Generally use NULL instead of explicitly casting 0 to some pointer type (part2).
[dragonfly.git] / libexec / bootpd / getif.c
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1/*
2 * getif.c : get an interface structure
3 *
4 * $FreeBSD: src/libexec/bootpd/getif.c,v 1.7 1999/08/28 00:09:18 peter Exp $
1de703da 5 * $DragonFly: src/libexec/bootpd/getif.c,v 1.2 2003/06/17 04:27:07 dillon Exp $
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6 */
7
8#include <sys/types.h>
9#include <sys/socket.h>
10#include <sys/ioctl.h>
11
12#if defined(SUNOS) || defined(SVR4)
13#include <sys/sockio.h>
14#endif
15#ifdef SVR4
16#include <sys/stropts.h>
17#endif
18
19#include <sys/time.h> /* for struct timeval in net/if.h */
20#include <net/if.h> /* for struct ifreq */
21#include <netinet/in.h>
22
23#ifndef NO_UNISTD
24#include <unistd.h>
25#endif
26#include <syslog.h>
27#include <errno.h>
28#include <assert.h>
29
30#include "getif.h"
31#include "report.h"
32
33#ifdef __bsdi__
34#define BSD 43
35#endif
36
37static struct ifreq ifreq[10]; /* Holds interface configuration */
38static struct ifconf ifconf; /* points to ifreq */
39
40static int nmatch();
41
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42/*
43 * Return a pointer to the interface struct for the passed address.
44 *
45 * s socket file descriptor
46 * addrp destination address on interface
47 */
984263bc 48struct ifreq *
953df15c 49getif(int s, struct in_addr *addrp)
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50{
51 int maxmatch;
52 int len, m, incr;
53 struct ifreq *ifrq, *ifrmax;
54 struct sockaddr_in *sip;
55 char *p;
56
57 /* If no address was supplied, just return NULL. */
58 if (!addrp)
902ec341 59 return NULL;
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60
61 /* Get the interface config if not done already. */
62 if (ifconf.ifc_len == 0) {
63#ifdef SVR4
64 /*
65 * SysVr4 returns garbage if you do this the obvious way!
66 * This one took a while to figure out... -gwr
67 */
68 struct strioctl ioc;
69 ioc.ic_cmd = SIOCGIFCONF;
70 ioc.ic_timout = 0;
71 ioc.ic_len = sizeof(ifreq);
72 ioc.ic_dp = (char *) ifreq;
73 m = ioctl(s, I_STR, (char *) &ioc);
74 ifconf.ifc_len = ioc.ic_len;
75 ifconf.ifc_req = ifreq;
76#else /* SVR4 */
77 ifconf.ifc_len = sizeof(ifreq);
78 ifconf.ifc_req = ifreq;
79 m = ioctl(s, SIOCGIFCONF, (caddr_t) & ifconf);
80#endif /* SVR4 */
81 if ((m < 0) || (ifconf.ifc_len <= 0)) {
82 report(LOG_ERR, "ioctl SIOCGIFCONF");
902ec341 83 return NULL;
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84 }
85 }
86 maxmatch = 7; /* this many bits or less... */
902ec341 87 ifrmax = NULL; /* ... is not a valid match */
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88 p = (char *) ifreq;
89 len = ifconf.ifc_len;
90 while (len > 0) {
91 ifrq = (struct ifreq *) p;
92 sip = (struct sockaddr_in *) &ifrq->ifr_addr;
93 m = nmatch(addrp, &(sip->sin_addr));
94 if (m > maxmatch) {
95 maxmatch = m;
96 ifrmax = ifrq;
97 }
98#ifndef IFNAMSIZ
99 /* BSD not defined or earlier than 4.3 */
100 incr = sizeof(*ifrq);
101#else
102 incr = ifrq->ifr_addr.sa_len + IFNAMSIZ;
103#endif
104
105 p += incr;
106 len -= incr;
107 }
108
109 return ifrmax;
110}
111
112/*
113 * Return the number of leading bits matching in the
114 * internet addresses supplied.
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115 *
116 * ca, cb ptrs to IP address, network order
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117 */
118static int
953df15c 119nmatch(u_char *ca, u_char *cb)
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120{
121 u_int m = 0; /* count of matching bits */
122 u_int n = 4; /* bytes left, then bitmask */
123
124 /* Count matching bytes. */
125 while (n && (*ca == *cb)) {
126 ca++;
127 cb++;
128 m += 8;
129 n--;
130 }
131 /* Now count matching bits. */
132 if (n) {
133 n = 0x80;
134 while (n && ((*ca & n) == (*cb & n))) {
135 m++;
136 n >>= 1;
137 }
138 }
139 return (m);
140}
141
142/*
143 * Local Variables:
144 * tab-width: 4
145 * c-indent-level: 4
146 * c-argdecl-indent: 4
147 * c-continued-statement-offset: 4
148 * c-continued-brace-offset: -4
149 * c-label-offset: -4
150 * c-brace-offset: 0
151 * End:
152 */