All network devices can only be of size < IFNAMSIZ. So let's spare the useless
heap allocations and use static memory.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

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

- check for error on ifindex retrieval
- free allocated memory
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

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

- Retrieve the host's veth device ifindex in the host's network namespace.
- Add a note why we retrieve the container's veth device ifindex in the host's
  network namespace.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

- On unprivileged veth network creation have lxc-user-nic send the names of the
  veth devices and their respective ifindeces. The advantage of retrieving this
  information from lxc-user-nic is that we spare us sending around more stuff
  via the netpipe in start.c. Also, lxc-user-nic operates in both namespaces
  (the container's namespace and the hosts's namespace) via setns and so is
  guaranteed to retrieve the correct ifindex via if_nametoindex() which is an
  network namespace aware ioctl() call. While I'm pretty sure the ifindeces for
  veth devices are identical across network namespaces I'm weary to rely on
  this. We need the ifindexes to guarantee safe deletion of unprivileged
  network devices via lxc-user-nic later on since we use them to identify the
  network devices in their corresponding network namespaces.
- Move the network device logging from the child to the parent. The child does
  not have all of the information about the network devices available only the
  few bits it actually needs to now. The monitor process is the only process
  that needs all this information.
- The network creation code for privileged and unprivileged networks was
  previously mangled into one single function but at the same time some of the
  privileged code had additional functions that were called in other places in
  start.c. Let's divide and conquer and split out the privileged and
  unprivileged network creation into completely separate functions. This makes
  what's happening way more clear. This will also have no performance impact
  since either you are privileged and only execute the privileged network
  creation functions or you are unprivileged and only execute the unprivileged
  network creation functions.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

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

This is menial work but I'll thank myself later... a lot.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

We should not just record the ifindex for the container's veth device but also
for the host's veth device. This is useful when {configuring,deconfiguring}
veth devices and becomes crucial when calling our lxc-user-nic setuid helper
where we rely on the ifindex to make decisions about whether we are licensed to
perform certain operations on the veth device in question.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

If the user specified lxc.net.[i].veth.pair attribute to request that the host
side of a veth pair be given a specific name let's log it at the trace level.
Otherwise, if the user didn't not specify lxc.net.[i].veth.pair veth_attr.veth1
will contain the name of the host side veth device.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

When lxc-user-nic is called with the "delete" subcommand we need to make sure
that we are actually privileged over the network namespace for which we are
supposed to delete devices on the host. To this end we require that path to the
affected network namespace is passed. We then setns() to the network namespace
and drop privilege to the caller's real user id. Then we try to delete the
loopback interface which is not possible. If we are privileged over the network
namespace this operation will fail with ENOTSUP. If we are not privileged over
the network namespace we will get EPERM.

This is the first part of the commit. As of now nothing guarantees that the
caller does not just give us a random path to a network namespace it is
privileged over.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

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

stable 2.0: cherry picks

This moves all of the network handling code into network.{c,h}. This makes what
is going on much clearer. Also it's easier to find relevant code if it is all
in one place.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

This will allow us log more detailed failures.
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>

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

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

We use the ifindex as an indicator that liblxc created the network so let's
record it for the unprivileged case as well.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

This should make things a little less convoluted.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

- lxc-user-nic gains the subcommands {create,delete}
- dup2() STDERR_FILENO as well so that we can show helpful messages in our logs
  on failure
- initialize output buffer so that we don't print garbage
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>

get_new_nicname() calls lxc_mkifname() which allocates memory and returns it to
the caller. The way get_new_nicname() and get_nic_if_avail() were implemented
they hid that fact by returning a boolean. That doesn't make sense. Let's
rather have them return a pointer to the allocated nic name which the caller
needs to free.
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>

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>

This will obviously not work.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

I'm ashamed at how aweful my previous code was.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

So far, when creating veth devices attached to openvswitch bridges we used to
fork() off a thread on container startup. This thread was kept around until the
container shut down. I have no good explanation why we did it that why but it's
certainly not necessary. Instead, let's fork() off the thread on container
shutdown to delete the veth.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Mimic the code from the debian template.
Signed-off-by: Dimitri John Ledkov <xnox@ubuntu.com>

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>

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>