[Qemu-devel] [PATCH 7/8] guest agent: add guest-pipe-open command on Windows

[Denis V. Lunev]

From: Simon Zolin <address@hidden>

Create anonymous pipe that can be passed as a stdin/stdout/stderr handle to
a child process spawned using forthcoming guest-file-exec command.  Working
with a pipe is done using the existing interfaces guest-file-*.

Signed-off-by: Simon Zolin <address@hidden>
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Michael Roth <address@hidden>
---
 qga/commands-win32.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 74 insertions(+), 4 deletions(-)

diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 8fb29fc..4160c2b 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -37,6 +37,7 @@
 typedef struct GuestFileHandle {
     int64_t id;
     HANDLE fh;
+    HANDLE pipe_other_end_fd; /* if set, it's a pipe fd of the other end. */
     QTAILQ_ENTRY(GuestFileHandle) next;
 } GuestFileHandle;
 
@@ -84,7 +85,8 @@ static OpenFlags *find_open_flag(const char *mode_str)
     return NULL;
 }
 
-static int64_t guest_file_handle_add(HANDLE fh, Error **errp)
+static int64_t guest_file_handle_add(HANDLE fh, HANDLE pipe_other_end_fd,
+                                     Error **errp)
 {
     GuestFileHandle *gfh;
     int64_t handle;
@@ -96,6 +98,7 @@ static int64_t guest_file_handle_add(HANDLE fh, Error **errp)
     gfh = g_malloc0(sizeof(GuestFileHandle));
     gfh->id = handle;
     gfh->fh = fh;
+    gfh->pipe_other_end_fd = pipe_other_end_fd;
     QTAILQ_INSERT_TAIL(&guest_file_state.filehandles, gfh, next);
 
     return handle;
@@ -143,7 +146,7 @@ int64_t qmp_guest_file_open(const char *path, bool has_mode,
         return -1;
     }
 
-    fd = guest_file_handle_add(fh, errp);
+    fd = guest_file_handle_add(fh, INVALID_HANDLE_VALUE, errp);
     if (fd < 0) {
         CloseHandle(&fh);
         error_setg(errp, "failed to add handle to qmp handle table");
@@ -154,9 +157,70 @@ int64_t qmp_guest_file_open(const char *path, bool 
has_mode,
     return fd;
 }
 
+/* Create an anonymous pipe.
+ * Emulate non-blocking UNIX behavior using PIPE_NOWAIT flag: ReadFile()
+ * will fail with ERROR_NO_DATA; WriteFile() will return 0 bytes written. */
 int64_t qmp_guest_pipe_open(const char *mode, Error **errp)
 {
-    error_set(errp, QERR_UNSUPPORTED);
+    HANDLE fd[2];
+    int this_end, other_end;
+    DWORD pipemode;
+    int64_t handle;
+    SECURITY_ATTRIBUTES sa = {
+        sizeof(SECURITY_ATTRIBUTES), NULL, 0
+    };
+
+    slog("guest-pipe-open called");
+
+    if ((mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0') {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "Only \"r\" or \"w\" are the valid modes to open a pipe");
+        return -1;
+    }
+
+    if (!CreatePipe(&fd[0], &fd[1], &sa, 0)) {
+        error_set_errno(errp, GetLastError(), QERR_QGA_COMMAND_FAILED,
+                        "CreatePipe() failed");
+        return -1;
+    }
+
+    this_end = (mode[0] == 'w');
+    other_end = !this_end;
+
+    pipemode = PIPE_READMODE_BYTE | PIPE_NOWAIT;
+    if (!SetNamedPipeHandleState(fd[this_end], &pipemode, NULL, NULL)) {
+        error_set_errno(errp, GetLastError(), QERR_QGA_COMMAND_FAILED,
+                        "SetNamedPipeHandleState() failed");
+        goto fail;
+    }
+
+    handle = guest_file_handle_add(fd[this_end], fd[other_end], errp);
+    if (handle == -1) {
+        goto fail;
+    }
+
+    slog("guest-pipe-open: handle: %" PRId64, handle);
+
+    return handle;
+
+fail:
+    CloseHandle(fd[0]);
+    CloseHandle(fd[1]);
+
+    return -1;
+}
+
+static int guest_pipe_close_other_end(GuestFileHandle *gfh)
+{
+    if (gfh->pipe_other_end_fd != INVALID_HANDLE_VALUE) {
+
+        if (!CloseHandle(gfh->pipe_other_end_fd)) {
+            return 1;
+        }
+
+        gfh->pipe_other_end_fd = INVALID_HANDLE_VALUE;
+    }
+
     return 0;
 }
 
@@ -168,6 +232,12 @@ void qmp_guest_file_close(int64_t handle, Error **errp)
     if (gfh == NULL) {
         return;
     }
+
+    if (guest_pipe_close_other_end(gfh) != 0) {
+        error_setg_errno(errp, GetLastError(), "failed to close pipe handle");
+        return;
+    }
+
     ret = CloseHandle(gfh->fh);
     if (!ret) {
         error_setg_errno(errp, GetLastError(), "failed close handle");
@@ -707,7 +777,7 @@ GList *ga_command_blacklist_init(GList *blacklist)
         "guest-suspend-hybrid", "guest-network-get-interfaces",
         "guest-get-vcpus", "guest-set-vcpus",
         "guest-fsfreeze-freeze-list", "guest-get-fsinfo",
-        "guest-fstrim", "guest-pipe-open", "guest-exec-status",
+        "guest-fstrim", "guest-exec-status",
         "guest-exec", NULL};
     char **p = (char **)list_unsupported;
 
-- 
1.9.1