1 /* 2 * $Id: wire.c,v 5.2.1.1 91/03/17 17:42:58 jsp Alpha $ 3 * 4 * Copyright (c) 1990 Jan-Simon Pendry 5 * Copyright (c) 1990 Imperial College of Science, Technology & Medicine 6 * Copyright (c) 1990 The Regents of the University of California. 7 * All rights reserved. 8 * 9 * This code is derived from software contributed to Berkeley by 10 * Jan-Simon Pendry at Imperial College, London. 11 * 12 * %sccs.include.redist.c% 13 * 14 * @(#)wire.c 5.2 (Berkeley) 03/17/91 15 */ 16 17 /* 18 * This routine returns the subnet (address&netmask) for the primary network 19 * interface. If the resulting address has an entry in the hosts file, the 20 * corresponding name is retuned, otherwise the address is returned in 21 * standard internet format. 22 * 23 * From: Paul Anderson (23/4/90) 24 */ 25 26 #include "am.h" 27 28 #include <sys/ioctl.h> 29 30 #define NO_SUBNET "notknown" 31 32 #ifdef SIOCGIFFLAGS 33 #include <net/if.h> 34 #include <netdb.h> 35 36 #if defined(IFF_LOCAL_LOOPBACK) && !defined(IFF_LOOPBACK) 37 #define IFF_LOOPBACK IFF_LOCAL_LOOPBACK 38 #endif 39 40 #define GFBUFLEN 1024 41 #define clist (ifc.ifc_ifcu.ifcu_req) 42 #define count (ifc.ifc_len/sizeof(struct ifreq)) 43 44 char *getwire P((void)); 45 char *getwire() 46 { 47 struct hostent *hp; 48 struct netent *np; 49 struct ifconf ifc; 50 struct ifreq *ifr; 51 caddr_t cp, cplim; 52 unsigned long address, netmask, subnet; 53 char buf[GFBUFLEN], *s; 54 int sk = -1; 55 56 /* 57 * Get suitable socket 58 */ 59 if ((sk = socket(AF_INET, SOCK_DGRAM, 0)) < 0) 60 goto out; 61 62 /* 63 * Fill in ifconf details 64 */ 65 ifc.ifc_len = sizeof buf; 66 ifc.ifc_buf = buf; 67 68 /* 69 * Get network interface configurations 70 */ 71 if (ioctl(sk, SIOCGIFCONF, (caddr_t) &ifc) < 0) 72 goto out; 73 74 /* 75 * Upper bound on array 76 */ 77 cplim = buf + ifc.ifc_len; 78 79 /* 80 * This is some magic to cope with both "traditional" and the 81 * new 4.4BSD-style struct sockaddrs. The new structure has 82 * variable length and a size field to support longer addresses. 83 * AF_LINK is a new definition for 4.4BSD. 84 */ 85 #ifdef AF_LINK 86 #define max(a, b) ((a) > (b) ? (a) : (b)) 87 #define size(p) max((p).sa_len, sizeof(p)) 88 #else 89 #define size(p) sizeof(p) 90 #endif 91 /* 92 * Scan the list looking for a suitable interface 93 */ 94 for (cp = buf; cp < cplim; cp += sizeof(ifr->ifr_name) + size(ifr->ifr_addr)) { 95 ifr = (struct ifreq *) cp; 96 97 if (ifr->ifr_addr.sa_family != AF_INET) 98 continue; 99 else 100 address = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr.s_addr; 101 102 /* 103 * Get interface flags 104 */ 105 if (ioctl(sk, SIOCGIFFLAGS, (caddr_t) ifr) < 0) 106 goto out; 107 108 /* 109 * If the interface is a loopback, or its not running 110 * then ignore it. 111 */ 112 if ((ifr->ifr_flags & IFF_LOOPBACK) != 0) 113 continue; 114 if ((ifr->ifr_flags & IFF_RUNNING) == 0) 115 continue; 116 117 /* 118 * Get the netmask of this interface 119 */ 120 if (ioctl(sk, SIOCGIFNETMASK, (caddr_t) ifr) < 0) 121 goto out; 122 123 netmask = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr.s_addr; 124 125 (void) close(sk); 126 127 /* 128 * Figure out the subnet's network address 129 */ 130 subnet = address & netmask; 131 /* 132 * Now get a usable name. 133 * First use the network database, 134 * then the host database, 135 * and finally just make a dotted quad. 136 */ 137 np = getnetbyaddr(subnet, AF_INET); 138 if (np) 139 s = np->n_name; 140 else { 141 hp = gethostbyaddr((char *) &subnet, 4, AF_INET); 142 if (hp) 143 s = hp->h_name; 144 else 145 s = inet_dquad(buf, subnet); 146 } 147 148 return strdup(s); 149 } 150 151 out: 152 if (sk >= 0) 153 (void) close(sk); 154 return strdup(NO_SUBNET); 155 } 156 157 #else 158 159 char *getwire P((void)); 160 char *getwire() 161 { 162 return strdup(NO_SUBNET); 163 } 164 * %sccs.include.redist.c% 165 #endif /* SIOCGIFFLAGS */ 166