[Bugfix] Check if port is used in publish flag [duplicate of #2190]

[swagatbora90]

This PR continues the work from #2190 (originally by @vsiravar) which checks for used ports while allocating host port in -p/--publish. The original PR is already approved and was just waiting for a rebase form the author. Most of the comments have already been addressed.

Addressing port cleanup on stop:

The original PR had some open discussion around handling port cleanups on container stop

I concur with it, but hold reservations about merging this PR. I believe we should first have nerdctl stop manage the release of ports.
The rest LGTM.

cc vsiravar, could you please fix the stop ( it can be a different PR) so we can merge this accordingly? Thanks

This is now already being addressed with this PR #2839 as network cleanup is part of both container stop and kill

Verified the fix:

 % sudo ./_output/nerdctl run -p 8080:80 --name=test -d nginx
57a24f8da7127aeacee8b888a90e0e4eda866b35513844620de4ad1d28200547

 % sudo ./_output/nerdctl run -p 8080:80  -d nginx
FATA[0000] failed to load networking flags: bind for :8080 failed: port is already allocated 

 % sudo nerdctl stop test
test

% sudo ./_output/nerdctl run -p 8080:80  -d nginx
4ad5ca030355b1eb537c3caa91dfd5a9944dd36e8dea1756a4334a986f96c682

Fixes: #2179

cc @fahedouch @vsiravar

[swagatbora90]

The current implementation breaks in rootless mode which is resulting in the test failures. I am guessing this is mainly due to how Rootlesskit uses slirp4netns to create a separate net ns and possibly the port allocation information is no longer visible in /proc/net/*.

We can either implement some mechanism to track the rootless state or may be add a generic port store to track all port usage.

[fahedouch]

The current implementation breaks in rootless mode which is resulting in the test failures. I am guessing this is mainly due to how Rootlesskit uses slirp4netns to create a separate net ns and possibly the port allocation information is no longer visible in /proc/net/*.

We can either implement some mechanism to track the rootless state or may be add a generic port store to track all port usage.

Rootless > 2.0 starts with a detached network namespace by default. You need to nsenter into the child network namespace, where the container's network is managed, and the ports should be checked there. You have several ways to nsenter, either by executing a child process or using the library https://pkg.go.dev/github.com/containernetworking/plugins/pkg/ns#WithNetNSPath (I prefer the containernetworking library)

[fahedouch]

Suggested change

	usedPort, err := getUsedPorts(ip, protocol)
	usedPorts, err := getUsedPorts(ip, protocol)

[fahedouch]

to make things simpler please declare allocateStart and allocateEnd with uint64 type