1 files changed, 654 insertions, 0 deletions

diff --git a/nacl/curvecp/curvecpmessage.c b/nacl/curvecp/curvecpmessage.c
new file mode 100644
index 00000000..df1e1664
--- /dev/null
+++ b/nacl/curvecp/curvecpmessage.c
@@ -0,0 +1,654 @@
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <signal.h>
+#include <poll.h>
+#include "open.h"
+#include "blocking.h"
+#include "e.h"
+#include "die.h"
+#include "randommod.h"
+#include "byte.h"
+#include "crypto_uint32.h"
+#include "uint16_pack.h"
+#include "uint32_pack.h"
+#include "uint64_pack.h"
+#include "uint16_unpack.h"
+#include "uint32_unpack.h"
+#include "uint64_unpack.h"
+#include "nanoseconds.h"
+#include "writeall.h"
+
+int flagverbose = 1;
+int flagserver = 1;
+int wantping = 0; /* 1: ping after a second; 2: ping immediately */
+
+#define USAGE "\
+curvecpmessage: how to use:\n\
+curvecpmessage:   -q (optional): no error messages\n\
+curvecpmessage:   -Q (optional): print error messages (default)\n\
+curvecpmessage:   -v (optional): print extra information\n\
+curvecpmessage:   -c (optional): program is a client; server starts first\n\
+curvecpmessage:   -C (optional): program is a client that starts first\n\
+curvecpmessage:   -s (optional): program is a server (default)\n\
+curvecpmessage:   prog: run this program\n\
+"
+
+void die_usage(const char *s)
+{
+  if (s) die_4(100,USAGE,"curvecpmessage: fatal: ",s,"\n");
+  die_1(100,USAGE);
+}
+
+void die_fatal(const char *trouble,const char *d,const char *fn)
+{
+  if (!flagverbose) die_0(111);
+  if (d) {
+    if (fn) die_9(111,"curvecpmessage: fatal: ",trouble," ",d,"/",fn,": ",e_str(errno),"\n");
+    die_7(111,"curvecpmessage: fatal: ",trouble," ",d,": ",e_str(errno),"\n");
+  }
+  if (errno) die_5(111,"curvecpmessage: fatal: ",trouble,": ",e_str(errno),"\n");
+  die_3(111,"curvecpmessage: fatal: ",trouble,"\n");
+}
+
+void die_badmessage(void)
+{
+  errno = EPROTO;
+  die_fatal("unable to read from file descriptor 8",0,0);
+}
+
+void die_internalerror(void)
+{
+  errno = EPROTO;
+  die_fatal("internal error",0,0);
+}
+
+
+int tochild[2] = {-1,-1};
+int fromchild[2] = {-1,-1};
+pid_t child = -1;
+int childstatus;
+
+struct pollfd p[3];
+
+long long sendacked = 0; /* number of initial bytes sent and fully acknowledged */
+long long sendbytes = 0; /* number of additional bytes to send */
+unsigned char sendbuf[131072]; /* circular queue with the additional bytes; size must be power of 2 */
+long long sendprocessed = 0; /* within sendbytes, number of bytes absorbed into blocks */
+
+crypto_uint16 sendeof = 0; /* 2048 for normal eof after sendbytes, 4096 for error after sendbytes */
+int sendeofprocessed = 0;
+int sendeofacked = 0;
+
+long long totalblocktransmissions = 0;
+long long totalblocks = 0;
+
+#define OUTGOING 128 /* must be power of 2 */
+long long blocknum = 0; /* number of outgoing blocks being tracked */
+long long blockfirst = 0; /* circular queue */
+long long blockpos[OUTGOING]; /* position of block's first byte within stream */
+long long blocklen[OUTGOING]; /* number of bytes in this block */
+crypto_uint16 blockeof[OUTGOING]; /* 0, 2048, 4096 */
+long long blocktransmissions[OUTGOING];
+long long blocktime[OUTGOING]; /* time of last message sending this block; 0 means acked */
+long long earliestblocktime = 0; /* if nonzero, minimum of active blocktime values */
+crypto_uint32 blockid[OUTGOING]; /* ID of last message sending this block */
+
+#define INCOMING 64 /* must be power of 2 */
+long long messagenum = 0; /* number of messages in incoming queue */
+long long messagefirst = 0; /* position of first message; circular queue */
+unsigned char messagelen[INCOMING]; /* times 16 */
+unsigned char message[INCOMING][1088];
+unsigned char messagetodo[2048];
+long long messagetodolen = 0;
+
+long long receivebytes = 0; /* number of initial bytes fully received */
+long long receivewritten = 0; /* within receivebytes, number of bytes given to child */
+crypto_uint16 receiveeof = 0; /* 0, 2048, 4096 */
+long long receivetotalbytes = 0; /* total number of bytes in stream, if receiveeof */
+unsigned char receivebuf[131072]; /* circular queue beyond receivewritten; size must be power of 2 */
+unsigned char receivevalid[131072]; /* 1 for byte successfully received; XXX: use buddy structure to speed this up */
+
+long long maxblocklen = 512;
+crypto_uint32 nextmessageid = 1;
+
+unsigned char buf[4096];
+
+long long lastblocktime = 0;
+long long nsecperblock = 1000000000;
+long long lastspeedadjustment = 0;
+long long lastedge = 0;
+long long lastdoubling = 0;
+
+long long rtt;
+long long rtt_delta;
+long long rtt_average = 0;
+long long rtt_deviation = 0;
+long long rtt_lowwater = 0;
+long long rtt_highwater = 0;
+long long rtt_timeout = 1000000000;
+long long rtt_seenrecenthigh = 0;
+long long rtt_seenrecentlow = 0;
+long long rtt_seenolderhigh = 0;
+long long rtt_seenolderlow = 0;
+long long rtt_phase = 0;
+
+long long lastpanic = 0;
+
+void earliestblocktime_compute(void) /* XXX: use priority queue */
+{
+  long long i;
+  long long pos;
+  earliestblocktime = 0;
+  for (i = 0;i < blocknum;++i) {
+    pos = (blockfirst + i) & (OUTGOING - 1);
+    if (blocktime[pos]) {
+      if (!earliestblocktime)
+        earliestblocktime = blocktime[pos];
+      else
+        if (blocktime[pos] < earliestblocktime)
+          earliestblocktime = blocktime[pos];
+    }
+  }
+}
+
+void acknowledged(unsigned long long start,unsigned long long stop)
+{
+  long long i;
+  long long pos;
+  if (stop == start) return;
+  for (i = 0;i < blocknum;++i) {
+    pos = (blockfirst + i) & (OUTGOING - 1);
+    if (blockpos[pos] >= start && blockpos[pos] + blocklen[pos] <= stop) {
+      blocktime[pos] = 0;
+      totalblocktransmissions += blocktransmissions[pos];
+      totalblocks += 1;
+    }
+  }
+  while (blocknum) {
+    pos = blockfirst & (OUTGOING - 1);
+    if (blocktime[pos]) break;
+    sendacked += blocklen[pos];
+    sendbytes -= blocklen[pos];
+    sendprocessed -= blocklen[pos];
+    ++blockfirst;
+    --blocknum;
+  }
+  if (sendeof)
+    if (start == 0)
+      if (stop > sendacked + sendbytes)
+        if (!sendeofacked) {
+          sendeofacked = 1;
+        }
+  earliestblocktime_compute();
+}
+
+int main(int argc,char **argv)
+{
+  long long pos;
+  long long len;
+  long long u;
+  long long r;
+  long long i;
+  long long k;
+  long long recent;
+  long long nextaction;
+  long long timeout;
+  struct pollfd *q;
+  struct pollfd *watch8;
+  struct pollfd *watchtochild;
+  struct pollfd *watchfromchild;
+
+  signal(SIGPIPE,SIG_IGN);
+
+  if (!argv[0]) die_usage(0);
+  for (;;) {
+    char *x;
+    if (!argv[1]) break;
+    if (argv[1][0] != '-') break;
+    x = *++argv;
+    if (x[0] == '-' && x[1] == 0) break;
+    if (x[0] == '-' && x[1] == '-' && x[2] == 0) break;
+    while (*++x) {
+      if (*x == 'q') { flagverbose = 0; continue; }
+      if (*x == 'Q') { flagverbose = 1; continue; }
+      if (*x == 'v') { if (flagverbose == 2) flagverbose = 3; else flagverbose = 2; continue; }
+      if (*x == 'c') { flagserver = 0; wantping = 2; continue; }
+      if (*x == 'C') { flagserver = 0; wantping = 1; continue; }
+      if (*x == 's') { flagserver = 1; wantping = 0; continue; }
+      die_usage(0);
+    }
+  }
+  if (!*++argv) die_usage("missing prog");
+
+  for (;;) {
+    r = open_read("/dev/null");
+    if (r == -1) die_fatal("unable to open /dev/null",0,0);
+    if (r > 9) { close(r); break; }
+  }
+
+  if (open_pipe(tochild) == -1) die_fatal("unable to create pipe",0,0);
+  if (open_pipe(fromchild) == -1) die_fatal("unable to create pipe",0,0);
+
+  blocking_enable(tochild[0]);
+  blocking_enable(fromchild[1]);
+
+  child = fork();
+  if (child == -1) die_fatal("unable to fork",0,0);
+  if (child == 0) {
+    close(8);
+    close(9);
+    if (flagserver) {
+      close(0);
+      if (dup(tochild[0]) != 0) die_fatal("unable to dup",0,0);
+      close(1);
+      if (dup(fromchild[1]) != 1) die_fatal("unable to dup",0,0);
+    } else {
+      close(6);
+      if (dup(tochild[0]) != 6) die_fatal("unable to dup",0,0);
+      close(7);
+      if (dup(fromchild[1]) != 7) die_fatal("unable to dup",0,0);
+    }
+    signal(SIGPIPE,SIG_DFL);
+    execvp(*argv,argv);
+    die_fatal("unable to run",*argv,0);
+  }
+
+  close(tochild[0]);
+  close(fromchild[1]);
+
+  recent = nanoseconds();
+  lastspeedadjustment = recent;
+  if (flagserver) maxblocklen = 1024;
+
+  for (;;) {
+    if (sendeofacked)
+      if (receivewritten == receivetotalbytes)
+        if (receiveeof)
+          if (tochild[1] < 0)
+            break; /* XXX: to re-ack should enter a TIME-WAIT state here */
+
+    q = p;
+
+    watch8 = q;
+    if (watch8) { q->fd = 8; q->events = POLLIN; ++q; }
+
+    watchtochild = q;
+    if (tochild[1] < 0) watchtochild = 0;
+    if (receivewritten >= receivebytes) watchtochild = 0;
+    if (watchtochild) { q->fd = tochild[1]; q->events = POLLOUT; ++q; }
+
+    watchfromchild = q;
+    if (sendeof) watchfromchild = 0;
+    if (sendbytes + 4096 > sizeof sendbuf) watchfromchild = 0;
+    if (watchfromchild) { q->fd = fromchild[0]; q->events = POLLIN; ++q; }
+
+    nextaction = recent + 60000000000LL;
+    if (wantping == 1) nextaction = recent + 1000000000;
+    if (wantping == 2)
+      if (nextaction > lastblocktime + nsecperblock) nextaction = lastblocktime + nsecperblock;
+    if (blocknum < OUTGOING)
+      if (!(sendeof ? sendeofprocessed : sendprocessed >= sendbytes))
+        if (nextaction > lastblocktime + nsecperblock) nextaction = lastblocktime + nsecperblock;
+    if (earliestblocktime)
+      if (earliestblocktime + rtt_timeout > lastblocktime + nsecperblock)
+        if (earliestblocktime + rtt_timeout < nextaction)
+          nextaction = earliestblocktime + rtt_timeout;
+
+    if (messagenum)
+      if (!watchtochild)
+        nextaction = 0;
+
+    if (nextaction <= recent)
+      timeout = 0;
+    else
+      timeout = (nextaction - recent) / 1000000 + 1;
+
+    if (poll(p,q - p,timeout) < 0) {
+      watch8 = 0;
+      watchtochild = 0;
+      watchfromchild = 0;
+    } else {
+      if (watch8) if (!watch8->revents) watch8 = 0;
+      if (watchtochild) if (!watchtochild->revents) watchtochild = 0;
+      if (watchfromchild) if (!watchfromchild->revents) watchfromchild = 0;
+    }
+
+    /* XXX: keepalives */
+
+    do { /* try receiving data from child: */
+      if (!watchfromchild) break;
+      if (sendeof) break;
+      if (sendbytes + 4096 > sizeof sendbuf) break;
+
+      pos = (sendacked & (sizeof sendbuf - 1)) + sendbytes;
+      if (pos < sizeof sendbuf) {
+        r = read(fromchild[0],sendbuf + pos,sizeof sendbuf - pos);
+      } else {
+        r = read(fromchild[0],sendbuf + pos - sizeof sendbuf,sizeof sendbuf - sendbytes);
+      }
+      if (r == -1) if (errno == EINTR || errno == EWOULDBLOCK || errno == EAGAIN) break;
+      if (r < 0) { sendeof = 4096; break; }
+      if (r == 0) { sendeof = 2048; break; }
+      sendbytes += r;
+      if (sendbytes >= 1152921504606846976LL) die_internalerror();
+    } while(0);
+
+    recent = nanoseconds();
+
+    do { /* try re-sending an old block: */
+      if (recent < lastblocktime + nsecperblock) break;
+      if (earliestblocktime == 0) break;
+      if (recent < earliestblocktime + rtt_timeout) break;
+
+      for (i = 0;i < blocknum;++i) {
+        pos = (blockfirst + i) & (OUTGOING - 1);
+        if (blocktime[pos] == earliestblocktime) {
+          if (recent > lastpanic + 4 * rtt_timeout) {
+            nsecperblock *= 2;
+            lastpanic = recent;
+            lastedge = recent;
+          }
+          goto sendblock;
+        }
+      }
+    } while(0);
+
+    do { /* try sending a new block: */
+      if (recent < lastblocktime + nsecperblock) break;
+      if (blocknum >= OUTGOING) break;
+      if (!wantping)
+        if (sendeof ? sendeofprocessed : sendprocessed >= sendbytes) break;
+      /* XXX: if any Nagle-type processing is desired, do it here */
+
+      pos = (blockfirst + blocknum) & (OUTGOING - 1);
+      ++blocknum;
+      blockpos[pos] = sendacked + sendprocessed;
+      blocklen[pos] = sendbytes - sendprocessed;
+      if (blocklen[pos] > maxblocklen) blocklen[pos] = maxblocklen;
+      if ((blockpos[pos] & (sizeof sendbuf - 1)) + blocklen[pos] > sizeof sendbuf)
+        blocklen[pos] = sizeof sendbuf - (blockpos[pos] & (sizeof sendbuf - 1));
+        /* XXX: or could have the full block in post-buffer space */
+      sendprocessed += blocklen[pos];
+      blockeof[pos] = 0;
+      if (sendprocessed == sendbytes) {
+        blockeof[pos] = sendeof;
+        if (sendeof) sendeofprocessed = 1;
+      }
+      blocktransmissions[pos] = 0;
+
+      sendblock:
+
+      blocktransmissions[pos] += 1;
+      blocktime[pos] = recent;
+      blockid[pos] = nextmessageid;
+      if (!++nextmessageid) ++nextmessageid;
+
+      /* constraints: u multiple of 16; u >= 16; u <= 1088; u >= 48 + blocklen[pos] */
+      u = 64 + blocklen[pos];
+      if (u <= 192) u = 192;
+      else if (u <= 320) u = 320;
+      else if (u <= 576) u = 576;
+      else if (u <= 1088) u = 1088;
+      else die_internalerror();
+      if (blocklen[pos] < 0 || blocklen[pos] > 1024) die_internalerror();
+
+      byte_zero(buf + 8,u);
+      buf[7] = u / 16;
+      uint32_pack(buf + 8,blockid[pos]);
+      /* XXX: include any acknowledgments that have piled up */
+      uint16_pack(buf + 46,blockeof[pos] | (crypto_uint16) blocklen[pos]);
+      uint64_pack(buf + 48,blockpos[pos]);
+      byte_copy(buf + 8 + u - blocklen[pos],blocklen[pos],sendbuf + (blockpos[pos] & (sizeof sendbuf - 1)));
+
+      if (writeall(9,buf + 7,u + 1) == -1) die_fatal("unable to write descriptor 9",0,0);
+      lastblocktime = recent;
+      wantping = 0;
+
+      earliestblocktime_compute();
+    } while(0);
+
+    do { /* try receiving messages: */
+      if (!watch8) break;
+      r = read(8,buf,sizeof buf);
+      if (r == -1) if (errno == EINTR || errno == EWOULDBLOCK || errno == EAGAIN) break;
+      if (r == 0) die_badmessage();
+      if (r < 0) die_fatal("unable to read from file descriptor 8",0,0);
+      for (k = 0;k < r;++k) {
+        messagetodo[messagetodolen++] = buf[k];
+        u = 16 * (unsigned long long) messagetodo[0];
+        if (u < 16) die_badmessage();
+        if (u > 1088) die_badmessage();
+        if (messagetodolen == 1 + u) {
+          if (messagenum < INCOMING) {
+            pos = (messagefirst + messagenum) & (INCOMING - 1);
+            messagelen[pos] = messagetodo[0];
+            byte_copy(message[pos],u,messagetodo + 1);
+            ++messagenum;
+          } else {
+            ; /* drop tail */
+          }
+          messagetodolen = 0;
+        }
+      }
+    } while(0);
+
+    do { /* try processing a message: */
+      if (!messagenum) break;
+      if (tochild[1] >= 0 && receivewritten < receivebytes) break;
+
+      maxblocklen = 1024;
+
+      pos = messagefirst & (INCOMING - 1);
+      len = 16 * (unsigned long long) messagelen[pos];
+      do { /* handle this message if it's comprehensible: */
+        unsigned long long D;
+        unsigned long long SF;
+        unsigned long long startbyte;
+        unsigned long long stopbyte;
+        crypto_uint32 id;
+        long long i;
+
+        if (len < 48) break;
+        if (len > 1088) break;
+
+        id = uint32_unpack(message[pos] + 4);
+        for (i = 0;i < blocknum;++i) {
+          k = (blockfirst + i) & (OUTGOING - 1);
+          if (blockid[k] == id) {
+            rtt = recent - blocktime[k];
+            if (!rtt_average) {
+              nsecperblock = rtt;
+              rtt_average = rtt;
+              rtt_deviation = rtt / 2;
+              rtt_highwater = rtt;
+              rtt_lowwater = rtt;
+            }
+
+            /* Jacobson's retransmission timeout calculation: */
+            rtt_delta = rtt - rtt_average;
+            rtt_average += rtt_delta / 8;
+            if (rtt_delta < 0) rtt_delta = -rtt_delta;
+            rtt_delta -= rtt_deviation;
+            rtt_deviation += rtt_delta / 4;
+            rtt_timeout = rtt_average + 4 * rtt_deviation;
+            /* adjust for delayed acks with anti-spiking: */
+            rtt_timeout += 8 * nsecperblock;
+
+            /* recognizing top and bottom of congestion cycle: */
+            rtt_delta = rtt - rtt_highwater;
+            rtt_highwater += rtt_delta / 1024;
+            rtt_delta = rtt - rtt_lowwater;
+            if (rtt_delta > 0) rtt_lowwater += rtt_delta / 8192;
+            else rtt_lowwater += rtt_delta / 256;
+
+            if (rtt_average > rtt_highwater + 5000000) rtt_seenrecenthigh = 1;
+            else if (rtt_average < rtt_lowwater) rtt_seenrecentlow = 1;
+
+            if (recent >= lastspeedadjustment + 16 * nsecperblock) {
+              if (recent - lastspeedadjustment > 10000000000LL) {
+                nsecperblock = 1000000000; /* slow restart */
+                nsecperblock += randommod(nsecperblock / 8);
+              }
+
+              lastspeedadjustment = recent;
+
+              if (nsecperblock >= 131072) {
+                /* additive increase: adjust 1/N by a constant c */
+                /* rtt-fair additive increase: adjust 1/N by a constant c every nanosecond */
+                /* approximation: adjust 1/N by cN every N nanoseconds */
+                /* i.e., N <- 1/(1/N + cN) = N/(1 + cN^2) every N nanoseconds */
+                if (nsecperblock < 16777216) {
+                  /* N/(1+cN^2) approx N - cN^3 */
+                  u = nsecperblock / 131072;
+                  nsecperblock -= u * u * u;
+                } else {
+                  double d = nsecperblock;
+                  nsecperblock = d/(1 + d*d / 2251799813685248.0);
+                }
+              }
+
+              if (rtt_phase == 0) {
+                if (rtt_seenolderhigh) {
+                  rtt_phase = 1;
+                  lastedge = recent;
+                  nsecperblock += randommod(nsecperblock / 4);
+                }
+              } else {
+                if (rtt_seenolderlow) {
+                  rtt_phase = 0;
+                }
+              }
+
+              rtt_seenolderhigh = rtt_seenrecenthigh;
+              rtt_seenolderlow = rtt_seenrecentlow;
+              rtt_seenrecenthigh = 0;
+              rtt_seenrecentlow = 0;
+            }
+
+            do {
+              if (recent - lastedge < 60000000000LL) {
+                if (recent < lastdoubling + 4 * nsecperblock + 64 * rtt_timeout + 5000000000LL) break;
+              } else {
+                if (recent < lastdoubling + 4 * nsecperblock + 2 * rtt_timeout) break;
+              }
+              if (nsecperblock <= 65535) break;
+
+              nsecperblock /= 2;
+              lastdoubling = recent;
+              if (lastedge) lastedge = recent;
+            } while(0);
+          }
+        }
+
+        stopbyte = uint64_unpack(message[pos] + 8);
+        acknowledged(0,stopbyte);
+        startbyte = stopbyte + (unsigned long long) uint32_unpack(message[pos] + 16);
+        stopbyte = startbyte + (unsigned long long) uint16_unpack(message[pos] + 20);
+        acknowledged(startbyte,stopbyte);
+        startbyte = stopbyte + (unsigned long long) uint16_unpack(message[pos] + 22);
+        stopbyte = startbyte + (unsigned long long) uint16_unpack(message[pos] + 24);
+        acknowledged(startbyte,stopbyte);
+        startbyte = stopbyte + (unsigned long long) uint16_unpack(message[pos] + 26);
+        stopbyte = startbyte + (unsigned long long) uint16_unpack(message[pos] + 28);
+        acknowledged(startbyte,stopbyte);
+        startbyte = stopbyte + (unsigned long long) uint16_unpack(message[pos] + 30);
+        stopbyte = startbyte + (unsigned long long) uint16_unpack(message[pos] + 32);
+        acknowledged(startbyte,stopbyte);
+        startbyte = stopbyte + (unsigned long long) uint16_unpack(message[pos] + 34);
+        stopbyte = startbyte + (unsigned long long) uint16_unpack(message[pos] + 36);
+        acknowledged(startbyte,stopbyte);
+
+        D = uint16_unpack(message[pos] + 38);
+        SF = D & (2048 + 4096);
+        D -= SF;
+        if (D > 1024) break;
+        if (48 + D > len) break;
+
+        startbyte = uint64_unpack(message[pos] + 40);
+        stopbyte = startbyte + D;
+
+        if (stopbyte > receivewritten + sizeof receivebuf) {
+          break;
+          /* of course, flow control would avoid this case */
+        }
+
+        if (SF) {
+          receiveeof = SF;
+          receivetotalbytes = stopbyte;
+        }
+
+        for (k = 0;k < D;++k) {
+          unsigned char ch = message[pos][len - D + k];
+          unsigned long long where = startbyte + k;
+          if (where >= receivewritten && where < receivewritten + sizeof receivebuf) {
+            receivevalid[where & (sizeof receivebuf - 1)] = 1;
+            receivebuf[where & (sizeof receivebuf - 1)] = ch;
+          }
+        }
+        for (;;) {
+          if (receivebytes >= receivewritten + sizeof receivebuf) break;
+          if (!receivevalid[receivebytes & (sizeof receivebuf - 1)]) break;
+          ++receivebytes;
+        }
+
+        if (!uint32_unpack(message[pos])) break; /* never acknowledge a pure acknowledgment */
+
+        /* XXX: delay acknowledgments */
+        u = 192;
+        byte_zero(buf + 8,u);
+        buf[7] = u / 16;
+        byte_copy(buf + 12,4,message[pos]);
+        if (receiveeof && receivebytes == receivetotalbytes) {
+          uint64_pack(buf + 16,receivebytes + 1);
+        } else
+          uint64_pack(buf + 16,receivebytes);
+        /* XXX: incorporate selective acknowledgments */
+  
+        if (writeall(9,buf + 7,u + 1) == -1) die_fatal("unable to write descriptor 9",0,0);
+      } while(0);
+
+      ++messagefirst;
+      --messagenum;
+    } while(0);
+
+    do { /* try sending data to child: */
+      if (!watchtochild) break;
+      if (tochild[1] < 0) { receivewritten = receivebytes; break; }
+      if (receivewritten >= receivebytes) break;
+
+      pos = receivewritten & (sizeof receivebuf - 1);
+      len = receivebytes - receivewritten;
+      if (pos + len > sizeof receivebuf) len = sizeof receivebuf - pos;
+      r = write(tochild[1],receivebuf + pos,len);
+      if (r == -1) if (errno == EINTR || errno == EWOULDBLOCK || errno == EAGAIN) break;
+      if (r <= 0) {
+        close(tochild[1]);
+        tochild[1] = -1;
+        break;
+      }
+      byte_zero(receivevalid + pos,r);
+      receivewritten += r;
+    } while(0);
+
+    do { /* try closing pipe to child: */
+      if (!receiveeof) break;
+      if (receivewritten < receivetotalbytes) break;
+      if (tochild[1] < 0) break;
+
+      if (receiveeof == 4096)
+        ; /* XXX: UNIX doesn't provide a way to signal an error through a pipe */
+      close(tochild[1]);
+      tochild[1] = -1;
+    } while(0);
+
+  }
+
+
+  do {
+    r = waitpid(child,&childstatus,0);
+  } while (r == -1 && errno == EINTR);
+
+  if (!WIFEXITED(childstatus)) { errno = 0; die_fatal("process killed by signal",0,0); }
+  return WEXITSTATUS(childstatus);
+}