libnetwork/util: add GetNetworkIPs()

Add helper function to get the first ipv4 and ipv6 from the network
status. Since this is stored as a map, calling this function multiple
times is not deterministic. The caller (Podman) should store this result
to make sure it will keep using the same ips.

Signed-off-by: Paul Holzinger <[email protected]>

libnetwork/util/ip.go

@@ -2,6 +2,8 @@ package util
 
 import (
 	"net"
+
+	"github.com/containers/common/libnetwork/types"
 )
 
 // IsIPv6 returns true if netIP is IPv6.
@@ -54,3 +56,27 @@ func NormalizeIP(ip *net.IP) {
 		*ip = ipv4
 	}
 }
+
+// GetNetworkIPs return one ipv4 and ipv6 address of this network status.
+// The first return value is the ipv4 and the second one the ipv6 address.
+// If there is no ipv4/6 address it will return an empty string instead.
+func GetNetworkIPs(netStatus map[string]types.StatusBlock) (ipv4, ipv6 string) {
+	for _, status := range netStatus {
+		for _, netInt := range status.Interfaces {
+			for _, netAddress := range netInt.Subnets {
+				if IsIPv4(netAddress.IPNet.IP) {
+					if ipv4 == "" {
+						ipv4 = netAddress.IPNet.IP.String()
+					}
+				} else if ipv6 == "" {
+					ipv6 = netAddress.IPNet.IP.String()
+				}
+
+				if ipv4 != "" && ipv6 != "" {
+					return ipv4, ipv6
+				}
+			}
+		}
+	}
+	return ipv4, ipv6
+}