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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ipv4
import (
"net"
"golang.org/x/net/internal/socket"
)
// BUG(mikio): On Windows, the ReadFrom and WriteTo methods of RawConn
// are not implemented.
// A packetHandler represents the IPv4 datagram handler.
type packetHandler struct {
*net.IPConn
*socket.Conn
rawOpt
}
func (c *packetHandler) ok() bool { return c != nil && c.IPConn != nil && c.Conn != nil }
// ReadFrom reads an IPv4 datagram from the endpoint c, copying the
// datagram into b. It returns the received datagram as the IPv4
// header h, the payload p and the control message cm.
func (c *packetHandler) ReadFrom(b []byte) (h *Header, p []byte, cm *ControlMessage, err error) {
if !c.ok() {
return nil, nil, nil, errInvalidConn
}
c.rawOpt.RLock()
m := socket.Message{
Buffers: [][]byte{b},
OOB: NewControlMessage(c.rawOpt.cflags),
}
c.rawOpt.RUnlock()
if err := c.RecvMsg(&m, 0); err != nil {
return nil, nil, nil, &net.OpError{Op: "read", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Err: err}
}
var hs []byte
if hs, p, err = slicePacket(b[:m.N]); err != nil {
return nil, nil, nil, &net.OpError{Op: "read", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Err: err}
}
if h, err = ParseHeader(hs); err != nil {
return nil, nil, nil, &net.OpError{Op: "read", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Err: err}
}
if m.NN > 0 {
if compatFreeBSD32 {
adjustFreeBSD32(&m)
}
cm = new(ControlMessage)
if err := cm.Parse(m.OOB[:m.NN]); err != nil {
return nil, nil, nil, &net.OpError{Op: "read", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Err: err}
}
}
if src, ok := m.Addr.(*net.IPAddr); ok && cm != nil {
cm.Src = src.IP
}
return
}
func slicePacket(b []byte) (h, p []byte, err error) {
if len(b) < HeaderLen {
return nil, nil, errHeaderTooShort
}
hdrlen := int(b[0]&0x0f) << 2
return b[:hdrlen], b[hdrlen:], nil
}
// WriteTo writes an IPv4 datagram through the endpoint c, copying the
// datagram from the IPv4 header h and the payload p. The control
// message cm allows the datagram path and the outgoing interface to be
// specified. Currently only Darwin and Linux support this. The cm
// may be nil if control of the outgoing datagram is not required.
//
// The IPv4 header h must contain appropriate fields that include:
//
// Version =
// Len =
// TOS =
// TotalLen =
// ID = platform sets an appropriate value if ID is zero
// FragOff =
// TTL =
// Protocol =
// Checksum = platform sets an appropriate value if Checksum is zero
// Src = platform sets an appropriate value if Src is nil
// Dst =
// Options = optional
func (c *packetHandler) WriteTo(h *Header, p []byte, cm *ControlMessage) error {
if !c.ok() {
return errInvalidConn
}
m := socket.Message{
OOB: cm.Marshal(),
}
wh, err := h.Marshal()
if err != nil {
return err
}
m.Buffers = [][]byte{wh, p}
dst := new(net.IPAddr)
if cm != nil {
if ip := cm.Dst.To4(); ip != nil {
dst.IP = ip
}
}
if dst.IP == nil {
dst.IP = h.Dst
}
m.Addr = dst
if err := c.SendMsg(&m, 0); err != nil {
return &net.OpError{Op: "write", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Addr: opAddr(dst), Err: err}
}
return nil
}
