mirror of
https://github.com/wader/fq.git
synced 2024-11-29 12:14:17 +03:00
124 lines
3.4 KiB
Go
124 lines
3.4 KiB
Go
package inet
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import (
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"encoding/binary"
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"net"
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"github.com/wader/fq/format"
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"github.com/wader/fq/pkg/bitio"
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"github.com/wader/fq/pkg/checksum"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/interp"
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"github.com/wader/fq/pkg/scalar"
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)
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var ipv4IpPacketGroup decode.Group
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func init() {
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interp.RegisterFormat(
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format.IPv4Packet,
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&decode.Format{
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Description: "Internet protocol v4 packet",
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Groups: []*decode.Group{
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format.INET_Packet,
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format.Link_Frame,
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},
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Dependencies: []decode.Dependency{
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{Groups: []*decode.Group{format.IP_Packet}, Out: &ipv4IpPacketGroup},
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},
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DecodeFn: decodeIPv4,
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})
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}
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const (
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ipv4OptionEnd = 0
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ipv4OptionNop = 1
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)
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var ipv4OptionsMap = scalar.UintMap{
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ipv4OptionEnd: {Sym: "end", Description: "End of options list"},
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ipv4OptionNop: {Sym: "nop", Description: "No operation"},
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2: {Description: "Security"},
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3: {Description: "Loose Source Routing"},
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9: {Description: "Strict Source Routing"},
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7: {Description: "Record Route"},
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8: {Description: "Stream ID"},
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4: {Description: "Internet Timestamp"},
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}
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var mapUToIPv4Sym = scalar.UintFn(func(s scalar.Uint) (scalar.Uint, error) {
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var b [4]byte
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binary.BigEndian.PutUint32(b[:], uint32(s.Actual))
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s.Sym = net.IP(b[:]).String()
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return s, nil
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})
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func decodeIPv4(d *decode.D) any {
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var ipi format.INET_Packet_In
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var lfi format.Link_Frame_In
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if d.ArgAs(&ipi) && ipi.EtherType != format.EtherTypeIPv4 {
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d.Fatalf("incorrect ethertype %d", ipi.EtherType)
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} else if d.ArgAs(&lfi) && lfi.Type != format.LinkTypeIPv4 && lfi.Type != format.LinkTypeRAW {
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d.Fatalf("incorrect linktype %d", lfi.Type)
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}
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d.FieldU4("version", d.UintAssert(4))
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ihl := d.FieldU4("ihl")
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d.FieldU6("dscp")
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d.FieldU2("ecn")
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totalLength := d.FieldU16("total_length")
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d.FieldU16("identification")
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d.FieldU1("reserved")
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d.FieldBool("dont_fragment")
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moreFragments := d.FieldBool("more_fragments")
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fragmentOffset := d.FieldU13("fragment_offset")
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d.FieldU8("ttl")
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protocol := d.FieldU8("protocol", format.IPv4ProtocolMap)
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checksumStart := d.Pos()
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d.FieldU16("header_checksum", scalar.UintHex)
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checksumEnd := d.Pos()
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d.FieldU32("source_ip", mapUToIPv4Sym, scalar.UintHex)
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d.FieldU32("destination_ip", mapUToIPv4Sym, scalar.UintHex)
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optionsLen := (int64(ihl) - 5) * 8 * 4
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if optionsLen > 0 {
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d.FramedFn(optionsLen, func(d *decode.D) {
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d.FieldArray("options", func(d *decode.D) {
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for !d.End() {
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d.FieldStruct("option", func(d *decode.D) {
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d.FieldBool("copied")
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d.FieldU2("class")
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kind := d.FieldU5("number", ipv4OptionsMap)
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switch kind {
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case ipv4OptionEnd, ipv4OptionNop:
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default:
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l := d.FieldU8("length")
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d.FieldRawLen("data", (int64(l-2))*8)
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}
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})
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}
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})
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})
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}
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headerEnd := d.Pos()
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ipv4Checksum := &checksum.IPv4{}
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d.Copy(ipv4Checksum, bitio.NewIOReader(d.BitBufRange(0, checksumStart)))
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d.Copy(ipv4Checksum, bitio.NewIOReader(d.BitBufRange(checksumEnd, headerEnd-checksumEnd)))
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_ = d.FieldMustGet("header_checksum").TryUintScalarFn(d.UintValidateBytes(ipv4Checksum.Sum(nil)), scalar.UintHex)
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dataLen := int64(totalLength-(ihl*4)) * 8
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if moreFragments || fragmentOffset > 0 {
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d.FieldRawLen("payload", dataLen)
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} else {
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d.FieldFormatOrRawLen(
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"payload",
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dataLen,
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&ipv4IpPacketGroup,
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format.IP_Packet_In{Protocol: int(protocol)},
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)
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}
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return nil
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}
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