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0829c167cc
Basic support, can also do CER and DER but without any extra validation. No schema support. Redo format doc.md usage a bit, now format/<dir>/<format>.md instead. Related to #20
116 lines
3.3 KiB
Go
116 lines
3.3 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/format/registry"
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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/scalar"
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)
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var udpPacketFormat decode.Group
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var tcpPacketFormat decode.Group
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var icmpFormat decode.Group
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func init() {
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registry.MustRegister(decode.Format{
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Name: format.IPV4_PACKET,
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Description: "Internet protocol v4 packet",
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Dependencies: []decode.Dependency{
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{Names: []string{format.UDP_DATAGRAM}, Group: &udpPacketFormat},
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{Names: []string{format.TCP_SEGMENT}, Group: &tcpPacketFormat},
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{Names: []string{format.ICMP}, Group: &icmpFormat},
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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.UToScalar{
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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 ipv4ProtocolFormat = map[uint64]*decode.Group{
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format.IPv4ProtocolUDP: &udpPacketFormat,
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format.IPv4ProtocolTCP: &tcpPacketFormat,
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format.IPv4ProtocolICMP: &icmpFormat,
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}
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var mapUToIPv4Sym = scalar.Fn(func(s scalar.S) (scalar.S, error) {
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var b [4]byte
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binary.BigEndian.PutUint32(b[:], uint32(s.ActualU()))
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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, in interface{}) interface{} {
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d.FieldU4("version")
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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.Hex)
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checksumEnd := d.Pos()
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d.FieldU32("source_ip", mapUToIPv4Sym, scalar.Hex)
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d.FieldU32("destination_ip", mapUToIPv4Sym, scalar.Hex)
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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.MustCopy(ipv4Checksum, bitio.NewIOReader(d.BitBufRange(0, checksumStart)))
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d.MustCopy(ipv4Checksum, bitio.NewIOReader(d.BitBufRange(checksumEnd, headerEnd-checksumEnd)))
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_ = d.FieldMustGet("header_checksum").TryScalarFn(d.ValidateUBytes(ipv4Checksum.Sum(nil)), scalar.Hex)
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dataLen := int64(totalLength-(ihl*4)) * 8
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g, ok := ipv4ProtocolFormat[protocol]
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if !ok || moreFragments || fragmentOffset > 0 {
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d.FieldRawLen("data", dataLen)
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} else {
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d.FieldFormatLen("data", dataLen, *g, nil)
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}
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return nil
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}
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