net.i2p.client.streaming.impl
Class PcapWriter
java.lang.Object
net.i2p.client.streaming.impl.PcapWriter
- All Implemented Interfaces:
- Closeable, Flushable
public class PcapWriter
- extends Object
- implements Closeable, Flushable
Write a standard pcap file with a "TCP" packet that can be analyzed with
standard tools such as wireshark.
The source and dest "IP" and "port" are fake but are generated from the
hashes of the Destinations and stream ID's, so they will be consistent.
The local "IP" will always be of the form 127.0.x.y
Initial IP for a conn will be 127.0.0.0 for the local and 0.0.0.0 for the remote.
Reference: http://wiki.wireshark.org/Development/LibpcapFileFormat
The Jpcap library http://netresearch.ics.uci.edu/kfujii/jpcap/doc/
was close to what I want, but it requires you to instantiate a "captor"
before you can write a file, and it requires a native lib to do so,
and even then, it only wants to read the file, not write it.
We even calculate a correct TCP header checksum to keep the tools happy.
We don't, however, convert I2P-style sequence numbers, which count packets,
to TCP-style byte counts. We don't track a lowest-acked-thru byte count atm, really.
We do represent the window size in bytes though, so that's real confusing.
This is designed to debug the streaming lib, but there are not log calls for every
single packet - pings and pongs, and various odd cases where received packets
are dropped, are not logged.
Yes we could dump it natively and write a wireshark dissector. That sounds hard.
And we wouldn't get the TCP stream analysis built into the tools.
- Since:
- 0.9.4
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
PcapWriter
public PcapWriter(I2PAppContext ctx,
String file)
throws IOException
- Throws:
IOException
close
public void close()
- Specified by:
close
in interface Closeable
flush
public void flush()
- Specified by:
flush
in interface Flushable
write
public void write(PacketLocal pkt)
throws IOException
- For outbound packets
- Throws:
IOException
write
public void write(Packet pkt,
Connection con)
throws IOException
- For inbound packets
- Parameters:
con
- may be null
- Throws:
IOException