one too many levels of indirection (from ks@purdue)

[unix-history] / usr / src / lib / libc / net / gethostnamadr.c

/*
* Copyright (c) 1983 Regents of the University of California.
* All rights reserved.  The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*/

#ifndef lint
static char sccsid[] = "@(#)gethostnamadr.c     5.1 (Berkeley) %G%";
#endif not lint

/*
* Copyright (c) 1985 Regents of the University of California
*      All Rights Reserved
*/

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <nameser.h>
#include <resolv.h>

#define MAXALIASES      35

static struct hostent host;
static char *host_aliases[MAXALIASES];
static char hostbuf[BUFSIZ+1];

static struct hostent *
getanswer(msg, msglen, iquery)
       char *msg;
       int msglen, iquery;
{
       register HEADER *hp;
       register char *cp;
       register int n;
       char answer[PACKETSZ];
       char *eom, *bp, **ap;
       int type, class, ancount, buflen;

       n = res_send(msg, msglen, answer, sizeof(answer));
       if (n < 0) {
               if (_res.options & RES_DEBUG)
                       printf("res_send failed\n");
               return (NULL);
       }
       eom = answer + n;
       /*
        * find first satisfactory answer
        */
       hp = (HEADER *) answer;
       ancount = ntohs(hp->ancount);
       if (hp->rcode != NOERROR || ancount == 0) {
               if (_res.options & RES_DEBUG)
                       printf("rcode = %d, ancount=%d\n", hp->rcode, ancount);
               return (NULL);
       }
       bp = hostbuf;
       buflen = sizeof(hostbuf);
       ap = host_aliases;
       cp = answer + sizeof(HEADER);
       if (hp->qdcount) {
               if (iquery) {
                       if ((n = dn_expand(answer, cp, bp, buflen)) < 0)
                               return (NULL);
                       cp += n + QFIXEDSZ;
                       host.h_name = bp;
                       n = strlen(bp) + 1;
                       bp += n;
                       buflen -= n;
               } else
                       cp += dn_skip(cp) + QFIXEDSZ;
       } else if (iquery)
               return (NULL);
       while (--ancount >= 0 && cp < eom) {
               if ((n = dn_expand(answer, cp, bp, buflen)) < 0)
                       return (NULL);
               cp += n;
               type = getshort(cp);
               cp += sizeof(u_short);
               class = getshort(cp);
               cp += sizeof(u_short) + sizeof(u_long);
               n = getshort(cp);
               cp += sizeof(u_short);
               if (type == T_CNAME) {
                       cp += n;
                       if (ap >= &host_aliases[MAXALIASES-1])
                               continue;
                       *ap++ = bp;
                       n = strlen(bp) + 1;
                       bp += n;
                       buflen -= n;
                       continue;
               }
               if (type != T_A || n != 4) {
                       if (_res.options & RES_DEBUG)
                               printf("unexpected answer type %d, size %d\n",
                                       type, n);
                       continue;
               }
               if (!iquery) {
                       host.h_name = bp;
                       bp += strlen(bp) + 1;
               }
               *ap = NULL;
               host.h_aliases = host_aliases;
               host.h_addrtype = class == C_IN ? AF_INET : AF_UNSPEC;
               if (bp + n >= &hostbuf[sizeof(hostbuf)]) {
                       if (_res.options & RES_DEBUG)
                               printf("size (%d) too big\n", n);
                       return (NULL);
               }
               bcopy(cp, host.h_addr = bp, host.h_length = n);
               return (&host);
       }
       return (NULL);
}

struct hostent *
gethostbyname(name)
       char *name;
{
       int n;

       n = res_mkquery(QUERY, name, C_ANY, T_A, NULL, 0, NULL,
               hostbuf, sizeof(hostbuf));
       if (n < 0) {
               if (_res.options & RES_DEBUG)
                       printf("res_mkquery failed\n");
               return (NULL);
       }
       return (getanswer(hostbuf, n, 0));
}

struct hostent *
gethostbyaddr(addr, len, type)
       char *addr;
       int len, type;
{
       int n;

       if (type != AF_INET)
               return (NULL);
       n = res_mkquery(IQUERY, NULL, C_IN, T_A, addr, len, NULL,
               hostbuf, sizeof(hostbuf));
       if (n < 0) {
               if (_res.options & RES_DEBUG)
                       printf("res_mkquery failed\n");
               return (NULL);
       }
       return (getanswer(hostbuf, n, 1));
}