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/*
* mxget.c -- fetch MX records for given DNS name
*
* Copyright 1996 by Eric S. Raymond
* All rights reserved.
* For license terms, see the file COPYING in this directory.
*/
#include <config.h>
#ifdef HAVE_GETHOSTBYNAME
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include "mx.h"
/*
* This ought to be in the bind library. It's adapted from sendmail.
*/
int getmxrecords(name, nmx, pmx)
/* get MX records for given host */
char *name;
int nmx;
struct mxentry *pmx;
{
unsigned char answer[PACKETSZ], MXHostBuf[PACKETSZ], *eom, *cp, *bp;
int n, ancount, qdcount, buflen, type, pref, ind;
HEADER *hp;
n = res_search(name,C_IN,T_MX,(unsigned char*)&answer, sizeof(answer));
if (n == -1)
return(-1);
hp = (HEADER *)&answer;
cp = answer + HFIXEDSZ;
eom = answer + n;
for (qdcount = ntohs(hp->qdcount); qdcount--; cp += n + QFIXEDSZ)
if ((n = dn_skipname(cp, eom)) < 0)
return(-1);
buflen = sizeof(MXHostBuf) - 1;
bp = MXHostBuf;
ind = 0;
ancount = ntohs(hp->ancount);
while (--ancount >= 0 && cp < eom)
{
if ((n = dn_expand(answer, eom, cp, bp, buflen)) < 0)
break;
cp += n;
GETSHORT(type, cp);
cp += INT16SZ + INT32SZ;
GETSHORT(n, cp);
if (type != T_MX)
{
cp += n;
continue;
}
GETSHORT(pref, cp);
if ((n = dn_expand(answer, eom, cp, bp, buflen)) < 0)
break;
cp += n;
pmx[ind].name = bp;
pmx[ind].pref = pref;
if (++ind > nmx)
break;
n = strlen(bp);
bp += n;
*bp++ = '\0';
buflen -= n + 1;
}
return(ind);
}
#endif /* HAVE_GETHOSTBYNAME */
/* mxget.c ends here */
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