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sudo docker exec -it 966f926484bc sh
/opt/Dockovpn # ifconfig

eth0      Link encap:Ethernet  HWaddr 02:42:AC:11:00:03
          inet addr:172.17.0.3  Bcast:172.17.255.255  Mask:255.255.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:20553 errors:0 dropped:0 overruns:0 frame:0
          TX packets:20539 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:14609434 (13.9 MiB)  TX bytes:14757264 (14.0 MiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
          inet addr:10.8.0.1  P-t-P:10.8.0.2  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:7825 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12572 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:1673378 (1.5 MiB)  TX bytes:12115333 (11.5 MiB)

/opt/Dockovpn # cat /etc/os-release

NAME="Alpine Linux"
ID=alpine
VERSION_ID=3.14.1
PRETTY_NAME="Alpine Linux v3.14"
HOME_URL="https://alpinelinux.org/"
BUG_REPORT_URL="https://bugs.alpinelinux.org/"

sudo docker exec -it 966f926484bc sh
apk update
apk add --update tcpdump

(1/2) Installing libpcap (1.10.0-r0)
(2/2) Installing tcpdump (4.99.0-r0)
Executing busybox-1.33.1-r3.trigger
OK: 20 MiB in 46 packages

RUN apk update \
            && apk add --update sudo \
            && apk add --update curl \
            && apk add --update busybox-extras \
            && apk add --update tcptraceroute \
            && apk add --update tcpdump \
            && apk add --update bind-tools \
            && apk add --update bash

tcpdump -i tun0 > dump.txt 2>&1

tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on tun0, link-type RAW (Raw IP), snapshot length 262144 bytes
14:11:23.685357 IP 10.8.0.6.54094 > 95.167.13.50.443: Flags [S], seq 636576023, win 65535, options [mss 1289,sackOK,TS val 3049079235 ecr 0,nop,wscale 10], length 0
14:11:23.685437 IP 10.8.0.6.54106 > 95.167.13.50.443: Flags [S], seq 693922812, win 65535, options [mss 1289,sackOK,TS val 3049079237 ecr 0,nop,wscale 10], length 0
14:11:23.685482 IP 10.8.0.6.56308 > 149.154.167.50.443: Flags [S], seq 3671445087, win 65535, options [mss 1289,sackOK,TS val 1433801443 ecr 0,nop,wscale 10], length 0
14:11:23.694025 IP 149.154.167.50.443 > 10.8.0.6.56308: Flags [S.], seq 63185511, ack 3671445088, win 24560, options [mss 1240,sackOK,TS val 1793857137 ecr 1433801443,nop,wscale 5], length 0
14:11:23.697859 IP 10.8.0.6.59494 > dns.opendns.com.853: Flags [S], seq 1260485743, win 65535, options [mss 1212,sackOK,TS val 2050917553 ecr 0,nop,wscale 10,tfo  cookiereq,nop,nop], length 0
14:11:23.700105 IP 10.8.0.6.54776 > dns.umbrella.com.853: Flags [S], seq 3581090777, win 65535, options [mss 1212,sackOK,TS val 3374423231 ecr 0,nop,wscale 10,tfo  cookiereq,nop,nop], length 0
14:11:23.733145 IP 10.8.0.6.54808 > dns.umbrella.com.53: 15255+ A? mtalk.google.com. (34)
14:11:23.747697 IP 10.8.0.6.22925 > dns.umbrella.com.53: 13744+ A? 0.pool.ntp.org. (32)
14:11:23.748423 IP 10.8.0.6.9703 > dns.umbrella.com.53: 59850+ A? 2.pool.ntp.org. (32)
...

sudo docker cp 966f926484bc:/opt/Dockovpn/dump.txt .
sudo chown dmitriano:dmitriano dump.txt