa(ifa_addr),       inet_ntoa(ifa_local),       ifa_label );      return 0;  }    int main()  {      int ret;      char if_name[PAGE_SIZE]={0};      int err;      struct nl_if_info if_info = { -1, "eth0" };    /*初始化nl_cmd*/    ret = nl_socket ( &nl_cmd, 0 );      if ( ret < 0 ) {          return ret;      }      ret = nl_request ( AF_INET, RTM_GETROUTE, &nl_cmd );  //获取路由信息    if ( ret < 0 ) {          return ret;      }      ret = nl_parse_info ( nl_get_oif, &nl_cmd, &index_oif );      if ( ret < 0 )          return ret;        printf ( "oif=%08x", index_oif );      if ( index_oif > 0 ) {       err = if_indextoname( index_oif, if_name );       if (err ) {           printf ( "interface=%s\n", if_name );       }     }            ret = nl_request ( AF_INET, RTM_GETADDR, &nl_cmd );  //获取地址信息    if ( ret < 0 )          return ret;         ret = nl_parse_info ( nl_get_if_addr, &nl_cmd, &if_info );      if ( ret < 0 )          return ret;              return 0;  }