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tcpconnect_example.txt
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tcpconnect_example.txt
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Demonstrations of tcpconnect, the Linux eBPF/bcc version.
This tool traces the kernel function performing active TCP connections
(eg, via a connect() syscall; accept() are passive connections). Some example
output (IP addresses changed to protect the innocent):
# ./tcpconnect
PID COMM IP SADDR DADDR DPORT
1479 telnet 4 127.0.0.1 127.0.0.1 23
1469 curl 4 10.201.219.236 54.245.105.25 80
1469 curl 4 10.201.219.236 54.67.101.145 80
1991 telnet 6 ::1 ::1 23
2015 ssh 6 fe80::2000:bff:fe82:3ac fe80::2000:bff:fe82:3ac 22
This output shows four connections, one from a "telnet" process, two from
"curl", and one from "ssh". The output details shows the IP version, source
address, destination address, and destination port. This traces attempted
connections: these may have failed.
The overhead of this tool should be negligible, since it is only tracing the
kernel functions performing connect. It is not tracing every packet and then
filtering.
The -t option prints a timestamp column:
# ./tcpconnect -t
TIME(s) PID COMM IP SADDR DADDR DPORT
31.871 2482 local_agent 4 10.103.219.236 10.251.148.38 7001
31.874 2482 local_agent 4 10.103.219.236 10.101.3.132 7001
31.878 2482 local_agent 4 10.103.219.236 10.171.133.98 7101
90.917 2482 local_agent 4 10.103.219.236 10.251.148.38 7001
90.928 2482 local_agent 4 10.103.219.236 10.102.64.230 7001
90.938 2482 local_agent 4 10.103.219.236 10.115.167.169 7101
The output shows some periodic connections (or attempts) from a "local_agent"
process to various other addresses. A few connections occur every minute.
The -d option tracks DNS responses and tries to associate each connection with
the a previous DNS query issued before it. If a DNS response matching the IP
is found, it will be printed. If no match was found, "No DNS Query" is printed
in this column. Queries for 127.0.0.1 and ::1 are automatically associated with
"localhost". If the time between when the DNS response was received and a
connect call was traced exceeds 100ms, the tool will print the time delta
after the query name. See below for www.domain.com for an example.
# ./tcpconnect -d
PID COMM IP SADDR DADDR DPORT QUERY
1543 amazon-ssm-a 4 10.66.75.54 176.32.119.67 443 ec2messages.us-west-1.amazonaws.com
1479 telnet 4 127.0.0.1 127.0.0.1 23 localhost
1469 curl 4 10.201.219.236 54.245.105.25 80 www.domain.com (123.342ms)
1469 curl 4 10.201.219.236 54.67.101.145 80 No DNS Query
1991 telnet 6 ::1 ::1 23 localhost
2015 ssh 6 fe80::2000:bff:fe82:3ac fe80::2000:bff:fe82:3ac 22 anotherhost.org
The -U option prints a UID column:
# ./tcpconnect -U
UID PID COMM IP SADDR DADDR DPORT
0 31333 telnet 6 ::1 ::1 23
0 31333 telnet 4 127.0.0.1 127.0.0.1 23
1000 31322 curl 4 127.0.0.1 127.0.0.1 80
1000 31322 curl 6 ::1 ::1 80
The -u option filtering UID:
# ./tcpconnect -Uu 1000
UID PID COMM IP SADDR DADDR DPORT
1000 31338 telnet 6 ::1 ::1 23
1000 31338 telnet 4 127.0.0.1 127.0.0.1 23
To spot heavy outbound connections quickly one can use the -c flag. It will
count all active connections per source ip and destination ip/port.
# ./tcpconnect.py -c
Tracing connect ... Hit Ctrl-C to end
^C
LADDR RADDR RPORT CONNECTS
192.168.10.50 172.217.21.194 443 70
192.168.10.50 172.213.11.195 443 34
192.168.10.50 172.212.22.194 443 21
[...]
The --cgroupmap option filters based on a cgroup set. It is meant to be used
with an externally created map.
# ./tcpconnect --cgroupmap /sys/fs/bpf/test01
For more details, see docs/special_filtering.md
USAGE message:
# ./tcpconnect -h
usage: tcpconnect.py [-h] [-t] [-p PID] [-P PORT] [-U] [-u UID] [-c]
[--cgroupmap CGROUPMAP] [--mntnsmap MNTNSMAP] [-d]
Trace TCP connects
optional arguments:
-h, --help show this help message and exit
-t, --timestamp include timestamp on output
-p PID, --pid PID trace this PID only
-P PORT, --port PORT comma-separated list of destination ports to trace.
-U, --print-uid include UID on output
-u UID, --uid UID trace this UID only
-c, --count count connects per src ip and dest ip/port
--cgroupmap CGROUPMAP
trace cgroups in this BPF map only
--mntnsmap MNTNSMAP trace mount namespaces in this BPF map only
-d, --dns include likely DNS query associated with each connect
examples:
./tcpconnect # trace all TCP connect()s
./tcpconnect -t # include timestamps
./tcpconnect -p 181 # only trace PID 181
./tcpconnect -P 80 # only trace port 80
./tcpconnect -P 80,81 # only trace port 80 and 81
./tcpconnect -U # include UID
./tcpconnect -u 1000 # only trace UID 1000
./tcpconnect -c # count connects per src ip and dest ip/port
./tcpconnect --cgroupmap mappath # only trace cgroups in this BPF map
./tcpconnect --mntnsmap mappath # only trace mount namespaces in the map