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@@ -0,0 +1,356 @@
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+package docker
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+
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+import (
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+ "bytes"
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+ "encoding/binary"
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+ "errors"
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+ "fmt"
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+ "log"
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+ "net"
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+ "os/exec"
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+ "strconv"
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+ "strings"
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+)
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+
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+const (
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+ networkBridgeIface = "lxcbr0"
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+ portRangeStart = 49153
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+ portRangeEnd = 65535
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+)
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+
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+// Calculates the first and last IP addresses in an IPNet
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+func networkRange(network *net.IPNet) (net.IP, net.IP) {
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+ netIP := network.IP.To4()
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+ firstIP := netIP.Mask(network.Mask)
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+ lastIP := net.IPv4(0, 0, 0, 0).To4()
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+ for i := 0; i < len(lastIP); i++ {
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+ lastIP[i] = netIP[i] | ^network.Mask[i]
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+ }
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+ return firstIP, lastIP
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+}
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+
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+// Converts a 4 bytes IP into a 32 bit integer
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+func ipToInt(ip net.IP) (int32, error) {
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+ buf := bytes.NewBuffer(ip.To4())
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+ var n int32
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+ if err := binary.Read(buf, binary.BigEndian, &n); err != nil {
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+ return 0, err
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+ }
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+ return n, nil
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+}
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+
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+// Converts 32 bit integer into a 4 bytes IP address
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+func intToIp(n int32) (net.IP, error) {
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+ var buf bytes.Buffer
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+ if err := binary.Write(&buf, binary.BigEndian, &n); err != nil {
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+ return net.IP{}, err
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+ }
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+ ip := net.IPv4(0, 0, 0, 0).To4()
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+ for i := 0; i < net.IPv4len; i++ {
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+ ip[i] = buf.Bytes()[i]
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+ }
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+ return ip, nil
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+}
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+
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+// Given a netmask, calculates the number of available hosts
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+func networkSize(mask net.IPMask) (int32, error) {
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+ m := net.IPv4Mask(0, 0, 0, 0)
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+ for i := 0; i < net.IPv4len; i++ {
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+ m[i] = ^mask[i]
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+ }
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+ buf := bytes.NewBuffer(m)
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+ var n int32
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+ if err := binary.Read(buf, binary.BigEndian, &n); err != nil {
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+ return 0, err
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+ }
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+ return n + 1, nil
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+}
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+
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+// Wrapper around the iptables command
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+func iptables(args ...string) error {
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+ if err := exec.Command("/sbin/iptables", args...).Run(); err != nil {
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+ return fmt.Errorf("iptables failed: iptables %v", strings.Join(args, " "))
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+ }
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+ return nil
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+}
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+
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+// Return the IPv4 address of a network interface
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+func getIfaceAddr(name string) (net.Addr, error) {
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+ iface, err := net.InterfaceByName(name)
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+ if err != nil {
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+ return nil, err
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+ }
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+ addrs, err := iface.Addrs()
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+ if err != nil {
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+ return nil, err
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+ }
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+ var addrs4 []net.Addr
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+ for _, addr := range addrs {
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+ ip := (addr.(*net.IPNet)).IP
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+ if ip4 := ip.To4(); len(ip4) == net.IPv4len {
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+ addrs4 = append(addrs4, addr)
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+ }
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+ }
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+ switch {
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+ case len(addrs4) == 0:
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+ return nil, fmt.Errorf("Interface %v has no IP addresses", name)
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+ case len(addrs4) > 1:
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+ return nil, fmt.Errorf("Interface %v has more than 1 IPv4 address", name)
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+ }
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+ return addrs4[0], nil
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+}
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+
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+// Port mapper takes care of mapping external ports to containers by setting
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+// up iptables rules.
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+// It keeps track of all mappings and is able to unmap at will
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+type PortMapper struct {
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+ mapping map[int]net.TCPAddr
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+}
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+
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+func (mapper *PortMapper) cleanup() error {
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+ // Ignore errors - This could mean the chains were never set up
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+ iptables("-t", "nat", "-D", "PREROUTING", "-j", "DOCKER")
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+ iptables("-t", "nat", "-F", "DOCKER")
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+ iptables("-t", "nat", "-X", "DOCKER")
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+ mapper.mapping = make(map[int]net.TCPAddr)
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+ return nil
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+}
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+
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+func (mapper *PortMapper) setup() error {
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+ if err := iptables("-t", "nat", "-N", "DOCKER"); err != nil {
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+ return errors.New("Unable to setup port networking: Failed to create DOCKER chain")
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+ }
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+ if err := iptables("-t", "nat", "-A", "PREROUTING", "-j", "DOCKER"); err != nil {
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+ return errors.New("Unable to setup port networking: Failed to inject docker in PREROUTING chain")
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+ }
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+ return nil
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+}
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+
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+func (mapper *PortMapper) iptablesForward(rule string, port int, dest net.TCPAddr) error {
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+ return iptables("-t", "nat", rule, "DOCKER", "-p", "tcp", "--dport", strconv.Itoa(port),
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+ "-j", "DNAT", "--to-destination", net.JoinHostPort(dest.IP.String(), strconv.Itoa(dest.Port)))
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+}
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+
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+func (mapper *PortMapper) Map(port int, dest net.TCPAddr) error {
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+ if err := mapper.iptablesForward("-A", port, dest); err != nil {
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+ return err
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+ }
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+ mapper.mapping[port] = dest
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+ return nil
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+}
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+
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+func (mapper *PortMapper) Unmap(port int) error {
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+ dest, ok := mapper.mapping[port]
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+ if !ok {
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+ return errors.New("Port is not mapped")
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+ }
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+ if err := mapper.iptablesForward("-D", port, dest); err != nil {
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+ return err
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+ }
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+ delete(mapper.mapping, port)
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+ return nil
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+}
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+
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+func newPortMapper() (*PortMapper, error) {
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+ mapper := &PortMapper{}
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+ if err := mapper.cleanup(); err != nil {
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+ return nil, err
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+ }
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+ if err := mapper.setup(); err != nil {
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+ return nil, err
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+ }
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+ return mapper, nil
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+}
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+
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+// Port allocator: Atomatically allocate and release networking ports
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+type PortAllocator struct {
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+ ports chan (int)
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+}
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+
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+func (alloc *PortAllocator) populate(start, end int) {
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+ alloc.ports = make(chan int, end-start)
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+ for port := start; port < end; port++ {
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+ alloc.ports <- port
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+ }
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+}
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+
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+func (alloc *PortAllocator) Acquire() (int, error) {
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+ select {
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+ case port := <-alloc.ports:
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+ return port, nil
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+ default:
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+ return -1, errors.New("No more ports available")
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+ }
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+ return -1, nil
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+}
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+
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+func (alloc *PortAllocator) Release(port int) error {
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+ select {
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+ case alloc.ports <- port:
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+ return nil
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+ default:
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+ return errors.New("Too many ports have been released")
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+ }
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+ return nil
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+}
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+
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+func newPortAllocator(start, end int) (*PortAllocator, error) {
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+ allocator := &PortAllocator{}
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+ allocator.populate(start, end)
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+ return allocator, nil
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+}
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+
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+// IP allocator: Atomatically allocate and release networking ports
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+type IPAllocator struct {
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+ network *net.IPNet
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+ queue chan (net.IP)
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+}
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+
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+func (alloc *IPAllocator) populate() error {
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+ firstIP, _ := networkRange(alloc.network)
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+ size, err := networkSize(alloc.network.Mask)
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+ if err != nil {
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+ return err
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+ }
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+ // The queue size should be the network size - 3
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+ // -1 for the network address, -1 for the broadcast address and
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+ // -1 for the gateway address
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+ alloc.queue = make(chan net.IP, size-3)
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+ for i := int32(1); i < size-1; i++ {
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+ ipNum, err := ipToInt(firstIP)
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+ if err != nil {
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+ return err
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+ }
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+ ip, err := intToIp(ipNum + int32(i))
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+ if err != nil {
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+ return err
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+ }
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+ // Discard the network IP (that's the host IP address)
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+ if ip.Equal(alloc.network.IP) {
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+ continue
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+ }
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+ alloc.queue <- ip
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+ }
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+ return nil
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+}
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+
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+func (alloc *IPAllocator) Acquire() (net.IP, error) {
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+ select {
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+ case ip := <-alloc.queue:
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+ return ip, nil
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+ default:
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+ return net.IP{}, errors.New("No more IP addresses available")
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+ }
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+ return net.IP{}, nil
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+}
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+
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+func (alloc *IPAllocator) Release(ip net.IP) error {
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+ select {
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+ case alloc.queue <- ip:
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+ return nil
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+ default:
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+ return errors.New("Too many IP addresses have been released")
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+ }
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+ return nil
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+}
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+
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+func newIPAllocator(network *net.IPNet) (*IPAllocator, error) {
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+ alloc := &IPAllocator{
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+ network: network,
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+ }
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+ if err := alloc.populate(); err != nil {
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+ return nil, err
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+ }
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+ return alloc, nil
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+}
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+
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+// Network interface represents the networking stack of a container
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+type NetworkInterface struct {
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+ IPNet net.IPNet
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+ Gateway net.IP
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+
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+ manager *NetworkManager
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+ extPorts []int
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+}
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+
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+// Allocate an external TCP port and map it to the interface
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+func (iface *NetworkInterface) AllocatePort(port int) (int, error) {
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+ extPort, err := iface.manager.portAllocator.Acquire()
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+ if err != nil {
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+ return -1, err
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+ }
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+ if err := iface.manager.portMapper.Map(extPort, net.TCPAddr{iface.IPNet.IP, port}); err != nil {
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+ iface.manager.portAllocator.Release(extPort)
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+ return -1, err
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+ }
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+ iface.extPorts = append(iface.extPorts, extPort)
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+ return extPort, nil
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+}
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+
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+// Release: Network cleanup - release all resources
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+func (iface *NetworkInterface) Release() error {
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+ for _, port := range iface.extPorts {
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+ if err := iface.manager.portMapper.Unmap(port); err != nil {
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+ log.Printf("Unable to unmap port %v: %v", port, err)
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+ }
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+ if err := iface.manager.portAllocator.Release(port); err != nil {
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+ log.Printf("Unable to release port %v: %v", port, err)
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+ }
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+
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+ }
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+ return iface.manager.ipAllocator.Release(iface.IPNet.IP)
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+}
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+
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+// Network Manager manages a set of network interfaces
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+// Only *one* manager per host machine should be used
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+type NetworkManager struct {
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+ bridgeIface string
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+ bridgeNetwork *net.IPNet
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+
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+ ipAllocator *IPAllocator
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+ portAllocator *PortAllocator
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+ portMapper *PortMapper
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+}
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+
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+// Allocate a network interface
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+func (manager *NetworkManager) Allocate() (*NetworkInterface, error) {
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+ ip, err := manager.ipAllocator.Acquire()
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+ if err != nil {
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+ return nil, err
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+ }
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+ iface := &NetworkInterface{
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+ IPNet: net.IPNet{ip, manager.bridgeNetwork.Mask},
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+ Gateway: manager.bridgeNetwork.IP,
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+ manager: manager,
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+ }
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+ return iface, nil
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+}
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+
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+func newNetworkManager(bridgeIface string) (*NetworkManager, error) {
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+ addr, err := getIfaceAddr(bridgeIface)
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+ if err != nil {
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+ return nil, err
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+ }
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+ network := addr.(*net.IPNet)
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+
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+ ipAllocator, err := newIPAllocator(network)
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+ if err != nil {
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+ return nil, err
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+ }
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+
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+ portAllocator, err := newPortAllocator(portRangeStart, portRangeEnd)
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+ if err != nil {
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+ return nil, err
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+ }
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+
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+ portMapper, err := newPortMapper()
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+
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+ manager := &NetworkManager{
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+ bridgeIface: bridgeIface,
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+ bridgeNetwork: network,
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+ ipAllocator: ipAllocator,
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+ portAllocator: portAllocator,
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+ portMapper: portMapper,
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+ }
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+ return manager, nil
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+}
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