148 lines
3.0 KiB
C
148 lines
3.0 KiB
C
/*
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* getif.c : get an interface structure
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*
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* $FreeBSD$
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*/
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <sys/ioctl.h>
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#if defined(SUNOS) || defined(SVR4)
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#include <sys/sockio.h>
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#endif
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#ifdef SVR4
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#include <sys/stropts.h>
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#endif
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#include <sys/time.h> /* for struct timeval in net/if.h */
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#include <net/if.h> /* for struct ifreq */
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#include <netinet/in.h>
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#ifndef NO_UNISTD
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#include <unistd.h>
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#endif
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#include <syslog.h>
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#include <errno.h>
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#include <assert.h>
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#include "getif.h"
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#include "report.h"
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#ifdef __bsdi__
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#define BSD 43
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#endif
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static struct ifreq ifreq[10]; /* Holds interface configuration */
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static struct ifconf ifconf; /* points to ifreq */
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static int nmatch();
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/* Return a pointer to the interface struct for the passed address. */
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struct ifreq *
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getif(s, addrp)
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int s; /* socket file descriptor */
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struct in_addr *addrp; /* destination address on interface */
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{
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int maxmatch;
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int len, m, incr;
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struct ifreq *ifrq, *ifrmax;
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struct sockaddr_in *sip;
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char *p;
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/* If no address was supplied, just return NULL. */
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if (!addrp)
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return (struct ifreq *) 0;
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/* Get the interface config if not done already. */
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if (ifconf.ifc_len == 0) {
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#ifdef SVR4
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/*
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* SysVr4 returns garbage if you do this the obvious way!
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* This one took a while to figure out... -gwr
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*/
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struct strioctl ioc;
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ioc.ic_cmd = SIOCGIFCONF;
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ioc.ic_timout = 0;
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ioc.ic_len = sizeof(ifreq);
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ioc.ic_dp = (char *) ifreq;
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m = ioctl(s, I_STR, (char *) &ioc);
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ifconf.ifc_len = ioc.ic_len;
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ifconf.ifc_req = ifreq;
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#else /* SVR4 */
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ifconf.ifc_len = sizeof(ifreq);
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ifconf.ifc_req = ifreq;
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m = ioctl(s, SIOCGIFCONF, (caddr_t) & ifconf);
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#endif /* SVR4 */
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if ((m < 0) || (ifconf.ifc_len <= 0)) {
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report(LOG_ERR, "ioctl SIOCGIFCONF");
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return (struct ifreq *) 0;
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}
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}
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maxmatch = 7; /* this many bits or less... */
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ifrmax = (struct ifreq *) 0;/* ... is not a valid match */
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p = (char *) ifreq;
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len = ifconf.ifc_len;
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while (len > 0) {
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ifrq = (struct ifreq *) p;
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sip = (struct sockaddr_in *) &ifrq->ifr_addr;
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m = nmatch((u_char *)addrp, (u_char *)&(sip->sin_addr));
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if (m > maxmatch) {
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maxmatch = m;
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ifrmax = ifrq;
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}
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#ifndef IFNAMSIZ
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/* BSD not defined or earlier than 4.3 */
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incr = sizeof(*ifrq);
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#else
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incr = ifrq->ifr_addr.sa_len + IFNAMSIZ;
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#endif
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p += incr;
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len -= incr;
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}
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return ifrmax;
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}
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/*
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* Return the number of leading bits matching in the
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* internet addresses supplied.
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*/
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static int
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nmatch(ca, cb)
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u_char *ca, *cb; /* ptrs to IP address, network order */
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{
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u_int m = 0; /* count of matching bits */
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u_int n = 4; /* bytes left, then bitmask */
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/* Count matching bytes. */
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while (n && (*ca == *cb)) {
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ca++;
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cb++;
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m += 8;
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n--;
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}
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/* Now count matching bits. */
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if (n) {
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n = 0x80;
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while (n && ((*ca & n) == (*cb & n))) {
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m++;
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n >>= 1;
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}
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}
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return (m);
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}
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/*
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* Local Variables:
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* tab-width: 4
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* c-indent-level: 4
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* c-argdecl-indent: 4
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* c-continued-statement-offset: 4
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* c-continued-brace-offset: -4
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* c-label-offset: -4
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* c-brace-offset: 0
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* End:
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*/
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