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feat(pcapgo): support cancellation with context.Context #12

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Merged
mosajjal merged 2 commits into from
Feb 22, 2023
Merged

feat(pcapgo): support cancellation with context.Context #12

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d4f7dea
feat(pcapgo): support cancellation with context.Context
prskr Feb 15, 2023
811d508
fix: unblock Go routine writing to packets channel if context was can…
prskr Feb 17, 2023
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1 change: 1 addition & 0 deletions .gitignore
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Original file line number Diff line number Diff line change
Expand Up @@ -36,3 +36,4 @@ examples/reassemblydump/reassemblydump
layers/gen
macs/gen
pcap/pcap_tester
.idea/
60 changes: 33 additions & 27 deletions layers/ip4.go
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Original file line number Diff line number Diff line change
Expand Up @@ -190,24 +190,9 @@ func (ip *IPv4) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
df.SetTruncated()
return fmt.Errorf("Invalid ip4 header. Length %d less than 20", len(data))
}
flagsfrags := binary.BigEndian.Uint16(data[6:8])

ip.Version = uint8(data[0]) >> 4
ip.IHL = uint8(data[0]) & 0x0F
ip.TOS = data[1]
ip.Length = binary.BigEndian.Uint16(data[2:4])
ip.Id = binary.BigEndian.Uint16(data[4:6])
ip.Flags = IPv4Flag(flagsfrags >> 13)
ip.FragOffset = flagsfrags & 0x1FFF
ip.TTL = data[8]
ip.Protocol = IPProtocol(data[9])
ip.Checksum = binary.BigEndian.Uint16(data[10:12])
ip.SrcIP = data[12:16]
ip.DstIP = data[16:20]
ip.Options = ip.Options[:0]
ip.Padding = nil
// Set up an initial guess for contents/payload... we'll reset these soon.
ip.BaseLayer = BaseLayer{Contents: data}
ip.IHL = uint8(data[0]) & 0x0F

// This code is added for the following enviroment:
// * Windows 10 with TSO option activated. ( tested on Hyper-V, RealTek ethernet driver )
Expand All @@ -224,6 +209,7 @@ func (ip *IPv4) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
} else if int(ip.IHL*4) > int(ip.Length) {
return fmt.Errorf("Invalid IP header length > IP length (%d > %d)", ip.IHL, ip.Length)
}

if cmp := len(data) - int(ip.Length); cmp > 0 {
data = data[:ip.Length]
} else if cmp < 0 {
Expand All @@ -232,45 +218,65 @@ func (ip *IPv4) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
return errors.New("Not all IP header bytes available")
}
}

ip.Options = ip.Options[:0]
ip.Contents = data[:ip.IHL*4]
ip.Payload = data[ip.IHL*4:]

// From here on, data contains the header options.
data = data[20 : ip.IHL*4]
headerOptionsData := data[20 : ip.IHL*4]
// Pull out IP options
for len(data) > 0 {
for len(headerOptionsData) > 0 {
if ip.Options == nil {
// Pre-allocate to avoid growing the slice too much.
ip.Options = make([]IPv4Option, 0, 4)
}
opt := IPv4Option{OptionType: data[0]}

opt := IPv4Option{OptionType: headerOptionsData[0]}
switch opt.OptionType {
case 0: // End of options
opt.OptionLength = 1
ip.Options = append(ip.Options, opt)
ip.Padding = data[1:]
ip.Padding = headerOptionsData[1:]

return nil
case 1: // 1 byte padding
opt.OptionLength = 1
data = data[1:]
headerOptionsData = headerOptionsData[1:]
ip.Options = append(ip.Options, opt)
default:
if len(data) < 2 {
if len(headerOptionsData) < 2 {
df.SetTruncated()
return fmt.Errorf("Invalid ip4 option length. Length %d less than 2", len(data))
return fmt.Errorf("Invalid ip4 option length. Length %d less than 2", len(headerOptionsData))
}
opt.OptionLength = data[1]
if len(data) < int(opt.OptionLength) {

opt.OptionLength = headerOptionsData[1]
if len(headerOptionsData) < int(opt.OptionLength) {
df.SetTruncated()
return fmt.Errorf("IP option length exceeds remaining IP header size, option type %v length %v", opt.OptionType, opt.OptionLength)
}
if opt.OptionLength <= 2 {
return fmt.Errorf("Invalid IP option type %v length %d. Must be greater than 2", opt.OptionType, opt.OptionLength)
}
opt.OptionData = data[2:opt.OptionLength]
data = data[opt.OptionLength:]
opt.OptionData = headerOptionsData[2:opt.OptionLength]
headerOptionsData = headerOptionsData[opt.OptionLength:]
ip.Options = append(ip.Options, opt)
}
}

flagsfrags := binary.BigEndian.Uint16(data[6:8])
ip.Version = data[0] >> 4
ip.TOS = data[1]
ip.Id = binary.BigEndian.Uint16(data[4:6])
ip.Flags = IPv4Flag(flagsfrags >> 13)
ip.FragOffset = flagsfrags & 0x1FFF
ip.TTL = data[8]
ip.Protocol = IPProtocol(data[9])
ip.Checksum = binary.BigEndian.Uint16(data[10:12])
ip.SrcIP = data[12:16]
ip.DstIP = data[16:20]
ip.Padding = nil

return nil
}

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