Make more Windows socket fixes and improvements

This change makes send() / sendto() always block on Windows. It's needed
because poll(POLLOUT) doesn't guarantee a socket is immediately writable
on Windows, and it caused rsync to fail because it made that assumption.
The only exception is when a SO_SNDTIMEO is specified which will EAGAIN.

Tests are added confirming MSG_WAITALL and MSG_NOSIGNAL work as expected
on all our supported OSes. Most of the platform-specific MSG_FOO magnums
have been deleted, with the exception of MSG_FASTOPEN. Your --strace log
will now show MSG_FOO flags as symbols rather than numbers.

I've also removed cv_wait_example_test because it's 0.3% flaky with Qemu
under system load since it depends on a process being readily scheduled.

libc/intrin/describeflags.h

@@ -8,8 +8,8 @@ struct thatispacked DescribeFlags {
   const char *name;
 };
 
-const char *_DescribeFlags(char *, size_t, const struct DescribeFlags *,
-                           size_t, const char *, unsigned) libcesque;
+const char *_DescribeFlags(char *, size_t, const struct DescribeFlags *, size_t,
+                           const char *, unsigned) libcesque;
 
 const char *_DescribeArchPrctlCode(char[12], int) libcesque;
 const char *_DescribeCancelState(char[12], int, int *) libcesque;
@@ -27,6 +27,7 @@ const char *_DescribeItimer(char[12], int) libcesque;
 const char *_DescribeMapFlags(char[64], int) libcesque;
 const char *_DescribeMapping(char[8], int, int) libcesque;
 const char *_DescribeMremapFlags(char[30], int) libcesque;
+const char *_DescribeMsg(char[16], int) libcesque;
 const char *_DescribeMsyncFlags(char[48], int) libcesque;
 const char *_DescribeNtConsoleInFlags(char[256], uint32_t) libcesque;
 const char *_DescribeNtConsoleOutFlags(char[128], uint32_t) libcesque;
@@ -84,6 +85,7 @@ const char *_DescribeWhichPrio(char[12], int) libcesque;
 #define DescribeMapFlags(x)          _DescribeMapFlags(alloca(64), x)
 #define DescribeMapping(x, y)        _DescribeMapping(alloca(8), x, y)
 #define DescribeMremapFlags(x)       _DescribeMremapFlags(alloca(30), x)
+#define DescribeMsg(x)               _DescribeMsg(alloca(16), x)
 #define DescribeMsyncFlags(x)        _DescribeMsyncFlags(alloca(48), x)
 #define DescribeNtConsoleInFlags(x)  _DescribeNtConsoleInFlags(alloca(256), x)
 #define DescribeNtConsoleOutFlags(x) _DescribeNtConsoleOutFlags(alloca(128), x)

libc/intrin/describemsg.c

@@ -0,0 +1,36 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2024 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/intrin/describeflags.h"
+#include "libc/macros.h"
+#include "libc/sysv/consts/msg.h"
+
+const char *_DescribeMsg(char buf[16], int x) {
+  const struct DescribeFlags kMsgFlags[] = {
+      {MSG_FASTOPEN, "FASTOPEN"},    // order matters
+      {MSG_OOB, "OOB"},              //
+      {MSG_PEEK, "PEEK"},            //
+      {MSG_DONTROUTE, "DONTROUTE"},  //
+      {MSG_DONTWAIT, "DONTWAIT"},    //
+      {MSG_WAITALL, "WAITALL"},      //
+      {MSG_NOSIGNAL, "NOSIGNAL"},    //
+      {MSG_TRUNC, "TRUNC"},          //
+      {MSG_CTRUNC, "CTRUNC"},        //
+  };
+  return _DescribeFlags(buf, 16, kMsgFlags, ARRAYLEN(kMsgFlags), "MSG_", x);
+}

libc/sock/internal.h

@@ -65,7 +65,7 @@ int sys_select_nt(int, fd_set *, fd_set *, fd_set *, struct timeval *,
 
 size_t __iovec2nt(struct NtIovec[hasatleast 16], const struct iovec *, size_t);
 
-ssize_t __winsock_block(int64_t, uint32_t, int, uint32_t, uint64_t,
+ssize_t __winsock_block(int64_t, uint32_t, bool, uint32_t, uint64_t,
                         int (*)(int64_t, struct NtOverlapped *, uint32_t *,
                                 void *),
                         void *);

libc/sock/recv-nt.c

@@ -17,22 +17,26 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
-#include "libc/calls/struct/iovec.h"
 #include "libc/calls/struct/sigset.internal.h"
-#include "libc/intrin/fds.h"
 #include "libc/nt/struct/iovec.h"
+#include "libc/nt/struct/overlapped.h"
+#include "libc/nt/thunk/msabi.h"
 #include "libc/nt/winsock.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/syscall_fd.internal.h"
+#include "libc/sysv/consts/fio.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/errfuns.h"
+#include "libc/vga/vga.internal.h"
 #ifdef __x86_64__
 
 #define _MSG_OOB      1
 #define _MSG_PEEK     2
 #define _MSG_WAITALL  8
 #define _MSG_DONTWAIT 64
 
+__msabi extern typeof(__sys_ioctlsocket_nt) *const __imp_ioctlsocket;
+
 struct RecvArgs {
   const struct iovec *iov;
   size_t iovlen;
@@ -54,13 +58,24 @@ textwindows ssize_t sys_recv_nt(int fd, const struct iovec *iov, size_t iovlen,
     return einval();
   ssize_t rc;
   struct Fd *f = g_fds.p + fd;
-  sigset_t m = __sig_block();
-  bool nonblock = !(flags & _MSG_WAITALL) &&
-                  ((f->flags & O_NONBLOCK) || (flags & _MSG_DONTWAIT));
-  flags &= ~_MSG_DONTWAIT;
-  rc = __winsock_block(f->handle, flags, nonblock, f->rcvtimeo, m,
-                       sys_recv_nt_start, &(struct RecvArgs){iov, iovlen});
-  __sig_unblock(m);
+  sigset_t waitmask = __sig_block();
+
+  // "Be aware that if the underlying transport provider does not
+  //  support MSG_WAITALL, or if the socket is in a non-blocking mode,
+  //  then this call will fail with WSAEOPNOTSUPP. Also, if MSG_WAITALL
+  //  is specified along with MSG_OOB, MSG_PEEK, or MSG_PARTIAL, then
+  //  this call will fail with WSAEOPNOTSUPP."
+  //                             —Quoth MSDN § WSARecv
+  if (flags & _MSG_WAITALL)
+    __imp_ioctlsocket(f->handle, FIONBIO, (uint32_t[]){0});
+
+  rc = __winsock_block(f->handle, flags & ~_MSG_DONTWAIT,
+                       (f->flags & O_NONBLOCK) || (flags & _MSG_DONTWAIT),
+                       f->rcvtimeo, waitmask, sys_recv_nt_start,
+                       &(struct RecvArgs){iov, iovlen});
+
+  __sig_unblock(waitmask);
+
   return rc;
 }
 

libc/sock/recv.c

@@ -20,20 +20,40 @@
 #include "libc/calls/internal.h"
 #include "libc/calls/struct/iovec.internal.h"
 #include "libc/dce.h"
+#include "libc/intrin/describeflags.h"
 #include "libc/intrin/strace.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
 #include "libc/sock/syscall_fd.internal.h"
+#include "libc/sysv/consts/msg.h"
 #include "libc/sysv/errfuns.h"
 
 /**
  * Receives data from network socket.
  *
+ * Calling `recv(fd, p, n, 0)` is equivalent to `read(fd, p, n)`.
+ *
+ * Unlike files where the OS tries very hard to fulfill the entire
+ * requested `size` before returning, read operations on sockets aim to
+ * return as quickly as possible. For example, if 10 bytes are requested
+ * and a packet comes in with only 5 bytes, then recv() will most likely
+ * return those 5 bytes before waiting longer. The `MSG_WAITALL` flag
+ * may be passed when waiting longer is desired. In that case, short
+ * reads should only be possible when the connection status changes or
+ * the receive operation is interrupted by a signal.
+ *
  * @param fd is the file descriptor returned by socket()
  * @param buf is where received network data gets copied
  * @param size is the byte capacity of buf
  * @param flags can have `MSG_OOB`, `MSG_PEEK`, `MSG_DONTWAIT`, `MSG_WAITALL`
  * @return number of bytes received, 0 on remote close, or -1 w/ errno
+ * @raise EINTR if signal handler was called instead
+ * @raise EINVAL if unknown bits were passed in `flags`
+ * @raise EINVAL if flag isn't supported by host operating system
+ * @raise EINVAL if `MSG_WAITALL` and `MSG_PEEK` were both passed
+ * @raise EBADF if `fd` is an invalid file descriptor
+ * @raise EAGAIN if `MSG_DONTWAIT` was passed and no data was available
+ * @raise EAGAIN if `O_NONBLOCK` is in play and no data was available
  * @error EINTR, EHOSTUNREACH, ECONNRESET (UDP ICMP Port Unreachable),
  *     EPIPE (if MSG_NOSIGNAL), EMSGSIZE, ENOTSOCK, EFAULT, etc.
  * @cancelationpoint
@@ -44,7 +64,11 @@ ssize_t recv(int fd, void *buf, size_t size, int flags) {
   ssize_t rc;
   BEGIN_CANCELATION_POINT;
 
-  if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
+  if ((flags & (MSG_WAITALL | MSG_PEEK)) == (MSG_WAITALL | MSG_PEEK)) {
+    // this is possible on some OSes like Linux but it breaks FreeBSD
+    // and Windows will raise EOPNOTSUPP when it gets passed together
+    return einval();
+  } else if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
     rc = enotsock();
   } else if (!IsWindows()) {
     rc = sys_recvfrom(fd, buf, size, flags, 0, 0);
@@ -65,7 +89,8 @@ ssize_t recv(int fd, void *buf, size_t size, int flags) {
   }
 
   END_CANCELATION_POINT;
-  DATATRACE("recv(%d, [%#.*hhs%s], %'zu, %#x) → %'ld% lm", fd,
-            MAX(0, MIN(40, rc)), buf, rc > 40 ? "..." : "", size, flags, rc);
+  DATATRACE("recv(%d, [%#.*hhs%s], %'zu, %s) → %'ld% lm", fd,
+            MAX(0, MIN(40, rc)), buf, rc > 40 ? "..." : "", size,
+            DescribeMsg(flags), rc);
   return rc;
 }

libc/sock/recvfrom-nt.c

@@ -59,14 +59,13 @@ textwindows ssize_t sys_recvfrom_nt(int fd, const struct iovec *iov,
     return einval();
   ssize_t rc;
   struct Fd *f = g_fds.p + fd;
-  sigset_t m = __sig_block();
-  bool nonblock = (f->flags & O_NONBLOCK) || (flags & _MSG_DONTWAIT);
-  flags &= ~_MSG_DONTWAIT;
-  rc = __winsock_block(f->handle, flags, nonblock, f->rcvtimeo, m,
-                       sys_recvfrom_nt_start,
+  sigset_t waitmask = __sig_block();
+  rc = __winsock_block(f->handle, flags & ~_MSG_DONTWAIT,
+                       (f->flags & O_NONBLOCK) || (flags & _MSG_DONTWAIT),
+                       f->rcvtimeo, waitmask, sys_recvfrom_nt_start,
                        &(struct RecvFromArgs){iov, iovlen, opt_out_srcaddr,
                                               opt_inout_srcaddrsize});
-  __sig_unblock(m);
+  __sig_unblock(waitmask);
   return rc;
 }
 

libc/sock/recvfrom.c

@@ -21,6 +21,7 @@
 #include "libc/calls/struct/iovec.h"
 #include "libc/calls/struct/iovec.internal.h"
 #include "libc/dce.h"
+#include "libc/intrin/describeflags.h"
 #include "libc/intrin/strace.h"
 #include "libc/nt/winsock.h"
 #include "libc/sock/internal.h"
@@ -95,7 +96,11 @@ ssize_t recvfrom(int fd, void *buf, size_t size, int flags,
   }
 
   END_CANCELATION_POINT;
-  DATATRACE("recvfrom(%d, [%#.*hhs%s], %'zu, %#x) → %'ld% lm", fd,
-            MAX(0, MIN(40, rc)), buf, rc > 40 ? "..." : "", size, flags, rc);
+  DATATRACE(
+      "recvfrom(%d, [%#.*hhs%s], %'zu, %s, %s) → %'ld% lm", fd,
+      MAX(0, MIN(40, rc)), buf, rc > 40 ? "..." : "", size, DescribeMsg(flags),
+      DescribeSockaddr(opt_out_srcaddr,
+                       opt_inout_srcaddrsize ? *opt_inout_srcaddrsize : 0),
+      rc);
   return rc;
 }

libc/sock/send-nt.c

@@ -17,20 +17,25 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
-#include "libc/calls/struct/iovec.h"
+#include "libc/calls/sig.internal.h"
+#include "libc/calls/struct/iovec.internal.h"
 #include "libc/calls/struct/sigset.internal.h"
-#include "libc/intrin/fds.h"
+#include "libc/errno.h"
+#include "libc/nt/errors.h"
 #include "libc/nt/struct/iovec.h"
+#include "libc/nt/struct/overlapped.h"
 #include "libc/nt/winsock.h"
 #include "libc/sock/internal.h"
-#include "libc/sock/syscall_fd.internal.h"
-#include "libc/sysv/consts/o.h"
+#include "libc/sysv/consts/sicode.h"
+#include "libc/sysv/consts/sig.h"
 #include "libc/sysv/errfuns.h"
+#include "libc/vga/vga.internal.h"
 #ifdef __x86_64__
 
 #define _MSG_OOB       1
 #define _MSG_DONTROUTE 4
 #define _MSG_DONTWAIT  64
+#define _MSG_NOSIGNAL  0x10000000
 
 struct SendArgs {
   const struct iovec *iov;
@@ -49,23 +54,24 @@ textwindows static int sys_send_nt_start(int64_t handle,
 
 textwindows ssize_t sys_send_nt(int fd, const struct iovec *iov, size_t iovlen,
                                 uint32_t flags) {
-  if (flags & ~(_MSG_DONTWAIT | _MSG_OOB | _MSG_DONTROUTE))
+  if (flags & ~(_MSG_DONTWAIT | _MSG_OOB | _MSG_DONTROUTE | _MSG_NOSIGNAL))
     return einval();
   ssize_t rc;
   struct Fd *f = g_fds.p + fd;
-  sigset_t m = __sig_block();
+  sigset_t waitmask = __sig_block();
 
-  // we don't check O_NONBLOCK because we want to avoid needing to call
-  // WSAPoll() every time we write() to a non-blocking socket. WIN32 is
-  // unsafe at canceling socket sends. lots of code doesn't check write
-  // return status. good programs that sincerely want to avoid blocking
-  // on send() operations should have already called poll() beforehand.
-  bool nonblock = flags & _MSG_DONTWAIT;
+  rc = __winsock_block(f->handle, flags & ~(_MSG_DONTWAIT | _MSG_NOSIGNAL),
+                       false, f->sndtimeo, waitmask, sys_send_nt_start,
+                       &(struct SendArgs){iov, iovlen});
+
+  __sig_unblock(waitmask);
+
+  if (rc == -1 && errno == WSAESHUTDOWN) {  // ESHUTDOWN
+    errno = kNtErrorBrokenPipe;             // EPIPE
+    if (!(flags & _MSG_NOSIGNAL))
+      __sig_raise(SIGPIPE, SI_KERNEL);
+  }
 
-  flags &= ~_MSG_DONTWAIT;
-  rc = __winsock_block(f->handle, flags, -nonblock, f->sndtimeo, m,
-                       sys_send_nt_start, &(struct SendArgs){iov, iovlen});
-  __sig_unblock(m);
   return rc;
 }
 

libc/sock/send.c

@@ -21,6 +21,7 @@
 #include "libc/calls/struct/iovec.h"
 #include "libc/calls/struct/iovec.internal.h"
 #include "libc/dce.h"
+#include "libc/intrin/describeflags.h"
 #include "libc/intrin/strace.h"
 #include "libc/macros.h"
 #include "libc/sock/internal.h"
@@ -78,7 +79,7 @@ ssize_t send(int fd, const void *buf, size_t size, int flags) {
   }
 
   END_CANCELATION_POINT;
-  DATATRACE("send(%d, %#.*hhs%s, %'zu, %#x) → %'ld% lm", fd,
-            MAX(0, MIN(40, rc)), buf, rc > 40 ? "..." : "", size, flags, rc);
+  DATATRACE("send(%d, %#.*hhs%s, %'zu, %s) → %'ld% lm", fd, MAX(0, MIN(40, rc)),
+            buf, rc > 40 ? "..." : "", size, DescribeMsg(flags), rc);
   return rc;
 }

libc/sock/sendto-nt.c

@@ -17,20 +17,26 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/sig.internal.h"
 #include "libc/calls/struct/iovec.h"
 #include "libc/calls/struct/sigset.internal.h"
+#include "libc/errno.h"
 #include "libc/intrin/fds.h"
+#include "libc/nt/errors.h"
 #include "libc/nt/struct/iovec.h"
 #include "libc/nt/winsock.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/syscall_fd.internal.h"
 #include "libc/sysv/consts/o.h"
+#include "libc/sysv/consts/sicode.h"
+#include "libc/sysv/consts/sig.h"
 #include "libc/sysv/errfuns.h"
 #ifdef __x86_64__
 
 #define _MSG_OOB       1
 #define _MSG_DONTROUTE 4
 #define _MSG_DONTWAIT  64
+#define _MSG_NOSIGNAL  0x10000000
 
 struct SendToArgs {
   const struct iovec *iov;
@@ -52,17 +58,25 @@ static textwindows int sys_sendto_nt_start(int64_t handle,
 textwindows ssize_t sys_sendto_nt(int fd, const struct iovec *iov,
                                   size_t iovlen, uint32_t flags,
                                   void *opt_in_addr, uint32_t in_addrsize) {
-  if (flags & ~(_MSG_DONTWAIT | _MSG_OOB | _MSG_DONTROUTE))
+  if (flags & ~(_MSG_DONTWAIT | _MSG_OOB | _MSG_DONTROUTE | _MSG_NOSIGNAL))
     return einval();
   ssize_t rc;
   struct Fd *f = g_fds.p + fd;
-  sigset_t m = __sig_block();
-  bool nonblock = (f->flags & O_NONBLOCK) || (flags & _MSG_DONTWAIT);
-  flags &= ~_MSG_DONTWAIT;
-  rc = __winsock_block(
-      f->handle, flags, -nonblock, f->sndtimeo, m, sys_sendto_nt_start,
-      &(struct SendToArgs){iov, iovlen, opt_in_addr, in_addrsize});
-  __sig_unblock(m);
+  sigset_t waitmask = __sig_block();
+
+  rc = __winsock_block(f->handle, flags & ~(_MSG_DONTWAIT | _MSG_NOSIGNAL),
+                       false, f->sndtimeo, waitmask, sys_sendto_nt_start,
+                       &(struct SendToArgs){iov, iovlen,  //
+                                            opt_in_addr, in_addrsize});
+
+  __sig_unblock(waitmask);
+
+  if (rc == -1 && errno == WSAESHUTDOWN) {  // ESHUTDOWN
+    errno = kNtErrorBrokenPipe;             // EPIPE
+    if (!(flags & _MSG_NOSIGNAL))
+      __sig_raise(SIGPIPE, SI_KERNEL);
+  }
+
   return rc;
 }