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Fixes #113

Signed-off-by: Marcos Lilljedahl <marcosnils@gmail.com>

vendor/github.com/opencontainers/runc/libcontainer/configs/config_unix.go

@@ -0,0 +1,51 @@
+// +build freebsd linux
+
+package configs
+
+import "fmt"
+
+// Gets the root uid for the process on host which could be non-zero
+// when user namespaces are enabled.
+func (c Config) HostUID() (int, error) {
+	if c.Namespaces.Contains(NEWUSER) {
+		if c.UidMappings == nil {
+			return -1, fmt.Errorf("User namespaces enabled, but no user mappings found.")
+		}
+		id, found := c.hostIDFromMapping(0, c.UidMappings)
+		if !found {
+			return -1, fmt.Errorf("User namespaces enabled, but no root user mapping found.")
+		}
+		return id, nil
+	}
+	// Return default root uid 0
+	return 0, nil
+}
+
+// Gets the root gid for the process on host which could be non-zero
+// when user namespaces are enabled.
+func (c Config) HostGID() (int, error) {
+	if c.Namespaces.Contains(NEWUSER) {
+		if c.GidMappings == nil {
+			return -1, fmt.Errorf("User namespaces enabled, but no gid mappings found.")
+		}
+		id, found := c.hostIDFromMapping(0, c.GidMappings)
+		if !found {
+			return -1, fmt.Errorf("User namespaces enabled, but no root group mapping found.")
+		}
+		return id, nil
+	}
+	// Return default root gid 0
+	return 0, nil
+}
+
+// Utility function that gets a host ID for a container ID from user namespace map
+// if that ID is present in the map.
+func (c Config) hostIDFromMapping(containerID int, uMap []IDMap) (int, bool) {
+	for _, m := range uMap {
+		if (containerID >= m.ContainerID) && (containerID <= (m.ContainerID + m.Size - 1)) {
+			hostID := m.HostID + (containerID - m.ContainerID)
+			return hostID, true
+		}
+	}
+	return -1, false
+}