Demonstrations of bindsnoop, the Linux eBPF/bcc version.

This tool traces the kernel function performing socket binding and
print socket options set before the system call invocation that might
impact bind behavior and bound interface:
SOL_IP     IP_FREEBIND              F....
SOL_IP     IP_TRANSPARENT           .T...
SOL_IP     IP_BIND_ADDRESS_NO_PORT  ..N..
SOL_SOCKET SO_REUSEADDR             ...R.
SOL_SOCKET SO_REUSEPORT             ....r


# ./bindsnoop.py
Tracing binds ... Hit Ctrl-C to end
PID COMM         PROT ADDR            PORT   OPTS IF
3941081 test_bind_op TCP  192.168.1.102       0 F.N..  0
3940194 dig          TCP  ::              62087 .....  0
3940219 dig          UDP  ::              48665 .....  0
3940893 Acceptor Thr TCP  ::              35343 ...R.  0

The output shows four bind system calls:
two "test_bind_op" instances, one with IP_FREEBIND and IP_BIND_ADDRESS_NO_PORT
options, dig process called bind for TCP and UDP sockets,
and Acceptor called bind for TCP with SO_REUSEADDR option set.


The -t option prints a timestamp column

# ./bindsnoop.py -t
TIME(s)        PID COMM         PROT ADDR            PORT   OPTS IF
0.000000   3956801 dig          TCP  ::              49611 .....  0
0.011045   3956822 dig          UDP  ::              56343 .....  0
2.310629   3956498 test_bind_op TCP  192.168.1.102   39609 F...r  0


The -U option prints a UID column:

# ./bindsnoop.py -U
Tracing binds ... Hit Ctrl-C to end
   UID      PID COMM         PROT ADDR            PORT   OPTS IF
127072  3956498 test_bind_op TCP  192.168.1.102   44491 F...r  0
127072  3960261 Acceptor Thr TCP  ::              48869 ...R.  0
     0  3960729 Acceptor Thr TCP  ::              44637 ...R.  0
     0  3959075 chef-client  UDP  ::              61722 .....  0


The -u option filtering UID:

# ./bindsnoop.py -Uu 0
Tracing binds ... Hit Ctrl-C to end
   UID      PID COMM         PROT ADDR            PORT   OPTS IF
     0  3966330 Acceptor Thr TCP  ::              39319 ...R.  0
     0  3968044 python3.7    TCP  ::1             59371 .....  0
     0    10224 fetch        TCP  0.0.0.0         42091 ...R.  0


The --cgroupmap option filters based on a cgroup set.
It is meant to be used with an externally created map.

# ./bindsnoop.py --cgroupmap /sys/fs/bpf/test01

For more details, see docs/filtering_by_cgroups.md


In order to track heavy bind usage one can use --count option
# ./bindsnoop.py --count
Tracing binds ... Hit Ctrl-C to end
LADDR                                           LPORT     BINDS
0.0.0.0                                          6771     4
0.0.0.0                                          4433     4
127.0.0.1                                       33665     1


Usage message:
# ./bindsnoop.py -h
usage: bindsnoop.py [-h] [-t] [-w] [-p PID] [-P PORT] [-E] [-U] [-u UID]
                  [--count] [--cgroupmap CGROUPMAP]

Trace TCP binds

optional arguments:
  -h, --help            show this help message and exit
  -t, --timestamp       include timestamp on output
  -w, --wide            wide column output (fits IPv6 addresses)
  -p PID, --pid PID     trace this PID only
  -P PORT, --port PORT  comma-separated list of ports to trace.
  -E, --errors          include errors in the output.
  -U, --print-uid       include UID on output
  -u UID, --uid UID     trace this UID only
  --count               count binds per src ip and port
  --cgroupmap CGROUPMAP
                        trace cgroups in this BPF map only

examples:
    ./bindsnoop           # trace all TCP bind()s
    ./bindsnoop -t        # include timestamps
    ./bindsnoop -w        # wider columns (fit IPv6)
    ./bindsnoop -p 181    # only trace PID 181
    ./bindsnoop -P 80     # only trace port 80
    ./bindsnoop -P 80,81  # only trace port 80 and 81
    ./bindsnoop -U        # include UID
    ./bindsnoop -u 1000   # only trace UID 1000
    ./bindsnoop -E        # report bind errors
    ./bindsnoop --count   # count bind per src ip
    ./bindsnoop --cgroupmap mappath  # only trace cgroups in this BPF map

    it is reporting socket options set before the bins call
    impacting system call behavior:
     SOL_IP     IP_FREEBIND              F....
     SOL_IP     IP_TRANSPARENT           .T...
     SOL_IP     IP_BIND_ADDRESS_NO_PORT  ..N..
     SOL_SOCKET SO_REUSEADDR             ...R.
     SOL_SOCKET SO_REUSEPORT             ....r

     SO_BINDTODEVICE interface is reported as "IF" index
