Add /statusz page to redbean plus other enhancements

redbean improvements:

- Explicitly disable corking
- Simulate Python regex API for Lua
- Send warmup requests in main process on startup
- Add Class-A granular IPv4 network classification
- Add /statusz page so you can monitor your redbean's health
- Fix regressions on OpenBSD/NetBSD caused by recent changes
- Plug Authorization header into Lua GetUser and GetPass APIs
- Recognize X-Forwarded-{For,Host} from local reverse proxies
- Add many additional functions to redbean Lua server page API
- Report resource usage of child processes on `/` listing page
- Introduce `-a` flag for logging child process resource usage
- Introduce `-t MILLIS` flag and `ProgramTimeout(ms)` init API
- Introduce `-H "Header: value"` flag and `ProgramHeader(k,v)` API

Cosmopolitan Libc improvements:

- Make strerror() simpler
- Make inet_pton() not depend on sscanf()
- Fix OpenExecutable() which broke .data section earlier
- Fix stdio in cases where it overflows kernel tty buffer
- Fix bugs in crash reporting w/o .com.dbg binary present
- Add polyfills for SO_LINGER, SO_RCVTIMEO, and SO_SNDTIMEO
- Polyfill TCP_CORK on BSD and XNU using TCP_NOPUSH magnums

New netcat clone in examples/nc.c:

While testing some of the failure conditions for redbean, I noticed that
BusyBox's `nc` command is pretty busted, if you use it as an interactive
tool, rather than having it be part of a pipeline. Unfortunately this'll
only work on UNIX since Windows doesn't let us poll on stdio and sockets
at the same time because I don't think they want tools like this running
on their platform. So if you want forbidden fruit, it's here so enjoy it

libc/stdio/fflush.c

@@ -37,7 +37,6 @@
  */
 int fflush(FILE *f) {
   size_t i;
-  ssize_t rc;
   if (!f) {
     for (i = __fflush.handles.i; i; --i) {
       if ((f = __fflush.handles.p[i - 1])) {
@@ -45,14 +44,7 @@ int fflush(FILE *f) {
       }
     }
   } else if (f->fd != -1) {
-    while (f->beg && !f->end && (f->iomode & O_ACCMODE) != O_RDONLY) {
-      if ((rc = write(f->fd, f->buf, f->beg)) == -1) {
-        f->state = errno;
-        return -1;
-      }
-      if (rc != f->beg) abort();
-      f->beg = 0;
-    }
+    if (__fflush_impl(f) == -1) return -1;
   } else if (f->beg && f->beg < f->size) {
     f->buf[f->beg] = 0;
   }

libc/stdio/fflushimpl.c

@@ -0,0 +1,37 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or 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 THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR 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.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/errno.h"
+#include "libc/stdio/internal.h"
+#include "libc/sysv/consts/o.h"
+
+int __fflush_impl(FILE *f) {
+  size_t i;
+  ssize_t rc;
+  if (f->beg && !f->end && (f->iomode & O_ACCMODE) != O_RDONLY) {
+    for (i = 0; i < f->beg; i += rc) {
+      if ((rc = write(f->fd, f->buf + i, f->beg - i)) == -1) {
+        f->state = errno;
+        return -1;
+      }
+    }
+    f->beg = 0;
+  }
+  return 0;
+}

libc/stdio/fseeko.c

@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/errno.h"
+#include "libc/stdio/internal.h"
 #include "libc/stdio/stdio.h"
 #include "libc/sysv/consts/o.h"
 
@@ -38,14 +39,7 @@ int fseeko(FILE *f, int64_t offset, int whence) {
   ssize_t rc;
   int64_t pos;
   if (f->fd != -1) {
-    if (f->beg && !f->end && (f->iomode & O_ACCMODE) != O_RDONLY) {
-      if ((rc = write(f->fd, f->buf, f->beg)) == -1) {
-        f->state = errno;
-        return -1;
-      }
-      if (rc != f->beg) abort();
-      f->beg = 0;
-    }
+    if (__fflush_impl(f) == -1) return -1;
     if (whence == SEEK_CUR && f->beg < f->end) {
       offset -= f->end - f->beg;
     }

libc/stdio/ftello.c

@@ -19,6 +19,7 @@
 #include "libc/calls/calls.h"
 #include "libc/errno.h"
 #include "libc/runtime/runtime.h"
+#include "libc/stdio/internal.h"
 #include "libc/stdio/stdio.h"
 #include "libc/sysv/consts/o.h"
 
@@ -29,18 +30,10 @@
  * @returns current byte offset from beginning, or -1 w/ errno
  */
 int64_t ftello(FILE *f) {
-  ssize_t rc;
   int64_t pos;
   uint32_t skew;
   if (f->fd != -1) {
-    if (f->beg && !f->end && (f->iomode & O_ACCMODE) != O_RDONLY) {
-      if ((rc = write(f->fd, f->buf, f->beg)) == -1) {
-        f->state = errno;
-        return -1;
-      }
-      if (rc != f->beg) abort();
-      f->beg = 0;
-    }
+    if (__fflush_impl(f) == -1) return -1;
     if ((pos = lseek(f->fd, 0, SEEK_CUR)) != -1) {
       if (f->beg < f->end) pos -= f->end - f->beg;
       return pos;

libc/stdio/fwrite.c

@@ -28,6 +28,30 @@
 #include "libc/str/str.h"
 #include "libc/sysv/consts/o.h"
 
+static ssize_t WritevAll(int fd, struct iovec *iov, int iovlen) {
+  ssize_t rc;
+  size_t wrote;
+  do {
+    if ((rc = writev(fd, iov, iovlen)) != -1) {
+      wrote = rc;
+      do {
+        if (wrote >= iov->iov_len) {
+          wrote -= iov->iov_len;
+          ++iov;
+          --iovlen;
+        } else {
+          iov->iov_base = (char *)iov->iov_base + wrote;
+          iov->iov_len -= wrote;
+          wrote = 0;
+        }
+      } while (wrote);
+    } else if (errno != EINTR) {
+      return -1;
+    }
+  } while (iovlen);
+  return 0;
+}
+
 /**
  * Writes data to stream.
  *
@@ -78,12 +102,10 @@ size_t fwrite(const void *data, size_t stride, size_t count, FILE *f) {
   iov[1].iov_base = data;
   iov[1].iov_len = n;
   n += f->beg;
-  if ((rc = writev(f->fd, iov, 2)) == -1) {
+  if (WritevAll(f->fd, iov, 2) == -1) {
     f->state = errno;
     return 0;
   }
-  m = rc;
-  if (n != m) abort();
   f->beg = 0;
   return count;
 }

libc/stdio/internal.h

@@ -11,6 +11,7 @@ extern char g_stdinbuf[BUFSIZ];
 extern char g_stdoutbuf[BUFSIZ];
 extern char g_stderrbuf[BUFSIZ];
 
+int __fflush_impl(FILE *) hidden;
 int __fflush_register(FILE *) hidden;
 void __fflush_unregister(FILE *) hidden;