fix incorrect host.containers.internal entry for rootless bridge mode

We have to exclude the ips in the rootless netns as they are not the
host. Now that fix only works if there are more than one ip one the
host available, if there is only one we do not set the entry at all
which I consider better as failing to resolve this name is a much better
error for users than connecting to a wrong ip. It also matches what
--network pasta already does.

The test is bit more compilcated as I would like, however it must deal
with both cases one ip, more than one so there is no way around it I
think.

Fixes containers#22653

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

Author: Luap99

libpod/container_internal_common.go

@@ -2299,6 +2299,15 @@ func (c *Container) addHosts() error {
 	var exclude []net.IP
 	if c.pastaResult != nil {
 		exclude = c.pastaResult.IPAddresses
+	} else if c.config.NetMode.IsBridge() {
+		// When running rootless we have to check the rootless netns ip addresses
+		// to not assign a ip that is already used in the rootless netns as it would
+		// not be routed to the host.
+		// https://github.com/containers/podman/issues/22653
+		info, err := c.runtime.network.RootlessNetnsInfo()
+		if err == nil {
+			exclude = info.IPAddresses
+		}
 	}
 
 	return etchosts.New(&etchosts.Params{

test/system/505-networking-pasta.bats

@@ -778,7 +778,7 @@ EOF
     assert "$output" =~ "$mac2" "mac address from cli is set on custom interface"
 }
 
-### Rootless unshare testins
+### Rootless unshare testing
 
 @test "Podman unshare --rootless-netns with Pasta" {
     skip_if_remote "unshare is local-only"
@@ -794,3 +794,30 @@ EOF
     run_podman unshare --rootless-netns ip addr
     is "$output" ".*${pasta_iface}.*"
 }
+
+# https://github.com/containers/podman/issues/22653
+@test "pasta/bridge and host.containers.internal" {
+    skip_if_no_ipv4 "IPv4 not routable on the host"
+    pasta_ip="$(default_addr 4)"
+
+    for network in "pasta" "bridge"; do
+        # special exit code logic needed here, it is possible that there is no host.containers.internal
+        # when there is only one ip one the host and that one is used by pasta.
+        # As such we have to deal with both cases.
+        run_podman '?' run --rm --network=$network $IMAGE grep host.containers.internal /etc/hosts
+        if [ "$status" -eq 0 ]; then
+            assert "$output" !~ "$pasta_ip" "pasta host ip must not be assigned ($network)"
+            assert "$(hostname -I)" =~ "$(cut -f1 <<<$output)" "ip is one of the host ips ($network)"
+        elif [ "$status" -eq 1 ]; then
+            # if only pasta ip then we cannot have a host.containers.internal entry
+            # make sure this fact is actually the case
+            assert "$pasta_ip" == "$(hostname -I | tr -d '[:space:]')" "pasta ip must the only one one the host ($network)"
+        else
+            die "unexpected exit code '$status' from grep or podman ($network)"
+        fi
+    done
+
+    host_ip=$(hostname -I | cut -f 1 -d " ")
+    run_podman run --rm --network=pasta:-a,169.254.0.2,-g,169.254.0.1,-n,24 $IMAGE grep host.containers.internal /etc/hosts
+    assert "$output" =~ "^$host_ip" "uses host first ip"
+}