获取网卡的实时网速

蚂蚁没问题

在Windows下面，我们可以看到360或者是qq安全卫士的“安全球”，上面显示实时的网速情况。那么在Linux里面如何获取网卡的实时网速？其实原理很简单，读取需要获取网速的网卡在某段时间dT内流量的变化dL，那么实时网速就出来了,Speed = dL / dt。

Linux在ifaddrs.h中提供了函数：

1. /* Create a linked list of `struct ifaddrs' structures, one for each
   
2.   network interface on the host machine.  If successful, store the
   
3.   list in *IFAP and return 0.  On errors, return -1 and set `errno'.
   
4.             
   
5.   The storage returned in *IFAP is allocated dynamically and can
   
6.   only be properly freed by passing it to `freeifaddrs'.  */
   
7. extern int getifaddrs (struct ifaddrs **__ifap) __THROW;
   
8.          
   
9. /* Reclaim the storage allocated by a previous `getifaddrs' call.  */
   
10. extern void freeifaddrs (struct ifaddrs *__ifa)  __THROW;

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系统会创建一个包含本机所有网卡信息链表，然后我们就可以在这个链表里面获取我们想要的信息。

1. /* The `getifaddrs' function generates a linked list of these structures.
   
2.   Each element of the list describes one network interface.  */
   
3. struct ifaddrs
   
4. {
   
5.   struct ifaddrs *ifa_next; /* Pointer to the next structure.  */
   
6. 
   
7.   char *ifa_name;      /* Name of this network interface.  */
   
8.   unsigned int ifa_flags;  /* Flags as from SIOCGIFFLAGS ioctl.  */
   
9. 
   
10.   struct sockaddr *ifa_addr;    /* Network address of this interface.  */
    
11.   struct sockaddr *ifa_netmask; /* Netmask of this interface.  */
    
12.   union
    
13.   {
    
14.     /* At most one of the following two is valid.  If the IFF_BROADCAST
    
15.       bit is set in `ifa_flags', then `ifa_broadaddr' is valid.  If the
    
16.       IFF_POINTOPOINT bit is set, then `ifa_dstaddr' is valid.
    
17.       It is never the case that both these bits are set at once.  */
    
18.     struct sockaddr *ifu_broadaddr; /* Broadcast address of this interface. */
    
19.     struct sockaddr *ifu_dstaddr; /* Point-to-point destination address.  */
    
20.   } ifa_ifu;
    
21.   /* These very same macros are defined by <net/if.h> for `struct ifaddr'.
    
22.     So if they are defined already, the existing definitions will be fine.  */
    
23. # ifndef ifa_broadaddr
    
24. #  define ifa_broadaddr ifa_ifu.ifu_broadaddr
    
25. # endif
    
26. # ifndef ifa_dstaddr
    
27. #  define ifa_dstaddr  ifa_ifu.ifu_dstaddr
    
28. # endif
    
29.         
    
30.   void *ifa_data;      /* Address-specific data (may be unused).  */
    
31. };

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另外这个链表我们是可以提前用ioctl来筛选的，可以通过ifa_name和ifa_flags来确定ifa_ifu里面到底选用那个union。不过这次我们是来测量实时网速的，不必要关心这个。

我们需要关心的是ifa_data这个项，关于这个项我百度了很多，一直没有发现他到底应该属于哪个结构体的。
后来无意在网上找了一些发现有类似的，但是我找不到头文件在那，所以后来干脆我直接把他放到我的头文件里面；

1. struct if_data{
   
2. /* generic interface information */
   
3. u_char ifi_type; /* ethernet, tokenring, etc */
   
4. u_char ifi_addrlen; /* media address length */
   
5. u_char ifi_hdrlen; /* media header length */
   
6. u_long ifi_mtu; /* maximum transmission unit */
   
7. u_long ifi_metric; /* routing metric (external only) */
   
8. u_long ifi_baudrate; /* linespeed */
   
9. /* volatile statistics */
   
10. u_long ifi_ipackets; /* packets received on interface */
    
11. u_long ifi_ierrors; /* input errors on interface */
    
12. u_long ifi_opackets; /* packets sent on interface */
    
13. u_long ifi_oerrors; /* output errors on interface */
    
14. u_long ifi_collisions; /* collisions on csma interfaces */
    
15. u_long ifi_ibytes; /* total number of octets received */
    
16. u_long ifi_obytes; /* total number of octets sent */
    
17. u_long ifi_imcasts; /* packets received via multicast */
    
18. u_long ifi_omcasts; /* packets sent via multicast */
    
19. u_long ifi_iqdrops; /* dropped on input, this interface */
    
20. u_long ifi_noproto; /* destined for unsupported protocol */
    
21. struct timeval ifi_lastchange;/* last updated */
    
22. };

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刚刚开始我就打印了ifi_iobytes,ifi_obytes这两个项，不管我怎么下载和上次文件，这两个量都是0。纠结了我半天，我就直接把所有变量都打印出来，发现ifi_mtu,ifi_metric,ifi_baudrate跟ifconfig eth0输出的数据很像。

1. [15:12 @ ~/program/netspeed]$ ifconfig eth0
   
2. eth0      Link encap:Ethernet  HWaddr 00:22:15:67:F8:16  
   
3.           inet addr:210.42.158.204  Bcast:210.42.158.255  Mask:255.255.255.0
   
4.           inet6 addr: fe80::222:15ff:fe67:f816/64 Scope:Link
   
5.           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
   
6.           RX packets:917978 errors:0 dropped:0 overruns:0 frame:0
   
7.           TX packets:1132894 errors:0 dropped:0 overruns:0 carrier:0
   
8.           collisions:0 txqueuelen:1000
   
9.           RX bytes:132866544 (126.7 MiB)  TX bytes:1250785627 (1.1 GiB)
   
10.           Interrupt:29 Base address:0x4000

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慢慢的我知道了规律，struct ifaddrs里面的ifa_data前四个字（32位）以此是发送数据包数，接收数据包数，发送字节数，接收字节数。

我就重新调整了struct if_data的结构体，由于后面的数据全为0，我就保留了4项：

1. struct if_data
   
2. {  
   
3.     /*  generic interface information */
   
4.     u_long ifi_opackets;    /*  packets sent on interface */
   
5.     u_long ifi_ipackets;    /*  packets received on interface */
   
6.     u_long ifi_obytes;      /*  total number of octets sent */
   
7.     u_long ifi_ibytes;      /*  total number of octets received */
   
8. };

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测试OK。

1. [15:17 @ ~/program/netspeed]$ ./netspeed
   
2. Get eth0 Speed                  [OK]
   
3. eth0: Up Speed: 1.671066 MB/s || Down Speed: 0.036335 MB/s

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附上我已经封装好的代码：

1. int get_if_dbytes(struct if_info* ndev)
   
2. {  
   
3.     assert(ndev);
   
4.    
   
5.     struct ifaddrs *ifa_list = NULL;
   
6.     struct ifaddrs *ifa = NULL;
   
7.     struct if_data *ifd = NULL;
   
8.     int    ret = 0;
   
9.    
   
10.     ret = getifaddrs(&ifa_list);
    
11.     if(ret < 0) {
    
12.         perror("Get Interface Address Fail:");
    
13.         goto end;
    
14.     }  
    
15.    
    
16.     for(ifa=ifa_list; ifa; ifa=ifa->ifa_next){
    
17.         if(!(ifa->ifa_flags & IFF_UP) && !(ifa->ifa_flags & IFF_RUNNING))
    
18.             continue;
    
19. 
    
20.         if(ifa->ifa_data == 0)
    
21.             continue;
    
22.         
    
23.         ret = strcmp(ifa->ifa_name,ndev->ifi_name);
    
24.         if(ret == 0){
    
25.           ifd = (struct if_data *)ifa->ifa_data;
    
26.          
    
27.           ndev->ifi_ibytes = ifd->ifi_ibytes;
    
28.           ndev->ifi_obytes = ifd->ifi_obytes;
    
29.           break;
    
30.         }
    
31.     }
    
32. 
    
33.     freeifaddrs(ifa_list);
    
34. end:
    
35.     return (ret ? -1 : 0);
    
36. }
    
37. 
    
38. int get_if_speed(struct if_speed *ndev)
    
39. {
    
40.     assert(ndev);
    
41. 
    
42.     struct if_info *p1=NULL,*p2=NULL;
    
43. 
    
44.     p1 = (struct if_info *)malloc(sizeof(struct if_info));
    
45.     p2 = (struct if_info *)malloc(sizeof(struct if_info));
    
46.     bzero(p1,sizeof(struct if_info));
    
47.     bzero(p2,sizeof(struct if_info));
    
48. 
    
49.     strncpy(p1->ifi_name,ndev->ifs_name,strlen(ndev->ifs_name));
    
50.     strncpy(p2->ifi_name,ndev->ifs_name,strlen(ndev->ifs_name));
    
51. 
    
52.     int ret = 0;
    
53.     ret = get_if_dbytes(p1);
    
54.     if(ret < 0)    goto end;
    
55.     usleep(ndev->ifs_us);
    
56.     ret = get_if_dbytes(p2);
    
57.     if(ret < 0)    goto end;
    
58. 
    
59.     ndev->ifs_ispeed = p2->ifi_ibytes - p1->ifi_ibytes;
    
60.     ndev->ifs_ospeed = p2->ifi_obytes - p1->ifi_obytes;
    
61. 
    
62. end:
    
63.     free(p1);
    
64.     free(p2);
    
65. 
    
66.     return 0;
    
67. }

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头文件：

1. #ifndef __TSPEED_H__
   
2. #define __TSPEED_H__
   
3. 
   
4. #ifdef __cplusplus
   
5. extern "C"
   
6. {
   
7. #endif
   
8.    
   
9. #include <stdio.h>
   
10. #include <stdlib.h>
    
11. #include <string.h>
    
12. #include <assert.h>
    
13. #include <error.h>
    
14. 
    
15.     /* For "open" function */
    
16. #include <sys/types.h>
    
17. #include <sys/stat.h>
    
18. #include <fcntl.h>
    
19. struct if_data
    
20. {  
    
21.     /*  generic interface information */
    
22.     u_long ifi_opackets;    /*  packets sent on interface */
    
23.     u_long ifi_ipackets;    /*  packets received on interface */
    
24.     u_long ifi_obytes;      /*  total number of octets sent */
    
25.     u_long ifi_ibytes;      /*  total number of octets received */
    
26. };
    
27.    
    
28. struct if_info
    
29. {  
    
30.     char ifi_name[16];
    
31.     unsigned long ifi_ibytes;
    
32.     unsigned long ifi_obytes;
    
33. };
    
34. struct if_speed
    
35. {  
    
36.     char ifs_name[16];
    
37.     unsigned long ifs_ispeed;
    
38.     unsigned long ifs_ospeed;
    
39.     unsigned long ifs_us;
    
40. };
    
41. 
    
42. extern int get_if_dbytes(struct if_info *ndev);
    
43. extern int get_if_speed(struct if_speed *ndev);
    
44. 
    
45. #ifdef __cplusplus
    
46. }
    
47. #endif
    
48. 
    
49. #endif

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测试代码：

1. int main (int argc, char **argv)
   
2. {
   
3.     struct if_speed ndev;
   
4.     int ret = 0;
   
5. 
   
6.     bzero(&ndev,sizeof(ndev));
   
7.     sprintf(ndev.ifs_name,"eth0");
   
8. 
   
9.     ndev.ifs_us = 100000;
   
10. 
    
11.     printf("Get %s Speed");
    
12.     ret = get_if_speed(&ndev);
    
13.     if(ret < 0)
    
14.         printf("\t\t\t[Fail]\n");
    
15.     else
    
16.         printf("\t\t\t[OK]\n");
    
17.     float ispeed ,ospeed;
    
18.     while(1){
    
19.         ispeed = ndev.ifs_ispeed * 1.0/(ndev.ifs_us/1000 * 0.001);
    
20.         ospeed = ndev.ifs_ospeed * 1.0/(ndev.ifs_us/1000 * 0.001);
    
21. 
    
22.         printf("%s: Up Speed: %f MB/s || Down Speed: %f MB/s                  \r",
    
23.                 ndev.ifs_name,ispeed/(1024.0*1024.0),ospeed/(1024.0*1024.0));
    
24. 
    
25.         get_if_speed(&ndev);
    
26.     }
    
27. 
    
28. 
    
29.     return 0;
    
30. } /* ----- End of main() ----- */

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