David K. Bainbridge | 215e024 | 2017-09-05 23:18:24 -0700 | [diff] [blame] | 1 | // Copyright 2014 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 icmp |
| 6 | |
| 7 | import ( |
| 8 | "encoding/binary" |
| 9 | "net" |
| 10 | "runtime" |
| 11 | |
| 12 | "golang.org/x/net/internal/socket" |
| 13 | "golang.org/x/net/ipv4" |
| 14 | ) |
| 15 | |
| 16 | // freebsdVersion is set in sys_freebsd.go. |
| 17 | // See http://www.freebsd.org/doc/en/books/porters-handbook/freebsd-versions.html. |
| 18 | var freebsdVersion uint32 |
| 19 | |
| 20 | // ParseIPv4Header parses b as an IPv4 header of ICMP error message |
| 21 | // invoking packet, which is contained in ICMP error message. |
| 22 | func ParseIPv4Header(b []byte) (*ipv4.Header, error) { |
| 23 | if len(b) < ipv4.HeaderLen { |
| 24 | return nil, errHeaderTooShort |
| 25 | } |
| 26 | hdrlen := int(b[0]&0x0f) << 2 |
| 27 | if hdrlen > len(b) { |
| 28 | return nil, errBufferTooShort |
| 29 | } |
| 30 | h := &ipv4.Header{ |
| 31 | Version: int(b[0] >> 4), |
| 32 | Len: hdrlen, |
| 33 | TOS: int(b[1]), |
| 34 | ID: int(binary.BigEndian.Uint16(b[4:6])), |
| 35 | FragOff: int(binary.BigEndian.Uint16(b[6:8])), |
| 36 | TTL: int(b[8]), |
| 37 | Protocol: int(b[9]), |
| 38 | Checksum: int(binary.BigEndian.Uint16(b[10:12])), |
| 39 | Src: net.IPv4(b[12], b[13], b[14], b[15]), |
| 40 | Dst: net.IPv4(b[16], b[17], b[18], b[19]), |
| 41 | } |
| 42 | switch runtime.GOOS { |
| 43 | case "darwin": |
| 44 | h.TotalLen = int(socket.NativeEndian.Uint16(b[2:4])) |
| 45 | case "freebsd": |
| 46 | if freebsdVersion >= 1000000 { |
| 47 | h.TotalLen = int(binary.BigEndian.Uint16(b[2:4])) |
| 48 | } else { |
| 49 | h.TotalLen = int(socket.NativeEndian.Uint16(b[2:4])) |
| 50 | } |
| 51 | default: |
| 52 | h.TotalLen = int(binary.BigEndian.Uint16(b[2:4])) |
| 53 | } |
| 54 | h.Flags = ipv4.HeaderFlags(h.FragOff&0xe000) >> 13 |
| 55 | h.FragOff = h.FragOff & 0x1fff |
| 56 | if hdrlen-ipv4.HeaderLen > 0 { |
| 57 | h.Options = make([]byte, hdrlen-ipv4.HeaderLen) |
| 58 | copy(h.Options, b[ipv4.HeaderLen:]) |
| 59 | } |
| 60 | return h, nil |
| 61 | } |