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https://github.com/wader/fq.git
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9b81d4d3ab
Preparation to make decoder use less memory and API more type safe. Now each scalar type has it's own struct type so it can store different things and enables to have a scalar interface. Also own types will enable experimenting with decode DLS designs like using chained methods that are type aware.
65 lines
1.8 KiB
Go
65 lines
1.8 KiB
Go
package inet
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// TODO: rename NetworkLayer? wireshark calls it "Family", pcap-linktype(7) calls it "network-layer protocol"
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import (
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"github.com/wader/fq/format"
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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 bsdLoopbackFrameInetPacketGroup decode.Group
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func init() {
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interp.RegisterFormat(decode.Format{
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Name: format.BSD_LOOPBACK_FRAME,
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Description: "BSD loopback frame",
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Groups: []string{format.LINK_FRAME},
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Dependencies: []decode.Dependency{
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{Names: []string{format.INET_PACKET}, Group: &bsdLoopbackFrameInetPacketGroup},
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},
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DecodeFn: decodeLoopbackFrame,
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})
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}
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const (
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bsdLoopbackNetworkLayerIPv4 = 0x2
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bsdLoopbackNetworkLayerIPv6 = 0x1e
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)
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var bsdLoopbackFrameNetworkLayerEtherType = map[uint64]int{
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bsdLoopbackNetworkLayerIPv4: format.EtherTypeIPv4,
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bsdLoopbackNetworkLayerIPv6: format.EtherTypeIPv6,
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}
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var bsdLookbackNetworkLayerMap = scalar.UintMap{
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bsdLoopbackNetworkLayerIPv4: {Sym: "ipv4", Description: `Internet protocol v4`},
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bsdLoopbackNetworkLayerIPv6: {Sym: "ipv6", Description: `Internet protocol v6`},
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}
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func decodeLoopbackFrame(d *decode.D, in any) any {
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if lfi, ok := in.(format.LinkFrameIn); ok {
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if lfi.Type != format.LinkTypeNULL {
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d.Fatalf("wrong link type %d", lfi.Type)
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}
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// TODO: where is this documented?
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if lfi.IsLittleEndian {
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d.Endian = decode.LittleEndian
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}
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}
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// if no LinkFrameIn assume big endian for now
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networkLayer := d.FieldU32("network_layer", bsdLookbackNetworkLayerMap, scalar.UintHex)
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d.FieldFormatOrRawLen(
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"payload",
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d.BitsLeft(),
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bsdLoopbackFrameInetPacketGroup,
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// TODO: unknown mapped to ether type 0 is ok?
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format.InetPacketIn{EtherType: bsdLoopbackFrameNetworkLayerEtherType[networkLayer]},
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)
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return nil
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}
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