Logo Search packages:      
Sourcecode: dcc version File versions  Download package

clnt_send.c

/* Distributed Checksum Clearinghouse
 *
 * send a request from client to server
 *
 * Copyright (c) 2005 by Rhyolite Software
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND RHYOLITE SOFTWARE DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL RHYOLITE SOFTWARE
 * BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
 * ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 *
 * Rhyolite Software DCC 1.2.74-1.108 $Revision$
 */

#include "dcc_clnt.h"
#ifdef USE_POLL
#include <poll.h>
#endif
#ifdef HAVE_ARPA_NAMESER_H
#include <arpa/nameser.h>
#endif
#ifdef HAVE_RESOLV_H
#include <resolv.h>
#endif

DCC_CLNT_INFO *dcc_clnt_info;       /* memory mapped shared data */
u_char dcc_all_srvrs = 0;           /* try to contact all servers */

/* #define CLNT_LOSSES */
#ifdef CLNT_LOSSES
static u_int clnt_losses;
#endif

#define DCC_SRVRS_MOD       59
#define DCC_SRVRS_MOD_IPV4  128

u_char dcc_clnt_debug;
u_int dcc_min_delay_us = DCC_INIT_RTT;  /* override minimum RTT */
int dcc_debug_ttl;


#define AGE_AVG(_v,_n,_a,_b) ((_v) = ((_v)*_a + (_n)*_b + (_a+_b)/2)/(_a+_b))
#define FAST_RTT_SECS   (15*60)


char dcc_clnt_hostname[MAXHOSTNAMELEN];
static u_int32_t dcc_clnt_hid;            /* our DCC host-ID */


/* Each client knows about one or more servers, lest the current server
 * crash.  To ensure that counts of spam accumulate as quickly as possible,
 * all of the processes on a client try to use a single server.  The
 * closest (or fastest) server is preferred.  It is desirable for the
 * servers to convert the hostnames of the servers to IP addresses
 * frequently enough to track changes in address records, but not so
 * often that a lot of time is wasted on the DNS.
 *
 * All of that implies that independent processes on the client need to
 * cooperate in measuring the round trip time to the servers and maintaining
 * their IP addresses.  On UNIX systems, this is accomplished with mmap()
 * and a well known file.
 */



/* the contexts must be locked to read or change these values */
static int info_fd = -1;
#ifdef DCC_WIN32
HANDLE info_map = INVALID_HANDLE_VALUE;
#endif
DCC_PATH dcc_info_nm;
static u_char info_locked;          /* kludge to prevent double-tripping */
static u_char resolve_locked;       /* ditto */

/* Some systems have a broken fcntl().  Examples include Solaris over NFS.
 * Their bug is that you can lock entire files, but not ranges within a file. */
#ifdef DCC_BAD_FCNTL_LOCKS
#define INFO_LOCK_NUM       DCC_LOCK_ALL_FILE
#define RESOLVE_LOCK_NUM    DCC_LOCK_ALL_FILE
#else
#define INFO_LOCK_NUM       0
#define RESOLVE_LOCK_NUM    1
#endif


/* The DCC client uses two levels of locking.  The first is for data
 * common to one process and shared among threads in that process,
 * and the second is among processes sharing the mmap()'ed information.
 * Threads are used in long lived processes such as the sendmail milter
 * filter server.  Multiple processes are needed to serve other
 * local clients of the DCC, such as procmail jobs */


#define AP2CLASS(ap) DCC_GREY2CLASS(ap >= dcc_clnt_info->grey.addrs)


static u_char                       /* 1=the addresses are equal */
dcc_cmp_ap2su(const DCC_SRVR_ADDR *ap, const DCC_SOCKU *su)
{
      struct in_addr ap_addr4, su_addr4;

      if (su->sa.sa_family != ap->family)
            return 0;

      if (su->sa.sa_family == AF_INET) {
            return (su->ipv4.sin_addr.s_addr == ap->ip.v4.s_addr
                  && su->ipv4.sin_port == ap->port);
      }

      if (su->ipv6.sin6_port != ap->port)
            return 0;

      if (dcc_ipv6toipv4(&ap_addr4, &ap->ip.v6)
          && dcc_ipv6toipv4(&su_addr4, &su->ipv6.sin6_addr))
            return ap_addr4.s_addr == su_addr4.s_addr;

      return !memcmp(&su->ipv6.sin6_addr, &ap->ip.v6,
                   sizeof(su->ipv6.sin6_addr));
}



const char *
dcc_ap2str(const DCC_SRVR_ADDR *ap)
{
      DCC_SOCKU su;

      dcc_mk_su(&su, ap->family, &ap->ip, ap->port);
      return dcc_su2str(&su);
}



const char *
dcc_ap2str_opt(const DCC_SRVR_ADDR *ap,
             u_int16_t def_port,
             char port_str)         /* '\0' or '-' */
{
      DCC_SOCKU su;

      memset(&su, 0, sizeof(su));
      if ((su.sa.sa_family = ap->family) == AF_INET) {
            su.ipv4.sin_addr.s_addr = ap->ip.v4.s_addr;
            su.ipv4.sin_port = ap->port;
      } else {
            memcpy(&su.ipv6.sin6_addr, &ap->ip.v6,
                   sizeof(su.ipv6.sin6_addr));
            su.ipv6.sin6_port = ap->port;
      }
      return dcc_su2str_opt(&su, def_port, port_str);
}



static const char *
addr2str(char *buf, u_int buf_len, DCC_SRVR_CLASS *class,
       int addrs_gen, const DCC_SRVR_ADDR *ap, const DCC_SOCKU *sup)
{
      if (class->gen == addrs_gen) {
            snprintf(buf, buf_len, "%s (%s)",
                   class->nms[ap->nm_inx].hostname,
                   sup ? dcc_su2str(sup) : dcc_ap2str(ap));
      } else if (sup) {
            snprintf(buf, buf_len, "%s",
                   dcc_su2str(sup));
      } else {
            snprintf(buf, buf_len, "DCC server");
      }
      return buf;
}



static const char *
addr_inx2str(char *buf, u_int buf_len, DCC_SRVR_CLASS *class,
           int addrs_gen, int addr_inx, const DCC_SOCKU *sup)
{
      return addr2str(buf, buf_len, class,
                  addrs_gen, &class->addrs[addr_inx], sup);
}


static void
trace_perf(const char *msg, const DCC_SRVR_ADDR *ap)
{
      DCC_SRVR_CLASS *class;
      char abuf[60];
      char rbuf[30];

      class = AP2CLASS(ap);
      if (class->nms[ap->nm_inx].rtt_adj == 0) {
            rbuf[0] = 0;
      } else {
            snprintf(rbuf, sizeof(rbuf), "%+d",
                   class->nms[ap->nm_inx].rtt_adj/1000);
      }

      if (ap->rtt == DCC_RTT_BAD) {
            dcc_trace_msg("%s %s with unknown RTT",
                        msg, addr2str(abuf, sizeof(abuf), class,
                                  class->gen, ap, 0));
      } else if (ap->total_xmits == 0) {
            dcc_trace_msg("%s %s with %.2f%s ms RTT, %d ms queue wait",
                        msg, addr2str(abuf, sizeof(abuf), class,
                                  class->gen, ap, 0),
                        ap->rtt/1000.0, rbuf,
                        ap->srvr_wait/1000);
      } else {
            dcc_trace_msg("%s %s with %.0f%% of %d requests answered,"
                        " %.2f%s ms RTT, %d ms queue wait",
                        msg, addr2str(abuf, sizeof(abuf), class,
                                  class->gen, ap, 0),
                        (ap->total_resps*100.0)/ap->total_xmits,
                        ap->total_xmits,
                        ap->rtt/1000.0, rbuf,
                        ap->srvr_wait/1000);
      }
}



/* If the socket isn't always connected, it can receive
 * datagrams from almost everywhere (for example, a DNS
 * datagram could leak-in if the local port range is small
 * and the local port has been recently doing DNS queries
 * in its previous life).
 *
 * If the socket is connected, it can still receive
 * datagrams not belonging to the connection per se. This
 * will happen if it has been disconnected recently and there
 * was pending data in the socket's queue.
 *
 * Before complaining, check that this datagram seems to be a response
 * to something we sent */
static void PATTRIB(3,4)
trace_bad_packet(const DCC_XLOG *xlog, const DCC_SOCKU *su, const char *p, ...)
{
      const DCC_XLOG_ENTRY *xloge;
      va_list args;

      if (!dcc_clnt_debug) {
            for (xloge = xlog->base; ; ++xloge) {
                  /* forget the error message if not from a DCC server */
                  if (xloge >= xlog->next)
                        return;

                  /* Don't check this server entry if we haven't
                   * transmitted anything to this host. */
                  if (xloge->op_nums.t == DCC_OP_NUMS_NULL)
                        continue;

                  if (!memcmp(su, &xloge->su, sizeof(*su)))
                        break;
            }
      }

      va_start(args, p);
      dcc_verror_msg(p, args);
      va_end(args);
}



#define FOREVER_SECS    1000
#define FOREVER_USECS   (FOREVER_SECS*DCC_USECS)
static long
tvs2us(struct timeval *tv1, struct timeval *tv2)
{
      long us;

      /* prevent overflow */
      us = tv1->tv_sec - tv2->tv_sec;
      if (us <= -FOREVER_SECS)
            return -FOREVER_USECS;
      if (us >= FOREVER_SECS)
            return FOREVER_USECS;
      us = us*DCC_USECS + (tv1->tv_usec - tv2->tv_usec);
      return us;
}



/* Compute the delay before the next retransmission
 *      It always should be long enough for the DCC server to do some disk
 *    operations even if the server and network have usually been faster. */
#define MIN_RETRANS_TIME(rtt,xmit_num) ((rtt)<<(xmit_num))
static int
dcc_retrans_time(u_int rtt, u_int xmit_num)
{
      if (rtt < DCC_INIT_RTT)
            rtt = DCC_INIT_RTT;
      rtt <<= xmit_num;
      if (rtt > DCC_MAX_RTT)
            rtt = DCC_MAX_RTT;
      if (rtt < dcc_min_delay_us)
            rtt = dcc_min_delay_us;
      return rtt;
}



static void
get_start_time(DCC_CLNT_CTXT *ctxt)
{
      gettimeofday(&ctxt->start, 0);
      ctxt->now = ctxt->start;
      ctxt->now_us = 0;
}



static u_char                       /* 1=ok, 0=time jumped */
get_now(DCC_EMSG emsg, DCC_CLNT_CTXT *ctxt)
{
      gettimeofday(&ctxt->now, 0);
      ctxt->now_us = tvs2us(&ctxt->now, &ctxt->start);
      if (ctxt->now_us >= 0 && ctxt->now_us < FOREVER_USECS)
            return 1;

      /* ignore tiny reverse time jumps on some systems such as BSD/OS 4.1 */
      if (ctxt->now_us < 0
          && ctxt->now_us > -1000) {
            ctxt->now = ctxt->start;
            ctxt->now_us = 0;
            return 1;
      }

      dcc_pemsg(EX_OSERR, emsg,
              "clock changed an impossible %.6f seconds",
              ctxt->now_us/(1000.0*1000.0));
      return 0;
}



/* All servers are broken, so make a note to not try for a while.
 *      The contexts and the mapped information must be locked */
static void
fail_more(DCC_SRVR_CLASS *class)
{
      if (++class->fail_exp > DCC_MAX_FAIL_EXP)
            class->fail_exp = DCC_MAX_FAIL_EXP;
      class->fail_time = (time(0) + (DCC_INIT_FAIL_SECS << class->fail_exp));
}



static u_char                       /* 0=failing */
ck_fail_time(DCC_EMSG emsg, DCC_CLNT_CTXT *ctxt, DCC_SRVR_CLASS *class)
{
      int dt;

      if (class->fail_exp == 0)
            return 1;

      dt = class->fail_time - ctxt->now.tv_sec;
      if (dt > 0 && dt <= DCC_MAX_FAIL_SECS) {
            dcc_pemsg(EX_IOERR, emsg,
                    "continue not asking %s %d seconds after failure",
                    DCC_IS_GREY_STR(class), dt);
            return 0;
      }

      class->fail_exp = 0;
      return 1;
}



/* Unlock the shared memory.
 *      The contexts must be locked */
u_char                              /* 0=failed 1=ok */
dcc_info_unlock(DCC_EMSG emsg)
{
      if (!info_locked)
            return 1;

      info_locked = 0;
#if INFO_LOCK_NUM==DCC_LOCK_ALL_FILE
      if (!resolve_locked) {
#endif
            if (!dcc_unlock_fd(emsg, info_fd, INFO_LOCK_NUM,
                           "DCC map ", dcc_info_nm))
                  return 0;
#if RESOLVE_LOCK_NUM==DCC_LOCK_ALL_FILE
      }
#endif
      return 1;
}



/* Lock the shared memory so we can read and perhaps change it
 *      The contexts must be locked */
u_char                              /* 0=failed, 1=ok */
dcc_info_lock(DCC_EMSG emsg)
{
      if (info_locked)
            return 1;

#if INFO_LOCK_NUM==DCC_LOCK_ALL_FILE
      if (!resolve_locked) {
#endif
            if (!dcc_exlock_fd(emsg, info_fd, INFO_LOCK_NUM,
                           "DCC map ", dcc_info_nm))
                  return 0;
#if INFO_LOCK_NUM==DCC_LOCK_ALL_FILE
      }
#endif
      info_locked = 1;
      return 1;
}



/* stop working on server IP addresses
 *      The contexts must be locked, and remain locked on exit. */
u_char                              /* 0=failed, 1=ok */
dcc_resolve_unlock(DCC_EMSG emsg)
{
      if (!resolve_locked) {
            if (dcc_clnt_debug)
                  dcc_trace_msg("unlocking unlocked resolve lock");
      } else {
            resolve_locked = 0;

#if RESOLVE_LOCK_NUM==DCC_LOCK_ALL_FILE
            if (!info_locked) {
#endif
                  if (!dcc_unlock_fd(emsg, info_fd, RESOLVE_LOCK_NUM,
                                 "resolve lock ", dcc_info_nm)) {
                        dcc_resolve_mutex_unlock();
                        return 0;
                  }
#if RESOLVE_LOCK_NUM==DCC_LOCK_ALL_FILE
            }
#endif
      }
      dcc_resolve_mutex_unlock();

      return 1;
}



/* Lock resolving server hostnames
 *      The contexts be locked, and the shared information may be locked.
 *      All three are locked on success.
 *      The contexts remain locked but the others are unlocked on failure. */
u_char                              /* 0=failed, 1=ok */
dcc_resolve_lock(DCC_EMSG emsg)
{
      /* unlock the shared data and the contexts while we wait for the
       * dual mutex & file lock to resolve server hostnames */
      if (!dcc_info_unlock(emsg))
            return 0;
      dcc_ctxts_unlock();

      if (!dcc_resolve_mutex_lock(0)) {
            dcc_ctxts_lock();
            return 0;
      }
      if (resolve_locked)
            dcc_logbad(EX_SOFTWARE, "locking locked resolve lock");
      if (!dcc_exlock_fd(emsg, info_fd, RESOLVE_LOCK_NUM,
                     "resolve lock ", dcc_info_nm)) {
            dcc_resolve_mutex_unlock();
            dcc_ctxts_lock();
            return 0;
      }
      resolve_locked = 1;

      dcc_ctxts_lock();
      if (!dcc_info_lock(emsg)) {
            dcc_resolve_unlock(0);
            return 0;
      }
      return 1;
}



/* Unlock and un-map the shared info.
 *      The contexts must be locked */
u_char                              /* 0=something wrong, 1=all over */
dcc_unmap_info(DCC_EMSG emsg)
{
      u_char result = 1;

      if (!dcc_clnt_info)
            return result;

      if (!dcc_info_unlock(emsg))
            result = 0;

#ifdef DCC_WIN32
      win32_unmap(&info_map, dcc_clnt_info, dcc_info_nm);
#else
      if (0 > munmap((void *)dcc_clnt_info, sizeof(*dcc_clnt_info))) {
            dcc_pemsg(EX_OSERR, emsg, "munmap(%s): %s",
                    dcc_info_nm, ERROR_STR());
            result = 0;
      }
#endif
      dcc_clnt_info = 0;

      if (0 > close(info_fd)) {
            if (emsg && *emsg == '\0')
                  dcc_pemsg(EX_IOERR, emsg, "close(%s): %s",
                          dcc_info_nm, ERROR_STR());
            result = 0;
      }
      info_fd = -1;

      return result;
}



/* discover our host ID if we do not already know it */
static u_char
get_clnt_hid(DCC_EMSG emsg)
{
      int i;

      if (dcc_clnt_hid)
            return 1;

#ifdef HAVE_GETHOSTID
      dcc_clnt_hid = gethostid();
#endif
      if (0 > gethostname(dcc_clnt_hostname,
                      sizeof(dcc_clnt_hostname)-1)) {
            dcc_pemsg(EX_NOHOST, emsg, "gethostname(): %s", ERROR_STR());
            return 0;
      }
      if (dcc_clnt_hostname[0] == '\0') {
            dcc_pemsg(EX_NOHOST, emsg, "null hostname from gethostname()");
            return 0;
      }
      for (i = 0; i < ISZ(dcc_clnt_hostname); ++i) {
            if (!dcc_clnt_hostname[i])
                  break;
            dcc_clnt_hid += dcc_clnt_hostname[i]*i;
      }
      return 1;
}



/* write a new DCC map file */
u_char
dcc_create_map(DCC_EMSG emsg, const DCC_PATH map_nm0, int *pfd,
             const DCC_SRVR_NM *dcc_nms, int dcc_nms_len,
             const DCC_SRVR_NM *grey_nms, int grey_nms_len,
             u_char flags)
{
      static int op_nums_r;
      DCC_CLNT_INFO info_clear;
      int fd;
      u_char created;
      DCC_PATH map_nm;
      int i;

      if (pfd && (fd = *pfd) >= 0) {
            created = 0;
      } else {
            dcc_fnm2path(map_nm, map_nm0);
            fd = open(map_nm, O_RDWR|O_CREAT|O_EXCL, 0600);
            if (fd < 0) {
                  dcc_pemsg(EX_SOFTWARE, emsg, "open(%s): %s",
                          map_nm, ERROR_STR());
                  return 0;
            }
            created = 1;
      }

      memset(&info_clear, 0, sizeof(info_clear));
      strcpy(info_clear.version, DCC_MAP_INFO_VERSION);

      if (dcc_nms_len != 0) {
            if (dcc_nms_len > DCC_MAX_SRVR_NMS)
                  dcc_nms_len = DCC_MAX_SRVR_NMS;
            memcpy(info_clear.dcc.nms, dcc_nms,
                   sizeof(info_clear.dcc.nms[0])*dcc_nms_len);
      }
      info_clear.dcc.act_inx = -1;

      if (grey_nms_len != 0) {
            if (grey_nms_len > DCC_MAX_SRVR_NMS)
                  grey_nms_len = DCC_MAX_SRVR_NMS;
            memcpy(info_clear.grey.nms, grey_nms,
                   sizeof(info_clear.grey.nms[0])*grey_nms_len);
      }
      info_clear.grey.act_inx = -1;

      info_clear.flags = flags;
      if (!get_clnt_hid(emsg)) {
            close(fd);
            if (pfd)
                  *pfd = -1;
            if (created)
                  unlink(map_nm);
            return 0;
      }
      info_clear.residue = dcc_clnt_hid % DCC_SRVRS_MOD;
      if (info_clear.residue == 0)
            info_clear.residue = 1;

      /* ensure that we have a new report # even if we are repeatedly
       * recreating a temporary map file */
      if (dcc_clnt_info)
            op_nums_r += dcc_clnt_info->proto_hdr.op_nums.r;
      info_clear.proto_hdr.op_nums.r = ++op_nums_r;

      i = write(fd, &info_clear, sizeof(info_clear));
      if (i != ISZ(info_clear)) {
            if (i < 0)
                  dcc_pemsg(EX_SOFTWARE, emsg, "write(%s): %s",
                          map_nm, ERROR_STR());
            else
                  dcc_pemsg(EX_SOFTWARE, emsg,
                          "write(%s)=%d instead of %d",
                          map_nm, i, ISZ(info_clear));
            close(fd);
            if (pfd)
                  *pfd = -1;
            if (created)
                  unlink(map_nm);
            return 0;
      }

      if (created) {
            if (pfd)
                  *pfd = fd;
            else
                  close(fd);
      }
      return 1;
}



#ifdef DCC_MAP_INFO_VERSION_5
static int                    /* -1=error, 0=wrong version, 1=done */
map_convert_start(DCC_EMSG emsg, void *old_info, int old_info_size,
              const char *old_magic, int old_magic_size,
              DCC_PATH new_info_nm)
{
      int i;

      /* only one process or thread can fix the file so wait for
       * exclusive access to the file */
      if (!dcc_info_lock(emsg))
            return -1;

      i = read(info_fd, old_info, old_info_size);
      if (i != old_info_size) {
            if (i < 0) {
                  dcc_pemsg(EX_IOERR, emsg, "read(%s): %s",
                          dcc_info_nm, ERROR_STR());
            } else {
                  dcc_pemsg(EX_IOERR, emsg, "read(%s)=%d instead of %d",
                          dcc_info_nm, i, old_info_size);
            }
            return -1;
      }

      if (-1 == lseek(info_fd, SEEK_SET, 0)) {
            dcc_pemsg(EX_IOERR, emsg, "lseek(%s): %s",
                    dcc_info_nm, ERROR_STR());
            return -1;
      }

      if (strncmp(old_info, old_magic, old_magic_size)) {
            if (!dcc_info_unlock(emsg))
                  return -1;
            return 0;
      }

      dcc_fnm2path(new_info_nm, dcc_info_nm);
      if (strlen(new_info_nm) >= sizeof(DCC_PATH) - sizeof("-new")) {
            dcc_pemsg(EX_IOERR, emsg, "too long map name \"%s\"",
                    dcc_info_nm);
            return -1;
      }
      strcat(new_info_nm, "-new");
      unlink(new_info_nm);
      return 1;
}



static int                    /* -1=error, 1=done */
map_convert_fin(DCC_EMSG emsg,
            DCC_PATH new_info_nm, int new_fd, struct stat *old_sb)
{
      /* if we are running as root,
       * don't change the owner of the file */
      if (getuid() == 0
          && 0 > fchown(new_fd, old_sb->st_uid, old_sb->st_gid)) {
            dcc_pemsg(EX_IOERR, emsg, "chown(%s,%d,%d): %s",
                    new_info_nm, (int)old_sb->st_uid, (int)old_sb->st_gid,
                    ERROR_STR());
            unlink(new_info_nm);
            close(new_fd);
            return -1;
      }

      if (0 > rename(new_info_nm, dcc_info_nm)) {
            dcc_pemsg(EX_IOERR, emsg, "rename(%s, %s): %s",
                    new_info_nm, dcc_info_nm, ERROR_STR());
            unlink(new_info_nm);
            close(new_fd);
            return -1;
      }

      close(new_fd);
      return 1;
}



/* Convert an old map file.
 *      The contexts must be locked on entry.
 *      The old file may be locked on exit */
static int                    /* -1=error, 0=wrong version, 1=done */
map_convert_v5(DCC_EMSG emsg, struct stat *old_sb)
{
      DCC_PATH new_info_nm;
      DCC_SRVR_NM new_nms[DCC_MAX_SRVR_NMS];
      DCC_V5_CLNT_INFO old_info;
      int new_fd;
      int i;

      if ((int)old_sb->st_size < ISZ(DCC_V5_CLNT_INFO))
            return 0;

      i = map_convert_start(emsg, &old_info, sizeof(DCC_V5_CLNT_INFO),
                        DCC_MAP_INFO_VERSION_5, sizeof(old_info.version),
                        new_info_nm);
      if (i <= 0)
            return i;

      memset(&new_nms, 0, sizeof(new_nms));
      for (i = 0; i < DIM(new_nms); ++i) {
            new_nms[i].clnt_id = old_info.nms[i].clnt_id;
            new_nms[i].port = old_info.nms[i].port;
            strcpy(new_nms[i].hostname, old_info.nms[i].hostname);
            memcpy(new_nms[i].passwd, old_info.nms[i].passwd,
                   sizeof(new_nms[i].passwd));
            new_nms[i].rtt_adj = old_info.nms[i].rtt_adj*10*1000;
      }
      new_fd = INVALID_HANDLE_VALUE;
      if (!dcc_create_map(emsg, new_info_nm, &new_fd,
                      new_nms, DIM(new_nms), 0, 0, old_info.flags))
            return -1;

      return map_convert_fin(emsg, new_info_nm, new_fd, old_sb);
}



#endif /* DCC_MAP_INFO_VERSION_5 */
#ifdef DCC_MAP_INFO_VERSION_6
/* Convert an old map file.
 *      The contexts must be locked on entry.
 *      The old file may be locked on exit */
static u_char
map_convert_v6(DCC_EMSG emsg, struct stat *old_sb)
{
      DCC_PATH new_info_nm;
      DCC_SRVR_NM new_nms[DCC_MAX_SRVR_NMS];
      DCC_V6_CLNT_INFO old_info;
      int new_fd;
      int i;

      if ((int)old_sb->st_size < ISZ(DCC_V6_CLNT_INFO))
            return 0;

      i = map_convert_start(emsg, &old_info, sizeof(DCC_V6_CLNT_INFO),
                        DCC_MAP_INFO_VERSION_6, sizeof(old_info.version),
                        new_info_nm);
      if (i <= 0)
            return i;

      memset(&new_nms, 0, sizeof(new_nms));
      for (i = 0; i < DIM(new_nms); ++i) {
            new_nms[i].clnt_id = old_info.nms[i].clnt_id;
            new_nms[i].port = old_info.nms[i].port;
            strcpy(new_nms[i].hostname, old_info.nms[i].hostname);
            memcpy(new_nms[i].passwd, old_info.nms[i].passwd,
                   sizeof(new_nms[i].passwd));
            new_nms[i].rtt_adj = old_info.nms[i].rtt_adj;
      }
      new_fd = INVALID_HANDLE_VALUE;
      if (!dcc_create_map(emsg, new_info_nm, &new_fd,
                      new_nms, DIM(new_nms), 0, 0, old_info.flags))
            return -1;

      return map_convert_fin(emsg, new_info_nm, new_fd, old_sb);
}



#endif /* DCC_MAP_INFO_VERSION_6 */
#ifdef DCC_MAP_INFO_VERSION_7
/* Convert an old map file.
 *      The contexts must be locked on entry.
 *      The old file may be locked on exit */
static u_char
map_convert_v7(DCC_EMSG emsg, struct stat *old_sb)
{
      DCC_PATH new_info_nm;
      union {
          DCC_V7_IPV6_CLNT_INFO   v6;
          DCC_V7_NOIPV6_CLNT_INFO nov6;
      } old;
      int new_fd;
      int i;

      if (old_sb->st_size == sizeof(old.v6)) {
            i = map_convert_start(emsg, &old.v6, sizeof(old.v6),
                              DCC_MAP_INFO_VERSION_7,
                              sizeof(old.v6.version),
                              new_info_nm);
            if (i <= 0)
                  return i;

            new_fd = INVALID_HANDLE_VALUE;
            if (!dcc_create_map(emsg, new_info_nm, &new_fd,
                            old.v6.dcc.nms, DIM(old.v6.dcc.nms),
                            old.v6.grey.nms, DIM(old.v6.grey.nms),
                            old.v6.flags))
                  return -1;

      } else if (old_sb->st_size == sizeof(old.nov6)) {
            i = map_convert_start(emsg, &old.nov6, sizeof(old.nov6),
                              DCC_MAP_INFO_VERSION_7,
                              sizeof(old.nov6.version),
                              new_info_nm);
            if (i <= 0)
                  return i;

            new_fd = INVALID_HANDLE_VALUE;
            if (!dcc_create_map(emsg, new_info_nm, &new_fd,
                            old.nov6.dcc.nms, DIM(old.nov6.dcc.nms),
                            old.nov6.grey.nms, DIM(old.nov6.grey.nms),
                            old.nov6.flags))
                  return -1;

      } else {
            return 0;
      }

      return map_convert_fin(emsg, new_info_nm, new_fd, old_sb);
}



#endif /* DCC_MAP_INFO_VERSION_7 */
/* Ensure that the shared information is available, but do not lock it.
 *      The contexts must be locked
 *      SUID privileges are often released */
u_char                              /* 0=problem, 1=nop, 2=mapped */
dcc_map_info(DCC_EMSG emsg, const char *new_info_nm, int new_info_fd)
{
      struct stat sb;
#ifndef DCC_WIN32
      void *p;
#endif
      u_char result;

      /* work only if needed, but always check for corruption */
      result = 1;
      while ((new_info_nm && strcmp(new_info_nm, dcc_info_nm))
             || new_info_fd >= 0
             || !dcc_clnt_info) {
            result = 2;
            if (!dcc_unmap_info(emsg)) {
                  if (new_info_fd >= 0)
                        close(new_info_fd);
                  return 0;
            }

            if (new_info_nm) {
                  dcc_fnm2path(dcc_info_nm, new_info_nm);
                  /* don't change name if we convert the file */
                  new_info_nm = 0;
            }
            if (dcc_info_nm[0] == '\0') {
                  dcc_pemsg(EX_USAGE, emsg, "missing map file");
                  return 0;
            }

            if (new_info_fd >= 0) {
                  info_fd = new_info_fd;
                  new_info_fd = -1;
            } else {
                  info_fd = open(dcc_info_nm, O_RDWR, 0600);
#ifndef DCC_WIN32
                  if (info_fd < 0
                      && dcc_get_priv_home(dcc_info_nm)) {
                        info_fd = open(dcc_info_nm, O_RDWR, 0600);
                        dcc_rel_priv();
                  }
#endif
                  if (info_fd < 0) {
                        dcc_pemsg(EX_NOINPUT, emsg, "open(%s): %s",
                                dcc_info_nm, ERROR_STR());
                        return 0;
                  }
            }

            /* refuse to use the file if it is not private */
            if (!dcc_ck_private(emsg, &sb, dcc_info_nm, info_fd)) {
                  dcc_unmap_info(0);
                  return 0;
            }

            if ((int)sb.st_size != ISZ(*dcc_clnt_info)) {
#ifdef DCC_MAP_INFO_VERSION_7
                  int i;

#ifdef DCC_MAP_INFO_VERSION_6
                  i = map_convert_v5(emsg, &sb);
                  if (i < 0) {
                        dcc_unmap_info(0);
                        return 0;
                  }
                  /* unlock old file and open & lock new file */
                  if (i > 0)
                        continue;

                  i = map_convert_v6(emsg, &sb);
                  if (i < 0) {
                        dcc_unmap_info(0);
                        return 0;
                  }
                  /* unlock old file and open & lock new file */
                  if (i > 0)
                        continue;
#endif /* DCC_MAP_INFO_VERSION_6 */
                  i = map_convert_v7(emsg, &sb);
                  if (i < 0) {
                        dcc_unmap_info(0);
                        return 0;
                  }
                  /* unlock old file and open & lock new file */
                  if (i > 0)
                        continue;
#endif /* DCC_MAP_INFO_VERSION_7 */
                  dcc_pemsg(EX_DATAERR, emsg,
                          "%s is not the size of a DCC map file",
                          dcc_info_nm);
                  close(info_fd);
                  info_fd = -1;
                  return 0;
            }

#ifdef DCC_WIN32
            dcc_clnt_info= win32_map(emsg, &info_map, dcc_info_nm,
                               info_fd, sizeof(*dcc_clnt_info));
            if (!dcc_clnt_info) {
                  close(info_fd);
                  info_fd = -1;
                  return 0;
            }
#else
            p = mmap(0, sizeof(*dcc_clnt_info),
                   PROT_READ|PROT_WRITE, MAP_SHARED, info_fd, 0);
            if (p == MAP_FAILED) {
                  dcc_pemsg(EX_IOERR, emsg, "mmap(%s): %s",
                          dcc_info_nm, ERROR_STR());
                  close(info_fd);
                  info_fd = -1;
                  return 0;
            }
            dcc_clnt_info = p;
#endif
      }

      if (strncmp(dcc_clnt_info->version, DCC_MAP_INFO_VERSION,
                sizeof(dcc_clnt_info->version))) {
            dcc_pemsg(EX_DATAERR, emsg, "unrecognized data in %s",
                    dcc_info_nm);
            dcc_unmap_info(0);
            return 0;
      }

      if (!get_clnt_hid(emsg)) {
            dcc_unmap_info(0);
            return 0;
      }

      if (result > 1)
            dcc_clnt_info->proto_hdr.op_nums.h = dcc_clnt_hid;

      return result;
}



/* SUID privileges are often released */
u_char                              /* 0=something wrong, 1=mapped */
dcc_map_lock_info(DCC_EMSG emsg, const char *new_info_nm, int new_info_fd)
{
      return(0 < dcc_map_info(emsg, new_info_nm, new_info_fd)
             && dcc_info_lock(emsg));
}



/* The shared memory must be locked */
static inline void
dcc_force_pick(DCC_SRVR_CLASS *class)
{
      class->act_inx = -1;
      class->fail_exp = 0;
}



/* Resolving host names must be locked */
static void
dcc_force_resolve(DCC_SRVR_CLASS *class)
{
      dcc_force_pick(class);
      class->resolve = 0;
}



/* Resolving host names must be locked */
void
dcc_force_measure_rtt(DCC_SRVR_CLASS *class, u_char new_avg_thold_rtt)
{
      dcc_force_resolve(class);
      if (new_avg_thold_rtt)
            class->avg_thold_rtt = -DCC_RTT_BAD;
      class->measure = 0;
}



/* pick the best server
 *      The client information and the contexts must be exclusively locked.
 *      Assume there is at least one hostname. */
static u_char                       /* 0=have none, 1=same, 2=changed */
pick_srvr(DCC_EMSG emsg, DCC_SRVR_CLASS *class)
{
      const DCC_SRVR_ADDR *ap, *min_ap;
      int rtt;
      int min_rtt;                  /* smallest RTT   */
      int min2_rtt;                 /* second smallest RTT */
      u_int16_t old_act_inx;

      old_act_inx = class->act_inx;
      min2_rtt = min_rtt = DCC_RTT_BAD;
      min_ap = 0;
      for (ap = class->addrs; ap <= LAST(class->addrs); ++ap) {
            rtt = ap->rtt;
            if (rtt == DCC_RTT_BAD
                || ap->family == 0)
                  continue;
            rtt += class->nms[ap->nm_inx].rtt_adj;
            if (min_rtt > rtt) {
                  if (min2_rtt > min_rtt)
                        min2_rtt = min_rtt;
                  min_rtt = rtt;
                  min_ap = ap;
            } else if (min2_rtt > rtt) {
                  min2_rtt = rtt;
            }
      }

      /* we found a usable server */
      if (min_ap) {
            /* Compute the basic RTT to the server including a variance
             * of the smaller of 50 milliseconds and half the real RTT. */
            rtt = min_ap->rtt/2;
            if (rtt > 50*1000)
                  rtt = 50*1000;
            class->base_rtt = min_rtt + rtt;
            if (min2_rtt == DCC_RTT_BAD) {
                  /* if there is no second choice, there is no
                   * point in a threshold for switching to it */
                  class->thold_rtt = DCC_RTT_BAD;
            } else {
                  class->thold_rtt = min(min2_rtt, class->base_rtt);
            }
            class->act_inx = (min_ap - class->addrs);
            if (class->act_inx != old_act_inx) {
                  if (dcc_clnt_debug
                      && old_act_inx < class->num_addrs) {
                        trace_perf("replacing",
                                 &class->addrs[old_act_inx]);
                        trace_perf("pick", min_ap);
                  }
                  return 2;
            }
            return 1;
      }

      /* we failed to find a server */
      if (emsg && *emsg == '\0') {
            dcc_pemsg(EX_IOERR, emsg,
                    "%s server%s %s%s%s%s%s%s at %s%s%s%s%s%s"
                    " not responding",
                    DCC_IS_GREY_STR(class),
                    class->nms[1].hostname[0] ? "s" : "",
                    class->nms[0].hostname,
                    class->nms[1].hostname[0] ? " " : "",
                    class->nms[1].hostname,
                    class->nms[2].hostname[0] ? " " : "",
                    class->nms[2].hostname,
                    class->nms[3].hostname[0] ? " ..." : "",

                    dcc_ap2str_opt(&class->addrs[0],
                               DCC_CLASS2PORT(class), '\0'),
                    class->num_addrs > 1 ? " " : "",
                    class->num_addrs > 1
                    ? dcc_ap2str_opt(&class->addrs[1],
                                 DCC_CLASS2PORT(class), '\0')
                    : "",
                    class->num_addrs > 2 ? " " : "",
                    class->num_addrs > 2
                    ? dcc_ap2str_opt(&class->addrs[2],
                                 DCC_CLASS2PORT(class), '\0')
                    : "",
                    class->num_addrs > 3 ? " ..." : "");
      }
      class->act_inx = -1;
      return 0;
}



/* count IP addresses per host name and per second level domain name */
typedef struct name_addrs {
    const char *sld;                /* domain name */
    u_char     sld_addrs;           /* # of addresses for domain name */
    u_char     host_addrs;          /* # of addresses for a host name */
    u_char     sld_addrs_inx;
} NAME_ADDRS[DCC_MAX_SRVR_NMS];


/* delete an address from a growing list of addresses */
static void
del_new_addr(DCC_SRVR_ADDR new_addrs[DCC_MAX_SRVR_ADDRS],
           int *num_new_addrs,
           NAME_ADDRS name_addrs,   /* addresses per server name */
           int tgt)                 /* delete this address */
{
      int nm_inx;
      int i;

      /* adjust that host's and domain's numbers of addresses and our
       * total number of addresses */
      nm_inx = new_addrs[tgt].nm_inx;
      --name_addrs[nm_inx].host_addrs;
      --name_addrs[name_addrs[nm_inx].sld_addrs_inx].sld_addrs;
      --*num_new_addrs;

      /* slide the array of addresses to get rid of the discarded address */
      i = *num_new_addrs - tgt;
      if (i > 0)
            memmove(&new_addrs[tgt], &new_addrs[tgt+1],
                  i * sizeof(new_addrs[0]));
      memset(&new_addrs[*num_new_addrs], 0, sizeof(new_addrs[0]));
}



static inline u_int
su_srvrs_mod(const DCC_SOCKU *su)
{
      struct in_addr addr4;
      DCC_SOCKU su_v4;
      u_int su_res;

      if (su->sa.sa_family == AF_INET)
            return su->ipv4.sin_addr.s_addr % DCC_SRVRS_MOD;

      if (dcc_ipv6toipv4(&addr4, &su->ipv6.sin6_addr)) {
            dcc_mk_su(&su_v4, AF_INET, &addr4, su->ipv6.sin6_port);
            su = &su_v4;
            su_res = su->ipv4.sin_addr.s_addr % DCC_SRVRS_MOD;
            su_res += DCC_SRVRS_MOD_IPV4;
            return su_res;
      }

      su_res = (su->ipv6.sin6_addr.s6_addr32[0]
              + su->ipv6.sin6_addr.s6_addr32[1]
              + su->ipv6.sin6_addr.s6_addr32[2]
              + su->ipv6.sin6_addr.s6_addr32[3]) % DCC_SRVRS_MOD;
      return su_res;
}



static int
sucmp(const DCC_SOCKU *su1, const DCC_SOCKU *su2)
{
      u_int su1_res, su2_res;
      int i;

      su1_res = su_srvrs_mod(su1);
      su2_res = su_srvrs_mod(su2);

      i = (int)su1_res - (int)su2_res;
      if (i)
            return i;
      return memcmp(su1, su2, sizeof(DCC_SOCKU));
}



/* deal with a list of IP addresses or aliases for one DCC server hostname
 * the contexts and the mmap()'ed info must be locked */
static void
get_addrs(DCC_SRVR_ADDR new_addrs[DCC_MAX_SRVR_ADDRS],
        int *num_new_addrs,
        const DCC_SRVR_CLASS *cur,
        DCC_SRVR_NM *nmp, int nm_inx,     /* server name being resolved */
        NAME_ADDRS name_addrs,      /* addresses per server name */
        u_int16_t port)
{
      DCC_SRVR_ADDR *ap;
      const DCC_SRVR_NM *nmp2;
      DCC_SOCKU *new, su, prev;
      u_char found;
      int nm1_inx, sld1_inx, sld2_inx;
      int host_max, sld_max;
      int i, j, k;

      /* Keep as many IP addresses as we have room, but for as many
       * named servers as possible
       * Sort the addresses to keep our list stable when we re-check.
       * Otherwise, we would start from scratch when nothing changes
       * but the order of responses from a DNS server.
       * Sort by residue class to pick a random subset when there
       * are too many servers to fit in our list. */

      memset(&prev, 0, sizeof(prev));
      prev.sa.sa_family = AF_INET;
      for (;;) {
            /* Pick the next address in the newly resolved list
             * to consider.  We want the smallest address larger
             * than the previous address we considered.
             * "Smallest" is defined using the local, presumably
             * random ordering of addresses. */
            found = 0;
            for (new = dcc_hostaddrs; new < dcc_hostaddrs_end; ++new) {
                  *DCC_SU_PORT(new) = port;
                  if (sucmp(new, &prev) > 0) {
                        if (found && sucmp(&su, new) <= 0)
                              continue;
                        su = *new;
                        found = 1;
                  }
            }
            /* quit if we've considered them all */
            if (!found)
                  break;
            /* found one to consider, so note it */
            memcpy(&prev, &su, sizeof(prev));

            /* ignore duplicate A records even for other hostnames,
             * unless the port numbers or address families differ */
            ap = &new_addrs[*num_new_addrs];
            while (--ap >= new_addrs) {
                  if (dcc_cmp_ap2su(ap, &su)) {
                        /* keep the entry with the non-anonymous ID
                         * or smallest RTT adjustment */
                        nmp2 = &cur->nms[ap->nm_inx];
                        i = (nmp->clnt_id == DCC_ID_ANON);
                        j = (nmp2->clnt_id == DCC_ID_ANON);
                        if (i != j) {
                              if (i)
                                  goto next_addr;
                        } else {
                              if (nmp->rtt_adj >= nmp2->rtt_adj)
                                  goto next_addr;
                        }
                        /* delete the previous instance */
                        del_new_addr(new_addrs, num_new_addrs,
                                   name_addrs, ap - new_addrs);
                        break;
                  }
            }

            /* If we already have as many addresses as we will use,
             * then pick one to discard. Discard the last address of
             * the host in the second level domain with the most
             * addresses but without eliminating all addresses for any
             * host name.  Look for the domain with the most IP addresses
             * and that has at least one host with at least two
             * addersses. */
            if (*num_new_addrs == DCC_MAX_SRVR_ADDRS) {
                  host_max = -1;
                  sld_max = -1;
                  nm1_inx = -1;
                  sld1_inx = -1;
                  for (i = 0; i <= nm_inx; i++) {
                        /* ignore hosts with only 1 IP address */
                        j = name_addrs[i].host_addrs;
                        if (j <= 1)
                              continue;
                        sld2_inx = name_addrs[i].sld_addrs_inx;
                        k = name_addrs[sld2_inx].sld_addrs;
                        if (sld_max <= k) {
                              if (sld1_inx != sld2_inx) {
                                  sld_max = k;
                                  sld1_inx = sld2_inx;
                                  host_max = j;
                                  nm1_inx = i;
                              } else if (host_max <= j) {
                                  host_max = j;
                                  nm1_inx = i;
                              }
                        }
                  }
                  /* no additional IP addresses for the target host if
                   * it has the most IP addresses */
                  if (nm1_inx == nm_inx)
                        return;

                  /* find the last address of the host with the most */
                  for (i = 0, j = 0; i < *num_new_addrs; i++) {
                        if (new_addrs[i].nm_inx == nm1_inx)
                              j = i;
                  }
                  /* and delete it */
                  del_new_addr(new_addrs, num_new_addrs, name_addrs, j);
            }

            /* install the new address in the growing list */
            ap = &new_addrs[*num_new_addrs];
            memset(ap, 0, sizeof(*ap));
            ap->rtt = DCC_RTT_BAD;
            ap->port = su.ipv4.sin_port;
            if ((ap->family = su.sa.sa_family) == AF_INET) {
                  ap->ip.v4.s_addr = su.ipv4.sin_addr.s_addr;
            } else {
                  memcpy(&ap->ip.v6, &su.ipv6.sin6_addr,
                         sizeof(ap->ip.v6));
            }
            /* If this is a previously known address,
             * preserve what we already knew about it */
            for (i = 0; i < DIM(cur->addrs); ++i) {
                  if (dcc_cmp_ap2su(&cur->addrs[i], &su)) {
                        memcpy(ap, &cur->addrs[i], sizeof(*ap));
                        break;
                  }
            }
            ap->nm_inx = nm_inx;
            ++*num_new_addrs;

            ++name_addrs[nm_inx].host_addrs;
            ++name_addrs[name_addrs[nm_inx].sld_addrs_inx].sld_addrs;
next_addr:;
      }
}



/* resolve a server name into addresses
 * the contexts and the mmap()'ed info must be locked */
static void
dcc_resolve_host(DCC_EMSG emsg,
             DCC_SRVR_ADDR new_addrs[DCC_MAX_SRVR_ADDRS],
             int *num_new_addrs,
             const DCC_SRVR_CLASS *cur,
             DCC_SRVR_NM *nmp, int nm_inx,      /* server name being resolved */
             NAME_ADDRS name_addrs) /* addresses per server name */
{
      const char *domain, *p1, *p2;
      int error;
      u_char result;
      int i;

      nmp->defined = 0;
      if (nmp->hostname[0] == '\0')
            return;

      /* find or create the total of addresses for this domain name */
      domain = nmp->hostname;
      p1 = strchr(domain, '.');
      if (p1) {
            for (;;) {
                  p2 = strchr(++p1, '.');
                  if (!p2)
                        break;
                  domain = p1;
                  p1 = p2;
            }
      }
      name_addrs[nm_inx].sld = domain;
      for (i = 0; i < nm_inx; ++i) {
            if (name_addrs[i].sld != 0
                && !strcmp(domain, name_addrs[i].sld))
                  break;
      }
      name_addrs[nm_inx].sld_addrs_inx = i;

      dcc_host_lock();
      if (dcc_clnt_info->flags & DCC_CLNT_INFO_FG_SOCKS)
            result = dcc_get_host_SOCKS(nmp->hostname,
                                  (dcc_clnt_info->flags
                                   & DCC_CLNT_INFO_FG_IPV6)
                                  ? 1 : 0,
                                  &error);
      else
            result = dcc_get_host(nmp->hostname,
                              (dcc_clnt_info->flags
                               & DCC_CLNT_INFO_FG_IPV6)
                              ? 1 : 0,
                              &error);
      if (!result) {
            dcc_pemsg(EX_NOHOST, emsg, "dcc_get_host(%s): %s",
                    nmp->hostname, DCC_HSTRERROR(error));
            dcc_host_unlock();
            return;
      }
      nmp->defined = 1;
      get_addrs(new_addrs, num_new_addrs, cur, nmp, nm_inx,
              name_addrs, nmp->port);
      dcc_host_unlock();
}



/* resolve server hostnames again
 *      The contexts, shared information, and resolving must be locked.
 *      Leaves the shared information locked only upon success.
 *      The contexts are locked on exit even on failure. */
static u_char                       /* 0=no good addresses, 1=at least 1 */
dcc_clnt_resolve(DCC_EMSG emsg, DCC_CLNT_CTXT *ctxt, DCC_SRVR_CLASS *class)
{
      DCC_SRVR_ADDR new_addrs[DCC_MAX_SRVR_ADDRS];
      int num_new_addrs;
      int nm_inx;
      NAME_ADDRS name_addrs;
      DCC_SRVR_ADDR *new_ap, *cur_ap;
      int i;

      if (dcc_clnt_debug > 1)
            dcc_trace_msg("resolve %s server host names",
                        DCC_IS_GREY_STR(class));

      memset(new_addrs, 0, sizeof(new_addrs));
      num_new_addrs = 0;
      memset(&name_addrs, 0, sizeof(name_addrs));

      if (dcc_clnt_info->residue == 0) {
            dcc_clnt_info->residue = dcc_clnt_hid % DCC_SRVRS_MOD;
            if (dcc_clnt_info->residue == 0)
                  dcc_clnt_info->residue = 1;
      }

      if (emsg)
            *emsg = '\0';
      for (nm_inx = 0; nm_inx < DIM(class->nms); ++nm_inx)
            dcc_resolve_host(emsg, new_addrs, &num_new_addrs,
                         class, &class->nms[nm_inx], nm_inx,
                         name_addrs);

      class->resolve = ctxt->now.tv_sec+DCC_RE_RESOLVE;

      /* see if anything changed */
      i = num_new_addrs;
      if (i != 0 && i == class->num_addrs) {
            new_ap = new_addrs;
            cur_ap = class->addrs;
            for (;;) {
                  if (!i)
                        return 1;   /* nothing changed */
                  if (new_ap->nm_inx != cur_ap->nm_inx
                      || memcmp(&new_ap->ip, cur_ap, sizeof(new_ap->ip))
                      || new_ap->port != cur_ap->port
                      || new_ap->family != cur_ap->family) {
                        ++class->gen;
                        break;
                  }
                  ++new_ap;
                  ++cur_ap;
                  --i;
            }
      }

      /* Something changed.
       * Get the new values and arrange to recompute RTTs */
      class->act_inx = -1;
      class->avg_thold_rtt = -DCC_RTT_BAD;
      class->measure = 0;
      memcpy(&class->addrs, &new_addrs, sizeof(class->addrs));
      class->num_addrs = num_new_addrs;

      if (!class->num_addrs) {
            /* failed to resolve any server host names */
            class->resolve = 0;
            dcc_info_unlock(0);
            if (emsg && *emsg == '\0')
                  dcc_pemsg(EX_USAGE, emsg,
                          "no valid %s server hostnames",
                          DCC_IS_GREY_STR(class));
            return 0;
      }
      return 1;
}



#ifdef DCC_UDP_CONNECT
/* it would be swell if there were a standard for
 * disconnecting a socket that everyone followed */
u_char
dcc_clnt_disconnect(DCC_EMSG emsg UATTRIB, DCC_CLNT_CTXT *ctxt)
{
      ctxt->conn_su.sa.sa_family = AF_UNSPEC;
      if (ctxt->soc == INVALID_SOCKET)
            return 1;

#ifdef DCC_UDP_DISCON_LEN
      ctxt->conn_su.ipv4.sin_port = 0;
      connect(ctxt->soc, &ctxt->conn_su.sa, DCC_UDP_DISCON_LEN);
      return 1;
#else
      return dcc_clnt_soc_open(emsg, ctxt);
#endif
}
#endif /* DCC_UDP_DISCON_LEN */



u_char
dcc_clnt_soc_open(DCC_EMSG emsg, DCC_CLNT_CTXT *ctxt)
{
      DCC_SOCKU su;
      int soc_len;
      int retries;

      if (ctxt->soc != INVALID_SOCKET) {
            close(ctxt->soc);
            ctxt->soc = INVALID_SOCKET;
      }
      /* the socket is now disconnected */
      ctxt->conn_su.sa.sa_family = AF_UNSPEC;

      retries = -1;
      if ((dcc_clnt_info->flags & DCC_CLNT_INFO_FG_IPV6)
          && !dcc_udp_bind(emsg, &ctxt->soc,
                       dcc_mk_su(&su, AF_INET6, 0, ctxt->port),
                       &retries)) {
            dcc_info_unlock(emsg);
            return 0;
      }
      if (ctxt->soc == INVALID_SOCKET) {
            dcc_clnt_info->flags &= ~DCC_CLNT_INFO_FG_IPV6;
            retries = -1;
            if (!dcc_udp_bind(emsg, &ctxt->soc,
                          dcc_mk_su(&su, AF_INET, 0, ctxt->port),
                          &retries)) {
                  dcc_info_unlock(emsg);
                  return 0;
            }
      }
#if !defined(USE_POLL) && !defined(DCC_WIN32)
      if (ctxt->soc >= FD_SETSIZE) {
            dcc_pemsg(EX_IOERR, emsg, "socket FD %d > FD_SETSIZE %d",
                    ctxt->soc, FD_SETSIZE);
            closesocket(ctxt->soc);
            ctxt->soc = INVALID_SOCKET;
            dcc_info_unlock(emsg);
            return 0;
      }
#endif

#if defined(IPPROTO_IP) && defined(IP_TTL)
      if (dcc_debug_ttl != 0
          && 0 > setsockopt(ctxt->soc, IPPROTO_IP, IP_TTL,
                        (void *)&dcc_debug_ttl, sizeof(dcc_debug_ttl))) {
            dcc_pemsg(EX_IOERR, emsg, "setsockopt(TTL=%d):%s",
                    dcc_debug_ttl, ERROR_STR());
            closesocket(ctxt->soc);
            ctxt->soc = INVALID_SOCKET;
            dcc_info_unlock(emsg);
            return 0;
      }
#endif

      soc_len = sizeof(su);
      if (0 > getsockname(ctxt->soc, &su.sa, &soc_len)) {
            dcc_pemsg(EX_IOERR, emsg, "getsockname(): %s", ERROR_STR());
            closesocket(ctxt->soc);
            ctxt->soc = INVALID_SOCKET;
            dcc_info_unlock(emsg);
            return 0;
      }
      ctxt->port = *DCC_SU_PORT(&su);
      ctxt->use_ipv6 = dcc_clnt_info->flags & DCC_CLNT_INFO_FG_IPV6;
      return 1;
}



/* send a single DCC message
 * the contexts and the shared information must be locked */
static u_char
clnt_xmit(DCC_EMSG emsg, DCC_CLNT_CTXT *ctxt, DCC_XLOG *xlog,
        DCC_SRVR_CLASS *class, DCC_SRVR_ADDR *ap,
        DCC_HDR *msg, int msg_len, u_char connect_ok)
{
      DCC_XLOG_ENTRY *xloge;
      char abuf[80];
      int i;
#ifdef DCC_UDP_CONNECT
      DCC_XLOG_ENTRY *xloge1;
      u_char was_connected;
      int j;
#else
      connect_ok = 0
#endif

      msg->len = htons(msg_len);

      xloge = xlog->next;
      if (xloge > xlog->last)
            abort();
      ++msg->op_nums.t;
      xloge->op_nums = msg->op_nums;
      xloge->addr_inx = ap - class->addrs;
      dcc_mk_su(&xloge->su, ap->family, &ap->ip, ap->port);
      xloge->addrs_gen = class->gen;
      xloge->sent_us = ctxt->now_us;
      xloge->op = msg->op;
      xloge->id = class->nms[ap->nm_inx].clnt_id;
      if (xloge->id == 0)
            dcc_logbad(EX_SOFTWARE, "clnt_xmit: zero client-ID");
      if (class->nms[ap->nm_inx].passwd[0] == '\0')
            xloge->id = DCC_ID_ANON;
      msg->sender = htonl(xloge->id);
      if (xloge->id != DCC_ID_ANON) {
            strncpy(xloge->passwd, class->nms[ap->nm_inx].passwd,
                  sizeof(xloge->passwd));
            dcc_sign(xloge->passwd, sizeof(xloge->passwd), msg, msg_len);
      } else {
            xloge->passwd[0] = '\0';
            memset((char *)msg + (msg_len-sizeof(DCC_SIGNATURE)), 0,
                   sizeof(DCC_SIGNATURE));
      }

#ifdef DCC_UDP_CONNECT
      /* Use connect() when possible to get ICMP Unreachable messages.
       * It is impossible with SOCKS
       * or when talking to more than one server. */
      if (dcc_clnt_info->flags & DCC_CLNT_INFO_FG_SOCKS)
            connect_ok = 0;
      for (xloge1 = xlog->base; connect_ok && xloge1 < xloge; ++xloge1) {
            if (xloge1->op_nums.t == DCC_OP_NUMS_NULL)
                  continue;
            if (xloge->addr_inx != xloge1->addr_inx) {
                  connect_ok = 0;
                  break;
            }
      }
      if (connect_ok) {
            if (memcmp(&ctxt->conn_su, &xloge->su, sizeof(ctxt->conn_su))) {
#ifdef linux
                  /* at least some versions of Linux do not allow
                   * connsecutive valid calls to connect()
                   * but work if the socket is first disconnected */
                  if (!dcc_clnt_disconnect(emsg, ctxt))
                        return 0;
#endif /* linux */
                  if (SOCKET_ERROR == connect(ctxt->soc, &xloge->su.sa,
                                        DCC_SU_LEN(&xloge->su))) {
                        dcc_pemsg(EX_IOERR, emsg, "connect(%s): %s",
                                addr2str(abuf, sizeof(abuf), class,
                                       class->gen, ap, 0),
                                ERROR_STR());
                        return 0;
                  }
                  ctxt->conn_su = xloge->su;
            }
            i = send(ctxt->soc,
#ifdef DCC_WIN32
                   (const char *)msg,
#else
                   msg,
#endif
                   msg_len, 0);

      } else {
            if (ctxt->conn_su.sa.sa_family == AF_UNSPEC) {
                  was_connected = 0;
            } else {
                  if (!dcc_clnt_disconnect(emsg, ctxt))
                        return 0;
                  was_connected = 1;
            }

            /* paranoid infinite loop prevention */
            j = DCC_MAX_XMITS*DCC_MAX_SRVR_ADDRS*2;
            do {
#endif /* DCC_UDP_CONNECT */
#ifdef HAVE_LIBSOCKS
                  if (dcc_clnt_info->flags & DCC_CLNT_INFO_FG_SOCKS)
                        i = Rsendto(ctxt->soc, msg, msg_len, 0,
                                  &xloge->su.sa,
                                  DCC_SU_LEN(&xloge->su));
                  else
#endif /* HAVE_LIBSOCKS */
                        i = sendto(ctxt->soc,
#ifdef DCC_WIN32
                                 (const char *)msg,
#else
                                 msg,
#endif
                                 msg_len, 0, &xloge->su.sa,
                                 DCC_SU_LEN(&xloge->su));
#ifdef DCC_UDP_CONNECT
                  /* deal with ICMP messages for a previous
                   * connected transmission */
            } while (i == SOCKET_ERROR && was_connected
                   && DCC_CONNECT_ERRORS() && --j > 0);
      }
#endif /* DCC_UDP_CONNECT */
      ++xlog->cur[ap - class->addrs].xmits;
      if (i == msg_len) {
            if (xloge < xlog->last) {
                  ++xlog->next;
                  ++xlog->outstanding;
            }
            return 1;
      }
      if (i < 0) {
            dcc_pemsg(EX_IOERR, emsg, "%s(%s): %s",
                    connect_ok ? "send" : "sendto",
                    addr2str(abuf, sizeof(abuf), class,
                           class->gen, ap, 0),
                    ERROR_STR());
      } else {
            dcc_pemsg(EX_IOERR, emsg, "%s(%s)=%d instead of %d",
                    connect_ok ? "send" : "sendto",
                    addr2str(abuf, sizeof(abuf), class,
                           class->gen, ap, 0),
                    i, msg_len);
      }
      return 0;
}



static void
update_rtt(DCC_CLNT_CTXT *ctxt, DCC_SRVR_CLASS *class,
         DCC_XLOG_ENTRY *xloge, int us)
{
      DCC_SRVR_ADDR *ap;

      if (us < 0)
            us = 0;
      else if (us > DCC_MAX_RTT)
            us = DCC_MAX_RTT;

      /* compute new RTT if the map data structure is locked,
       * the clock did not jump,
       * and we're talking about the same hosts */
      if (info_locked
          && xloge->addrs_gen == class->gen) {
            ap = &class->addrs[xloge->addr_inx];
            if (ap->rtt == DCC_RTT_BAD) {
                  ap->rtt = us;
                  ap->total_xmits = 0;
                  ap->total_resps = 0;
                  ap->resp_mem = 0;
                  ap->rtt_updated = 0;

            } else if (ctxt->now.tv_sec < (ap->rtt_updated
                                     + FAST_RTT_SECS)) {
                  /* adjust the RTT quickly if this is the first
                   * measurement in a long time */
                  AGE_AVG(ap->rtt, us, 2, 1);
                  ap->rtt_updated = ctxt->now.tv_sec;

            } else {
                  AGE_AVG(ap->rtt, us, 9, 1);
                  ap->rtt_updated = ctxt->now.tv_sec;
            }
            return;
      }
}



/* update response rate and penalize the RTT of servers that failed to respond
 * the data must be locked */
static void
resp_rates(DCC_CLNT_CTXT *ctxt, DCC_SRVR_CLASS *class,
         DCC_XLOG *xlog, u_char measuring)
{
      DCC_SRVR_ADDR *ap;
      DCC_XLOG_ENTRY *xloge;
      int us;
      int i;

      for (xloge = xlog->base; xloge < xlog->next; ++xloge) {
            /* ignore responses we've already handled */
            if (xloge->op_nums.t == DCC_OP_NUMS_NULL)
                  continue;

            ap = &class->addrs[xloge->addr_inx];

            /* if no response has ever been seen from the server,
             * we can't guess */
            if (ap->rtt == DCC_RTT_BAD)
                  continue;

            /* Update the RTT of this server as if we had just received
             * its response unless we didn't give it an RTT's worth.
             * Guess that the missing responses would have arrived
             * a little late */
            us = ctxt->now_us - xloge->sent_us;
            if (us >= ap->rtt)
                  update_rtt(ctxt, class, xloge, us + DCC_INIT_RTT);
      }

      /* maintain the response rate */
      for (i = 0, ap = class->addrs; i < DIM(xlog->cur); ++i, ++ap) {
            if (ap->rtt == DCC_RTT_BAD
                || xlog->cur[i].xmits == 0)
                  continue;
            if (measuring) {
                  if (xlog->cur[i].resps != 0) {
                        ++xlog->working_addrs;
                  } else if (!(ap->resp_mem & ((1<<DCC_MAX_XMITS)-1))) {
                        /* this server is bad if there were no answers
                         * at all for this mesurement cycle */
                        ap->rtt = DCC_RTT_BAD;
                        continue;
                  }
            }
            ap->total_xmits += xlog->cur[i].xmits;
            if (ap->total_xmits > DCC_TOTAL_XMITS_MAX)
                  ap->total_xmits = DCC_TOTAL_XMITS_MAX;
            do {
                  ap->total_resps -= (ap->resp_mem
                                  >> (DCC_TOTAL_XMITS_MAX-1));
                  ap->resp_mem <<= 1;
                  if (xlog->cur[i].resps != 0) {
                        ap->resp_mem |= 1;
                        ++ap->total_resps;
                        --xlog->cur[i].resps;
                  }
            } while (--xlog->cur[i].xmits != 0);
      }
}



/* receive a single DCC response
 *      The contexts must be locked.
 *      The mapped or common info ought to be locked, but reception
 *      works if it is not. */
static int      /* -1=fatal error, 0=no data, 1=unreachable, 2=ok */
clnt_recv(DCC_EMSG emsg, DCC_CLNT_CTXT *ctxt, DCC_SRVR_CLASS *class,
        DCC_HDR *resp, int resp_len,
        const DCC_HDR *msg, DCC_XLOG *xlog, DCC_XLOG_ENTRY **xlogep)
{
      DCC_SOCKLEN_T su_len;
      DCC_SOCKU su;
      DCC_XLOG_ENTRY *xloge, *xloge1;
      char abuf[80];
      int pkt_len;

      *xlogep = 0;
      for (;;) {
            su_len = sizeof(su);
            memset(&su, 0, sizeof(su));
#ifdef HAVE_LIBSOCKS
            if (dcc_clnt_info->flags & DCC_CLNT_INFO_FG_SOCKS)
                  pkt_len = Rrecvfrom(ctxt->soc, resp, resp_len, 0,
                                  &su.sa, &su_len);
            else
#endif /* HAVE_LIBSOCKS */
                  pkt_len = recvfrom(ctxt->soc,
#ifdef DCC_WIN32
                                 (char *)resp,
#else
                                 resp,
#endif
                                 resp_len, 0, &su.sa, &su_len);
            if (pkt_len < 0) {
                  /* Stop looking when there are no more packets */
                  if (DCC_BLOCK_ERROR())
                        return 0;

                  /* ignore ICMP Unreachables unless we have a
                   * single outstanding request */
                  if (ctxt->conn_su.sa.sa_family != AF_UNSPEC
                      && DCC_CONNECT_ERRORS()) {
                        for (xloge1 = xlog->base, xloge = 0;
                             xloge1 < xlog->next;
                             ++xloge1) {
                              if (xloge1->op_nums.t==DCC_OP_NUMS_NULL)
                                  continue;
                              if (xloge)
                                  xloge->op_nums.t = DCC_OP_NUMS_NULL;
                              xloge = xloge1;
                        }
                        if (!xloge) {
                              if (dcc_clnt_debug)
                                  dcc_trace_msg("ignore unmatched:"
                                          " %s", ERROR_STR());
                              continue;
                        }
                        if (dcc_clnt_debug)
                              dcc_trace_msg("note recvfrom(%s): %s",
                                          dcc_su2str(&su),
                                          ERROR_STR());
                        xloge->op_nums.t = DCC_OP_NUMS_NULL;
                        xlog->outstanding = 0;
                        class->addrs[xloge->addr_inx].rtt = DCC_RTT_BAD;
                        ++xlog->cur[xloge->addr_inx].resps;
                        *xlogep = xloge;
                        return 1;
                  }

                  dcc_pemsg(EX_IOERR, emsg, "recvfrom(%s): %s",
                          su.sa.sa_family ? dcc_su2str(&su) : "",
                          ERROR_STR());
                  return -1;
            }

            if (pkt_len < (int)(sizeof(DCC_HDR)+sizeof(DCC_SIGNATURE))) {
                  trace_bad_packet(xlog, &su, "recv(%s)=%d < %d",
                               dcc_su2str(&su), pkt_len,
                               ISZ(DCC_HDR)+ISZ(DCC_SIGNATURE));
                  continue;
            }
            if (pkt_len != ntohs(resp->len)) {
                  trace_bad_packet(xlog, &su,
                               "recv(%s)=%d but hdr len=%d from %s",
                               dcc_su2str(&su), pkt_len,
                               ntohs(resp->len), dcc_su2str(&su));
                  continue;
            }

            if (resp->pkt_vers < DCC_PKT_VERSION_MIN
                || resp->pkt_vers > DCC_PKT_VERSION_MAX) {
                  trace_bad_packet(xlog, &su,
                               "unrecognized version #%d from %s",
                               resp->pkt_vers, dcc_su2str(&su));
                  continue;
            }

            /* We cannot use the server's apparent IP address because it
             * might be multihomed and respond with an address other than
             * to which we sent.  So use our records of which OP_NUMS was
             * sent to which server address. */
            if (resp->op_nums.r != msg->op_nums.r
                || resp->op_nums.p != msg->op_nums.p
                || resp->op_nums.h != msg->op_nums.h) {
                  if (dcc_clnt_debug)
                        dcc_trace_msg("unmatched response from %s"
                                    " h=%#x/%#x p=%#x/%#x r=%#x/%#x"
                                    " t=%#x",
                                    dcc_su2str(&su),
                                    resp->op_nums.h, msg->op_nums.h,
                                    resp->op_nums. p, msg->op_nums.p,
                                    resp->op_nums.r, msg->op_nums.r,
                                    resp->op_nums.t);
                  continue;
            }

            for (xloge = xlog->base; xloge < xlog->next; ++xloge) {
                  if (resp->op_nums.t == xloge->op_nums.t)
                        break;
            }
            if (xloge >= xlog->next) {
                  if (dcc_clnt_debug)
                        dcc_trace_msg("stray response from %s"
                                    " h=%#x/%#x p=%#x/%#x r=%#x/%#x"
                                    " t=%#x",
                                    dcc_su2str(&su),
                                    resp->op_nums.h, msg->op_nums.h,
                                    resp->op_nums.p, msg->op_nums.p,
                                    resp->op_nums.r, msg->op_nums.r,
                                    resp->op_nums.t);
                  continue;
            }


#ifdef CLNT_LOSSES
            if ((++clnt_losses % 5) == 0) {
                  dcc_trace_msg("dropped answer from %s",
                              addr_inx2str(abuf, sizeof(abuf), class,
                                       xloge->addrs_gen,
                                       xloge->addr_inx, &su));
                  continue;
            }
#endif
            if (xloge->passwd[0] != '\0'
                && dcc_ck_signature(xloge->passwd, sizeof(xloge->passwd),
                              resp, pkt_len))
                  break;            /* good signature */

            if (dcc_ck_signature((char *)&xloge->op_nums,
                             sizeof(xloge->op_nums),
                             resp, pkt_len)) {
                  /* server did not sign with our password,
                   * but with our transaction numbers */
                  if (xloge->passwd[0] != '\0')
                        dcc_error_msg("%s rejected our password"
                                    " for ID %d",
                                    addr_inx2str(abuf, sizeof(abuf),
                                          class,
                                          xloge->addrs_gen,
                                          xloge->addr_inx,
                                          &su),
                                    xloge->id);
                  break;
            }

            dcc_error_msg("badly signed %s response from %s",
                        dcc_hdr_op2str(msg),
                        addr_inx2str(abuf, sizeof(abuf), class,
                                 xloge->addrs_gen, xloge->addr_inx,
                                 &su));
      }

      /* Found a record of this transmission */
      xloge->op_nums.t = DCC_OP_NUMS_NULL;    /* don't find it again */
      if (xlog->outstanding != 0)
            --xlog->outstanding;
      ++xlog->cur[xloge->addr_inx].resps;

      *xlogep = xloge;
      return 2;
}



/* wait for an answer */
int                           /* -1=error, 0=timeout, 1=ready */
dcc_select_poll(DCC_EMSG emsg,
            SOCKET fd,
            u_char rd,        /* 1=read 0=write */
            int usec)         /* <0=forever until signal */
{
#ifdef USE_POLL
      struct pollfd fds;
      int nfds;
      int delay;

      if (usec < 0)
            delay = -1;
      else
            delay = (usec+999)/1000;

      for (;;) {
            fds.fd = fd;
            /* At least some versions of Linux have POLLRDNORM etc. in
             * asm/poll.h, but with definitions of POLLIN, POLLPRI, etc.
             * that conflict with their definitions in sys/poll.h.
             * Perhaps it is not necessary to check for high or
             * low priority data, but the poll() documentation on
             * some systems says that asking about POLLIN does not
             * say anything about other data */
#ifdef POLLRDNORM
            if (rd)
                  fds.events = POLLIN | POLLRDNORM | POLLRDBAND | POLLPRI;
            else
                  fds.events = POLLOUT| POLLWRNORM | POLLWRBAND | POLLPRI;
#else
            if (rd)
                  fds.events = POLLIN;
            else
                  fds.events = POLLOUT;
#endif
            fds.revents = 0;
            nfds = poll(&fds, 1, delay);
            if (nfds >= 0)
                  return nfds;
            if (!DCC_SELECT_NERROR()) {
                  dcc_pemsg(EX_OSERR, emsg, "poll(): %s", ERROR_STR());
                  return -1;
            }
            if (usec < 0)           /* stop forever on a signal */
                  return 0;
      }
#else
      struct timeval delay, *delayp;
      fd_set fds;
      int nfds;

      if (usec < 0) {
            delayp = 0;
      } else {
            delay.tv_usec = usec % DCC_USECS;
            delay.tv_sec = usec / DCC_USECS;
            delayp = &delay;
      }

      FD_ZERO(&fds);
      for (;;) {
            FD_SET(fd, &fds);
            if (rd)
                  nfds = select(fd+1, &fds, 0, 0, delayp);
            else
                  nfds = select(fd+1, 0, &fds, 0, delayp);
            if (nfds >= 0)
                  return nfds;
            if (!DCC_SELECT_NERROR()) {
                  dcc_pemsg(EX_OSERR, emsg, "select(): %s", ERROR_STR());
                  return -1;
            }
            if (usec < 0)           /* stop forever on a signal */
                  return 0;
      }
#endif
}



/* Make initial estimates of the RTT to all known servers
 *      The RTT's help the client pick a server that will respond quickly and
 *      reliably and to know when to retransmit a request that is lost due
 *      to network congestion or bit rot.
 *  The contexts, shared information, and resolving must all be locked on entry.
 *  The shared information is unlocked on failure but the contexts are locked */
static u_char                       /* 0=failed, 1=at least 1 good server */
measure_rtt(DCC_EMSG emsg, DCC_CLNT_CTXT *ctxt, DCC_SRVR_CLASS *class)
{
      DCC_SRVR_ADDR *ap;
      DCC_NOP nop;
      union {
          DCC_HDR     hdr;
          DCC_OK      ok;
          DCC_ERROR   error;
      } resp;
      int rtt, us, delay_us, next_xmit, end_us;
      int nfds, xmit_num;
      int tgt_addrs;
      DCC_XLOG xlog;
      DCC_XLOG_ENTRY xlog_entries[DCC_MAX_SRVR_ADDRS*DCC_MAX_XMITS];
      DCC_XLOG_ENTRY *xloge;
      char abuf[80];
      u_char vers;
      int i;

      /* Send NOP's to all addresses and wait for responses to
       * measure each server's health and RTT.
       * Treat all addresses as if they are of independent hosts */

      memcpy(&nop.hdr, &dcc_clnt_info->proto_hdr, sizeof(nop.hdr));
      /* servers ignore the version on NOPs */
      nop.hdr.pkt_vers = DCC_PKT_VERSION_MIN;
      nop.hdr.op_nums.p = getpid();
      nop.hdr.op = DCC_OP_NOP;
      nop.hdr.op_nums.r = ++dcc_clnt_info->proto_hdr.op_nums.r;

      if (!get_now(emsg, ctxt)) {
            dcc_info_unlock(0);
            return 0;
      }
      if (emsg)
            *emsg = '\0';

      /* Figure out the earliest when we could be finished
       * by finding the largest current RTT */
      rtt = DCC_INIT_RTT;
      for (ap = class->addrs; ap <= LAST(class->addrs); ++ap) {
            if (ap->family == 0)
                  continue;
            if (!(ap->resp_mem & 1))
                  continue;
            us = ap->rtt - ap->srvr_wait;
            if (rtt < us)
                  rtt = us;
      }
      end_us = MIN_RETRANS_TIME(rtt, 1);
      end_us += ctxt->now_us;

      tgt_addrs = class->num_addrs;
      if (tgt_addrs <= 0) {
            dcc_pemsg(EX_NOHOST, emsg, "no server addresses");
            dcc_info_unlock(0);
            return 0;
      }
      /* stop waiting for responses when we have enough working servers */
      if (!dcc_all_srvrs && tgt_addrs > 4)
            tgt_addrs = 4;

      memset(&xlog, 0, sizeof(xlog));
      xlog.base = xlog.next = xlog_entries;
      xlog.last = LAST(xlog_entries);
      delay_us = 0;
      next_xmit = 0;
      xmit_num = 0;
      /* wait for the responses to the NOPs and retransmit as needed */
      for (;;) {
            /* wait quietly until time to retransmit */
            if (delay_us <= 0) {
                  if (xmit_num >= DCC_MAX_XMITS)
                        break;
                  if (xlog.working_addrs < tgt_addrs) {
                        int tgts = 0;
                        for (i = 0, ap = class->addrs;
                             ap <= LAST(class->addrs);
                             ++i, ++ap) {
                              if (ap->family == 0
                                  || xlog.cur[i].resps != 0)
                                  continue;
                              if (++tgts > 1)
                                  break;
                        }
                        if (tgts > 0) {
                              tgts = (tgts == 1);
                              for (i = 0, ap = class->addrs;
                                   ap <= LAST(class->addrs);
                                   ++i, ++ap) {
                                  if (ap->family == 0
                                    || xlog.cur[i].resps != 0)
                                    continue;
                                  clnt_xmit(emsg, ctxt, &xlog,
                                          class, ap,
                                          &nop.hdr, sizeof(nop),
                                          tgts);
                              }
                        }
                  }

                  /* stop if nothing to wait for */
                  if (!xlog.outstanding)
                        break;
                  delay_us = dcc_retrans_time(DCC_INIT_RTT, ++xmit_num);
                  next_xmit = delay_us + ctxt->now_us;
                  if (next_xmit > end_us
                      && xlog.working_addrs >= tgt_addrs) {
                        next_xmit = end_us;
                        delay_us = next_xmit - ctxt->now_us;
                        if (delay_us <= 0)
                              break;
                  }
            }

            if (!dcc_info_unlock(emsg))
                  return 0;
            dcc_ctxts_unlock();
            nfds = dcc_select_poll(emsg, ctxt->soc, 1, delay_us);
            if (nfds < 0) {
                  dcc_ctxts_lock();
                  return 0;
            }
            i = get_now(emsg, ctxt);
            dcc_ctxts_lock();
            /* give up someone changed the local clock */
            if (!i)
                  return 0;
            if (!dcc_info_lock(emsg))
                  return 0;

            if (nfds > 0) for (;;) {
                  i = clnt_recv(emsg, ctxt, class,
                              &resp.hdr, sizeof(resp),
                              &nop.hdr, &xlog, &xloge);
                  if (i <= 0)
                        break;

                  if (i == 1)     /* otherwise ignore Unreachable */
                        continue;

                  /* record the results of a probe, and notice
                   * if the server is the best so far */
                  ap = &class->addrs[xloge->addr_inx];

                  if (resp.hdr.op != DCC_OP_OK) {
                        if (dcc_clnt_debug)
                              dcc_trace_msg("RTT NOP answered"
                                          " with %s by %s",
                                          dcc_hdr_op2str(&resp.hdr),
                                          addr2str(abuf,
                                            sizeof(abuf),
                                            class,
                                            xloge->addrs_gen,
                                            ap, 0));
                        ap->rtt = DCC_RTT_BAD;
                        continue;
                  }

                  vers = resp.ok.max_pkt_vers;
                  if (vers >= DCC_PKT_VERSION_MAX)
                        vers = DCC_PKT_VERSION_MAX;
                  else if (vers < DCC_PKT_VERSION_MIN)
                        vers = DCC_PKT_VERSION_MIN;
                  ap->srvr_pkt_vers = vers;
                  ap->srvr_id = ntohl(resp.hdr.sender);
                  memcpy(ap->brand, resp.ok.brand, sizeof(ap->brand));
                  ap->srvr_wait = ntohs(resp.ok.qdelay_ms)*1000;

                  update_rtt(ctxt, class, xloge,
                           ctxt->now_us - xloge->sent_us
                           + ap->srvr_wait);
            }

            if (xlog.outstanding == 0)
                  delay_us = 0;
            else
                  delay_us = next_xmit - ctxt->now_us;
            if (xlog.working_addrs >= tgt_addrs) {
                  us = end_us - ctxt->now_us;
                  if (us <= 0)
                        break;
                  if (delay_us > us)
                        delay_us = us;
            }
      }

      resp_rates(ctxt, class, &xlog, 1);

      if (!pick_srvr(emsg, class)) {
            fail_more(class);
            dcc_info_unlock(0);
            return 0;
      }

      /* maintain long term average that is used to switch back to
       * good servers that temporarily go bad */
      if (class->thold_rtt == DCC_RTT_BAD) {
            class->avg_thold_rtt = DCC_RTT_BAD;
      } else if (class->avg_thold_rtt == -DCC_RTT_BAD) {
            class->avg_thold_rtt = class->base_rtt;
      } else {
            AGE_AVG(class->avg_thold_rtt, class->base_rtt, 9, 1);
      }

      class->measure = ctxt->now.tv_sec+FAST_RTT_SECS;

      return 1;
}



/* Get and write-lock common info
 *      The contexts must be locked.
 *      The contexts remain locked on failure.  The shared information
 *        is locked only on success. */
u_char                              /* 0=failed 1=ok */
dcc_clnt_rdy(DCC_EMSG emsg,
           DCC_CLNT_CTXT *ctxt,
           u_char flags)            /* DCC_CLNT_FG_* */
{
      DCC_SRVR_CLASS *class;
      DCC_SRVR_ADDR *cur_addr;
      int inx, rtt;
      u_char srvr_ok, locked;

      if (!dcc_info_lock(emsg))
            return 0;

      get_start_time(ctxt);

      /* just fail if things were broken and it's too soon to try again */
      class = DCC_GREY2CLASS(flags & DCC_CLNT_FG_GREY);
      if (!(flags & DCC_CLNT_FG_NO_FAIL)
          && !ck_fail_time(emsg, ctxt, class)) {
            dcc_info_unlock(emsg);
            return 0;
      }

      /* Try to bind a socket with IPv6 first if allowed.
       * If that doesn't work, try IPv4 */
      if (!ctxt->use_ipv6 != !(dcc_clnt_info->flags & DCC_CLNT_INFO_FG_IPV6)
          && ctxt->soc != INVALID_SOCKET) {
            if (SOCKET_ERROR == closesocket(ctxt->soc)
                && dcc_clnt_debug)
                  dcc_trace_msg("closesocket(ctxt): %s", ERROR_STR());
            ctxt->soc = INVALID_SOCKET;
      }

      if (ctxt->soc == INVALID_SOCKET
          && !dcc_clnt_soc_open(emsg, ctxt))
            return 0;

      if (flags & DCC_CLNT_FG_NO_SRVR_OK) {
            /* assume server is ok if the caller doesn't care */
            srvr_ok = 1;
      } else {
            inx = class->act_inx;
            if (inx >= class->num_addrs) {
                  srvr_ok = pick_srvr(emsg, class);
            } else {
                  /* try to pick a new server if the current server
                   * has become slow or unreliable */
                  cur_addr = &class->addrs[inx];
                  rtt = (class->nms[cur_addr->nm_inx].rtt_adj
                         + cur_addr->rtt);
                  if (rtt <= class->thold_rtt)
                        srvr_ok = 1;
                  else
                        srvr_ok = pick_srvr(emsg, class);
            }
      }

      /* Check for new IP addresses occassionally
       * If we cannot awaken a separate thread, do it ourself */
      if (srvr_ok
          && DCC_IS_TIME(ctxt->now.tv_sec, class->resolve,
                     DCC_RE_RESOLVE)
          && !dcc_clnt_wake_resolve())
            srvr_ok = 0;

      locked = 0;
      if (!srvr_ok) {
            if (!dcc_resolve_lock(emsg))
                  return 0;
            locked = 1;
            /* if after waiting for the lock,
             * do the work if it is still needed */

            /* just fail if things became badly broken while we waited
             * and it's too soon to try again  */
            if (!get_now(emsg, ctxt)
                || (!(flags & DCC_CLNT_FG_NO_FAIL)
                  && !ck_fail_time(emsg, ctxt, class))) {
                  dcc_resolve_unlock(0);
                  dcc_info_unlock(0);
                  return 0;
            }

            inx = class->act_inx;
            if (inx < class->num_addrs
                && !DCC_IS_TIME(ctxt->now.tv_sec, class->resolve,
                            DCC_RE_RESOLVE)) {
                  /* everything was fixed while we waited for the lock */
                  srvr_ok = 1;
            } else {
                  /* check for new A RRs */
                  if (!dcc_clnt_resolve(emsg, ctxt, class)) {
                        dcc_resolve_unlock(0);
                        dcc_info_unlock(emsg);
                        return 0;
                  }
            }
      }
      /* srvr_ok == 0 if we should take a measurement */

      /* We might have switched to the current server when our
       * best server became slow.
       * If it has been a while, see if our best server is back. */
      if (srvr_ok
          && DCC_IS_TIME(ctxt->now.tv_sec, class->measure, FAST_RTT_SECS)
          && !(flags & DCC_CLNT_FG_NO_SRVR_OK)) {
            inx = class->act_inx;
            if (inx >= class->num_addrs) {
                  srvr_ok = 0;
            } else {
                  cur_addr = &class->addrs[inx];
                  rtt = (class->nms[cur_addr->nm_inx].rtt_adj
                         + cur_addr->rtt);
                  if (rtt > class->avg_thold_rtt)
                        srvr_ok = 0;
            }
      }

      /* measure the RTTs to all of the servers and pick one */
      if (!srvr_ok) {
            if (!locked) {
                  if (!dcc_resolve_lock(emsg))
                        return 0;
                  locked = 1;
            }
            if (!measure_rtt(emsg, ctxt, class)
                && !(flags & DCC_CLNT_FG_NO_SRVR_OK)) {
                  dcc_resolve_unlock(0);
                  return 0;
            }
      }

      if (locked && !dcc_resolve_unlock(emsg)) {
            dcc_info_unlock(0);
            return 0;
      }
      return 1;
}



/* send an operation to the server and get a response
 *      The operation and response buffers must be distinct, because the
 *        response buffer is changed before the last use of the operation
 *        buffer */
u_char                              /* 0=failed 1=ok */
dcc_clnt_op(DCC_EMSG emsg,
          DCC_CLNT_CTXT *ctxt,
          u_char flags,
          const int *act_inxp,      /* null or ptr to server index or -1 */
          DCC_SRVR_ID *srvr_idp,    /* ID of server used */
          DCC_HDR *msg, int msg_len, DCC_OPS op,
          DCC_HDR *resp, int resp_max_len, DCC_SOCKU *resp_su)
{
      DCC_SRVR_CLASS *class;
      DCC_SRVR_ADDR *cur_addr;
      int addrs_gen;
      union {
          DCC_HDR     hdr;
          DCC_QUERY_RESP query_resp;
          DCC_ADMN_RESP admin_resp;
          char    c[80];
      } buf;
      DCC_XLOG_ENTRY *xloge;
      int act_inx, xmit_num;
      int next_xmit, us, nfds;
      u_char unreachable, gotit;
      int i;

      if (emsg)
            *emsg = '\0';
      dcc_ctxts_lock();
      if (!dcc_clnt_info
          && !dcc_map_info(emsg, 0, -1)) {
            dcc_ctxts_unlock();
            if (srvr_idp)
                  *srvr_idp = DCC_ID_INVALID;
            return 0;
      }
      /* get & lock common info */
      if (!dcc_clnt_rdy(emsg, ctxt, flags)) {
            dcc_ctxts_unlock();
            if (srvr_idp)
                  *srvr_idp = DCC_ID_INVALID;
            return 0;
      }
      class = DCC_GREY2CLASS(flags & DCC_CLNT_FG_GREY);

      if (resp_max_len > ISZ(buf))
            resp_max_len = ISZ(buf);

      /* use server that the caller wants,
       * if the caller specified the valid index of a server */
      if (!act_inxp
          || (act_inx = *act_inxp) < 0
          || act_inx >= class->num_addrs) {
            act_inx = class->act_inx;
      }
      cur_addr = &class->addrs[act_inx];
      if (srvr_idp)
            *srvr_idp = cur_addr->srvr_id;
      if (resp_su)
            dcc_mk_su(resp_su,
                    cur_addr->family, &cur_addr->ip, cur_addr->port);
      addrs_gen = class->gen;

      ++dcc_clnt_info->proto_hdr.op_nums.r;
      memcpy(msg, &dcc_clnt_info->proto_hdr, sizeof(*msg));
      if (cur_addr->srvr_pkt_vers > DCC_PKT_VERSION_MAX
          || cur_addr->srvr_pkt_vers < DCC_PKT_VERSION_MIN) {
            dcc_pemsg(EX_DATAERR, emsg, "impossible pkt_vers %d for %s",
                    cur_addr->srvr_pkt_vers,
                    addr2str(buf.c, sizeof(buf.c), class,
                           addrs_gen, cur_addr, 0));
            dcc_info_unlock(0);
            dcc_ctxts_unlock();
            if (srvr_idp)
                  *srvr_idp = DCC_ID_INVALID;
            return 0;
      }
      msg->pkt_vers = cur_addr->srvr_pkt_vers;
      msg->op_nums.p = getpid();
      msg->op = op;
      gotit = 0;
      unreachable = 0;

      /* The measured RTT's to servers is to help the client pick a server
       * that will respond quickly and reliably and to know when to
       * retransmit a request that is lost due to network congestion or
       * bit rot.
       *
       * It is desirable for a client to try to concentrate its reports to
       * a single server.  That makes detecting spam by this and other
       * clients quicker.
       *
       * A client should retransmit when its initial transmission is lost
       * due to bit rot or congestion.  In case the loss is due to
       * congestion, it should retransmit only a limited number of
       * times and with increasing delays between retransmissions.
       *
       * It is more important that some requests from clients reach
       * a DCC server than others.  Most DCC checksum reports are not about
       * spam, and so it is best to not spend too much network bandwidth
       * retransmitting checksum reports or to delay the processing of the
       * messages. Administrative commands must be tried harder.
       * Therefore, let the caller of this routine decide whether to try
       * again, while this routine merely increases the measured RTT after
       * failures. */

      memset(&ctxt->xlog, 0, sizeof(ctxt->xlog));
      ctxt->xlog.base = ctxt->xlog.next = ctxt->xlog_entries;
      ctxt->xlog.last = LAST(ctxt->xlog_entries);
      xmit_num = 0;
      next_xmit = ctxt->now_us;

      /* Transmit, wait for a response, and retransmit as needed.
       * The initial transmission is done as if it were a retransmission. */
      for (;;) {
            us = next_xmit - ctxt->now_us;
            if (us <= 0) {
                  if (xmit_num >= DCC_MAX_XMITS)
                        break;

                  /* because of the flooding algorithm among DCC servers,
                   * it is important that only a single server receive
                   * reports of the checksums for a mail message.
                   * That implies that retransmissions of reports must
                   * go to the original server, even if some other local
                   * client has re-resolved hostnames or switched
                   * to a better server.
                   * And that means we should not retransmit
                   * if the server address table is changed. */
                  if (addrs_gen != class->gen)
                        break;

                  if (!clnt_xmit(emsg, ctxt, &ctxt->xlog,
                               class, cur_addr, msg, msg_len, 1))
                        break;
                  us = dcc_retrans_time(cur_addr->rtt, ++xmit_num);
                  next_xmit = us + ctxt->now_us;
            }

            /* release the mapped info while we wait for an answer */
            if (!dcc_info_unlock(emsg)) {
                  dcc_ctxts_unlock();
                  if (srvr_idp)
                        *srvr_idp = DCC_ID_INVALID;
                  return 0;
            }
            dcc_ctxts_unlock();
            nfds = dcc_select_poll(emsg, ctxt->soc, 1, us);
            if (nfds < 0) {
                  /* note error, but we may already have an answer */
                  dcc_ctxts_lock();
                  class = DCC_GREY2CLASS(flags & DCC_CLNT_FG_GREY);
                  break;
            }
            if (!get_now(emsg, ctxt))
                  return 0;       /* simply give up if time jumped */

            /* recover the lock so that we can record the result of the
             * newly arrived answer in the shared and mapped file */
            dcc_ctxts_lock();
            class = DCC_GREY2CLASS(flags & DCC_CLNT_FG_GREY);
            if (!dcc_info_lock(emsg)) {
                  dcc_ctxts_unlock();
                  if (srvr_idp)
                        *srvr_idp = DCC_ID_INVALID;
                  return 0;
            }

            if (nfds > 0) {
                  for (;;) {
                        i = clnt_recv(emsg, ctxt, class, &buf.hdr,
                                    min(ISZ(buf), resp_max_len),
                                    msg, &ctxt->xlog, &xloge);
                        if (i <= 0)
                              break;
                        if (i == 1) {
                              /* stop delaying after the first
                               * ICMP Unreachable message,
                               * but collect everything that has
                               * already arrived */
                              unreachable = 1;
                              continue;
                        }

                        update_rtt(ctxt, class, xloge,
                                 ctxt->now_us - xloge->sent_us
                                 + ((xloge->op != DCC_OP_REPORT
                                     && xloge->op != DCC_OP_QUERY)
                                    ? cur_addr->srvr_wait : 0));

                        /* save the last answer we get */
                        memcpy(resp, &buf, ntohs(buf.hdr.len));
                        gotit = 1;
                  }
                  if (i < 0 || unreachable || gotit)
                        break;
            }
      }

      /* penalize server for lost packets */
      resp_rates(ctxt, class, &ctxt->xlog, 0);

      /* fail if the server did not answer at all */
      if (!gotit) {
#if 0
            system("./abort_dccd");
#endif
            if (dcc_clnt_debug
                && emsg && *emsg != '\0')
                  dcc_trace_msg("%s", emsg);
            dcc_pemsg(EX_TEMPFAIL, emsg, "no answer from %s after %d ms",
                    addr2str(buf.c, sizeof(buf.c), class,
                           addrs_gen, cur_addr, 0),
                    ctxt->now_us/1000);
            /* Since we got no answer at all, look for a different server.
             * If we can't find any server or a different server,
             * then don't try again for a while to not delay sendmail.
             * If we find another server, then return a valid server-ID
             * to let the caller know that it can try again immediately */
            if (pick_srvr(0, class) != 2) {
                  fail_more(class);
                  if (srvr_idp)
                        *srvr_idp = DCC_ID_INVALID;
            }
            dcc_info_unlock(0);
            dcc_ctxts_unlock();
            return 0;
      }

      if (!dcc_info_unlock(emsg)) {
            dcc_ctxts_unlock();
            if (srvr_idp)
                  *srvr_idp = DCC_ID_INVALID;
            return 0;
      }
      dcc_ctxts_unlock();

      if (dcc_clnt_debug
          && emsg && *emsg != '\0') {
            dcc_trace_msg("%s", emsg);
            *emsg = '\0';
      }
      return 1;
}

Generated by  Doxygen 1.6.0   Back to index