Switch to using libnetwork's resolvconf package

Libnetwork provides a well-tested package for generating
resolv.conf from the host's that has some features our current
implementation does not. Swap to using their code and remove our
built-in implementation.

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

vendor/github.com/docker/libnetwork/netutils/utils.go

@@ -0,0 +1,201 @@
+// Network utility functions.
+
+package netutils
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+
+	"github.com/docker/libnetwork/types"
+)
+
+// constants for the IP address type
+const (
+	IP = iota // IPv4 and IPv6
+	IPv4
+	IPv6
+)
+
+var (
+	// ErrNetworkOverlapsWithNameservers preformatted error
+	ErrNetworkOverlapsWithNameservers = errors.New("requested network overlaps with nameserver")
+	// ErrNetworkOverlaps preformatted error
+	ErrNetworkOverlaps = errors.New("requested network overlaps with existing network")
+	// ErrNoDefaultRoute preformatted error
+	ErrNoDefaultRoute = errors.New("no default route")
+)
+
+// CheckNameserverOverlaps checks whether the passed network overlaps with any of the nameservers
+func CheckNameserverOverlaps(nameservers []string, toCheck *net.IPNet) error {
+	if len(nameservers) > 0 {
+		for _, ns := range nameservers {
+			_, nsNetwork, err := net.ParseCIDR(ns)
+			if err != nil {
+				return err
+			}
+			if NetworkOverlaps(toCheck, nsNetwork) {
+				return ErrNetworkOverlapsWithNameservers
+			}
+		}
+	}
+	return nil
+}
+
+// NetworkOverlaps detects overlap between one IPNet and another
+func NetworkOverlaps(netX *net.IPNet, netY *net.IPNet) bool {
+	return netX.Contains(netY.IP) || netY.Contains(netX.IP)
+}
+
+// NetworkRange calculates the first and last IP addresses in an IPNet
+func NetworkRange(network *net.IPNet) (net.IP, net.IP) {
+	if network == nil {
+		return nil, nil
+	}
+
+	firstIP := network.IP.Mask(network.Mask)
+	lastIP := types.GetIPCopy(firstIP)
+	for i := 0; i < len(firstIP); i++ {
+		lastIP[i] = firstIP[i] | ^network.Mask[i]
+	}
+
+	if network.IP.To4() != nil {
+		firstIP = firstIP.To4()
+		lastIP = lastIP.To4()
+	}
+
+	return firstIP, lastIP
+}
+
+// GetIfaceAddr returns the first IPv4 address and slice of IPv6 addresses for the specified network interface
+func GetIfaceAddr(name string) (net.Addr, []net.Addr, error) {
+	iface, err := net.InterfaceByName(name)
+	if err != nil {
+		return nil, nil, err
+	}
+	addrs, err := iface.Addrs()
+	if err != nil {
+		return nil, nil, err
+	}
+	var addrs4 []net.Addr
+	var addrs6 []net.Addr
+	for _, addr := range addrs {
+		ip := (addr.(*net.IPNet)).IP
+		if ip4 := ip.To4(); ip4 != nil {
+			addrs4 = append(addrs4, addr)
+		} else if ip6 := ip.To16(); len(ip6) == net.IPv6len {
+			addrs6 = append(addrs6, addr)
+		}
+	}
+	switch {
+	case len(addrs4) == 0:
+		return nil, nil, fmt.Errorf("Interface %v has no IPv4 addresses", name)
+	case len(addrs4) > 1:
+		fmt.Printf("Interface %v has more than 1 IPv4 address. Defaulting to using %v\n",
+			name, (addrs4[0].(*net.IPNet)).IP)
+	}
+	return addrs4[0], addrs6, nil
+}
+
+func genMAC(ip net.IP) net.HardwareAddr {
+	hw := make(net.HardwareAddr, 6)
+	// The first byte of the MAC address has to comply with these rules:
+	// 1. Unicast: Set the least-significant bit to 0.
+	// 2. Address is locally administered: Set the second-least-significant bit (U/L) to 1.
+	hw[0] = 0x02
+	// The first 24 bits of the MAC represent the Organizationally Unique Identifier (OUI).
+	// Since this address is locally administered, we can do whatever we want as long as
+	// it doesn't conflict with other addresses.
+	hw[1] = 0x42
+	// Fill the remaining 4 bytes based on the input
+	if ip == nil {
+		rand.Read(hw[2:])
+	} else {
+		copy(hw[2:], ip.To4())
+	}
+	return hw
+}
+
+// GenerateRandomMAC returns a new 6-byte(48-bit) hardware address (MAC)
+func GenerateRandomMAC() net.HardwareAddr {
+	return genMAC(nil)
+}
+
+// GenerateMACFromIP returns a locally administered MAC address where the 4 least
+// significant bytes are derived from the IPv4 address.
+func GenerateMACFromIP(ip net.IP) net.HardwareAddr {
+	return genMAC(ip)
+}
+
+// GenerateRandomName returns a new name joined with a prefix.  This size
+// specified is used to truncate the randomly generated value
+func GenerateRandomName(prefix string, size int) (string, error) {
+	id := make([]byte, 32)
+	if _, err := io.ReadFull(rand.Reader, id); err != nil {
+		return "", err
+	}
+	return prefix + hex.EncodeToString(id)[:size], nil
+}
+
+// ReverseIP accepts a V4 or V6 IP string in the canonical form and returns a reversed IP in
+// the dotted decimal form . This is used to setup the IP to service name mapping in the optimal
+// way for the DNS PTR queries.
+func ReverseIP(IP string) string {
+	var reverseIP []string
+
+	if net.ParseIP(IP).To4() != nil {
+		reverseIP = strings.Split(IP, ".")
+		l := len(reverseIP)
+		for i, j := 0, l-1; i < l/2; i, j = i+1, j-1 {
+			reverseIP[i], reverseIP[j] = reverseIP[j], reverseIP[i]
+		}
+	} else {
+		reverseIP = strings.Split(IP, ":")
+
+		// Reversed IPv6 is represented in dotted decimal instead of the typical
+		// colon hex notation
+		for key := range reverseIP {
+			if len(reverseIP[key]) == 0 { // expand the compressed 0s
+				reverseIP[key] = strings.Repeat("0000", 8-strings.Count(IP, ":"))
+			} else if len(reverseIP[key]) < 4 { // 0-padding needed
+				reverseIP[key] = strings.Repeat("0", 4-len(reverseIP[key])) + reverseIP[key]
+			}
+		}
+
+		reverseIP = strings.Split(strings.Join(reverseIP, ""), "")
+
+		l := len(reverseIP)
+		for i, j := 0, l-1; i < l/2; i, j = i+1, j-1 {
+			reverseIP[i], reverseIP[j] = reverseIP[j], reverseIP[i]
+		}
+	}
+
+	return strings.Join(reverseIP, ".")
+}
+
+// ParseAlias parses and validates the specified string as a alias format (name:alias)
+func ParseAlias(val string) (string, string, error) {
+	if val == "" {
+		return "", "", fmt.Errorf("empty string specified for alias")
+	}
+	arr := strings.Split(val, ":")
+	if len(arr) > 2 {
+		return "", "", fmt.Errorf("bad format for alias: %s", val)
+	}
+	if len(arr) == 1 {
+		return val, val, nil
+	}
+	return arr[0], arr[1], nil
+}
+
+// ValidateAlias validates that the specified string has a valid alias format (containerName:alias).
+func ValidateAlias(val string) (string, error) {
+	if _, _, err := ParseAlias(val); err != nil {
+		return val, err
+	}
+	return val, nil
+}