When I get the pcap file from the s3 client, I need to generate the packetsource of gopacket to read the packets in it. But I only found the openofflinefile function in gopacket documentation, how can I generate packetsource with []byte (read from s3 file).
I have read the source code of the openofflinefile function in gopacket, but I am still confused because I am not familiar with uintptr, can I directly generate a unitptr with []byte and then use it to generate packetsource?
func openOffline(file string) (handle *Handle, err error) { err = LoadWinPCAP() if err != nil { return nil, err } buf := make([]byte, errorBufferSize) f, err := syscall.BytePtrFromString(file) if err != nil { return nil, err } var cptr uintptr if pcapOpenOfflineWithTstampPrecisionPtr == 0 { cptr, _, _ = syscall.Syscall(pcapOpenOfflinePtr, 2, uintptr(unsafe.Pointer(f)), uintptr(unsafe.Pointer(&buf[0])), 0) } else { cptr, _, _ = syscall.Syscall(pcapOpenOfflineWithTstampPrecisionPtr, 3, uintptr(unsafe.Pointer(f)), uintptr(pcapTstampPrecisionNano), uintptr(unsafe.Pointer(&buf[0]))) } if cptr == 0 { return nil, errors.New(byteSliceToString(buf)) } h := &Handle{cptr: pcapTPtr(cptr)} return h, nil }
Correct answer
Try github.com/google/gopacket/pcapgo
If the github.com/google/gopacket/pcapgo
package supports this file format, consider using it as it is easy:
package main import ( "bytes" "io" "log" "os" "github.com/google/gopacket" "github.com/google/gopacket/layers" "github.com/google/gopacket/pcapgo" ) func main() { f, err := os.open("test.pcap") if err != nil { panic(err) } // as described in the question, buf is read from s3 file. in order to // make this demo simple and executable, we read it from a local file. buf, err := io.readall(f) if err != nil { panic(err) } // convert []byte into a reader. the s3 client should give us a reader // that we can use directly in the place of the filereader. try the best // to avoid reading the response as []byte and then convert it into a reader. filereader := bytes.newreader(buf) r, err := pcapgo.newreader(filereader) if err != nil { panic(err) } source := gopacket.newpacketsource(r, layers.layertypeethernet) for packet := range source.packets() { log.printf("%v", packet) } }
Use os.pipe
with github.com/google/gopacket/pcap
If github.com/google/gopacket/pcapgo
does not support the file format and we must use github.com/google/gopacket/pcap
, the solution is to create one Pipe and pass the r
file to pcap.openofflinefile
:
package main import ( "bytes" "io" "log" "os" "github.com/google/gopacket" "github.com/google/gopacket/layers" "github.com/google/gopacket/pcap" ) func main() { f, err := os.Open("test.pcap") if err != nil { panic(err) } // As described in the question, buf is read from S3 file. In order to // make this demo simple and executable, we read it from a local file. buf, err := io.ReadAll(f) if err != nil { panic(err) } r, w, err := os.Pipe() if err != nil { panic(err) } go func() { // Convert []byte into a reader. The S3 client should give us a reader // that we can use directly in the place of the fileReader. Try the best // to avoid reading the response as []byte and then convert it into a reader. fileReader := bytes.NewReader(buf) _, err := io.Copy(w, fileReader) defer w.Close() if err != nil { panic(err) } }() handle, err := pcap.OpenOfflineFile(r) if err != nil { panic(err) } source := gopacket.NewPacketSource(handle, layers.LayerTypeEthernet) for packet := range source.Packets() { log.Printf("%v", packet) } }
Comments:
- This was only tested on linux. But it should work on windows.
-
github.com/google/gopacket/pcap
is a wrapper forlibpcap
(orwinpcap
ornpcap
on windows) . That's why using[]byte
orio.reader
is a bit complicated. - When you download a file from s3, the client should provide you with a reader. You can use the reader directly (see comments in my demo). Avoid reading the reader's content yourself.
The above is the detailed content of Create gopacket's packetSource using s3 files. For more information, please follow other related articles on the PHP Chinese website!

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