/* ip2name.c - ip2name */ #include <conf.h> #include <kernel.h> #include <network.h> /*------------------------------------------------------------------------ * ip2name - return DARPA Domain name for a host given its IP address *------------------------------------------------------------------------ */ SYSCALL ip2name(ip, nam) 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, "%d", 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); /* Broadcast query */ dg = open(INTERNET, 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) panic("No response from name server"); close(dg); if (net2hs(dnptr->dn_opparm) & DN_RESP || net2hs(dnptr->dn_acount) <= 0) { freemem(buf, DN_MLEN); return(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 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; freemem(buf, DN_MLEN); return(OK); }