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Fix bug with send() on Windows in O_NONBLOCK mode

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There is a bug in WIN32 where using CancelIoEx() on an overlapped i/o op
initiated by WSASend() will cause WSAGetOverlappedResult() to report the
operation failed when it actually succeeded. We now work around that, by
having send and sendto initially consult WSAPoll() on O_NONBLOCK sockets
This commit is contained in:
Justine Tunney 2024-09-16 20:49:58 -07:00
parent 5aa970bc4e
commit 3c58ecd00c
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
4 changed files with 22 additions and 5 deletions
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2
libc/sock/internal.h
View file

@ -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, bool, uint32_t, uint64_t,
ssize_t __winsock_block(int64_t, uint32_t, int, uint32_t, uint64_t,
int (*)(int64_t, struct NtOverlapped *, uint32_t *,
void *),
void *);

2
libc/sock/send-nt.c
View file

@ -56,7 +56,7 @@ textwindows ssize_t sys_send_nt(int fd, const struct iovec *iov, size_t iovlen,
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,
rc = __winsock_block(f->handle, flags, -nonblock, f->sndtimeo, m,
sys_send_nt_start, &(struct SendArgs){iov, iovlen});
__sig_unblock(m);
return rc;

2
libc/sock/sendto-nt.c
View file

@ -60,7 +60,7 @@ textwindows ssize_t sys_sendto_nt(int fd, const struct iovec *iov,
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,
f->handle, flags, -nonblock, f->sndtimeo, m, sys_sendto_nt_start,
&(struct SendToArgs){iov, iovlen, opt_in_addr, in_addrsize});
__sig_unblock(m);
return rc;

21
libc/sock/winsockblock.c
View file

@ -30,17 +30,19 @@
#include "libc/nt/events.h"
#include "libc/nt/runtime.h"
#include "libc/nt/struct/overlapped.h"
#include "libc/nt/struct/pollfd.h"
#include "libc/nt/synchronization.h"
#include "libc/nt/thread.h"
#include "libc/nt/winsock.h"
#include "libc/sock/internal.h"
#include "libc/sysv/consts/poll.h"
#include "libc/sysv/consts/sicode.h"
#include "libc/sysv/errfuns.h"
#include "libc/thread/posixthread.internal.h"
#ifdef __x86_64__
textwindows ssize_t
__winsock_block(int64_t handle, uint32_t flags, bool nonblock,
__winsock_block(int64_t handle, uint32_t flags, int nonblock,
uint32_t srwtimeout, sigset_t waitmask,
int StartSocketOp(int64_t handle, struct NtOverlapped *overlap,
uint32_t *flags, void *arg),
@ -61,6 +63,21 @@ __winsock_block(int64_t handle, uint32_t flags, bool nonblock,
bool got_eagain = false;
uint32_t other_error = 0;
// send() and sendto() provide O_NONBLOCK as a negative number
// because winsock has a bug that causes CancelIoEx() to cause
// WSAGetOverlappedResult() to report errors when it succeeded
if (nonblock < 0) {
struct sys_pollfd_nt fds[1] = {{handle, POLLOUT}};
switch (WSAPoll(fds, 1, 0)) {
case -1:
return __winsockerr();
case 0:
return eagain();
default:
break;
}
}
// create event handle for overlapped i/o
intptr_t event;
if (!(event = WSACreateEvent()))
@ -69,7 +86,7 @@ __winsock_block(int64_t handle, uint32_t flags, bool nonblock,
struct NtOverlapped overlap = {.hEvent = event};
bool32 ok = !StartSocketOp(handle, &overlap, &flags, arg);
if (!ok && WSAGetLastError() == kNtErrorIoPending) {
if (nonblock) {
if (nonblock > 0) {
CancelIoEx(handle, &overlap);
got_eagain = true;
} else {