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payload_cmsg.go (2889B)

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