Currently if lxc-usernsexec is run on a kernel without user namespaces
enabled the error message is

	unshare: Invalid argument
	read pipe: Success

This error message 'Invalid argument' does not point at the root cause
of the error.  We can help the user out by giving a more detailed error
message and also not using perror() if errno==0.

Improve error message by
 - Printing unshare flags
 - Printing suggested cause of failure (user namespace not enabled)
 - Print error message with fprintf() if errno==0 (EOF)
Signed-off-by: Tobin C. Harding <me@tobin.cc>

lxccontainer: minor fixes

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

lxccontainer: improve file locking

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

lxccontainer: fix F_OFD_GETLK checks

When we check whether an open file description lock has been taken on a file we
need to set the l_pid field to 0 otherwise the kernel will send back EINVAL.
Additionally, the kernel will not do pid translation and simply set the l_pid
value to -1.

Fixes https://discuss.linuxcontainers.org/t/container-deleted-or-stopped-when-lxc-ls-executed-concurrently/2439Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

coverity: #1438392

Dereference before null check
Signed-off-by: 2xsec <dh48.jeong@samsung.com>

fix thread-safe issue (localtime => localtime_r)

Signed-off-by: 2xsec <dh48.jeong@samsung.com>

Signed-off-by: 2xsec <dh48.jeong@samsung.com>

netlink: add __netlink_{send,recv,transaction}

These allow to pass a struct nlmsghdr directly and are used in the higher level
netlink_{send,rcv,transaction}.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

netns: improve netnsid allocation

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

fix assignment of signed to bigger unsigned issue

Signed-off-by: 2xsec <dh48.jeong@samsung.com>

tests: containertests: fix dereference pointer c

Signed-off-by: 2xsec <dh48.jeong@samsung.com>

Signed-off-by: 2xsec <dh48.jeong@samsung.com>

network: type fixes lxc_netns_set_nsid()

The kernel expects a __s32 for NETNSA_NSID and a __u32 for NETNSA_FD.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

netns: allocate network namespace id

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Start to allocate a new network namespace id for each container.

Relates to https://github.com/lxc/lxd/issues/4831.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

templates: avoid endless loop

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Closes #2512.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

add default log priority & cleanups

fix coverity issues

Failure to restore non-local value
Signed-off-by: 2xsec <dh48.jeong@samsung.com>

Signed-off-by: 2xsec <dh48.jeong@samsung.com>

Dereference after null check
Signed-off-by: 2xsec <dh48.jeong@samsung.com>