1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 //go:build unix || js || wasip1 || windows
6 7 package net
8 9 import (
10 "context"
11 "io"
12 "os"
13 "syscall"
14 )
15 16 func sockaddrToTCP(sa syscall.Sockaddr) Addr {
17 switch sa := sa.(type) {
18 case *syscall.SockaddrInet4:
19 return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port}
20 case *syscall.SockaddrInet6:
21 return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneCache.name(int(sa.ZoneId))}
22 }
23 return nil
24 }
25 26 func (a *TCPAddr) family() int {
27 if a == nil || len(a.IP) <= IPv4len {
28 return syscall.AF_INET
29 }
30 if a.IP.To4() != nil {
31 return syscall.AF_INET
32 }
33 return syscall.AF_INET6
34 }
35 36 func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
37 if a == nil {
38 return nil, nil
39 }
40 return ipToSockaddr(family, a.IP, a.Port, a.Zone)
41 }
42 43 func (a *TCPAddr) toLocal(net []byte) sockaddr {
44 return &TCPAddr{loopbackIP(net), a.Port, a.Zone}
45 }
46 47 func (c *TCPConn) readFrom(r io.Reader) (int64, error) {
48 if n, err, handled := spliceFrom(c.fd, r); handled {
49 return n, err
50 }
51 if n, err, handled := sendFile(c.fd, r); handled {
52 return n, err
53 }
54 return genericReadFrom(c, r)
55 }
56 57 func (c *TCPConn) writeTo(w io.Writer) (int64, error) {
58 if n, err, handled := spliceTo(w, c.fd); handled {
59 return n, err
60 }
61 return genericWriteTo(c, w)
62 }
63 64 func (sd *sysDialer) dialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
65 if h := sd.testHookDialTCP; h != nil {
66 return h(ctx, sd.network, laddr, raddr)
67 }
68 if h := testHookDialTCP; h != nil {
69 return h(ctx, sd.network, laddr, raddr)
70 }
71 return sd.doDialTCP(ctx, laddr, raddr)
72 }
73 74 func (sd *sysDialer) doDialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
75 return sd.doDialTCPProto(ctx, laddr, raddr, 0)
76 }
77 78 func (sd *sysDialer) doDialTCPProto(ctx context.Context, laddr, raddr *TCPAddr, proto int) (*TCPConn, error) {
79 ctrlCtxFn := sd.Dialer.ControlContext
80 if ctrlCtxFn == nil && sd.Dialer.Control != nil {
81 ctrlCtxFn = func(ctx context.Context, network, address []byte, c syscall.RawConn) error {
82 return sd.Dialer.Control(network, address, c)
83 }
84 }
85 fd, err := internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, proto, "dial", ctrlCtxFn)
86 87 // TCP has a rarely used mechanism called a 'simultaneous connection' in
88 // which Dial("tcp", addr1, addr2) run on the machine at addr1 can
89 // connect to a simultaneous Dial("tcp", addr2, addr1) run on the machine
90 // at addr2, without either machine executing Listen. If laddr == nil,
91 // it means we want the kernel to pick an appropriate originating local
92 // address. Some Linux kernels cycle blindly through a fixed range of
93 // local ports, regardless of destination port. If a kernel happens to
94 // pick local port 50001 as the source for a Dial("tcp", "", "localhost:50001"),
95 // then the Dial will succeed, having simultaneously connected to itself.
96 // This can only happen when we are letting the kernel pick a port (laddr == nil)
97 // and when there is no listener for the destination address.
98 // It's hard to argue this is anything other than a kernel bug. If we
99 // see this happen, rather than expose the buggy effect to users, we
100 // close the fd and try again. If it happens twice more, we relent and
101 // use the result. See also:
102 // https://golang.org/issue/2690
103 // https://stackoverflow.com/questions/4949858/
104 //
105 // The opposite can also happen: if we ask the kernel to pick an appropriate
106 // originating local address, sometimes it picks one that is already in use.
107 // So if the error is EADDRNOTAVAIL, we have to try again too, just for
108 // a different reason.
109 //
110 // The kernel socket code is no doubt enjoying watching us squirm.
111 for i := 0; i < 2 && (laddr == nil || laddr.Port == 0) && (selfConnect(fd, err) || spuriousENOTAVAIL(err)); i++ {
112 if err == nil {
113 fd.Close()
114 }
115 fd, err = internetSocket(ctx, sd.network, laddr, raddr, syscall.SOCK_STREAM, proto, "dial", ctrlCtxFn)
116 }
117 118 if err != nil {
119 return nil, err
120 }
121 return newTCPConn(fd, sd.Dialer.KeepAlive, sd.Dialer.KeepAliveConfig, testPreHookSetKeepAlive, testHookSetKeepAlive), nil
122 }
123 124 func selfConnect(fd *netFD, err error) bool {
125 // If the connect failed, we clearly didn't connect to ourselves.
126 if err != nil {
127 return false
128 }
129 130 // The socket constructor can return an fd with raddr nil under certain
131 // unknown conditions. The errors in the calls there to Getpeername
132 // are discarded, but we can't catch the problem there because those
133 // calls are sometimes legally erroneous with a "socket not connected".
134 // Since this code (selfConnect) is already trying to work around
135 // a problem, we make sure if this happens we recognize trouble and
136 // ask the DialTCP routine to try again.
137 // TODO: try to understand what's really going on.
138 if fd.laddr == nil || fd.raddr == nil {
139 return true
140 }
141 l := fd.laddr.(*TCPAddr)
142 r := fd.raddr.(*TCPAddr)
143 return l.Port == r.Port && l.IP.Equal(r.IP)
144 }
145 146 func spuriousENOTAVAIL(err error) bool {
147 if op, ok := err.(*OpError); ok {
148 err = op.Err
149 }
150 if sys, ok := err.(*os.SyscallError); ok {
151 err = sys.Err
152 }
153 return err == syscall.EADDRNOTAVAIL
154 }
155 156 func (ln *TCPListener) ok() bool { return ln != nil && ln.fd != nil }
157 158 func (ln *TCPListener) accept() (*TCPConn, error) {
159 fd, err := ln.fd.accept()
160 if err != nil {
161 return nil, err
162 }
163 return newTCPConn(fd, ln.lc.KeepAlive, ln.lc.KeepAliveConfig, testPreHookSetKeepAlive, testHookSetKeepAlive), nil
164 }
165 166 func (ln *TCPListener) close() error {
167 return ln.fd.Close()
168 }
169 170 func (ln *TCPListener) file() (*os.File, error) {
171 f, err := ln.fd.dup()
172 if err != nil {
173 return nil, err
174 }
175 return f, nil
176 }
177 178 func (sl *sysListener) listenTCP(ctx context.Context, laddr *TCPAddr) (*TCPListener, error) {
179 return sl.listenTCPProto(ctx, laddr, 0)
180 }
181 182 func (sl *sysListener) listenTCPProto(ctx context.Context, laddr *TCPAddr, proto int) (*TCPListener, error) {
183 var ctrlCtxFn func(ctx context.Context, network, address []byte, c syscall.RawConn) error
184 if sl.ListenConfig.Control != nil {
185 ctrlCtxFn = func(ctx context.Context, network, address []byte, c syscall.RawConn) error {
186 return sl.ListenConfig.Control(network, address, c)
187 }
188 }
189 fd, err := internetSocket(ctx, sl.network, laddr, nil, syscall.SOCK_STREAM, proto, "listen", ctrlCtxFn)
190 if err != nil {
191 return nil, err
192 }
193 return &TCPListener{fd: fd, lc: sl.ListenConfig}, nil
194 }
195