payload_cmsg.go

Documentation: golang.org/x/net/ipv4

     1  // Copyright 2012 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 || linux || netbsd || openbsd || solaris || zos
     6  
     7  package ipv4
     8  
     9  import (
    10  	"net"
    11  
    12  	"golang.org/x/net/internal/socket"
    13  )
    14  
    15  // ReadFrom reads a payload of the received IPv4 datagram, from the
    16  // endpoint c, copying the payload into b. It returns the number of
    17  // bytes copied into b, the control message cm and the source address
    18  // src of the received datagram.
    19  func (c *payloadHandler) ReadFrom(b []byte) (n int, cm *ControlMessage, src net.Addr, err error) {
    20  	if !c.ok() {
    21  		return 0, nil, nil, errInvalidConn
    22  	}
    23  	c.rawOpt.RLock()
    24  	m := socket.Message{
    25  		OOB: NewControlMessage(c.rawOpt.cflags),
    26  	}
    27  	c.rawOpt.RUnlock()
    28  	switch c.PacketConn.(type) {
    29  	case *net.UDPConn:
    30  		m.Buffers = [][]byte{b}
    31  		if err := c.RecvMsg(&m, 0); err != nil {
    32  			return 0, nil, nil, &net.OpError{Op: "read", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Err: err}
    33  		}
    34  	case *net.IPConn:
    35  		h := make([]byte, HeaderLen)
    36  		m.Buffers = [][]byte{h, b}
    37  		if err := c.RecvMsg(&m, 0); err != nil {
    38  			return 0, nil, nil, &net.OpError{Op: "read", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Err: err}
    39  		}
    40  		hdrlen := int(h[0]&0x0f) << 2
    41  		if hdrlen > len(h) {
    42  			d := hdrlen - len(h)
    43  			copy(b, b[d:])
    44  			m.N -= d
    45  		} else {
    46  			m.N -= hdrlen
    47  		}
    48  	default:
    49  		return 0, nil, nil, &net.OpError{Op: "read", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Err: errInvalidConnType}
    50  	}
    51  	if m.NN > 0 {
    52  		if compatFreeBSD32 {
    53  			adjustFreeBSD32(&m)
    54  		}
    55  		cm = new(ControlMessage)
    56  		if err := cm.Parse(m.OOB[:m.NN]); err != nil {
    57  			return 0, nil, nil, &net.OpError{Op: "read", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Err: err}
    58  		}
    59  		cm.Src = netAddrToIP4(m.Addr)
    60  	}
    61  	return m.N, cm, m.Addr, nil
    62  }
    63  
    64  // WriteTo writes a payload of the IPv4 datagram, to the destination
    65  // address dst through the endpoint c, copying the payload from b. It
    66  // returns the number of bytes written. The control message cm allows
    67  // the datagram path and the outgoing interface to be specified.
    68  // Currently only Darwin and Linux support this. The cm may be nil if
    69  // control of the outgoing datagram is not required.
    70  func (c *payloadHandler) WriteTo(b []byte, cm *ControlMessage, dst net.Addr) (n int, err error) {
    71  	if !c.ok() {
    72  		return 0, errInvalidConn
    73  	}
    74  	m := socket.Message{
    75  		Buffers: [][]byte{b},
    76  		OOB:     cm.Marshal(),
    77  		Addr:    dst,
    78  	}
    79  	err = c.SendMsg(&m, 0)
    80  	if err != nil {
    81  		err = &net.OpError{Op: "write", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Addr: opAddr(dst), Err: err}
    82  	}
    83  	return m.N, err
    84  }
    85
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