// ParseIPv4Header parses b as an IPv4 header of ICMP error message
// invoking packet, which is contained in ICMP error message.
func ParseIPv4Header(b []byte) (*ipv4.Header, error) {
if len(b) < ipv4.HeaderLen {
return nil, errHeaderTooShort
}
hdrlen := int(b[0]&0x0f) << 2
if hdrlen > len(b) {
return nil, errBufferTooShort
}
h := &ipv4.Header{
Version: int(b[0] >> 4),
Len: hdrlen,
TOS: int(b[1]),
ID: int(b[4])<<8 | int(b[5]),
FragOff: int(b[6])<<8 | int(b[7]),
TTL: int(b[8]),
Protocol: int(b[9]),
Checksum: int(b[10])<<8 | int(b[11]),
Src: net.IPv4(b[12], b[13], b[14], b[15]),
Dst: net.IPv4(b[16], b[17], b[18], b[19]),
}
switch runtime.GOOS {
case "darwin":
// TODO(mikio): fix potential misaligned memory access
h.TotalLen = int(*(*uint16)(unsafe.Pointer(&b[2:3][0])))
case "freebsd":
if freebsdVersion >= 1000000 {
h.TotalLen = int(b[2])<<8 | int(b[3])
} else {
// TODO(mikio): fix potential misaligned memory access
h.TotalLen = int(*(*uint16)(unsafe.Pointer(&b[2:3][0])))
}
default:
h.TotalLen = int(b[2])<<8 | int(b[3])
}
h.Flags = ipv4.HeaderFlags(h.FragOff&0xe000) >> 13
h.FragOff = h.FragOff & 0x1fff
if hdrlen-ipv4.HeaderLen > 0 {
h.Options = make([]byte, hdrlen-ipv4.HeaderLen)
copy(h.Options, b[ipv4.HeaderLen:])
}
return h, nil
}
// ParseIPv4Header parses b as an IPv4 header of ICMP error message
// invoking packet, which is contained in ICMP error message.
func ParseIPv4Header(b []byte) (*ipv4.Header, error) {
if len(b) < ipv4.HeaderLen {
return nil, errHeaderTooShort
}
hdrlen := int(b[0]&0x0f) << 2
if hdrlen > len(b) {
return nil, errBufferTooShort
}
h := &ipv4.Header{
Version: int(b[0] >> 4),
Len: hdrlen,
TOS: int(b[1]),
ID: int(binary.BigEndian.Uint16(b[4:6])),
FragOff: int(binary.BigEndian.Uint16(b[6:8])),
TTL: int(b[8]),
Protocol: int(b[9]),
Checksum: int(binary.BigEndian.Uint16(b[10:12])),
Src: net.IPv4(b[12], b[13], b[14], b[15]),
Dst: net.IPv4(b[16], b[17], b[18], b[19]),
}
switch runtime.GOOS {
case "darwin":
h.TotalLen = int(nativeEndian.Uint16(b[2:4]))
case "freebsd":
if freebsdVersion >= 1000000 {
h.TotalLen = int(binary.BigEndian.Uint16(b[2:4]))
} else {
h.TotalLen = int(nativeEndian.Uint16(b[2:4]))
}
default:
h.TotalLen = int(binary.BigEndian.Uint16(b[2:4]))
}
h.Flags = ipv4.HeaderFlags(h.FragOff&0xe000) >> 13
h.FragOff = h.FragOff & 0x1fff
if hdrlen-ipv4.HeaderLen > 0 {
h.Options = make([]byte, hdrlen-ipv4.HeaderLen)
copy(h.Options, b[ipv4.HeaderLen:])
}
return h, nil
}