mirror of
https://github.com/wader/fq.git
synced 2024-12-25 14:23:18 +03:00
108 lines
3.0 KiB
Go
108 lines
3.0 KiB
Go
package pcap
|
|
|
|
// https://wiki.wireshark.org/Development/LibpcapFileFormat
|
|
// TODO: tshark seems to not support sll2 in pcap, confusing
|
|
|
|
import (
|
|
"github.com/wader/fq/format"
|
|
"github.com/wader/fq/format/inet/flowsdecoder"
|
|
"github.com/wader/fq/format/registry"
|
|
"github.com/wader/fq/pkg/decode"
|
|
"github.com/wader/fq/pkg/scalar"
|
|
)
|
|
|
|
var pcapLinkFrameFormat decode.Group
|
|
var pcapTCPStreamFormat decode.Group
|
|
var pcapIPv4PacketFormat decode.Group
|
|
|
|
const (
|
|
bigEndian = 0xa1b2c3d4
|
|
littleEndian = 0xd4c3b2a1
|
|
)
|
|
|
|
var endianMap = scalar.UToSymStr{
|
|
bigEndian: "big_endian",
|
|
littleEndian: "little_endian",
|
|
}
|
|
|
|
func init() {
|
|
registry.MustRegister(decode.Format{
|
|
Name: format.PCAP,
|
|
Description: "PCAP packet capture",
|
|
Groups: []string{format.PROBE},
|
|
Dependencies: []decode.Dependency{
|
|
{Names: []string{format.LINK_FRAME}, Group: &pcapLinkFrameFormat},
|
|
{Names: []string{format.TCP_STREAM}, Group: &pcapTCPStreamFormat},
|
|
{Names: []string{format.IPV4_PACKET}, Group: &pcapIPv4PacketFormat},
|
|
},
|
|
DecodeFn: decodePcap,
|
|
})
|
|
}
|
|
|
|
func decodePcap(d *decode.D, in interface{}) interface{} {
|
|
endian := d.FieldU32("magic", d.AssertU(bigEndian, littleEndian), endianMap, scalar.Hex)
|
|
switch endian {
|
|
case bigEndian:
|
|
d.Endian = decode.BigEndian
|
|
case littleEndian:
|
|
d.Endian = decode.LittleEndian
|
|
default:
|
|
d.Fatalf("unknown endian %d", endian)
|
|
}
|
|
d.FieldU16("version_major")
|
|
d.FieldU16("version_minor")
|
|
d.FieldS32("thiszone")
|
|
d.FieldU32("sigfigs")
|
|
d.FieldU32("snaplen")
|
|
linkType := int(d.FieldU32("network", format.LinkTypeMap))
|
|
|
|
fd := flowsdecoder.New()
|
|
|
|
d.FieldArray("packets", func(d *decode.D) {
|
|
for !d.End() {
|
|
d.FieldStruct("packet", func(d *decode.D) {
|
|
d.FieldU32("ts_sec")
|
|
d.FieldU32("ts_usec")
|
|
inclLen := d.FieldU32("incl_len")
|
|
origLen := d.FieldU32("orig_len")
|
|
|
|
// "incl_len: the number of bytes of packet data actually captured and saved in the file. This value should never become larger than orig_len or the snaplen value of the global header"
|
|
// "orig_len: the length of the packet as it appeared on the network when it was captured. If incl_len and orig_len differ, the actually saved packet size was limited by snaplen."
|
|
|
|
// TODO: incl_len seems to be larger than snaplen in real pcap files
|
|
// if inclLen > snapLen {
|
|
// d.Errorf("incl_len %d > snaplen %d", inclLen, snapLen)
|
|
// }
|
|
|
|
if inclLen > origLen {
|
|
d.Errorf("incl_len %d > orig_len %d", inclLen, origLen)
|
|
}
|
|
|
|
bb := d.BitBufRange(d.Pos(), int64(inclLen)*8)
|
|
bs, err := bb.Bytes()
|
|
if err != nil {
|
|
// TODO:
|
|
d.IOPanic(err, "BitBufRange: inclLen")
|
|
}
|
|
|
|
if fn, ok := linkToDecodeFn[linkType]; ok {
|
|
// TODO: report decode errors
|
|
_ = fn(fd, bs)
|
|
}
|
|
|
|
if dv, _, _ := d.TryFieldFormatLen("packet", int64(inclLen)*8, pcapLinkFrameFormat, format.LinkFrameIn{
|
|
Type: linkType,
|
|
LittleEndian: d.Endian == decode.LittleEndian,
|
|
}); dv == nil {
|
|
d.FieldRawLen("packet", int64(inclLen)*8)
|
|
}
|
|
})
|
|
}
|
|
})
|
|
fd.Flush()
|
|
|
|
fieldFlows(d, fd, pcapTCPStreamFormat, pcapIPv4PacketFormat)
|
|
|
|
return nil
|
|
}
|