Now that most uses of reexec have been replaced with non-reexec
solutions, most of the reexec.Init() calls peppered throughout the test
suites are unnecessary. Furthermore, most of the reexec.Init() calls in
test code neglects to check the return value to determine whether to
exit, which would result in the reexec'ed subprocesses proceeding to run
the tests, which would reexec another subprocess which would proceed to
run the tests, recursively. (That would explain why every reexec
callback used to unconditionally call os.Exit() instead of returning...)

Remove unneeded reexec.Init() calls from test and example code which no
longer needs it, and fix the reexec.Init() calls which are not inert to
exit after a reexec callback is invoked.

Signed-off-by: Cory Snider <csnider@mirantis.com>

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libnetwork/drivers/overlay: make VNI matcher IPv6-compatible

daemon: set docker0 subpool as the IPAM pool

Since cc19eba (backported to v23.0.4), the PreferredPool for docker0 is
set only when the user provides the bip config parameter or when the
default bridge already exist. That means, if a user provides the
fixed-cidr parameter on a fresh install or reboot their computer/server
without bip set, dockerd throw the following error when it starts:

> failed to start daemon: Error initializing network controller: Error
> creating default "bridge" network: failed to parse pool request for
> address space "LocalDefault" pool "" subpool "100.64.0.0/26": Invalid
> Address SubPool

See #45356.

Signed-off-by: Albin Kerouanton <albinker@gmail.com>

Use Linux BPF extensions to locate the offset of the VXLAN header within
the packet so that the same BPF program works with VXLAN packets
received over either IPv4 or IPv6.

Signed-off-by: Cory Snider <csnider@mirantis.com>

Signed-off-by: Cory Snider <csnider@mirantis.com>

This commit removes iptables rules configured for secure overlay
networks when a network is deleted. Prior to this commit, only
CreateNetwork() was taking care of removing stale iptables rules.

If one of the iptables rule can't be removed, the erorr is logged but
it doesn't prevent network deletion.

Signed-off-by: Albin Kerouanton <albinker@gmail.com>

libnetwork/overlay: remove dead code

Linux kernel prior to v3.16 was not supporting netns for vxlan
interfaces. As such, moby/libnetwork#821 introduced a "host mode" to the
overlay driver. The related kernel fix is available for rhel7 users
since v7.2.

This mode could be forced through the use of the env var
_OVERLAY_HOST_MODE. However this env var has never been documented and
is not referenced in any blog post, so there's little chance many people
rely on it. Moreover, this host mode is deemed as an implementation
details by maintainers. As such, we can consider it dead and we can
remove it without a prior deprecation warning.

Signed-off-by: Albin Kerouanton <albinker@gmail.com>