initial commit

vendor/golang.org/x/net/ipv4/header.go

@@ -0,0 +1,149 @@
+// 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 (
+	"errors"
+	"fmt"
+	"net"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+var (
+	errMissingAddress  = errors.New("missing address")
+	errMissingHeader   = errors.New("missing header")
+	errHeaderTooShort  = errors.New("header too short")
+	errBufferTooShort  = errors.New("buffer too short")
+	errInvalidConnType = errors.New("invalid conn type")
+)
+
+const (
+	Version      = 4  // protocol version
+	HeaderLen    = 20 // header length without extension headers
+	maxHeaderLen = 60 // sensible default, revisit if later RFCs define new usage of version and header length fields
+)
+
+type HeaderFlags int
+
+const (
+	MoreFragments HeaderFlags = 1 << iota // more fragments flag
+	DontFragment                          // don't fragment flag
+)
+
+// A Header represents an IPv4 header.
+type Header struct {
+	Version  int         // protocol version
+	Len      int         // header length
+	TOS      int         // type-of-service
+	TotalLen int         // packet total length
+	ID       int         // identification
+	Flags    HeaderFlags // flags
+	FragOff  int         // fragment offset
+	TTL      int         // time-to-live
+	Protocol int         // next protocol
+	Checksum int         // checksum
+	Src      net.IP      // source address
+	Dst      net.IP      // destination address
+	Options  []byte      // options, extension headers
+}
+
+func (h *Header) String() string {
+	if h == nil {
+		return "<nil>"
+	}
+	return fmt.Sprintf("ver: %v, hdrlen: %v, tos: %#x, totallen: %v, id: %#x, flags: %#x, fragoff: %#x, ttl: %v, proto: %v, cksum: %#x, src: %v, dst: %v", h.Version, h.Len, h.TOS, h.TotalLen, h.ID, h.Flags, h.FragOff, h.TTL, h.Protocol, h.Checksum, h.Src, h.Dst)
+}
+
+// Marshal returns the binary encoding of the IPv4 header h.
+func (h *Header) Marshal() ([]byte, error) {
+	if h == nil {
+		return nil, syscall.EINVAL
+	}
+	if h.Len < HeaderLen {
+		return nil, errHeaderTooShort
+	}
+	hdrlen := HeaderLen + len(h.Options)
+	b := make([]byte, hdrlen)
+	b[0] = byte(Version<<4 | (hdrlen >> 2 & 0x0f))
+	b[1] = byte(h.TOS)
+	flagsAndFragOff := (h.FragOff & 0x1fff) | int(h.Flags<<13)
+	switch runtime.GOOS {
+	case "darwin", "dragonfly", "freebsd", "netbsd":
+		// TODO(mikio): fix potential misaligned memory access
+		*(*uint16)(unsafe.Pointer(&b[2:3][0])) = uint16(h.TotalLen)
+		*(*uint16)(unsafe.Pointer(&b[6:7][0])) = uint16(flagsAndFragOff)
+	default:
+		b[2], b[3] = byte(h.TotalLen>>8), byte(h.TotalLen)
+		b[6], b[7] = byte(flagsAndFragOff>>8), byte(flagsAndFragOff)
+	}
+	b[4], b[5] = byte(h.ID>>8), byte(h.ID)
+	b[8] = byte(h.TTL)
+	b[9] = byte(h.Protocol)
+	b[10], b[11] = byte(h.Checksum>>8), byte(h.Checksum)
+	if ip := h.Src.To4(); ip != nil {
+		copy(b[12:16], ip[:net.IPv4len])
+	}
+	if ip := h.Dst.To4(); ip != nil {
+		copy(b[16:20], ip[:net.IPv4len])
+	} else {
+		return nil, errMissingAddress
+	}
+	if len(h.Options) > 0 {
+		copy(b[HeaderLen:], h.Options)
+	}
+	return b, nil
+}
+
+// See http://www.freebsd.org/doc/en/books/porters-handbook/freebsd-versions.html.
+var freebsdVersion uint32
+
+// ParseHeader parses b as an IPv4 header.
+func ParseHeader(b []byte) (*Header, error) {
+	if len(b) < HeaderLen {
+		return nil, errHeaderTooShort
+	}
+	hdrlen := int(b[0]&0x0f) << 2
+	if hdrlen > len(b) {
+		return nil, errBufferTooShort
+	}
+	h := &Header{
+		Version:  int(b[0] >> 4),
+		Len:      hdrlen,
+		TOS:      int(b[1]),
+		ID:       int(b[4])<<8 | int(b[5]),
+		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", "dragonfly", "netbsd":
+		// TODO(mikio): fix potential misaligned memory access
+		h.TotalLen = int(*(*uint16)(unsafe.Pointer(&b[2:3][0]))) + hdrlen
+		// TODO(mikio): fix potential misaligned memory access
+		h.FragOff = int(*(*uint16)(unsafe.Pointer(&b[6:7][0])))
+	case "freebsd":
+		// TODO(mikio): fix potential misaligned memory access
+		h.TotalLen = int(*(*uint16)(unsafe.Pointer(&b[2:3][0])))
+		if freebsdVersion < 1000000 {
+			h.TotalLen += hdrlen
+		}
+		// TODO(mikio): fix potential misaligned memory access
+		h.FragOff = int(*(*uint16)(unsafe.Pointer(&b[6:7][0])))
+	default:
+		h.TotalLen = int(b[2])<<8 | int(b[3])
+		h.FragOff = int(b[6])<<8 | int(b[7])
+	}
+	h.Flags = HeaderFlags(h.FragOff&0xe000) >> 13
+	h.FragOff = h.FragOff & 0x1fff
+	if hdrlen-HeaderLen > 0 {
+		h.Options = make([]byte, hdrlen-HeaderLen)
+		copy(h.Options, b[HeaderLen:])
+	}
+	return h, nil
+}