Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
freebsd
GitHub Repository: freebsd/freebsd-src
 Path: blob/main/libexec/bootpd/getif.c
34822 views
1
/*

2
 * getif.c : get an interface structure

3
 */

4


5
#include <sys/types.h>

6
#include <sys/socket.h>

7
#include <sys/ioctl.h>

8


9
#if defined(SUNOS) || defined(SVR4)

10
#include <sys/sockio.h>

11
#endif

12
#ifdef	SVR4

13
#include <sys/stropts.h>

14
#endif

15


16
#include <sys/time.h>		/* for struct timeval in net/if.h */	

17
#include <net/if.h>				/* for struct ifreq */

18
#include <netinet/in.h>

19


20
#ifndef	NO_UNISTD

21
#include <unistd.h>

22
#endif

23
#include <syslog.h>

24
#include <errno.h>

25
#include <assert.h>

26


27
#include "getif.h"

28
#include "report.h"

29


30
#ifdef	__bsdi__

31
#define BSD 43

32
#endif

33


34
static struct ifreq ifreq[10];	/* Holds interface configuration */

35
static struct ifconf ifconf;	/* points to ifreq */

36


37
static int nmatch(u_char *ca, u_char *cb);

38


39
/* Return a pointer to the interface struct for the passed address. */

40
struct ifreq *

41
getif(int s, struct in_addr *addrp)

42
{

43
	int maxmatch;

44
	int len, m, incr;

45
	struct ifreq *ifrq, *ifrmax;

46
	struct sockaddr_in *sip;

47
	char *p;

48


49
	/* If no address was supplied, just return NULL. */

50
	if (!addrp)

51
		return (struct ifreq *) 0;

52


53
	/* Get the interface config if not done already. */

54
	if (ifconf.ifc_len == 0) {

55
#ifdef	SVR4

56
		/*

57
		 * SysVr4 returns garbage if you do this the obvious way!

58
		 * This one took a while to figure out... -gwr

59
		 */

60
		struct strioctl ioc;

61
		ioc.ic_cmd = SIOCGIFCONF;

62
		ioc.ic_timout = 0;

63
		ioc.ic_len = sizeof(ifreq);

64
		ioc.ic_dp = (char *) ifreq;

65
		m = ioctl(s, I_STR, (char *) &ioc);

66
		ifconf.ifc_len = ioc.ic_len;

67
		ifconf.ifc_req = ifreq;

68
#else	/* SVR4 */

69
		ifconf.ifc_len = sizeof(ifreq);

70
		ifconf.ifc_req = ifreq;

71
		m = ioctl(s, SIOCGIFCONF, (caddr_t) & ifconf);

72
#endif	/* SVR4 */

73
		if ((m < 0) || (ifconf.ifc_len <= 0)) {

74
			report(LOG_ERR, "ioctl SIOCGIFCONF");

75
			return (struct ifreq *) 0;

76
		}

77
	}

78
	maxmatch = 7;				/* this many bits or less... */

79
	ifrmax = (struct ifreq *) 0;/* ... is not a valid match  */

80
	p = (char *) ifreq;

81
	len = ifconf.ifc_len;

82
	while (len > 0) {

83
		ifrq = (struct ifreq *) p;

84
		sip = (struct sockaddr_in *) &ifrq->ifr_addr;

85
		m = nmatch((u_char *)addrp, (u_char *)&(sip->sin_addr));

86
		if (m > maxmatch) {

87
			maxmatch = m;

88
			ifrmax = ifrq;

89
		}

90
#ifndef IFNAMSIZ

91
		/* BSD not defined or earlier than 4.3 */

92
		incr = sizeof(*ifrq);

93
#else

94
		incr = ifrq->ifr_addr.sa_len + IFNAMSIZ;

95
#endif

96


97
		p += incr;

98
		len -= incr;

99
	}

100


101
	return ifrmax;

102
}

103


104
/*

105
 * Return the number of leading bits matching in the

106
 * internet addresses supplied.

107
 */

108
static int

109
nmatch(u_char *ca, u_char *cb)

110
{

111
	u_int m = 0;				/* count of matching bits */

112
	u_int n = 4;				/* bytes left, then bitmask */

113


114
	/* Count matching bytes. */

115
	while (n && (*ca == *cb)) {

116
		ca++;

117
		cb++;

118
		m += 8;

119
		n--;

120
	}

121
	/* Now count matching bits. */

122
	if (n) {

123
		n = 0x80;

124
		while (n && ((*ca & n) == (*cb & n))) {

125
			m++;

126
			n >>= 1;

127
		}

128
	}

129
	return (m);

130
}

131


132
/*

133
 * Local Variables:

134
 * tab-width: 4

135
 * c-indent-level: 4

136
 * c-argdecl-indent: 4

137
 * c-continued-statement-offset: 4

138
 * c-continued-brace-offset: -4

139
 * c-label-offset: -4

140
 * c-brace-offset: 0

141
 * End:

142
 */

143


144