Implement pod-network-reload

This adds a new command, 'podman network reload', to reload the
networks of existing containers, forcing recreation of firewall
rules after e.g. `firewall-cmd --reload` wipes them out.

Under the hood, this works by calling CNI to tear down the
existing network, then recreate it using identical settings. We
request that CNI preserve the old IP and MAC address in most
cases (where the container only had 1 IP/MAC), but there will be
some downtime inherent to the teardown/bring-up approach. The
architecture of CNI doesn't really make doing this without
downtime easy (or maybe even possible...).

At present, this only works for root Podman, and only locally.
I don't think there is much of a point to adding remote support
(this is very much a local debugging command), but I think adding
rootless support (to kill/recreate slirp4netns) could be
valuable.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>
Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

1 files changed, 62 insertions, 0 deletions

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+% podman-network-reload(1)
+
+## NAME
+podman\-network\-reload - Reload network configuration for containers
+
+## SYNOPSIS
+**podman network reload** [*options*] [*container...*]
+
+## DESCRIPTION
+Reload one or more container network configurations.
+
+Rootful Podman relies on iptables rules in order to provide network connectivity. If the iptables rules are deleted,
+this happens for example with `firewall-cmd --reload`, the container loses network connectivity. This command restores
+the network connectivity.
+
+This command is not available for rootless users since rootless containers are not affected by such connectivity problems.
+
+## OPTIONS
+#### **--all**, **-a**
+
+Reload network configuration of all containers.
+
+#### **--latest**, **-l**
+
+Instead of providing the container name or ID, use the last created container. If you use methods other than Podman
+to run containers such as CRI-O, the last started container could be from either of those methods.
+
+The latest option is not supported on the remote client.
+
+## EXAMPLE
+
+Reload the network configuration after a firewall reload.
+
+```
+# podman run -p 80:80 -d nginx
+b1b538e8bc4078fc3ee1c95b666ebc7449b9a97bacd15bcbe464a29e1be59c1c
+# curl 127.0.0.1
+works
+# sudo firewall-cmd --reload
+success
+# curl 127.0.0.1
+hangs
+# podman network reload b1b538e8bc40
+b1b538e8bc4078fc3ee1c95b666ebc7449b9a97bacd15bcbe464a29e1be59c1c
+# curl 127.0.0.1
+works
+```
+
+Reload the network configuration for all containers.
+
+```
+# podman network reload --all
+b1b538e8bc4078fc3ee1c95b666ebc7449b9a97bacd15bcbe464a29e1be59c1c
+fe7e8eca56f844ec33af10f0aa3b31b44a172776e3277b9550a623ed5d96e72b
+```
+
+
+## SEE ALSO
+podman(1), podman-network(1)
+
+## HISTORY
+December 2020, Originally compiled by Paul Holzinger <paul.holzinger@web.de>