/proc/net/route 파싱

본것중에 가장 간단하게 /proc/net/route를 파싱하는 소스인 듯하다.

# cat /proc/net/route Iface   Destination     Gateway         Flags   RefCnt  Use     Metric  Mask            MTU     Window  IRTT eth0    000AA8C0        00000000        0001    0       0       0       00FFFFFF        0       0       0 eth0    00000000        010AA8C0        0003    0       0       0       00000000        0       0       0 # route Kernel IP routing table Destination     Gateway         Genmask         Flags Metric Ref    Use Iface 192.168.10.0    *               255.255.255.0   U     0      0        0 eth0 default         192.168.10.1    0.0.0.0         UG    0      0        0 eth0

아무튼 route로 출력하는 default가 UG 플래그로 default gateway이며,
파일에서는 Destination과 Mask가 0x00000000 인 녀석이 default gateway이다.

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01	#include "stdio.h"

02	#include "stdlib.h"

03	#include "unistd.h"

04

05	#define IP_PRINT(a) \

06	*((unsigned char *)(&a)), \

07	*(((unsigned char *)(&a)) + 1), \

08	*(((unsigned char *)(&a)) + 2), \

09	*(((unsigned char *)(&a)) + 3)

10

11	int main()

12

{

13	FILE* fp = fopen("/proc/net/route", "r");

14	char buf[256];

15	static char iface[256];

16	unsigned int destination, gateway, flags, refcnt, use, metric, mask;

17

int ret;

18

19	if (fp == NULL)

20

exit(-1);

21

22	while (fgets(buf, 255, fp)) {

23	if (!strncmp(buf, "Iface", 5))

24

continue;

25

26	ret = sscanf(buf, "%s\t%x\t%x\t%d\t%d\t%d\t%d\t%x",

27	iface, &destination, &gateway, &flags,

28	&refcnt, &use, &metric, &mask);

29

30	if (ret < 8) {

31	fprintf(stderr, "ERROR: line read error\n");

32

continue;

33

}

34

35	if (destination != 0) {

36	fprintf(stderr, "%s: gateway %u.%u.%u.%u, "

37	"destination %u.%u.%u.%u netmask %u.%u.%u.%u\n",

38

iface,

39	IP_PRINT(gateway),

40	IP_PRINT(destination),

41	IP_PRINT(mask));

42

continue;

43

}

44

45	if (mask != 0) {

46	fprintf(stderr, "%s: gateway %u.%u.%u.%u, default, "

47	"but have netmask %u.%u.%u.%u???\n",

48

iface,

49	IP_PRINT(gateway),

50	IP_PRINT(mask));

51

continue;

52

}

53

54	fprintf(stderr, "%s: gateway %u.%u.%u.%u, default\n",

55

iface,

56	IP_PRINT(gateway));

57

}

58	fclose(fp);

59

}

[링크 : http://elenoa.tistory.com/72]