Passing tap devices to KVM as file descriptors requires that the respective
file decriptors remain open during utils.RunCmd execution. To this direction,
we add a “noclose_fds” keyword argument to utils.RunCmd, accepting a list of
file descriptors to keep open. The actual fd handling is implemented in
_RunCmdPipe and _RunCmdFile using subprocess.Popen's “preexec_fn”[1],
since subprocess.Popen provides no other way to selectively handle fds.
A small modification is also made to test/ganeti.utils_unittest.py to comply
with _RunCmdPipe's new API.
[1] “If preexec_fn is set to a callable object, this object will be called in
the child process just before the child is executed. (Unix only)”
Subprocess documentation
Signed-off-by: Apollon Oikonomopoulos <[email protected]>
---
lib/utils.py | 45 ++++++++++++++++++++++++++++++++--------
test/ganeti.utils_unittest.py | 2 +-
2 files changed, 37 insertions(+), 10 deletions(-)
diff --git a/lib/utils.py b/lib/utils.py
index 359c443..fd2c7fb 100644
--- a/lib/utils.py
+++ b/lib/utils.py
@@ -190,7 +190,7 @@ def _BuildCmdEnvironment(env, reset):
def RunCmd(cmd, env=None, output=None, cwd="/", reset_env=False,
- interactive=False, timeout=None):
+ interactive=False, timeout=None, noclose_fds=None):
"""Execute a (shell) command.
The command should not read from its standard input, as it will be
@@ -215,6 +215,9 @@ def RunCmd(cmd, env=None, output=None, cwd="/",
reset_env=False,
@type timeout: int
@param timeout: If not None, timeout in seconds until child process gets
killed
+ @type noclose_fds: list
+ @param noclose_fds: list of additional (fd >=3) file descriptors to leave
+ open for the child process
@rtype: L{RunResult}
@return: RunResult instance
@raise errors.ProgrammerError: if we call this when forks are disabled
@@ -245,10 +248,11 @@ def RunCmd(cmd, env=None, output=None, cwd="/",
reset_env=False,
try:
if output is None:
out, err, status, timeout_action = _RunCmdPipe(cmd, cmd_env, shell, cwd,
- interactive, timeout)
+ interactive, timeout,
+ noclose_fds)
else:
timeout_action = _TIMEOUT_NONE
- status = _RunCmdFile(cmd, cmd_env, shell, output, cwd)
+ status = _RunCmdFile(cmd, cmd_env, shell, output, cwd, noclose_fds)
out = err = ""
except OSError, err:
if err.errno == errno.ENOENT:
@@ -510,7 +514,7 @@ def _WaitForProcess(child, timeout):
pass
-def _RunCmdPipe(cmd, env, via_shell, cwd, interactive, timeout,
+def _RunCmdPipe(cmd, env, via_shell, cwd, interactive, timeout, noclose_fds,
_linger_timeout=constants.CHILD_LINGER_TIMEOUT):
"""Run a command and return its output.
@@ -526,6 +530,9 @@ def _RunCmdPipe(cmd, env, via_shell, cwd, interactive,
timeout,
@param interactive: Run command interactive (without piping)
@type timeout: int
@param timeout: Timeout after the programm gets terminated
+ @type noclose_fds: list
+ @param noclose_fds: list of additional (fd >=3) file descriptors to leave
+ open for the child process
@rtype: tuple
@return: (out, err, status)
@@ -539,12 +546,20 @@ def _RunCmdPipe(cmd, env, via_shell, cwd, interactive,
timeout,
if interactive:
stderr = stdout = stdin = None
+ if noclose_fds:
+ preexec_fn = lambda: CloseFDs(noclose_fds)
+ close_fds = False
+ else:
+ preexec_fn = None
+ close_fds = True
+
child = subprocess.Popen(cmd, shell=via_shell,
stderr=stderr,
stdout=stdout,
stdin=stdin,
- close_fds=True, env=env,
- cwd=cwd)
+ close_fds=close_fds, env=env,
+ cwd=cwd,
+ preexec_fn=preexec_fn)
out = StringIO()
err = StringIO()
@@ -637,7 +652,7 @@ def _RunCmdPipe(cmd, env, via_shell, cwd, interactive,
timeout,
return out, err, status, timeout_action
-def _RunCmdFile(cmd, env, via_shell, output, cwd):
+def _RunCmdFile(cmd, env, via_shell, output, cwd, noclose_fds):
"""Run a command and save its output to a file.
@type cmd: string or list
@@ -650,18 +665,30 @@ def _RunCmdFile(cmd, env, via_shell, output, cwd):
@param output: the filename in which to save the output
@type cwd: string
@param cwd: the working directory for the program
+ @type noclose_fds: list
+ @param noclose_fds: list of additional (fd >=3) file descriptors to leave
+ open for the child process
@rtype: int
@return: the exit status
"""
fh = open(output, "a")
+
+ if noclose_fds:
+ preexec_fn = lambda: CloseFDs(noclose_fds + [fh.fileno()])
+ close_fds = False
+ else:
+ preexec_fn = None
+ close_fds = True
+
try:
child = subprocess.Popen(cmd, shell=via_shell,
stderr=subprocess.STDOUT,
stdout=fh,
stdin=subprocess.PIPE,
- close_fds=True, env=env,
- cwd=cwd)
+ close_fds=close_fds, env=env,
+ cwd=cwd,
+ preexec_fn=preexec_fn)
child.stdin.close()
status = child.wait()
diff --git a/test/ganeti.utils_unittest.py b/test/ganeti.utils_unittest.py
index d01a005..e8afad4 100755
--- a/test/ganeti.utils_unittest.py
+++ b/test/ganeti.utils_unittest.py
@@ -299,7 +299,7 @@ class TestRunCmd(testutils.GanetiTestCase):
cmd = ["/bin/sh", "-c", "trap '' TERM; read < %s" % self.fifo_file]
timeout = 0.2
out, err, status, ta = utils._RunCmdPipe(cmd, {}, False, "/", False,
- timeout, _linger_timeout=0.2)
+ timeout, None,
_linger_timeout=0.2)
self.assert_(status < 0)
self.assertEqual(-status, signal.SIGKILL)
--
1.7.1
