named/ns_forw.c

/*
 * Copyright (c) 1986 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char sccsid[] = "@(#)ns_forw.c   4.27 (Berkeley) 6/18/88";
#endif /* not lint */

#include <stdio.h>
#include <sys/param.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <syslog.h>
#include <arpa/nameser.h>
#include "ns.h"
#include "db.h"

struct  qinfo *qhead = QINFO_NULL;      /* head of allocated queries */
struct  qinfo *retryqp = QINFO_NULL;    /* list of queries to retry */
struct  fwdinfo *fwdtab;                /* list of forwarding hosts */

int     nsid;                           /* next forwarded query id */
extern int forward_only;                /* you are only a slave */
extern int errno;
extern short ns_port;

time_t  retrytime();

/*
 * Forward the query to get the answer since its not in the database.
 * Returns FW_OK if a request struct is allocated and the query sent.
 * Returns FW_DUP if this is a duplicate of a pending request.
 * Returns FW_NOSERVER if there were no addresses for the nameservers.
 * Returns FW_SERVFAIL on malloc error.
 * (no action is taken on errors and qpp is not filled in.)
 */
ns_forw(nsp, msg, msglen, fp, qsp, dfd, qpp)
        struct databuf *nsp[];
        char *msg;
        int msglen;
        struct sockaddr_in *fp;
        struct qstream *qsp;
        int dfd;
        struct qinfo **qpp;
{
        register struct qinfo *qp;
        HEADER *hp;
        u_short id;
        extern char *calloc();

#ifdef DEBUG
        if (debug >= 3)
                fprintf(ddt,"ns_forw()\n");
#endif

        /* Don't forward if we're already working on it. */
        hp = (HEADER *) msg;
        id = hp->id;
        hp->rd = 0;
        /* Look at them all */
        for (qp = qhead; qp!=QINFO_NULL; qp = qp->q_link) {
                if (qp->q_id == id &&
                    bcmp((char *)&qp->q_from, fp, sizeof(qp->q_from)) == 0 &&
                    (qp->q_cmsglen == 0 && qp->q_msglen == msglen &&
                     bcmp((char *)qp->q_msg+2, msg+2, msglen-2) == 0) ||
                    (qp->q_cmsglen == msglen &&
                     bcmp((char *)qp->q_cmsg+2, msg+2, msglen-2) == 0)) {
#ifdef DEBUG
                        if (debug >= 3)
                                fprintf(ddt,"forw: dropped DUP id=%d\n", ntohs(id));
#endif
#ifdef STATS
                        stats[S_DUPQUERIES].cnt++;
#endif
                        return (FW_DUP);
                }
        }

        qp = qnew();
        if (nslookup(nsp, qp) == 0) {
#ifdef DEBUG
                if (debug >= 2)
                        fprintf(ddt,"forw: no nameservers found\n");
#endif
                qfree(qp);
                hp->rd = 1;
                return (FW_NOSERVER);
        }
        qp->q_stream = qsp;
        qp->q_curaddr = 0;
        qp->q_fwd = fwdtab;
        qp->q_dfd = dfd;
        qp->q_id = id;
        hp->id = qp->q_nsid = htons((u_short)++nsid);
        hp->ancount = 0;
        hp->nscount = 0;
        hp->arcount = 0;
        if (qp->q_fwd)
                hp->rd = 1;
        else
                qp->q_addr[0].stime = tt;
        qp->q_from = *fp;
        if ((qp->q_msg = malloc((unsigned)msglen)) == NULL) {
                syslog(LOG_ERR, "forw: %m");
                qfree(qp);
                return (FW_SERVFAIL);
        }
        bcopy(msg, qp->q_msg, qp->q_msglen = msglen);

        schedretry(qp, retrytime(qp));
#ifdef DEBUG
        if (debug)
                fprintf(ddt,
                   "forw: forw -> %s %d (%d) nsid=%d id=%d %dms retry %d sec\n",
                        inet_ntoa(Q_NEXTADDR(qp,0)->sin_addr),
                        ds, ntohs(Q_NEXTADDR(qp,0)->sin_port),
                        ntohs(qp->q_nsid), ntohs(qp->q_id),
                        qp->q_addr[0].nsdata->d_nstime,
                        qp->q_time - tt.tv_sec);
        if ( debug >= 10)
                fp_query(msg, ddt);
#endif
        if (sendto(ds, msg, msglen, 0, (struct sockaddr *)Q_NEXTADDR(qp,0),
                   sizeof(struct sockaddr_in)) < 0){
#ifdef DEBUG
                if (debug >= 5)
                        fprintf(ddt,"error returning msg errno=%d\n",errno);
#endif
        }
#ifdef STATS
        stats[S_OUTPKTS].cnt++;
#endif
        if (qpp)
                *qpp = qp;
        hp->rd = 0;
        return (0);
}

/*
 * Lookup the address for each nameserver in `nsp' and add it to
 * the list saved in the qinfo structure.
 */
nslookup(nsp, qp)
        struct databuf *nsp[];
        register struct qinfo *qp;
{
        register struct namebuf *np;
        register struct databuf *dp, *nsdp;
        register struct qserv *qs;
        register int n, i;
        struct hashbuf *tmphtp;
        char *dname, *fname;
        int oldn, naddr, class, found_arr;
        time_t curtime;
        int qcomp();

#ifdef DEBUG
        if (debug >= 3)
                fprintf(ddt,"nslookup(nsp=x%x,qp=x%x)\n",nsp,qp);
#endif

        naddr = n = qp->q_naddr;
        curtime = (u_long) tt.tv_sec;
        while ((nsdp = *nsp++) != NULL) {
                class = nsdp->d_class;
                dname = nsdp->d_data;
#ifdef DEBUG
                if (debug >= 3)
                        fprintf(ddt,"nslookup: NS %s c%d t%d (x%x)\n",
                                dname, class, nsdp->d_type, nsdp->d_flags);
#endif
                /* don't put in people we have tried */
                for (i = 0; i < qp->q_nusedns; i++)
                        if (qp->q_usedns[i] == nsdp) {
#ifdef DEBUG
                                if (debug >= 2)
fprintf(ddt, "skipping used NS w/name %s\n", nsdp->d_data);
#endif DEBUG
                                goto skipserver;
                        }

                tmphtp = ((nsdp->d_flags & DB_F_HINT) ? fcachetab : hashtab);
                np = nlookup(dname, &tmphtp, &fname, 1);
                if (np == NULL || fname != dname) {
#ifdef DEBUG
                        if (debug >= 3)
                            fprintf(ddt,"%s: not found %s %x\n",dname,fname,np);
#endif
                        continue;
                }
                found_arr = 0;
                oldn = n;
                /* look for name server addresses */
                for (dp = np->n_data; dp != NULL; dp = dp->d_next) {
                        if (dp->d_type != T_A || dp->d_class != class)
                                continue;
                        /*
                         * Don't use records that may become invalid to
                         * reference later when we do the rtt computation.
                         * Never delete our safety-belt information!
                         */
                        if ((dp->d_zone == 0) &&
                            (dp->d_ttl < (curtime+900)) &&
                            !(dp->d_flags & DB_F_HINT) )
                        {
#ifdef DEBUG
                                if (debug >= 3)
                                        fprintf(ddt,"nslookup: stale entry '%s'\n",
                                            np->n_dname);
#endif
                                /* Cache invalidate the NS RR's */
                                if (dp->d_ttl < curtime)
                                        delete_all(np, class, T_A);
                                n = oldn;
                                break;
                        }

                        found_arr++;
                        /* don't put in duplicates */
                        qs = qp->q_addr;
                        for (i = 0; i < n; i++, qs++)
                                if (bcmp((char *)&qs->ns_addr.sin_addr,
                                    dp->d_data, sizeof(struct in_addr)) == 0)
                                        goto skipaddr;
                        qs->ns_addr.sin_family = AF_INET;
                        qs->ns_addr.sin_port = (u_short)ns_port;
                        qs->ns_addr.sin_addr =
                                    *(struct in_addr *)dp->d_data;
                        qs->ns = nsdp;
                        qs->nsdata = dp;
                        qp->q_addr[n].nretry = 0;
                        n++;
                        if (n >= NSMAX)
                                goto out;
        skipaddr:       ;
                }
#ifdef DEBUG
                if (debug >= 3)
                        fprintf(ddt,"nslookup: %d ns addrs\n", n);
#endif
                if (found_arr == 0 && qp->q_system == 0)
                        (void) sysquery(dname, class, T_A);
skipserver:     ;
        }
out:
#ifdef DEBUG
        if (debug >= 3)
                fprintf(ddt,"nslookup: %d ns addrs total\n", n);
#endif
        qp->q_naddr = n;
        if (n > 1)
                qsort((char *)qp->q_addr, n, sizeof(struct qserv), qcomp);
        return (n - naddr);
}

qcomp(qs1, qs2)
        struct qserv *qs1, *qs2;
{

        return (qs1->nsdata->d_nstime - qs2->nsdata->d_nstime);
}

/*
 * Arrange that forwarded query (qp) is retried after t seconds.
 */
schedretry(qp, t)
        struct qinfo *qp;
        time_t t;
{
        register struct qinfo *qp1, *qp2;

#ifdef DEBUG
        if (debug > 3) {
                fprintf(ddt,"schedretry(%#x, %dsec)\n", qp, t);
                if (qp->q_time)
                   fprintf(ddt,"WARNING: schedretry(%x,%d) q_time already %d\n", qp->q_time);
        }
#endif
        t += (u_long) tt.tv_sec;
        qp->q_time = t;

        if ((qp1 = retryqp) == NULL) {
                retryqp = qp;
                qp->q_next = NULL;
                return;
        }
        while ((qp2 = qp1->q_next) != NULL && qp2->q_time < t)
                qp1 = qp2;
        qp1->q_next = qp;
        qp->q_next = qp2;
}

/*
 * Unsched is called to remove a forwarded query entry.
 */
unsched(qp)
        struct qinfo *qp;
{
        register struct qinfo *np;

#ifdef DEBUG
        if (debug > 3) {
                fprintf(ddt,"unsched(%#x, %d )\n", qp, ntohs(qp->q_id));
        }
#endif
        if( retryqp == qp )  {
                retryqp = qp->q_next;
        } else {
                for( np=retryqp; np->q_next != QINFO_NULL; np = np->q_next ) {
                        if( np->q_next != qp)
                                continue;
                        np->q_next = qp->q_next;        /* dequeue */
                        break;
                }
        }
        qp->q_next = QINFO_NULL;                /* sanity check */
        qp->q_time = 0;
}

/*
 * Retry is called to retransmit query 'qp'.
 */
retry(qp)
        register struct qinfo *qp;
{
        register int n;
        register HEADER *hp;

#ifdef DEBUG
        if (debug > 3)
                fprintf(ddt,"retry(x%x) id=%d\n", qp, ntohs(qp->q_id));
#endif
        if((HEADER *)qp->q_msg == NULL) {               /*** XXX ***/
                qremove(qp);
                return;
        }                                               /*** XXX ***/

        /* try next address */
        n = qp->q_curaddr;
        if (qp->q_fwd) {
                qp->q_fwd = qp->q_fwd->next;
                if (qp->q_fwd)
                        goto found;
                /* out of forwarders, try direct queries */
        } else
                ++qp->q_addr[n].nretry;
        if (!forward_only) {
                do {
                        if (++n >= qp->q_naddr)
                                n = 0;
                        if (qp->q_addr[n].nretry < MAXRETRY)
                                goto found;
                } while (n != qp->q_curaddr);
        }
        /*
         * Give up. Can't reach destination.
         */
        hp = (HEADER *)(qp->q_cmsg ? qp->q_cmsg : qp->q_msg);
        if (qp->q_system == PRIMING_CACHE) {
                /* Can't give up priming */
                unsched(qp);
                schedretry(qp, (time_t)60*60);  /* 1 hour */
                hp->rcode = NOERROR;    /* Lets be safe, reset the query */
                hp->qr = hp->aa = 0;
                qp->q_fwd = fwdtab;
                for (n = 0; n < qp->q_naddr; n++)
                        qp->q_addr[n].nretry = 0;
                return;
        }
#ifdef DEBUG
        if (debug >= 5)
                fprintf(ddt,"give up\n");
#endif
        n = ((HEADER *)qp->q_cmsg ? qp->q_cmsglen : qp->q_msglen);
        hp->id = qp->q_id;
        hp->qr = 1;
        hp->ra = 1;
        hp->rd = 1;
        hp->rcode = SERVFAIL;
#ifdef DEBUG
        if (debug >= 10)
                fp_query(qp->q_msg, ddt);
#endif
        if (send_msg((char *)hp, n, qp)) {
#ifdef DEBUG
                if (debug)
                        fprintf(ddt,"gave up retry(x%x) nsid=%d id=%d\n",
                                qp, ntohs(qp->q_nsid), ntohs(qp->q_id));
#endif
        }
        qremove(qp);
        return;

found:
        if (qp->q_fwd == 0 && qp->q_addr[n].nretry == 0)
                qp->q_addr[n].stime = tt;
        qp->q_curaddr = n;
        hp = (HEADER *)qp->q_msg;
        hp->rd = (qp->q_fwd ? 1 : 0);
#ifdef DEBUG
        if (debug)
                fprintf(ddt,"%s(addr=%d n=%d) -> %s %d (%d) nsid=%d id=%d %dms\n",
                        (qp->q_fwd ? "reforw" : "resend"),
                        n, qp->q_addr[n].nretry,
                        inet_ntoa(Q_NEXTADDR(qp,n)->sin_addr),
                        ds, ntohs(Q_NEXTADDR(qp,n)->sin_port),
                        ntohs(qp->q_nsid), ntohs(qp->q_id),
                        qp->q_addr[n].nsdata->d_nstime);
        if ( debug >= 10)
                fp_query(qp->q_msg, ddt);
#endif
        /* NOSTRICT */
        if (sendto(ds, qp->q_msg, qp->q_msglen, 0,
            (struct sockaddr *)Q_NEXTADDR(qp,n),
            sizeof(struct sockaddr_in)) < 0){
#ifdef DEBUG
                if (debug > 3)
                        fprintf(ddt,"error resending msg errno=%d\n",errno);
#endif
        }
        hp->rd = 0;     /* leave set to 0 for dup detection */
#ifdef STATS
        stats[S_OUTPKTS].cnt++;
#endif
        unsched(qp);
        schedretry(qp, qp->q_fwd ? (2*RETRYBASE) : retrytime(qp));
}

/*
 * Compute retry time for the next server for a query.
 * Use a minimum time of RETRYBASE (4 sec.) or twice the estimated
 * service time; * back off exponentially on retries, but place a 45-sec.
 * ceiling on retry times for now.  (This is because we don't hold a reference
 * on servers or their addresses, and we have to finish before they time out.)
 */
time_t
retrytime(qp)
register struct qinfo *qp;
{
        time_t t;
        struct qserv *ns = &qp->q_addr[qp->q_curaddr];

#ifdef DEBUG
        if (debug > 3)
                fprintf(ddt,"retrytime: nstime %dms.\n",
                    ns->nsdata->d_nstime / 1000);
#endif
        t = (time_t) MAX(RETRYBASE, 2 * ns->nsdata->d_nstime / 1000);
        t <<= ns->nretry;
        t = MIN(t, 45);                 /* max. retry timeout for now */
#ifdef notdef
        if (qp->q_system)
                return ((2 * t) + 5);   /* system queries can wait. */
#endif
        return (t);
}

qflush()
{
        while (qhead)
                qremove(qhead);
        qhead = QINFO_NULL;
}

qremove(qp)
register struct qinfo *qp;
{
#ifdef DEBUG
        if(debug > 3)
                fprintf(ddt,"qremove(x%x)\n", qp);
#endif
        unsched(qp);                    /* get off queue first */
        qfree(qp);
}

struct qinfo *
qfindid(id)
register u_short id;
{
        register struct qinfo *qp;

#ifdef DEBUG
        if(debug > 3)
                fprintf(ddt,"qfindid(%d)\n", ntohs(id));
#endif
        for (qp = qhead; qp!=QINFO_NULL; qp = qp->q_link) {
                if (qp->q_nsid == id)
                        return(qp);
        }
#ifdef DEBUG
        if (debug >= 5)
                fprintf(ddt,"qp not found\n");
#endif
        return(NULL);
}

struct qinfo *
qnew()
{
        register struct qinfo *qp;

        if ((qp = (struct qinfo *)calloc(1, sizeof(struct qinfo))) == NULL) {
#ifdef DEBUG
                if (debug >= 5)
                        fprintf(ddt,"qnew: calloc error\n");
#endif
                syslog(LOG_ERR, "forw: %m");
                exit(12);
        }
#ifdef DEBUG
        if (debug >= 5)
                fprintf(ddt,"qnew(x%x)\n", qp);
#endif
        qp->q_link = qhead;
        qhead = qp;
        return( qp );
}

qfree(qp)
struct qinfo *qp;
{
        register struct qinfo *np;

#ifdef DEBUG
        if(debug > 3)
                fprintf(ddt,"qfree( x%x )\n", qp);
        if(debug && qp->q_next)
                fprintf(ddt,"WARNING:  qfree of linked ptr x%x\n", qp);
#endif
        if (qp->q_msg)
                free(qp->q_msg);
        if (qp->q_cmsg)
                free(qp->q_cmsg);
        if( qhead == qp )  {
                qhead = qp->q_link;
        } else {
                for( np=qhead; np->q_link != QINFO_NULL; np = np->q_link )  {
                        if( np->q_link != qp )  continue;
                        np->q_link = qp->q_link;        /* dequeue */
                        break;
                }
        }
        (void)free((char *)qp);
}