tcpsubnet_example.txt

Demonstrations of tcpsubnet, the Linux eBPF/bcc version.


tcpsubnet summarizes throughput by destination subnet.
It works only for IPv4. Eg:

# tcpsubnet
Tracing... Output every 1 secs. Hit Ctrl-C to end
[03/05/18 22:32:47]
127.0.0.1/32               8
[03/05/18 22:32:48]
[03/05/18 22:32:49]
[03/05/18 22:32:50]
[03/05/18 22:32:51]
[03/05/18 22:32:52]
127.0.0.1/32              10
[03/05/18 22:32:53]

This example output shows the number of bytes sent to 127.0.0.1/32 (the
loopback interface). For demo purposes, I set netcat listening on port
8080, connected to it and sent the following payloads.

# nc 127.0.0.1 8080
1111111
111111111

The first line sends 7 digits plus the null character (8 bytes)
The second line sends 9 digits plus the null character (10 bytes)

Notice also, how tcpsubnet prints a header line with the current date
and time formatted in the current locale.

Try it yourself to get a feeling of how tcpsubnet works.

By default, tcpsubnet will categorize traffic in the following subnets:

- 127.0.0.1/32
- 10.0.0.0/8
- 172.16.0.0/12
- 192.168.0.0/16
- 0.0.0.0/0

The last subnet is a catch-all. In other words, anything that doesn't
match the first 4 defaults will be categorized under 0.0.0.0/0
You can change this default behavoir by passing a comma separated list
of subnets. Let's say we would like to know how much traffic we
are sending to github.com. We first find out what IPs github.com resolves
to, Eg:

# dig +short github.com
192.30.253.112
192.30.253.113

With this information, we can come up with a reasonable range of IPs
to monitor, Eg:
 
# tcpsubnet.py 192.30.253.110/27,0.0.0.0/0
Tracing... Output every 1 secs. Hit Ctrl-C to end
[03/05/18 22:38:58]
0.0.0.0/0               5780
192.30.253.110/27       2205
[03/05/18 22:38:59]
0.0.0.0/0               2036
192.30.253.110/27       1183
[03/05/18 22:39:00]
[03/05/18 22:39:01]
192.30.253.110/27      12537

If we would like to be more accurate, we can use the two IPs returned
by dig, Eg:

# tcpsubnet 192.30.253.113/32,192.130.253.112/32,0.0.0.0/0
Tracing... Output every 1 secs. Hit Ctrl-C to end
[03/05/18 22:42:56]
0.0.0.0/0               1177
192.30.253.113/32        910
[03/05/18 22:42:57]
0.0.0.0/0              48704
192.30.253.113/32        892
[03/05/18 22:42:58]
192.30.253.113/32        891
0.0.0.0/0                858
[03/05/18 22:42:59]
0.0.0.0/0              11159
192.30.253.113/32        894
[03/05/18 22:43:00]
0.0.0.0/0              60601

NOTE: When used in production, it is expected that you will have full
information about your network topology. In which case you won't need
to approximate subnets nor need to put individual IP addresses like
we just did.

Notice that the order of the subnet matters. Say, we put 0.0.0.0/0 as
the first element of the list and 192.130.253.112/32 as the second, all the
traffic going to 192.130.253.112/32 will have been categorized in
0.0.0.0/0 as 192.130.253.112/32 is contained in 0.0.0.0/0.

The default ouput unit is bytes. You can change it by using the
-f [--format] flag. tcpsubnet uses the same flags as iperf for the unit
format and adds mM. When using kmKM, the output will be rounded to floor.
Eg:

# tcpsubnet -fK 0.0.0.0/0
[03/05/18 22:44:04]
0.0.0.0/0                  1
[03/05/18 22:44:05]
0.0.0.0/0                  5
[03/05/18 22:44:06]
0.0.0.0/0                 31

Just like the majority of the bcc tools, tcpsubnet supports -i and --ebpf

It also supports -v [--verbose] which gives useful debugging information
on how the subnets are evaluated and the BPF program is constructed.

Last but not least, it supports -J [--json] to print the output in
JSON format. This is handy if you're calling tcpsubnet from another
program (say a nodejs server) and would like to have a structured stdout.
The output in JSON format will also include the date and time.
Eg:

# tcpsubnet -J -fK 192.130.253.110/27,0.0.0.0/0
{"date": "03/05/18", "entries": {"0.0.0.0/0": 2}, "time": "22:46:27"}
{"date": "03/05/18", "entries": {}, "time": "22:46:28"}
{"date": "03/05/18", "entries": {}, "time": "22:46:29"}
{"date": "03/05/18", "entries": {}, "time": "22:46:30"}
{"date": "03/05/18", "entries": {"192.30.253.110/27": 0}, "time": "22:46:31"}
{"date": "03/05/18", "entries": {"192.30.253.110/27": 1}, "time": "22:46:32"}
{"date": "03/05/18", "entries": {"192.30.253.110/27": 18}, "time": "22:46:32"}


USAGE:

# ./tcpsubnet -h
usage: tcpsubnet.py [-h] [-v] [-J] [-f {b,k,m,B,K,M}] [-i INTERVAL] [subnets]

Summarize TCP send and aggregate by subnet

positional arguments:
  subnets               comma separated list of subnets

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose         output debug statements
  -J, --json            format output in JSON
  -f {b,k,m,B,K,M}, --format {b,k,m,B,K,M}
                        [bkmBKM] format to report: bits, Kbits, Mbits, bytes,
                        KBytes, MBytes (default B)
  -i INTERVAL, --interval INTERVAL
                        output interval, in seconds (default 1)

examples:
    ./tcpsubnet                 # Trace TCP sent to the default subnets:
                                # 127.0.0.1/32,10.0.0.0/8,172.16.0.0/12,
                                # 192.168.0.0/16,0.0.0.0/0
    ./tcpsubnet -f K            # Trace TCP sent to the default subnets
                                # aggregated in KBytes.
    ./tcpsubnet 10.80.0.0/24    # Trace TCP sent to 10.80.0.0/24 only
    ./tcpsubnet -J              # Format the output in JSON.