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- // Network utility functions.
- package netutils
- import (
- "crypto/rand"
- "encoding/hex"
- "errors"
- "fmt"
- "io"
- "net"
- "strings"
- "github.com/docker/docker/libnetwork/types"
- )
- var (
- // ErrNetworkOverlapsWithNameservers preformatted error
- ErrNetworkOverlapsWithNameservers = errors.New("requested network overlaps with nameserver")
- // ErrNetworkOverlaps preformatted error
- ErrNetworkOverlaps = errors.New("requested network overlaps with existing network")
- )
- // 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
- }
- 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 string of the specified length, created by joining the prefix to random hex characters.
- // The length must be strictly larger than len(prefix), or an error will be returned.
- func GenerateRandomName(prefix string, length int) (string, error) {
- if length <= len(prefix) {
- return "", fmt.Errorf("invalid length %d for prefix %s", length, prefix)
- }
- // We add 1 here as integer division will round down, and we want to round up.
- b := make([]byte, (length-len(prefix)+1)/2)
- if _, err := io.ReadFull(rand.Reader, b); err != nil {
- return "", err
- }
- // By taking a slice here, we ensure that the string is always the correct length.
- return (prefix + hex.EncodeToString(b))[:length], 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, ".")
- }
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