David K. Bainbridge | 215e024 | 2017-09-05 23:18:24 -0700 | [diff] [blame] | 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 | package ipv4 |
| 6 | |
| 7 | import ( |
| 8 | "net" |
| 9 | "syscall" |
| 10 | |
| 11 | "golang.org/x/net/internal/socket" |
| 12 | ) |
| 13 | |
| 14 | // BUG(mikio): On Windows, the ReadFrom and WriteTo methods of RawConn |
| 15 | // are not implemented. |
| 16 | |
| 17 | // A packetHandler represents the IPv4 datagram handler. |
| 18 | type packetHandler struct { |
| 19 | *net.IPConn |
| 20 | *socket.Conn |
| 21 | rawOpt |
| 22 | } |
| 23 | |
| 24 | func (c *packetHandler) ok() bool { return c != nil && c.IPConn != nil && c.Conn != nil } |
| 25 | |
| 26 | // ReadFrom reads an IPv4 datagram from the endpoint c, copying the |
| 27 | // datagram into b. It returns the received datagram as the IPv4 |
| 28 | // header h, the payload p and the control message cm. |
| 29 | func (c *packetHandler) ReadFrom(b []byte) (h *Header, p []byte, cm *ControlMessage, err error) { |
| 30 | if !c.ok() { |
| 31 | return nil, nil, nil, syscall.EINVAL |
| 32 | } |
| 33 | return c.readFrom(b) |
| 34 | } |
| 35 | |
| 36 | func slicePacket(b []byte) (h, p []byte, err error) { |
| 37 | if len(b) < HeaderLen { |
| 38 | return nil, nil, errHeaderTooShort |
| 39 | } |
| 40 | hdrlen := int(b[0]&0x0f) << 2 |
| 41 | return b[:hdrlen], b[hdrlen:], nil |
| 42 | } |
| 43 | |
| 44 | // WriteTo writes an IPv4 datagram through the endpoint c, copying the |
| 45 | // datagram from the IPv4 header h and the payload p. The control |
| 46 | // message cm allows the datagram path and the outgoing interface to be |
| 47 | // specified. Currently only Darwin and Linux support this. The cm |
| 48 | // may be nil if control of the outgoing datagram is not required. |
| 49 | // |
| 50 | // The IPv4 header h must contain appropriate fields that include: |
| 51 | // |
| 52 | // Version = <must be specified> |
| 53 | // Len = <must be specified> |
| 54 | // TOS = <must be specified> |
| 55 | // TotalLen = <must be specified> |
| 56 | // ID = platform sets an appropriate value if ID is zero |
| 57 | // FragOff = <must be specified> |
| 58 | // TTL = <must be specified> |
| 59 | // Protocol = <must be specified> |
| 60 | // Checksum = platform sets an appropriate value if Checksum is zero |
| 61 | // Src = platform sets an appropriate value if Src is nil |
| 62 | // Dst = <must be specified> |
| 63 | // Options = optional |
| 64 | func (c *packetHandler) WriteTo(h *Header, p []byte, cm *ControlMessage) error { |
| 65 | if !c.ok() { |
| 66 | return syscall.EINVAL |
| 67 | } |
| 68 | return c.writeTo(h, p, cm) |
| 69 | } |