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Re: [PATCH v4 04/11] osdep: implement qemu_socketpair() for win32
From: |
Marc-André Lureau |
Subject: |
Re: [PATCH v4 04/11] osdep: implement qemu_socketpair() for win32 |
Date: |
Wed, 8 Mar 2023 10:53:13 +0400 |
Hi
On Tue, Mar 7, 2023 at 6:50 PM Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> On Mon, Mar 06, 2023 at 04:27:44PM +0400, marcandre.lureau@redhat.com wrote:
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >
> > Manually implement a socketpair() function, using UNIX sockets and
> > simple peer credential checking.
> >
> > QEMU doesn't make much use of socketpair, beside vhost-user which is not
> > available for win32 at this point. However, I intend to use it for
> > writing some new portable tests.
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> > include/qemu/sockets.h | 2 -
> > util/oslib-win32.c | 110 +++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 110 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/qemu/sockets.h b/include/qemu/sockets.h
> > index 2b0698a7c9..d935fd80da 100644
> > --- a/include/qemu/sockets.h
> > +++ b/include/qemu/sockets.h
> > @@ -15,7 +15,6 @@ int inet_aton(const char *cp, struct in_addr *ia);
> > bool fd_is_socket(int fd);
> > int qemu_socket(int domain, int type, int protocol);
> >
> > -#ifndef WIN32
> > /**
> > * qemu_socketpair:
> > * @domain: specifies a communication domain, such as PF_UNIX
> > @@ -30,7 +29,6 @@ int qemu_socket(int domain, int type, int protocol);
> > * Return 0 on success.
> > */
> > int qemu_socketpair(int domain, int type, int protocol, int sv[2]);
> > -#endif
> >
> > int qemu_accept(int s, struct sockaddr *addr, socklen_t *addrlen);
> > /*
> > diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> > index 29a667ae3d..16f8a67f7e 100644
> > --- a/util/oslib-win32.c
> > +++ b/util/oslib-win32.c
> > @@ -310,6 +310,116 @@ bool qemu_socket_unselect(int sockfd, Error **errp)
> > return qemu_socket_select(sockfd, NULL, 0, errp);
> > }
> >
> > +int qemu_socketpair(int domain, int type, int protocol, int sv[2])
> > +{
> > + struct sockaddr_un addr = {
> > + 0,
> > + };
> > + socklen_t socklen;
> > + int listener = -1;
> > + int client = -1;
> > + int server = -1;
> > + g_autofree char *path = NULL;
> > + int tmpfd;
> > + u_long arg;
> > + int ret = -1;
> > +
> > + g_return_val_if_fail(sv != NULL, -1);
> > +
> > + addr.sun_family = AF_UNIX;
> > + socklen = sizeof(addr);
> > +
> > + tmpfd = g_file_open_tmp(NULL, &path, NULL);
> > + if (tmpfd == -1 || !path) {
> > + errno = EACCES;
> > + goto out;
> > + }
> > +
> > + close(tmpfd);
> > +
> > + if (strlen(path) >= sizeof(addr.sun_path)) {
> > + errno = EINVAL;
> > + goto out;
> > + }
> > +
> > + strncpy(addr.sun_path, path, sizeof(addr.sun_path) - 1);
> > +
> > + listener = socket(domain, type, protocol);
> > + if (listener == -1) {
> > + goto out;
> > + }
> > +
> > + if (DeleteFile(path) == 0 && GetLastError() != ERROR_FILE_NOT_FOUND) {
> > + errno = EACCES;
> > + goto out;
> > + }
> > + g_clear_pointer(&path, g_free);
> > +
> > + if (bind(listener, (struct sockaddr *)&addr, socklen) == -1) {
> > + goto out;
> > + }
> > +
> > + if (listen(listener, 1) == -1) {
> > + goto out;
> > + }
> > +
> > + client = socket(domain, type, protocol);
> > + if (client == -1) {
> > + goto out;
> > + }
> > +
> > + arg = 1;
> > + if (ioctlsocket(client, FIONBIO, &arg) != NO_ERROR) {
> > + goto out;
> > + }
> > +
> > + if (connect(client, (struct sockaddr *)&addr, socklen) == -1 &&
> > + WSAGetLastError() != WSAEWOULDBLOCK) {
> > + goto out;
> > + }
> > +
> > + server = accept(listener, NULL, NULL);
> > + if (server == -1) {
> > + goto out;
> > + }
>
> In theory at this point 'client' if connect() returned WSAEWOULDBLOCK,
> then at this point it should be fully connected. I wonder if that is
> actually guaranteed though, or should we do something to validate
> there's no race condition ?
>
> > +
> > + arg = 0;
> > + if (ioctlsocket(client, FIONBIO, &arg) != NO_ERROR) {
> > + goto out;
> > + }
> > +
> > + arg = 0;
> > + if (ioctlsocket(client, SIO_AF_UNIX_GETPEERPID, &arg) != NO_ERROR) {
> > + goto out;
> > + }
>
> Maybe this will force a synchronization point ?
yeah, I guess switching back to sync and getting the peer pid,
I assume the unix socket pair to be ready at this point.
>
> Alteratively select() + getsockopt(SO_ERROR) is what we used to
> do to check for connect() completion (logic removed now but can
> be seen in b2587932582333197c88bf663785b19f441989d7)
>
That's hopefully not necessary.
thanks
>
>
> > +
> > + if (arg != GetCurrentProcessId()) {
> > + errno = EPERM;
> > + goto out;
> > + }
> > +
> > + sv[0] = server;
> > + server = -1;
> > + sv[1] = client;
> > + client = -1;
> > + ret = 0;
> > +
> > +out:
> > + if (listener != -1) {
> > + close(listener);
> > + }
> > + if (client != -1) {
> > + close(client);
> > + }
> > + if (server != -1) {
> > + close(server);
> > + }
> > + if (path) {
> > + DeleteFile(path);
> > + }
> > + return ret;
> > +}
> > +
> > #undef connect
> > int qemu_connect_wrap(int sockfd, const struct sockaddr *addr,
> > socklen_t addrlen)
> > --
> > 2.39.2
> >
>
> With regards,
> Daniel
> --
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>
>
--
Marc-André Lureau