一、struct ifreq結構體

1. /* Interface request structure used for socket ioctl‘s. All interface
2. ioctl‘s must have parameter definitions which begin with ifr_name.
3. The remainder may be interface specific. */
5. struct ifreq
6. {
7. # define IFHWADDRLEN 6
8. # define IFNAMSIZ IF_NAMESIZE
9. union
10. {
11. char ifrn_name[IFNAMSIZ]; /* Interface name, e.g. "en0". */
12. } ifr_ifrn;
14. union
15. {
16. struct sockaddr ifru_addr;
17. struct sockaddr ifru_dstaddr;
18. struct sockaddr ifru_broadaddr;
19. struct sockaddr ifru_netmask;
20. struct sockaddr ifru_hwaddr;
21. short int ifru_flags;
22. int ifru_ivalue;
23. int ifru_mtu;
24. struct ifmap ifru_map;
25. char ifru_slave[IFNAMSIZ]; /* Just fits the size */
26. char ifru_newname[IFNAMSIZ];
27. __caddr_t ifru_data;
28. } ifr_ifru;
29. };
30. # define ifr_name ifr_ifrn.ifrn_name /* interface name */
31. # define ifr_hwaddr ifr_ifru.ifru_hwaddr /* MAC address */
32. # define ifr_addr ifr_ifru.ifru_addr /* address */
33. # define ifr_dstaddr ifr_ifru.ifru_dstaddr /* other end of p-p lnk */
34. # define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */
35. # define ifr_netmask ifr_ifru.ifru_netmask /* interface net mask */
36. # define ifr_flags ifr_ifru.ifru_flags /* flags */
37. # define ifr_metric ifr_ifru.ifru_ivalue /* metric */
38. # define ifr_mtu ifr_ifru.ifru_mtu /* mtu */
39. # define ifr_map ifr_ifru.ifru_map /* device map */
40. # define ifr_slave ifr_ifru.ifru_slave /* slave device */
41. # define ifr_data ifr_ifru.ifru_data /* for use by interface */
42. # define ifr_ifindex ifr_ifru.ifru_ivalue /* interface index */
43. # define ifr_bandwidth ifr_ifru.ifru_ivalue /* link bandwidth */
44. # define ifr_qlen ifr_ifru.ifru_ivalue /* queue length */
45. # define ifr_newname ifr_ifru.ifru_newname /* New name */
46. # define _IOT_ifreq _IOT(_IOTS(char),IFNAMSIZ,_IOTS(char),16,0,0)
47. # define _IOT_ifreq_short _IOT(_IOTS(char),IFNAMSIZ,_IOTS(short),1,0,0)
48. # define _IOT_ifreq_int _IOT(_IOTS(char),IFNAMSIZ,_IOTS(int),1,0,0)

二、用法：

通過ioctl()函數調用
下表列出了網絡相關ioctl請求的request 參數以及arg 地址必須指向的數據類型：

實例一，獲取網卡的IP地址：

1. #include <string.h>
2. #include <sys/socket.h>
3. #include <sys/ioctl.h>
4. #include <net/if.h>
5. #include <stdio.h>
6. #include <netinet/in.h>
7. #include <arpa/inet.h>
8. int main()
9. {
10. int inet_sock;
11. struct ifreq ifr;
12. inet_sock = socket(AF_INET, SOCK_DGRAM, 0);
14. strcpy(ifr.ifr_name, "eth0");
15. //SIOCGIFADDR標誌代表獲取接口地址
16. if (ioctl(inet_sock, SIOCGIFADDR, &ifr) < 0)
17. perror("ioctl");
18. printf("%s\n", inet_ntoa(((struct sockaddr_in*)&(ifr.ifr_addr))->sin_addr));
19. return 0;
20. }

實例二，實現簡單ifconfig功能：

1. /**
2. * \file getifstat.c
3. * \author wzj
4. * \brief 訪問這個struct ifconf 修改，查詢狀態
5. * \version
6. * \note
7. * \date: 2012年08月11日星期六22:55:25
8. */
9. #include <net/if.h> /* for ifconf */
10. #include <linux/sockios.h> /* for net status mask */
11. #include <netinet/in.h> /* for sockaddr_in */
12. #include <sys/socket.h>
13. #include <sys/types.h>
14. #include <sys/ioctl.h>
15. #include <stdio.h>
17. #define MAX_INTERFACE (16)
19. void port_status(unsigned int flags);
21. /* set == 0: do clean , set == 1: do set! */
22. int set_if_flags(char *pif_name, int sock, int status, int set)
23. {
24. struct ifreq ifr;
25. int ret = 0;
27. strncpy(ifr.ifr_name, pif_name, strlen(pif_name) + 1);
28. ret = ioctl(sock, SIOCGIFFLAGS, &ifr);
29. if(ret)
30. return -1;
31. /* set or clean */
32. if(set)
33. ifr.ifr_flags |= status;
34. else
35. ifr.ifr_flags &= ~status;
36. /* set flags */
37. ret = ioctl(sock, SIOCSIFFLAGS, &ifr);
38. if(ret)
39. return -1;
41. return 0;
42. }
44. int get_if_info(int fd)
45. {
46. struct ifreq buf[MAX_INTERFACE];
47. struct ifconf ifc;
48. int ret = 0;
49. int if_num = 0;
51. ifc.ifc_len = sizeof(buf);
52. ifc.ifc_buf = (caddr_t) buf;
54. ret = ioctl(fd, SIOCGIFCONF, (char*)&ifc);
55. if(ret)
56. {
57. printf("get if config info failed");
58. return -1;
59. }
60. /* 網口總數 ifc.ifc_len 應該是一個出入參數 */
61. if_num = ifc.ifc_len/sizeof(struct ifreq);
62. printf("interface num is interface = %d\n", if_num);
63. while(if_num-- > 0)
64. {
65. printf("net device: %s\n", buf[if_num].ifr_name);
66. /* 獲取第n個網口信息 */
67. ret = ioctl(fd, SIOCGIFFLAGS, (char*)&buf[if_num]);
68. if(ret)
69. continue;
71. /* 獲取網口狀態 */
72. port_status(buf[if_num].ifr_flags);
74. /* 獲取當前網卡的ip地址 */
75. ret = ioctl(fd, SIOCGIFADDR, (char*)&buf[if_num]);
76. if(ret)
77. continue;
78. printf("IP address is: \n%s\n", inet_ntoa(((struct sockaddr_in *)(&buf[if_num].ifr_addr))->sin_addr));
80. /* 獲取當前網卡的mac */
81. ret = ioctl(fd, SIOCGIFHWADDR, (char*)&buf[if_num]);
82. if(ret)
83. continue;
85. printf("%02x:%02x:%02x:%02x:%02x:%02x\n\n",
86. (unsigned char)buf[if_num].ifr_hwaddr.sa_data[0],
87. (unsigned char)buf[if_num].ifr_hwaddr.sa_data[1],
88. (unsigned char)buf[if_num].ifr_hwaddr.sa_data[2],
89. (unsigned char)buf[if_num].ifr_hwaddr.sa_data[3],
90. (unsigned char)buf[if_num].ifr_hwaddr.sa_data[4],
91. (unsigned char)buf[if_num].ifr_hwaddr.sa_data[5]
92. );
93. }
94. }
96. void port_status(unsigned int flags)
97. {
98. if(flags & IFF_UP)
99. {
100. printf("is up\n");
101. }
102. if(flags & IFF_BROADCAST)
103. {
104. printf("is broadcast\n");
105. }
106. if(flags & IFF_LOOPBACK)
107. {
108. printf("is loop back\n");
109. }
110. if(flags & IFF_POINTOPOINT)
111. {
112. printf("is point to point\n");
113. }
114. if(flags & IFF_RUNNING)
115. {
116. printf("is running\n");
117. }
118. if(flags & IFF_PROMISC)
119. {
120. printf("is promisc\n");
121. }
122. }
124. int main()
125. {
126. int fd;
128. fd = socket(AF_INET, SOCK_DGRAM, 0);
129. if(fd > 0)
130. {
131. get_if_info(fd);
132. close(fd);
133. }
135. return 0;
136. }

運行結果：

interface num is interface = 2
net device: eth0
is up
is broadcast
is running
IP address is:
192.168.100.200
54:be:f7:33:57:26


net device: lo
is up
is loop back
is running
IP address is:
127.0.0.1
00:00:00:00:00:00

struct ifreq學習和實例