tcpsock_posix.go

Documentation: net

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