net.i2p.client.streaming.impl
Class PcapWriter

java.lang.Object
  extended by 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

Constructor Summary
PcapWriter(I2PAppContext ctx, String file)
           
 
Method Summary
 void close()
           
 void flush()
           
 void write(Packet pkt, Connection con)
          For inbound packets
 void write(PacketLocal pkt)
          For outbound packets
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PcapWriter

public PcapWriter(I2PAppContext ctx,
                  String file)
           throws IOException
Throws:
IOException
Method Detail

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