github.com/mh-cbon/go@v0.0.0-20160603070303-9e112a3fe4c0/src/net/iprawsock_posix.go (about)

     1  // Copyright 2010 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  // +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
     6  
     7  package net
     8  
     9  import (
    10  	"context"
    11  	"syscall"
    12  )
    13  
    14  // BUG(mikio): On every POSIX platform, reads from the "ip4" network
    15  // using the ReadFrom or ReadFromIP method might not return a complete
    16  // IPv4 packet, including its header, even if there is space
    17  // available. This can occur even in cases where Read or ReadMsgIP
    18  // could return a complete packet. For this reason, it is recommended
    19  // that you do not uses these methods if it is important to receive a
    20  // full packet.
    21  //
    22  // The Go 1 compatibility guidelines make it impossible for us to
    23  // change the behavior of these methods; use Read or ReadMsgIP
    24  // instead.
    25  
    26  func sockaddrToIP(sa syscall.Sockaddr) Addr {
    27  	switch sa := sa.(type) {
    28  	case *syscall.SockaddrInet4:
    29  		return &IPAddr{IP: sa.Addr[0:]}
    30  	case *syscall.SockaddrInet6:
    31  		return &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
    32  	}
    33  	return nil
    34  }
    35  
    36  func (a *IPAddr) family() int {
    37  	if a == nil || len(a.IP) <= IPv4len {
    38  		return syscall.AF_INET
    39  	}
    40  	if a.IP.To4() != nil {
    41  		return syscall.AF_INET
    42  	}
    43  	return syscall.AF_INET6
    44  }
    45  
    46  func (a *IPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
    47  	if a == nil {
    48  		return nil, nil
    49  	}
    50  	return ipToSockaddr(family, a.IP, 0, a.Zone)
    51  }
    52  
    53  func (c *IPConn) readFrom(b []byte) (int, *IPAddr, error) {
    54  	// TODO(cw,rsc): consider using readv if we know the family
    55  	// type to avoid the header trim/copy
    56  	var addr *IPAddr
    57  	n, sa, err := c.fd.readFrom(b)
    58  	switch sa := sa.(type) {
    59  	case *syscall.SockaddrInet4:
    60  		addr = &IPAddr{IP: sa.Addr[0:]}
    61  		n = stripIPv4Header(n, b)
    62  	case *syscall.SockaddrInet6:
    63  		addr = &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
    64  	}
    65  	return n, addr, err
    66  }
    67  
    68  func stripIPv4Header(n int, b []byte) int {
    69  	if len(b) < 20 {
    70  		return n
    71  	}
    72  	l := int(b[0]&0x0f) << 2
    73  	if 20 > l || l > len(b) {
    74  		return n
    75  	}
    76  	if b[0]>>4 != 4 {
    77  		return n
    78  	}
    79  	copy(b, b[l:])
    80  	return n - l
    81  }
    82  
    83  func (c *IPConn) readMsg(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err error) {
    84  	var sa syscall.Sockaddr
    85  	n, oobn, flags, sa, err = c.fd.readMsg(b, oob)
    86  	switch sa := sa.(type) {
    87  	case *syscall.SockaddrInet4:
    88  		addr = &IPAddr{IP: sa.Addr[0:]}
    89  	case *syscall.SockaddrInet6:
    90  		addr = &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
    91  	}
    92  	return
    93  }
    94  
    95  func (c *IPConn) writeTo(b []byte, addr *IPAddr) (int, error) {
    96  	if c.fd.isConnected {
    97  		return 0, ErrWriteToConnected
    98  	}
    99  	if addr == nil {
   100  		return 0, errMissingAddress
   101  	}
   102  	sa, err := addr.sockaddr(c.fd.family)
   103  	if err != nil {
   104  		return 0, err
   105  	}
   106  	return c.fd.writeTo(b, sa)
   107  }
   108  
   109  func (c *IPConn) writeMsg(b, oob []byte, addr *IPAddr) (n, oobn int, err error) {
   110  	if c.fd.isConnected {
   111  		return 0, 0, ErrWriteToConnected
   112  	}
   113  	if addr == nil {
   114  		return 0, 0, errMissingAddress
   115  	}
   116  	sa, err := addr.sockaddr(c.fd.family)
   117  	if err != nil {
   118  		return 0, 0, err
   119  	}
   120  	return c.fd.writeMsg(b, oob, sa)
   121  }
   122  
   123  func dialIP(ctx context.Context, netProto string, laddr, raddr *IPAddr) (*IPConn, error) {
   124  	network, proto, err := parseNetwork(ctx, netProto)
   125  	if err != nil {
   126  		return nil, err
   127  	}
   128  	switch network {
   129  	case "ip", "ip4", "ip6":
   130  	default:
   131  		return nil, UnknownNetworkError(netProto)
   132  	}
   133  	if raddr == nil {
   134  		return nil, errMissingAddress
   135  	}
   136  	fd, err := internetSocket(ctx, network, laddr, raddr, syscall.SOCK_RAW, proto, "dial")
   137  	if err != nil {
   138  		return nil, err
   139  	}
   140  	return newIPConn(fd), nil
   141  }
   142  
   143  func listenIP(ctx context.Context, netProto string, laddr *IPAddr) (*IPConn, error) {
   144  	network, proto, err := parseNetwork(ctx, netProto)
   145  	if err != nil {
   146  		return nil, err
   147  	}
   148  	switch network {
   149  	case "ip", "ip4", "ip6":
   150  	default:
   151  		return nil, UnknownNetworkError(netProto)
   152  	}
   153  	fd, err := internetSocket(ctx, network, laddr, nil, syscall.SOCK_RAW, proto, "listen")
   154  	if err != nil {
   155  		return nil, err
   156  	}
   157  	return newIPConn(fd), nil
   158  }