/usr/share/gocode/src/github.com/docker/go-connections/proxy/udp_proxy.go is in golang-github-docker-go-connections-dev 0.3.0-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 | package proxy
import (
"encoding/binary"
"net"
"strings"
"sync"
"syscall"
"time"
)
const (
// UDPConnTrackTimeout is the timeout used for UDP connection tracking
UDPConnTrackTimeout = 90 * time.Second
// UDPBufSize is the buffer size for the UDP proxy
UDPBufSize = 65507
)
// A net.Addr where the IP is split into two fields so you can use it as a key
// in a map:
type connTrackKey struct {
IPHigh uint64
IPLow uint64
Port int
}
func newConnTrackKey(addr *net.UDPAddr) *connTrackKey {
if len(addr.IP) == net.IPv4len {
return &connTrackKey{
IPHigh: 0,
IPLow: uint64(binary.BigEndian.Uint32(addr.IP)),
Port: addr.Port,
}
}
return &connTrackKey{
IPHigh: binary.BigEndian.Uint64(addr.IP[:8]),
IPLow: binary.BigEndian.Uint64(addr.IP[8:]),
Port: addr.Port,
}
}
type connTrackMap map[connTrackKey]*net.UDPConn
// UDPProxy is proxy for which handles UDP datagrams. It implements the Proxy
// interface to handle UDP traffic forwarding between the frontend and backend
// addresses.
type UDPProxy struct {
Logger logger
listener *net.UDPConn
frontendAddr *net.UDPAddr
backendAddr *net.UDPAddr
connTrackTable connTrackMap
connTrackLock sync.Mutex
}
// NewUDPProxy creates a new UDPProxy.
func NewUDPProxy(frontendAddr, backendAddr *net.UDPAddr, ops ...func(*UDPProxy)) (*UDPProxy, error) {
listener, err := net.ListenUDP("udp", frontendAddr)
if err != nil {
return nil, err
}
proxy := &UDPProxy{
listener: listener,
frontendAddr: listener.LocalAddr().(*net.UDPAddr),
backendAddr: backendAddr,
connTrackTable: make(connTrackMap),
Logger: &noopLogger{},
}
for _, op := range ops {
op(proxy)
}
return proxy, nil
}
func (proxy *UDPProxy) replyLoop(proxyConn *net.UDPConn, clientAddr *net.UDPAddr, clientKey *connTrackKey) {
defer func() {
proxy.connTrackLock.Lock()
delete(proxy.connTrackTable, *clientKey)
proxy.connTrackLock.Unlock()
proxyConn.Close()
}()
readBuf := make([]byte, UDPBufSize)
for {
proxyConn.SetReadDeadline(time.Now().Add(UDPConnTrackTimeout))
again:
read, err := proxyConn.Read(readBuf)
if err != nil {
if err, ok := err.(*net.OpError); ok && err.Err == syscall.ECONNREFUSED {
// This will happen if the last write failed
// (e.g: nothing is actually listening on the
// proxied port on the container), ignore it
// and continue until UDPConnTrackTimeout
// expires:
goto again
}
return
}
for i := 0; i != read; {
written, err := proxy.listener.WriteToUDP(readBuf[i:read], clientAddr)
if err != nil {
return
}
i += written
}
}
}
// Run starts forwarding the traffic using UDP.
func (proxy *UDPProxy) Run() {
readBuf := make([]byte, UDPBufSize)
for {
read, from, err := proxy.listener.ReadFromUDP(readBuf)
if err != nil {
// NOTE: Apparently ReadFrom doesn't return
// ECONNREFUSED like Read do (see comment in
// UDPProxy.replyLoop)
if !isClosedError(err) {
proxy.Logger.Printf("Stopping proxy on udp/%v for udp/%v (%s)", proxy.frontendAddr, proxy.backendAddr, err)
}
break
}
fromKey := newConnTrackKey(from)
proxy.connTrackLock.Lock()
proxyConn, hit := proxy.connTrackTable[*fromKey]
if !hit {
proxyConn, err = net.DialUDP("udp", nil, proxy.backendAddr)
if err != nil {
proxy.Logger.Printf("Can't proxy a datagram to udp/%s: %s\n", proxy.backendAddr, err)
proxy.connTrackLock.Unlock()
continue
}
proxy.connTrackTable[*fromKey] = proxyConn
go proxy.replyLoop(proxyConn, from, fromKey)
}
proxy.connTrackLock.Unlock()
for i := 0; i != read; {
written, err := proxyConn.Write(readBuf[i:read])
if err != nil {
proxy.Logger.Printf("Can't proxy a datagram to udp/%s: %s\n", proxy.backendAddr, err)
break
}
i += written
}
}
}
// Close stops forwarding the traffic.
func (proxy *UDPProxy) Close() {
proxy.listener.Close()
proxy.connTrackLock.Lock()
defer proxy.connTrackLock.Unlock()
for _, conn := range proxy.connTrackTable {
conn.Close()
}
}
// FrontendAddr returns the UDP address on which the proxy is listening.
func (proxy *UDPProxy) FrontendAddr() net.Addr { return proxy.frontendAddr }
// BackendAddr returns the proxied UDP address.
func (proxy *UDPProxy) BackendAddr() net.Addr { return proxy.backendAddr }
func isClosedError(err error) bool {
/* This comparison is ugly, but unfortunately, net.go doesn't export errClosing.
* See:
* http://golang.org/src/pkg/net/net.go
* https://code.google.com/p/go/issues/detail?id=4337
* https://groups.google.com/forum/#!msg/golang-nuts/0_aaCvBmOcM/SptmDyX1XJMJ
*/
return strings.HasSuffix(err.Error(), "use of closed network connection")
}
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