1 /* $NetBSD: getif.c,v 1.5 2002/07/14 00:26:17 wiz Exp $ */ 2 3 #include <sys/cdefs.h> 4 #ifndef lint 5 __RCSID("$NetBSD: getif.c,v 1.5 2002/07/14 00:26:17 wiz Exp $"); 6 #endif 7 8 /* 9 * getif.c : get an interface structure 10 */ 11 12 #include <sys/types.h> 13 #include <sys/socket.h> 14 #include <sys/ioctl.h> 15 #include <sys/param.h> 16 17 #if defined(SUNOS) || defined(SVR4) 18 #include <sys/sockio.h> 19 #endif 20 #ifdef SVR4 21 #include <sys/stropts.h> 22 #endif 23 24 #include <net/if.h> /* for struct ifreq */ 25 #include <netinet/in.h> 26 27 #ifndef NO_UNISTD 28 #include <unistd.h> 29 #endif 30 #include <syslog.h> 31 #include <errno.h> 32 #include <assert.h> 33 34 #include "getif.h" 35 #include "report.h" 36 37 #ifdef __bsdi__ 38 #define BSD 43 39 #endif 40 41 static struct ifreq ifreq[10]; /* Holds interface configuration */ 42 static struct ifconf ifconf; /* points to ifreq */ 43 44 static int nmatch(u_char *, u_char *); 45 46 /* Return a pointer to the interface struct for the passed address. */ 47 struct ifreq * 48 getif(int s, struct in_addr *addrp) 49 /* socket file descriptor */ 50 /* destination address on interface */ 51 { 52 int maxmatch; 53 int len, m, incr; 54 struct ifreq *ifrq, *ifrmax; 55 struct sockaddr_in *sip; 56 char *p; 57 58 /* If no address was supplied, just return NULL. */ 59 if (!addrp) 60 return (struct ifreq *) 0; 61 62 /* Get the interface config if not done already. */ 63 if (ifconf.ifc_len == 0) { 64 #ifdef SVR4 65 /* 66 * SysVr4 returns garbage if you do this the obvious way! 67 * This one took a while to figure out... -gwr 68 */ 69 struct strioctl ioc; 70 ioc.ic_cmd = SIOCGIFCONF; 71 ioc.ic_timout = 0; 72 ioc.ic_len = sizeof(ifreq); 73 ioc.ic_dp = (char *) ifreq; 74 m = ioctl(s, I_STR, (char *) &ioc); 75 ifconf.ifc_len = ioc.ic_len; 76 ifconf.ifc_req = ifreq; 77 #else /* SVR4 */ 78 ifconf.ifc_len = sizeof(ifreq); 79 ifconf.ifc_req = ifreq; 80 m = ioctl(s, SIOCGIFCONF, (caddr_t) & ifconf); 81 #endif /* SVR4 */ 82 if ((m < 0) || (ifconf.ifc_len <= 0)) { 83 report(LOG_ERR, "ioctl SIOCGIFCONF"); 84 return (struct ifreq *) 0; 85 } 86 } 87 maxmatch = 7; /* this many bits or less... */ 88 ifrmax = (struct ifreq *) 0;/* ... is not a valid match */ 89 p = (char *) ifreq; 90 len = ifconf.ifc_len; 91 while (len > 0) { 92 ifrq = (struct ifreq *) p; 93 sip = (struct sockaddr_in *) &ifrq->ifr_addr; 94 m = nmatch((u_char *)addrp, (u_char *)&(sip->sin_addr)); 95 if (m > maxmatch) { 96 maxmatch = m; 97 ifrmax = ifrq; 98 } 99 /* XXX - Could this be just #ifndef IFNAMSIZ instead? -gwr */ 100 #if (BSD - 0) < 43 101 /* BSD not defined or earlier than 4.3 */ 102 incr = sizeof(*ifrq); 103 #else /* NetBSD */ 104 incr = ifrq->ifr_addr.sa_len + IFNAMSIZ; 105 #endif /* NetBSD */ 106 107 p += incr; 108 len -= incr; 109 } 110 111 return ifrmax; 112 } 113 114 /* 115 * Return the number of leading bits matching in the 116 * internet addresses supplied. 117 */ 118 static int 119 nmatch(u_char *ca, u_char *cb) 120 /* ptrs to IP address, network order */ 121 { 122 u_int m = 0; /* count of matching bits */ 123 u_int n = 4; /* bytes left, then bitmask */ 124 125 /* Count matching bytes. */ 126 while (n && (*ca == *cb)) { 127 ca++; 128 cb++; 129 m += 8; 130 n--; 131 } 132 /* Now count matching bits. */ 133 if (n) { 134 n = 0x80; 135 while (n && ((*ca & n) == (*cb & n))) { 136 m++; 137 n >>= 1; 138 } 139 } 140 return (m); 141 } 142 143 /* 144 * Local Variables: 145 * tab-width: 4 146 * c-indent-level: 4 147 * c-argdecl-indent: 4 148 * c-continued-statement-offset: 4 149 * c-continued-brace-offset: -4 150 * c-label-offset: -4 151 * c-brace-offset: 0 152 * End: 153 */ 154