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