use etchosts package from c/common

Use the new logic from c/common to create the hosts file. This will help
to better allign the hosts files between buildah and podman.

Also this fixes several bugs:
- remove host entries when container is stopped and has a netNsCtr
- add entries for containers in a pod
- do not duplicate entries in the hosts file
- use the correct slirp ip when an userns is used

Features:
- configure host.containers.internal entry in containers.conf
- configure base hosts file in containers.conf

Fixes #12003
Fixes #13224

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

vendor/github.com/containers/common/libnetwork/etchosts/ip.go

@@ -0,0 +1,91 @@
+package etchosts
+
+import (
+	"net"
+
+	"github.com/containers/common/libnetwork/types"
+	"github.com/containers/common/libnetwork/util"
+	"github.com/containers/common/pkg/config"
+	"github.com/containers/storage/pkg/unshare"
+)
+
+// GetHostContainersInternalIP return the host.containers.internal ip
+// if netStatus is not nil then networkInterface also must be non nil otherwise this function panics
+func GetHostContainersInternalIP(conf *config.Config, netStatus map[string]types.StatusBlock, networkInterface types.ContainerNetwork) string {
+	switch conf.Containers.HostContainersInternalIP {
+	case "":
+		// if empty (default) we will automatically choose one below
+		// if machine we let the gvproxy dns server handle the dns name so do not add it
+		if conf.Engine.MachineEnabled {
+			return ""
+		}
+	case "none":
+		return ""
+	default:
+		return conf.Containers.HostContainersInternalIP
+	}
+	ip := ""
+	// Only use the bridge ip when root, as rootless the interfaces are created
+	// inside the special netns and not the host so we cannot use them.
+	if unshare.IsRootless() {
+		return getLocalIP()
+	}
+	for net, status := range netStatus {
+		network, err := networkInterface.NetworkInspect(net)
+		// only add the host entry for bridge networks
+		// ip/macvlan gateway is normally not on the host
+		if err != nil || network.Driver != types.BridgeNetworkDriver {
+			continue
+		}
+		for _, netInt := range status.Interfaces {
+			for _, netAddress := range netInt.Subnets {
+				if netAddress.Gateway != nil {
+					if util.IsIPv4(netAddress.Gateway) {
+						return netAddress.Gateway.String()
+					}
+					// ipv6 address but keep looking since we prefer to use ipv4
+					ip = netAddress.Gateway.String()
+				}
+			}
+		}
+	}
+	if ip != "" {
+		return ip
+	}
+	return getLocalIP()
+}
+
+// getLocalIP returns the non loopback local IP of the host
+func getLocalIP() string {
+	addrs, err := net.InterfaceAddrs()
+	if err != nil {
+		return ""
+	}
+	ip := ""
+	for _, address := range addrs {
+		// check the address type and if it is not a loopback the display it
+		if ipnet, ok := address.(*net.IPNet); ok && ipnet.IP.IsGlobalUnicast() {
+			if util.IsIPv4(ipnet.IP) {
+				return ipnet.IP.String()
+			}
+			// if ipv6 we keep looking for an ipv4 address
+			ip = ipnet.IP.String()
+		}
+	}
+	return ip
+}
+
+// GetNetworkHostEntries returns HostEntries for all ips in the network status
+// with the given hostnames.
+func GetNetworkHostEntries(netStatus map[string]types.StatusBlock, names ...string) HostEntries {
+	hostEntries := make(HostEntries, 0, len(netStatus))
+	for _, status := range netStatus {
+		for _, netInt := range status.Interfaces {
+			for _, netAddress := range netInt.Subnets {
+				e := HostEntry{IP: netAddress.IPNet.IP.String(), Names: names}
+				hostEntries = append(hostEntries, e)
+			}
+		}
+	}
+	return hostEntries
+}