/*------------------------------------------------------------------------
* ip2name - return DNS name for a host given its IP address
*------------------------------------------------------------------------
*/
char *
ip2name(IPaddr ip, char *nam)
{
char tmpstr[20]; /* temporary string buffer */
char *buf; /* buffer to hold domain query */
int dg, i;
register char *p;
register struct dn_mesg *dnptr;
dnptr = (struct dn_mesg *) (buf = (char *) getmem(DN_MLEN));
*nam = NULLCH;
dnptr->dn_id = 0;
dnptr->dn_opparm = hs2net(DN_RD);
dnptr->dn_qcount = hs2net(1);
dnptr->dn_acount = dnptr->dn_ncount = dnptr->dn_dcount = 0;
p = dnptr->dn_qaaa;
/* Fill in question with ip[3].ip[2].ip[1].ip[0].in-addr.arpa */
for (i=3 ; i >= 0 ; i--) {
sprintf(tmpstr, "%u", ((char *)&ip)[i] & LOWBYTE);
dn_cat(p, tmpstr);
}
dn_cat(p, "in-addr");
dn_cat(p, "arpa");
*p++ = NULLCH; /* terminate name */
/* Add query type and query class fields to name */
( (struct dn_qsuf *)p )->dn_type = hs2net(DN_QTPR);
( (struct dn_qsuf *)p )->dn_clas = hs2net(DN_QCIN);
p += sizeof(struct dn_qsuf);
/* Send query */
dg = open(UDP, NSERVER, ANYLPORT);
control(dg, DG_SETMODE, DG_DMODE | DG_TMODE);
if (write (dg, buf, p - buf) == SYSERR)
panic("ip2name write(%d) failed\n", dg);
i = read(dg, buf, DN_MLEN);
if (i == SYSERR)
panic("ip2name read(%d) failed\n", dg);
if (i == TIMEOUT) {
close(dg);
return ip2dot(nam, ip);
}
close(dg);
if (net2hs(dnptr->dn_opparm) & DN_RESP ||
net2hs(dnptr->dn_acount) <= 0) {
freemem(buf, DN_MLEN);
return ip2dot(nam, ip);
}
/* In answer, skip name and remainder of resource record header */
while (*p != NULLCH)
if (*p & DN_CMPRS) /* compressed section of name */
*++p = NULLCH;
else
p += *p + 1;
p += DN_RLEN + 1;
/* Copy name to user */
*nam = NULLCH;
while (*p != NULLCH) {
if (*p & DN_CMPRS)
p = buf + (net2hs(*(int *)p) & DN_CPTR);
else {
strncat(nam, p+1, *p);
strcat(nam, ".");
p += *p + 1;
}
}
if (strlen(nam)) /* remove trailing dot */
nam[strlen(nam) - 1] = NULLCH;
else
ip2dot(nam, ip);
freemem(buf, DN_MLEN);
return nam;
}
/*------------------------------------------------------------------------
* gname - use the DNS to look up the name
*------------------------------------------------------------------------
*/
static IPaddr
gname(char *nam)
{
IPaddr ip;
char tmpstr[64]; /* temporary string buffer */
char *buf; /* buffer to hold domain query */
int dg, i;
register char *p, *p2, *p3;
register struct dn_mesg *dnptr;
dnptr = (struct dn_mesg *) (buf = (char *) getmem(DN_MLEN));
dnptr->dn_id = 0;
dnptr->dn_opparm = hs2net(DN_RD);
dnptr->dn_qcount = hs2net(1);
dnptr->dn_acount = dnptr->dn_ncount = dnptr->dn_dcount = 0;
p = dnptr->dn_qaaa;
strcpy(tmpstr, nam);
p2 = tmpstr;
while (p3=index(p2, '.')) {
*p3 = '\0';
dn_cat(p, p2);
p2 = p3+1;
}
dn_cat(p, p2);
*p++ = NULLCH; /* terminate name */
/* Add query type and query class fields to name */
( (struct dn_qsuf *)p )->dn_type = hs2net(DN_QTHA);
( (struct dn_qsuf *)p )->dn_clas = hs2net(DN_QCIN);
p += sizeof(struct dn_qsuf);
/* send query */
dg = open(UDP, NSERVER, ANYLPORT);
control(dg, DG_SETMODE, DG_DMODE | DG_TMODE);
write (dg, buf, p - buf);
if ( (i = read(dg, buf, DN_MLEN)) == SYSERR || i == TIMEOUT) {
close(dg);
freemem(buf, DN_MLEN);
return (IPaddr)SYSERR;
}
close(dg);
if (net2hs(dnptr->dn_opparm) & DN_RESP ||
net2hs(dnptr->dn_acount) <= 0) {
freemem(buf, DN_MLEN);
return (IPaddr)SYSERR;
}
/* In answer, skip name and remainder of resource record header */
while (*p != NULLCH)
if (*p & DN_CMPRS) /* compressed section of name */
*++p = NULLCH;
else
p += *p + 1;
p += DN_RLEN + 1;
/* Copy IP to user */
for (i=0; i < IP_ALEN; ++i)
((char *)&ip)[i] = *p++;
freemem(buf, DN_MLEN);
return ip;
}
