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Annotation of xinu/sys/ip2name.c, revision 1.1

1.1     ! root        1: /* ip2name.c - ip2name */
        !             2: 
        !             3: #include <conf.h>
        !             4: #include <kernel.h>
        !             5: #include <network.h>
        !             6: 
        !             7: /*------------------------------------------------------------------------
        !             8:  *  ip2name  -  return DARPA Domain name for a host given its IP address
        !             9:  *------------------------------------------------------------------------
        !            10:  */
        !            11: SYSCALL        ip2name(ip, nam)
        !            12: IPaddr ip;
        !            13: char   *nam;
        !            14: {
        !            15:        char    tmpstr[20];             /* temporary string buffer      */
        !            16:        char    *buf;                   /* buffer to hold domain query  */
        !            17:        int     dg, i;
        !            18:        register char   *p;
        !            19:        register struct dn_mesg *dnptr;
        !            20: 
        !            21:        dnptr = (struct dn_mesg *) (buf = (char *) getmem(DN_MLEN));
        !            22:        *nam = NULLCH;
        !            23:        dnptr->dn_id = 0;
        !            24:        dnptr->dn_opparm = hs2net(DN_RD);
        !            25:        dnptr->dn_qcount = hs2net(1);
        !            26:        dnptr->dn_acount = dnptr->dn_ncount = dnptr->dn_dcount = 0;
        !            27:        p = dnptr->dn_qaaa;
        !            28: 
        !            29:        /* Fill in question with  ip[3].ip[2].ip[1].ip[0].in-addr.arpa  */
        !            30: 
        !            31:        for (i=3 ; i >= 0 ; i--) {
        !            32:                sprintf(tmpstr, "%d", ip[i] & LOWBYTE);
        !            33:                dn_cat(p, tmpstr);
        !            34:        }
        !            35:        dn_cat(p, "in-addr");
        !            36:        dn_cat(p, "arpa");
        !            37:        *p++ = NULLCH;  /* terminate name */
        !            38: 
        !            39:        /* Add query type and query class fields to name */
        !            40: 
        !            41:        ( (struct dn_qsuf *)p )->dn_type = hs2net(DN_QTPR);
        !            42:        ( (struct dn_qsuf *)p )->dn_clas = hs2net(DN_QCIN);
        !            43:        p += sizeof(struct dn_qsuf);
        !            44: 
        !            45:        /* Broadcast query */
        !            46: 
        !            47:        dg = open(INTERNET, DSERVER, ANYLPORT);
        !            48:        control(dg, DG_SETMODE, DG_DMODE | DG_TMODE);
        !            49:        write (dg, buf, p - buf);
        !            50:        if ( (i = read(dg, buf, DN_MLEN)) == SYSERR || i == TIMEOUT)
        !            51:                panic("No response from name server");
        !            52:        close(dg);
        !            53:        if (net2hs(dnptr->dn_opparm) & DN_RESP ||
        !            54:            net2hs(dnptr->dn_acount) <= 0) {
        !            55:                freemem(buf, DN_MLEN);
        !            56:                return(SYSERR);
        !            57:        }
        !            58: 
        !            59:        /* In answer, skip name and remainder of resource record header */
        !            60: 
        !            61:        while (*p != NULLCH)
        !            62:                if (*p & DN_CMPRS)      /* compressed section of name   */
        !            63:                        *++p = NULLCH;
        !            64:                else
        !            65:                        p += *p + 1;
        !            66:        p += DN_RLEN + 1;
        !            67: 
        !            68:        /* Copy name to user */
        !            69: 
        !            70:        *nam = NULLCH;
        !            71: 
        !            72:        while (*p != NULLCH) {
        !            73:                if (*p & DN_CMPRS)
        !            74:                        p = buf + (net2hs(*(int *)p) & DN_CPTR);
        !            75:                else {
        !            76:                        strncat(nam, p+1, *p);
        !            77:                        strcat(nam, ".");
        !            78:                        p += *p + 1;
        !            79:                }
        !            80:        }
        !            81:        if (strlen(nam))        /* remove trailing dot */
        !            82:                nam[strlen(nam) - 1] = NULLCH;
        !            83:        freemem(buf, DN_MLEN);
        !            84:        return(OK);
        !            85: }

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