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Re: [PATCH 1/3] win32: add qemu_close_to_socket()
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH 1/3] win32: add qemu_close_to_socket() |
Date: |
Mon, 20 Mar 2023 12:10:07 +0000 |
User-agent: |
Mutt/2.2.9 (2022-11-12) |
On Mon, Mar 20, 2023 at 03:14:10PM +0400, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> Close the given file descriptor, but returns the underlying SOCKET.
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
> include/sysemu/os-win32.h | 1 +
> util/oslib-win32.c | 68 +++++++++++++++++++++------------------
> 2 files changed, 38 insertions(+), 31 deletions(-)
>
> diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h
> index e2849f88ab..95cba6b284 100644
> --- a/include/sysemu/os-win32.h
> +++ b/include/sysemu/os-win32.h
> @@ -174,6 +174,7 @@ bool qemu_socket_unselect(int sockfd, Error **errp);
> /* We wrap all the sockets functions so that we can
> * set errno based on WSAGetLastError()
> */
> +SOCKET qemu_close_to_socket(int fd);
Took me a while to understand what this function is actually doing.
IIUC, it assumes 'fd' was previously created by _open_osfhandle,
and close this OSF handle, leaving the SOCKET still open.
Could we call this one 'qemu_close_socket_osfhandle' and also
add a comment describing what this does.
>
> #undef close
> #define close qemu_close_wrap
> diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> index 16f8a67f7e..e37276b414 100644
> --- a/util/oslib-win32.c
> +++ b/util/oslib-win32.c
> @@ -479,52 +479,58 @@ int qemu_bind_wrap(int sockfd, const struct sockaddr
> *addr,
> return ret;
> }
>
> -
> #undef close
> -int qemu_close_wrap(int fd)
> +SOCKET qemu_close_to_socket(int fd)
> {
> - int ret;
> + SOCKET s = _get_osfhandle(fd);
> DWORD flags = 0;
> - SOCKET s = INVALID_SOCKET;
> -
> - if (fd_is_socket(fd)) {
> - s = _get_osfhandle(fd);
>
> - /*
> - * If we were to just call _close on the descriptor, it would close
> the
> - * HANDLE, but it wouldn't free any of the resources associated to
> the
> - * SOCKET, and we can't call _close after calling closesocket,
> because
> - * closesocket has already closed the HANDLE, and _close would
> attempt to
> - * close the HANDLE again, resulting in a double free. We can however
> - * protect the HANDLE from actually being closed long enough to
> close the
> - * file descriptor, then close the socket itself.
> - */
> - if (!GetHandleInformation((HANDLE)s, &flags)) {
> - errno = EACCES;
> - return -1;
> - }
> -
> - if (!SetHandleInformation((HANDLE)s, HANDLE_FLAG_PROTECT_FROM_CLOSE,
> HANDLE_FLAG_PROTECT_FROM_CLOSE)) {
> - errno = EACCES;
> - return -1;
> - }
> + /*
> + * If we were to just call _close on the descriptor, it would close the
> + * HANDLE, but it wouldn't free any of the resources associated to the
> + * SOCKET, and we can't call _close after calling closesocket, because
> + * closesocket has already closed the HANDLE, and _close would attempt to
> + * close the HANDLE again, resulting in a double free. We can however
> + * protect the HANDLE from actually being closed long enough to close the
> + * file descriptor, then close the socket itself.
> + */
> + if (!GetHandleInformation((HANDLE)s, &flags)) {
> + errno = EACCES;
> + return INVALID_SOCKET;
> }
>
> - ret = close(fd);
> -
> - if (s != INVALID_SOCKET && !SetHandleInformation((HANDLE)s, flags,
> flags)) {
> + if (!SetHandleInformation((HANDLE)s, HANDLE_FLAG_PROTECT_FROM_CLOSE,
> HANDLE_FLAG_PROTECT_FROM_CLOSE)) {
> errno = EACCES;
> - return -1;
> + return INVALID_SOCKET;
> }
>
> /*
> * close() returns EBADF since we PROTECT_FROM_CLOSE the underlying
> handle,
> * but the FD is actually freed
> */
> - if (ret < 0 && (s == INVALID_SOCKET || errno != EBADF)) {
> - return ret;
> + if (close(fd) < 0 && errno != EBADF) {
> + return INVALID_SOCKET;
> + }
> +
> + if (!SetHandleInformation((HANDLE)s, flags, flags)) {
> + errno = EACCES;
> + return INVALID_SOCKET;
> + }
> +
> + return s;
> +}
> +
> +int qemu_close_wrap(int fd)
> +{
> + SOCKET s = INVALID_SOCKET;
> + int ret = -1;
> +
> + if (!fd_is_socket(fd)) {
> + return close(fd);
> }
>
> + s = qemu_close_to_socket(fd);
> +
> if (s != INVALID_SOCKET) {
> ret = closesocket(s);
> if (ret < 0) {
> --
> 2.39.2
>
With regards,
Daniel
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