sock_posix.go

     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 || windows
     6  
     7  package net
     8  
     9  import (
    10  	"context"
    11  	"internal/poll"
    12  	"os"
    13  	"syscall"
    14  )
    15  
    16  // socket returns a network file descriptor that is ready for
    17  // asynchronous I/O using the network poller.
    18  func socket(ctx context.Context, net string, family, sotype, proto int, ipv6only bool, laddr, raddr sockaddr, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) (fd *netFD, err error) {
    19  	s, err := sysSocket(family, sotype, proto)
    20  	if err != nil {
    21  		return nil, err
    22  	}
    23  	if err = setDefaultSockopts(s, family, sotype, ipv6only); err != nil {
    24  		poll.CloseFunc(s)
    25  		return nil, err
    26  	}
    27  	if fd, err = newFD(s, family, sotype, net); err != nil {
    28  		poll.CloseFunc(s)
    29  		return nil, err
    30  	}
    31  
    32  	// This function makes a network file descriptor for the
    33  	// following applications:
    34  	//
    35  	// - An endpoint holder that opens a passive stream
    36  	//   connection, known as a stream listener
    37  	//
    38  	// - An endpoint holder that opens a destination-unspecific
    39  	//   datagram connection, known as a datagram listener
    40  	//
    41  	// - An endpoint holder that opens an active stream or a
    42  	//   destination-specific datagram connection, known as a
    43  	//   dialer
    44  	//
    45  	// - An endpoint holder that opens the other connection, such
    46  	//   as talking to the protocol stack inside the kernel
    47  	//
    48  	// For stream and datagram listeners, they will only require
    49  	// named sockets, so we can assume that it's just a request
    50  	// from stream or datagram listeners when laddr is not nil but
    51  	// raddr is nil. Otherwise we assume it's just for dialers or
    52  	// the other connection holders.
    53  
    54  	if laddr != nil && raddr == nil {
    55  		switch sotype {
    56  		case syscall.SOCK_STREAM, syscall.SOCK_SEQPACKET:
    57  			if err := fd.listenStream(ctx, laddr, listenerBacklog(), ctrlCtxFn); err != nil {
    58  				fd.Close()
    59  				return nil, err
    60  			}
    61  			return fd, nil
    62  		case syscall.SOCK_DGRAM:
    63  			if err := fd.listenDatagram(ctx, laddr, ctrlCtxFn); err != nil {
    64  				fd.Close()
    65  				return nil, err
    66  			}
    67  			return fd, nil
    68  		}
    69  	}
    70  	if err := fd.dial(ctx, laddr, raddr, ctrlCtxFn); err != nil {
    71  		fd.Close()
    72  		return nil, err
    73  	}
    74  	return fd, nil
    75  }
    76  
    77  func (fd *netFD) ctrlNetwork() string {
    78  	switch fd.net {
    79  	case "unix", "unixgram", "unixpacket":
    80  		return fd.net
    81  	}
    82  	switch fd.net[len(fd.net)-1] {
    83  	case '4', '6':
    84  		return fd.net
    85  	}
    86  	if fd.family == syscall.AF_INET {
    87  		return fd.net + "4"
    88  	}
    89  	return fd.net + "6"
    90  }
    91  
    92  func (fd *netFD) dial(ctx context.Context, laddr, raddr sockaddr, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) error {
    93  	var c *rawConn
    94  	if ctrlCtxFn != nil {
    95  		c = newRawConn(fd)
    96  		var ctrlAddr string
    97  		if raddr != nil {
    98  			ctrlAddr = raddr.String()
    99  		} else if laddr != nil {
   100  			ctrlAddr = laddr.String()
   101  		}
   102  		if err := ctrlCtxFn(ctx, fd.ctrlNetwork(), ctrlAddr, c); err != nil {
   103  			return err
   104  		}
   105  	}
   106  
   107  	var lsa syscall.Sockaddr
   108  	var err error
   109  	if laddr != nil {
   110  		if lsa, err = laddr.sockaddr(fd.family); err != nil {
   111  			return err
   112  		} else if lsa != nil {
   113  			if err = syscall.Bind(fd.pfd.Sysfd, lsa); err != nil {
   114  				return os.NewSyscallError("bind", err)
   115  			}
   116  		}
   117  	}
   118  	var rsa syscall.Sockaddr  // remote address from the user
   119  	var crsa syscall.Sockaddr // remote address we actually connected to
   120  	if raddr != nil {
   121  		if rsa, err = raddr.sockaddr(fd.family); err != nil {
   122  			return err
   123  		}
   124  		if crsa, err = fd.connect(ctx, lsa, rsa); err != nil {
   125  			return err
   126  		}
   127  		fd.isConnected = true
   128  	} else {
   129  		if err := fd.init(); err != nil {
   130  			return err
   131  		}
   132  	}
   133  	// Record the local and remote addresses from the actual socket.
   134  	// Get the local address by calling Getsockname.
   135  	// For the remote address, use
   136  	// 1) the one returned by the connect method, if any; or
   137  	// 2) the one from Getpeername, if it succeeds; or
   138  	// 3) the one passed to us as the raddr parameter.
   139  	lsa, _ = syscall.Getsockname(fd.pfd.Sysfd)
   140  	if crsa != nil {
   141  		fd.setAddr(fd.addrFunc()(lsa), fd.addrFunc()(crsa))
   142  	} else if rsa, _ = syscall.Getpeername(fd.pfd.Sysfd); rsa != nil {
   143  		fd.setAddr(fd.addrFunc()(lsa), fd.addrFunc()(rsa))
   144  	} else {
   145  		fd.setAddr(fd.addrFunc()(lsa), raddr)
   146  	}
   147  	return nil
   148  }
   149  
   150  func (fd *netFD) listenStream(ctx context.Context, laddr sockaddr, backlog int, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) error {
   151  	var err error
   152  	if err = setDefaultListenerSockopts(fd.pfd.Sysfd); err != nil {
   153  		return err
   154  	}
   155  	var lsa syscall.Sockaddr
   156  	if lsa, err = laddr.sockaddr(fd.family); err != nil {
   157  		return err
   158  	}
   159  
   160  	if ctrlCtxFn != nil {
   161  		c := newRawConn(fd)
   162  		if err := ctrlCtxFn(ctx, fd.ctrlNetwork(), laddr.String(), c); err != nil {
   163  			return err
   164  		}
   165  	}
   166  
   167  	if err = syscall.Bind(fd.pfd.Sysfd, lsa); err != nil {
   168  		return os.NewSyscallError("bind", err)
   169  	}
   170  	if err = listenFunc(fd.pfd.Sysfd, backlog); err != nil {
   171  		return os.NewSyscallError("listen", err)
   172  	}
   173  	if err = fd.init(); err != nil {
   174  		return err
   175  	}
   176  	lsa, _ = syscall.Getsockname(fd.pfd.Sysfd)
   177  	fd.setAddr(fd.addrFunc()(lsa), nil)
   178  	return nil
   179  }
   180  
   181  func (fd *netFD) listenDatagram(ctx context.Context, laddr sockaddr, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) error {
   182  	switch addr := laddr.(type) {
   183  	case *UDPAddr:
   184  		// We provide a socket that listens to a wildcard
   185  		// address with reusable UDP port when the given laddr
   186  		// is an appropriate UDP multicast address prefix.
   187  		// This makes it possible for a single UDP listener to
   188  		// join multiple different group addresses, for
   189  		// multiple UDP listeners that listen on the same UDP
   190  		// port to join the same group address.
   191  		if addr.IP != nil && addr.IP.IsMulticast() {
   192  			if err := setDefaultMulticastSockopts(fd.pfd.Sysfd); err != nil {
   193  				return err
   194  			}
   195  			addr := *addr
   196  			switch fd.family {
   197  			case syscall.AF_INET:
   198  				addr.IP = IPv4zero
   199  			case syscall.AF_INET6:
   200  				addr.IP = IPv6unspecified
   201  			}
   202  			laddr = &addr
   203  		}
   204  	}
   205  	var err error
   206  	var lsa syscall.Sockaddr
   207  	if lsa, err = laddr.sockaddr(fd.family); err != nil {
   208  		return err
   209  	}
   210  
   211  	if ctrlCtxFn != nil {
   212  		c := newRawConn(fd)
   213  		if err := ctrlCtxFn(ctx, fd.ctrlNetwork(), laddr.String(), c); err != nil {
   214  			return err
   215  		}
   216  	}
   217  	if err = syscall.Bind(fd.pfd.Sysfd, lsa); err != nil {
   218  		return os.NewSyscallError("bind", err)
   219  	}
   220  	if err = fd.init(); err != nil {
   221  		return err
   222  	}
   223  	lsa, _ = syscall.Getsockname(fd.pfd.Sysfd)
   224  	fd.setAddr(fd.addrFunc()(lsa), nil)
   225  	return nil
   226  }
   227
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