libpod: addHosts() prevent nil deref

In theory RootlessNetnsInfo() should never return nil here. However that
was actually only true when the rootless netns was set up before and
wrote the right cache file with the ip addresses.

Given this cache file is a new feature just added in 5.3 if you updated
from 5.2 or earlier the file will not exists thus cause failures for all
following started containers.
The fix for this is to stop all containers and make sure the
rootless-netns was removed so the next start creates it new with the
proper 5.3 cache file. However as there is no way to rely on users doing
that and it is also not requirement so simply handle the nil deref here.

The only way to test this would be to run the old version then the new
version which we cannot really do in CI. We do have upgrade test for
that but they are root only and likely need a lot more work to get them
going rootless but certainly worth to explore to prevent such problems
in the future.

Fixes: a1e6603133 ("libpod: make use of new pasta option from c/common")
Fixes: #24566

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

libpod/container_internal_common.go

@@ -2323,7 +2323,7 @@ func (c *Container) addHosts() error {
 		// not be routed to the host.
 		// https://github.com/containers/podman/issues/22653
 		info, err := c.runtime.network.RootlessNetnsInfo()
-		if err == nil {
+		if err == nil && info != nil {
 			exclude = info.IPAddresses
 			if len(info.MapGuestIps) > 0 {
 				// we used --map-guest-addr to setup pasta so prefer this address

libpod/container_internal_linux.go

@@ -624,7 +624,7 @@ func (c *Container) addSpecialDNS(nameservers []string) []string {
 	switch {
 	case c.config.NetMode.IsBridge():
 		info, err := c.runtime.network.RootlessNetnsInfo()
-		if err == nil {
+		if err == nil && info != nil {
 			nameservers = append(nameservers, info.DnsForwardIps...)
 		}
 	case c.pastaResult != nil: