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https://gitlab.com/qemu-project/qemu
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![Stefan Hajnoczi](/assets/img/avatar_default.png)
AF_UNIX and AF_VSOCK listen sockets can be passed in by systemd on startup. This allows systemd to manage the listen socket until the first client connects and between restarts. Advantages of socket activation are that parallel startup of network services becomes possible and that unused daemons do not consume memory. The key to achieving this is the LISTEN_FDS environment variable, which is a stable ABI as shown here: https://www.freedesktop.org/wiki/Software/systemd/InterfacePortabilityAndStabilityChart/ We could link against libsystemd and use sd_listen_fds(3) but it's easy to implement the tiny LISTEN_FDS ABI so that qemu-ga does not depend on libsystemd. Some systems may not have systemd installed and wish to avoid the dependency. Other init systems or socket activation servers may implement the same ABI without systemd involvement. Test as follows: $ cat ~/.config/systemd/user/qga.service [Unit] Description=qga [Service] WorkingDirectory=/tmp ExecStart=/path/to/qemu-ga --logfile=/tmp/qga.log --pidfile=/tmp/qga.pid --statedir=/tmp $ cat ~/.config/systemd/user/qga.socket [Socket] ListenStream=/tmp/qga.sock [Install] WantedBy=default.target $ systemctl --user daemon-reload $ systemctl --user start qga.socket $ nc -U /tmp/qga.sock Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
357 lines
9.9 KiB
C
357 lines
9.9 KiB
C
#include "qemu/osdep.h"
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#include <windows.h>
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#include <io.h>
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#include "qga/guest-agent-core.h"
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#include "qga/channel.h"
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typedef struct GAChannelReadState {
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guint thread_id;
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uint8_t *buf;
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size_t buf_size;
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size_t cur; /* current buffer start */
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size_t pending; /* pending buffered bytes to read */
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OVERLAPPED ov;
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bool ov_pending; /* whether on async read is outstanding */
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} GAChannelReadState;
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struct GAChannel {
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HANDLE handle;
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GAChannelCallback cb;
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gpointer user_data;
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GAChannelReadState rstate;
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GIOCondition pending_events; /* TODO: use GAWatch.pollfd.revents */
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GSource *source;
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};
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typedef struct GAWatch {
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GSource source;
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GPollFD pollfd;
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GAChannel *channel;
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GIOCondition events_mask;
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} GAWatch;
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/*
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* Called by glib prior to polling to set up poll events if polling is needed.
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*
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*/
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static gboolean ga_channel_prepare(GSource *source, gint *timeout_ms)
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{
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GAWatch *watch = (GAWatch *)source;
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GAChannel *c = (GAChannel *)watch->channel;
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GAChannelReadState *rs = &c->rstate;
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DWORD count_read, count_to_read = 0;
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bool success;
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GIOCondition new_events = 0;
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g_debug("prepare");
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/* go ahead and submit another read if there's room in the buffer
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* and no previous reads are outstanding
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*/
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if (!rs->ov_pending) {
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if (rs->cur + rs->pending >= rs->buf_size) {
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if (rs->cur) {
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memmove(rs->buf, rs->buf + rs->cur, rs->pending);
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rs->cur = 0;
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}
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}
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count_to_read = rs->buf_size - rs->cur - rs->pending;
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}
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if (rs->ov_pending || count_to_read <= 0) {
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goto out;
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}
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/* submit the read */
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success = ReadFile(c->handle, rs->buf + rs->cur + rs->pending,
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count_to_read, &count_read, &rs->ov);
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if (success) {
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rs->pending += count_read;
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rs->ov_pending = false;
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} else {
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if (GetLastError() == ERROR_IO_PENDING) {
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rs->ov_pending = true;
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} else {
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new_events |= G_IO_ERR;
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}
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}
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out:
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/* don't block forever, iterate the main loop every once in a while */
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*timeout_ms = 500;
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/* if there's data in the read buffer, or another event is pending,
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* skip polling and issue user cb.
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*/
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if (rs->pending) {
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new_events |= G_IO_IN;
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}
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c->pending_events |= new_events;
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return !!c->pending_events;
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}
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/*
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* Called by glib after an outstanding read request is completed.
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*/
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static gboolean ga_channel_check(GSource *source)
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{
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GAWatch *watch = (GAWatch *)source;
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GAChannel *c = (GAChannel *)watch->channel;
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GAChannelReadState *rs = &c->rstate;
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DWORD count_read, error;
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BOOL success;
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GIOCondition new_events = 0;
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g_debug("check");
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/* failing this implies we issued a read that completed immediately,
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* yet no data was placed into the buffer (and thus we did not skip
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* polling). but since EOF is not obtainable until we retrieve an
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* overlapped result, it must be the case that there was data placed
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* into the buffer, or an error was generated by Readfile(). in either
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* case, we should've skipped the polling for this round.
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*/
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g_assert(rs->ov_pending);
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success = GetOverlappedResult(c->handle, &rs->ov, &count_read, FALSE);
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if (success) {
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g_debug("thread: overlapped result, count_read: %d", (int)count_read);
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rs->pending += count_read;
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new_events |= G_IO_IN;
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} else {
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error = GetLastError();
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if (error == 0 || error == ERROR_HANDLE_EOF ||
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error == ERROR_NO_SYSTEM_RESOURCES ||
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error == ERROR_OPERATION_ABORTED) {
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/* note: On WinXP SP3 with rhel6ga virtio-win-1.1.16 vioser drivers,
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* ENSR seems to be synonymous with when we'd normally expect
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* ERROR_HANDLE_EOF. So treat it as such. Microsoft's
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* recommendation for ERROR_NO_SYSTEM_RESOURCES is to
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* retry the read, so this happens to work out anyway. On newer
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* virtio-win driver, this seems to be replaced with EOA, so
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* handle that in the same fashion.
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*/
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new_events |= G_IO_HUP;
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} else if (error != ERROR_IO_INCOMPLETE) {
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g_critical("error retrieving overlapped result: %d", (int)error);
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new_events |= G_IO_ERR;
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}
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}
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if (new_events) {
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rs->ov_pending = 0;
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}
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c->pending_events |= new_events;
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return !!c->pending_events;
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}
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/*
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* Called by glib after either prepare or check routines signal readiness
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*/
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static gboolean ga_channel_dispatch(GSource *source, GSourceFunc unused,
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gpointer user_data)
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{
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GAWatch *watch = (GAWatch *)source;
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GAChannel *c = (GAChannel *)watch->channel;
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GAChannelReadState *rs = &c->rstate;
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gboolean success;
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g_debug("dispatch");
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success = c->cb(watch->pollfd.revents, c->user_data);
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if (c->pending_events & G_IO_ERR) {
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g_critical("channel error, removing source");
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return false;
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}
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/* TODO: replace rs->pending with watch->revents */
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c->pending_events &= ~G_IO_HUP;
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if (!rs->pending) {
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c->pending_events &= ~G_IO_IN;
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} else {
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c->pending_events = 0;
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}
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return success;
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}
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static void ga_channel_finalize(GSource *source)
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{
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g_debug("finalize");
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}
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GSourceFuncs ga_channel_watch_funcs = {
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ga_channel_prepare,
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ga_channel_check,
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ga_channel_dispatch,
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ga_channel_finalize
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};
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static GSource *ga_channel_create_watch(GAChannel *c)
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{
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GSource *source = g_source_new(&ga_channel_watch_funcs, sizeof(GAWatch));
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GAWatch *watch = (GAWatch *)source;
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watch->channel = c;
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watch->pollfd.fd = (gintptr) c->rstate.ov.hEvent;
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g_source_add_poll(source, &watch->pollfd);
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return source;
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}
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GIOStatus ga_channel_read(GAChannel *c, char *buf, size_t size, gsize *count)
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{
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GAChannelReadState *rs = &c->rstate;
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GIOStatus status;
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size_t to_read = 0;
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if (c->pending_events & G_IO_ERR) {
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return G_IO_STATUS_ERROR;
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}
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*count = to_read = MIN(size, rs->pending);
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if (to_read) {
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memcpy(buf, rs->buf + rs->cur, to_read);
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rs->cur += to_read;
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rs->pending -= to_read;
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status = G_IO_STATUS_NORMAL;
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} else {
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status = G_IO_STATUS_AGAIN;
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}
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return status;
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}
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static GIOStatus ga_channel_write(GAChannel *c, const char *buf, size_t size,
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size_t *count)
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{
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GIOStatus status;
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OVERLAPPED ov = {0};
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BOOL ret;
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DWORD written;
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ov.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
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ret = WriteFile(c->handle, buf, size, &written, &ov);
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if (!ret) {
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if (GetLastError() == ERROR_IO_PENDING) {
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/* write is pending */
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ret = GetOverlappedResult(c->handle, &ov, &written, TRUE);
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if (!ret) {
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if (!GetLastError()) {
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status = G_IO_STATUS_AGAIN;
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} else {
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status = G_IO_STATUS_ERROR;
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}
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} else {
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/* write is complete */
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status = G_IO_STATUS_NORMAL;
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*count = written;
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}
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} else {
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status = G_IO_STATUS_ERROR;
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}
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} else {
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/* write returned immediately */
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status = G_IO_STATUS_NORMAL;
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*count = written;
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}
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if (ov.hEvent) {
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CloseHandle(ov.hEvent);
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ov.hEvent = NULL;
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}
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return status;
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}
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GIOStatus ga_channel_write_all(GAChannel *c, const char *buf, size_t size)
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{
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GIOStatus status = G_IO_STATUS_NORMAL;
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size_t count = 0;
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while (size) {
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status = ga_channel_write(c, buf, size, &count);
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if (status == G_IO_STATUS_NORMAL) {
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size -= count;
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buf += count;
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} else if (status != G_IO_STATUS_AGAIN) {
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break;
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}
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}
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return status;
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}
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static gboolean ga_channel_open(GAChannel *c, GAChannelMethod method,
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const gchar *path)
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{
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COMMTIMEOUTS comTimeOut = {0};
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gchar newpath[MAXPATHLEN] = {0};
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comTimeOut.ReadIntervalTimeout = 1;
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if (method != GA_CHANNEL_VIRTIO_SERIAL && method != GA_CHANNEL_ISA_SERIAL) {
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g_critical("unsupported communication method");
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return false;
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}
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if (method == GA_CHANNEL_ISA_SERIAL){
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snprintf(newpath, sizeof(newpath), "\\\\.\\%s", path);
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}else {
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g_strlcpy(newpath, path, sizeof(newpath));
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}
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c->handle = CreateFile(newpath, GENERIC_READ | GENERIC_WRITE, 0, NULL,
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OPEN_EXISTING,
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FILE_FLAG_NO_BUFFERING | FILE_FLAG_OVERLAPPED, NULL);
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if (c->handle == INVALID_HANDLE_VALUE) {
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g_critical("error opening path %s", newpath);
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return false;
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}
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if (method == GA_CHANNEL_ISA_SERIAL && !SetCommTimeouts(c->handle,&comTimeOut)) {
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g_critical("error setting timeout for com port: %lu",GetLastError());
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CloseHandle(c->handle);
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return false;
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}
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return true;
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}
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GAChannel *ga_channel_new(GAChannelMethod method, const gchar *path,
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int listen_fd, GAChannelCallback cb, gpointer opaque)
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{
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GAChannel *c = g_new0(GAChannel, 1);
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SECURITY_ATTRIBUTES sec_attrs;
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if (!ga_channel_open(c, method, path)) {
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g_critical("error opening channel");
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g_free(c);
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return NULL;
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}
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c->cb = cb;
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c->user_data = opaque;
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sec_attrs.nLength = sizeof(SECURITY_ATTRIBUTES);
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sec_attrs.lpSecurityDescriptor = NULL;
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sec_attrs.bInheritHandle = false;
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c->rstate.buf_size = QGA_READ_COUNT_DEFAULT;
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c->rstate.buf = g_malloc(QGA_READ_COUNT_DEFAULT);
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c->rstate.ov.hEvent = CreateEvent(&sec_attrs, FALSE, FALSE, NULL);
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c->source = ga_channel_create_watch(c);
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g_source_attach(c->source, NULL);
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return c;
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}
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void ga_channel_free(GAChannel *c)
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{
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if (c->source) {
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g_source_destroy(c->source);
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}
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if (c->rstate.ov.hEvent) {
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CloseHandle(c->rstate.ov.hEvent);
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}
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g_free(c->rstate.buf);
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g_free(c);
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}
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