ืืขืื ืึทืืขืืขื, ืืืื ื ืึธืืขื ืืื ืกืึทืฉืึท, ืืื ืคืืจื ืืึทืงืขื ื ืืขืกืืื ื ืืื FunCorp. ืืืจ, ืืื ืคืืืข ืื ืืขืจืข, ืืึธืื ืืืคึผืืึทืืขื ืึทื ืึท ืืื ืกื-ืึธืจืืขื ืืื ืึทืจืงืึทืืขืงืืฉืขืจ. ืืืืฃ ืื ืืืื ืืึทื ื, ืืึธืก ืกืืืคึผืืึทืคืืื ืื ืึทืจืืขื, ืืืืึทื ... ืขืก ืืื ืืจืื ืืขืจ ืฆื ืคึผืจืืืืจื ืืขืืขืจ ืืื ืกื ืกืขืคึผืขืจืึทืืื, ืึธืืขืจ ืืืืฃ ืื ืื ืืขืจืข ืืึทื ื, ืขืก ืืื ืึท ื ืืื ืฆื ืคึผืจืืืืจื ืื ืื ืืขืจืึทืงืฉืึทื ืคืื ืกืขืจืืืืกืขืก ืืื ืืขืืขืจ ืื ืืขืจืข, ืืืึธืก ืึธืคื ืึทืงืขืจื ืืืืขืจ ืื ื ืขืฅ.
ืืื ืืขื ืึทืจืืืงื, ืืื ืืืขื ืจืขืื ืืืขืื ืฆืืืื ืืืืืืึทืืื ืืืึธืก ืงืขื ืขื ืืืขืจื ืืขื ืืฆื ืฆื ืงืึธื ืืจืึธืืืจื ืืงืขืจืืืง ืกืื ืขืจืืึธืื ืืืึธืก ืืึทืฉืจืืึทืื ืื ืึธืคึผืขืจืึทืฆืืข ืคืื โโืึท ืึทืคึผืืึทืงืืืฉืึทื ืืื ืืขื ืืืึทืืืึทื ืคืื ื ืขืฅ ืคึผืจืึธืืืขืืก.
ืกืืืืืึทืืื ื ื ืขืฅ ืคึผืจืึธืืืขืืก
ืืืคึผืืงืึทืืื, ืืืืืืืืืจื ืืื ืืขืกืืขื ืืืืฃ ืคึผืจืืืืจื ืกืขืจืืืขืจืก ืืื ืึท ืืื ืืื ืืขืจื ืขื ืคึฟืึทืจืืื ืืื ื. ืืื ืืึทืจื ืคึผืจืึธืืืงืฆืืข ืื ืืืืืจืึทื ืืึทื ืฅ, ืื ืืื ืื ืงืขื ื ืืฉื ืืืื ืึทืืื ืืืึทื, ืึทืืื ืืื ืืืจ ืืึทืจืคึฟื ืฆื ืคึผืจืืืืจื ืืืืื ืืื ื ืขืืขื ืงืฉืจ ืื ืึธืื. ืืืืฃ ืืื ืืงืก, ืื ื ืืฆื ืืืขื ืืขืืคื ืืื ืื ืึทืจืืขื ืคืื ืกืืืืึทืืืืืื ื ืึทืืึท ืื ืึธืื tc.
ืืง(ืึทืืจ. ืคืื ืคืึทืจืงืขืจ ืงืึธื ืืจืึธื) ืึทืืึทืื ืืืจ ืฆื ืงืึทื ืคืืืืขืจ ืื ืืจืึทื ืกืืืกืืข ืคืื โโื ืขืฅ ืคึผืึทืงืืฅ ืืื ืื ืกืืกืืขื. ืืขื ื ืืฆื ืืื ืืจืืืก ืงืืืคึผืึทืืืืึทืืื, ืืืจ ืงืขื ืขื ืืืืขื ืขื ืืขืจ ืืืขืื ืืื . ืืึธ ืืื ืืืขื ืืึทืืจืึทืืื ืืืืื ืึท ืืืกื ืคืื ืืื: ืืืจ ืืขื ืขื ืืื ืืขืจืขืกืืจื ืืื ืคืึทืจืงืขืจ ืกืงืขืืืฉืืืื ื, ืคึฟืึทืจ ืืืึธืก ืืืจ ื ืืฆื qdisc, ืืื ืืื ื ืืืจ ืืึทืจืคึฟื ืฆื ืขืืืึทืืืื ืึทื ืึทื ืกืืืืืึทื ื ืขืฅ, ืืืจ ืืืขืื ื ืืฆื ืงืืึทืกืืขืกืก ืงืืืกืง .
ืืึธืืืจ ืงืึทืืขืจ ืึทื ืขืงืึธื ืกืขืจืืืขืจ ืืืืฃ ืื ืกืขืจืืืขืจ (ืืื ืืขืืืืื ื ):
ncat -l 127.0.0.1 12345 -k -c 'xargs -n1 -i echo "Response: {}"'
ืืื ืกืืจ ืฆื ืืืืึทืื ืืื ืืขืืึทื ืึทืืข ืื ืืืืขืกืืึทืืคึผืก ืืื ืืขืืขืจ ืฉืจืื ืคืื ืื ืืขืจืึทืงืฉืึทื ืฆืืืืฉื ืืขื ืงืืืขื ื ืืื ืื ืกืขืจืืืขืจ, ืืื ืืขืฉืจืืื ืึท ืคึผืฉืื ืคึผืืืืึธื ืฉืจืืคื ืืืึธืก ืกืขื ืื ืึท ืืงืฉื ืคึผืจืืืืจื ืฆื ืืื ืืืขืจ ืขืงืึธื ืกืขืจืืืขืจ.
ืงืืืขื ื ืืงืืจ ืงืึธื
#!/bin/python
import socket
import time
HOST = '127.0.0.1'
PORT = 12345
BUFFER_SIZE = 1024
MESSAGE = "Testn"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
t1 = time.time()
print "[time before connection: %.5f]" % t1
s.connect((HOST, PORT))
print "[time after connection, before sending: %.5f]" % time.time()
s.send(MESSAGE)
print "[time after sending, before receiving: %.5f]" % time.time()
data = s.recv(BUFFER_SIZE)
print "[time after receiving, before closing: %.5f]" % time.time()
s.close()
t2 = time.time()
print "[time after closing: %.5f]" % t2
print "[total duration: %.5f]" % (t2 - t1)
print data
ืืื ืก ืงืึทืืขืจ ืขืก ืืื ืงืืง ืืื ืื ืคืึทืจืงืขืจ ืืืืฃ ืื ืฆืืืื ื lo ืืื ืคึผืึธืจื 12345:
[user@host ~]# python client.py
[time before connection: 1578652979.44837]
[time after connection, before sending: 1578652979.44889]
[time after sending, before receiving: 1578652979.44894]
[time after receiving, before closing: 1578652979.45922]
[time after closing: 1578652979.45928]
[total duration: 0.01091]
Response: Test
ืคืึทืจืงืขืจ ืืึทืืคึผ
[user@host ~]# tcpdump -i lo -nn port 12345
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
10:42:59.448601 IP 127.0.0.1.54054 > 127.0.0.1.12345: Flags [S], seq 3383332866, win 43690, options [mss 65495,sackOK,TS val 606325685 ecr 0,nop,wscale 7], length 0
10:42:59.448612 IP 127.0.0.1.12345 > 127.0.0.1.54054: Flags [S.], seq 2584700178, ack 3383332867, win 43690, options [mss 65495,sackOK,TS val 606325685 ecr 606325685,nop,wscale 7], length 0
10:42:59.448622 IP 127.0.0.1.54054 > 127.0.0.1.12345: Flags [.], ack 1, win 342, options [nop,nop,TS val 606325685 ecr 606325685], length 0
10:42:59.448923 IP 127.0.0.1.54054 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 606325685 ecr 606325685], length 5
10:42:59.448930 IP 127.0.0.1.12345 > 127.0.0.1.54054: Flags [.], ack 6, win 342, options [nop,nop,TS val 606325685 ecr 606325685], length 0
10:42:59.459118 IP 127.0.0.1.12345 > 127.0.0.1.54054: Flags [P.], seq 1:15, ack 6, win 342, options [nop,nop,TS val 606325696 ecr 606325685], length 14
10:42:59.459213 IP 127.0.0.1.54054 > 127.0.0.1.12345: Flags [.], ack 15, win 342, options [nop,nop,TS val 606325696 ecr 606325696], length 0
10:42:59.459268 IP 127.0.0.1.54054 > 127.0.0.1.12345: Flags [F.], seq 6, ack 15, win 342, options [nop,nop,TS val 606325696 ecr 606325696], length 0
10:42:59.460184 IP 127.0.0.1.12345 > 127.0.0.1.54054: Flags [F.], seq 15, ack 7, win 342, options [nop,nop,TS val 606325697 ecr 606325696], length 0
10:42:59.460196 IP 127.0.0.1.54054 > 127.0.0.1.12345: Flags [.], ack 16, win 342, options [nop,nop,TS val 606325697 ecr 606325697], length 0
ืึทืืฅ ืืื ื ืึธืจืืึทื: ืึท ืืจืื-ืืืขื ืืึทื ืืฉืืืง, PSH / ACK ืืื ACK ืืื ืขื ืืคืขืจ ืฆืืืื ืืึธื - ืืึธืก ืืื ืืขืจ ืืืขืงืกื ืคืื ืืขืื ืืื ืขื ืืคืขืจ ืฆืืืืฉื ืืขื ืงืืืขื ื ืืื ืกืขืจืืืขืจ, ืืื FIN / ACK ืืื ACK ืฆืืืื ืืึธื - ืงืึทืืคึผืืืืื ื ืื ืงืฉืจ.
ืคึผืึทืงืึทื ืคืึทืจืืึทืืื
ืืืฆื ืืึธืืืจ ืฉืืขืื ืื ืคืึทืจืืึทืืื ืฆื 500 ืืืืืกืขืงืึทื ืื:
tc qdisc add dev lo root netem delay 500ms
ืืืจ ืงืึทืืขืจ ืืขื ืงืืืขื ื ืืื ืืขื ืึทื ืื ืฉืจืืคื ืืืืคื ืืืฆื ืคึฟืึทืจ 2 ืกืขืงืื ืืขืก:
[user@host ~]# ./client.py
[time before connection: 1578662612.71044]
[time after connection, before sending: 1578662613.71059]
[time after sending, before receiving: 1578662613.71065]
[time after receiving, before closing: 1578662614.72011]
[time after closing: 1578662614.72019]
[total duration: 2.00974]
Response: Test
ืืืึธืก ืืื ืืื ืื ืคืึทืจืงืขืจ? ืืืืืจ ืงืืงื:
ืคืึทืจืงืขืจ ืืึทืืคึผ
13:23:33.210520 IP 127.0.0.1.58694 > 127.0.0.1.12345: Flags [S], seq 1720950927, win 43690, options [mss 65495,sackOK,TS val 615958947 ecr 0,nop,wscale 7], length 0
13:23:33.710554 IP 127.0.0.1.12345 > 127.0.0.1.58694: Flags [S.], seq 1801168125, ack 1720950928, win 43690, options [mss 65495,sackOK,TS val 615959447 ecr 615958947,nop,wscale 7], length 0
13:23:34.210590 IP 127.0.0.1.58694 > 127.0.0.1.12345: Flags [.], ack 1, win 342, options [nop,nop,TS val 615959947 ecr 615959447], length 0
13:23:34.210657 IP 127.0.0.1.58694 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 615959947 ecr 615959447], length 5
13:23:34.710680 IP 127.0.0.1.12345 > 127.0.0.1.58694: Flags [.], ack 6, win 342, options [nop,nop,TS val 615960447 ecr 615959947], length 0
13:23:34.719371 IP 127.0.0.1.12345 > 127.0.0.1.58694: Flags [P.], seq 1:15, ack 6, win 342, options [nop,nop,TS val 615960456 ecr 615959947], length 14
13:23:35.220106 IP 127.0.0.1.58694 > 127.0.0.1.12345: Flags [.], ack 15, win 342, options [nop,nop,TS val 615960957 ecr 615960456], length 0
13:23:35.220188 IP 127.0.0.1.58694 > 127.0.0.1.12345: Flags [F.], seq 6, ack 15, win 342, options [nop,nop,TS val 615960957 ecr 615960456], length 0
13:23:35.720994 IP 127.0.0.1.12345 > 127.0.0.1.58694: Flags [F.], seq 15, ack 7, win 342, options [nop,nop,TS val 615961457 ecr 615960957], length 0
13:23:36.221025 IP 127.0.0.1.58694 > 127.0.0.1.12345: Flags [.], ack 16, win 342, options [nop,nop,TS val 615961957 ecr 615961457], length 0
ืืืจ ืงืขื ืขื ืืขื ืึทื ืื ืืขืจืืืึทืจื ืึธืคึผืฉืืื ืคืื ืึท ืืึทืื ืจืืข ืืื ืืจืืืก ืืื ืื ืื ืืขืจืึทืงืฉืึทื ืฆืืืืฉื ืืขื ืงืืืขื ื ืืื ืื ืกืขืจืืืขืจ. ืื ืกืืกืืขื ืืืืืืืื ืคืื ืืขืจ ืื ืืขืจืขืกืืื ืืื ืืืื ืื ืึธืคึผืฉืืื ืืื ืืจืขืกืขืจ: ืืขืจ ืงืขืจื ืืืืื ืฆื ืจืขืกืขื ื ืขืืืขืืข ืืงืคึผ ืคึผืึทืงืืฅ. ืืึธืืืจ ืืืืฉื ืื ืคืึทืจืืึทืืื ืฆื 1 ืกืขืงืื ืืข ืืื ืงืืง ืืื ืื ืคืึทืจืงืขืจ (ืืื ืืืขื ื ืืฉื ืืืืึทืื ืื ืจืขืืืืืึทื ืคืื ืืขื ืงืืืขื ื, ืขืก ืืขื ืขื ืื ืืขืจืืืึทืจื 4 ืกืขืงืื ืืขืก ืืื ืืึทื ืฅ ืืขืืืืขืจ):
tc qdisc change dev lo root netem delay 1s
ืคืึทืจืงืขืจ ืืึทืืคึผ
13:29:07.709981 IP 127.0.0.1.39306 > 127.0.0.1.12345: Flags [S], seq 283338334, win 43690, options [mss 65495,sackOK,TS val 616292946 ecr 0,nop,wscale 7], length 0
13:29:08.710018 IP 127.0.0.1.12345 > 127.0.0.1.39306: Flags [S.], seq 3514208179, ack 283338335, win 43690, options [mss 65495,sackOK,TS val 616293946 ecr 616292946,nop,wscale 7], length 0
13:29:08.711094 IP 127.0.0.1.39306 > 127.0.0.1.12345: Flags [S], seq 283338334, win 43690, options [mss 65495,sackOK,TS val 616293948 ecr 0,nop,wscale 7], length 0
13:29:09.710048 IP 127.0.0.1.39306 > 127.0.0.1.12345: Flags [.], ack 1, win 342, options [nop,nop,TS val 616294946 ecr 616293946], length 0
13:29:09.710152 IP 127.0.0.1.39306 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 616294947 ecr 616293946], length 5
13:29:09.711120 IP 127.0.0.1.12345 > 127.0.0.1.39306: Flags [S.], seq 3514208179, ack 283338335, win 43690, options [mss 65495,sackOK,TS val 616294948 ecr 616292946,nop,wscale 7], length 0
13:29:10.710173 IP 127.0.0.1.12345 > 127.0.0.1.39306: Flags [.], ack 6, win 342, options [nop,nop,TS val 616295947 ecr 616294947], length 0
13:29:10.711140 IP 127.0.0.1.39306 > 127.0.0.1.12345: Flags [.], ack 1, win 342, options [nop,nop,TS val 616295948 ecr 616293946], length 0
13:29:10.714782 IP 127.0.0.1.12345 > 127.0.0.1.39306: Flags [P.], seq 1:15, ack 6, win 342, options [nop,nop,TS val 616295951 ecr 616294947], length 14
13:29:11.714819 IP 127.0.0.1.39306 > 127.0.0.1.12345: Flags [.], ack 15, win 342, options [nop,nop,TS val 616296951 ecr 616295951], length 0
13:29:11.714893 IP 127.0.0.1.39306 > 127.0.0.1.12345: Flags [F.], seq 6, ack 15, win 342, options [nop,nop,TS val 616296951 ecr 616295951], length 0
13:29:12.715562 IP 127.0.0.1.12345 > 127.0.0.1.39306: Flags [F.], seq 15, ack 7, win 342, options [nop,nop,TS val 616297952 ecr 616296951], length 0
13:29:13.715596 IP 127.0.0.1.39306 > 127.0.0.1.12345: Flags [.], ack 16, win 342, options [nop,nop,TS val 616298952 ecr 616297952], length 0
ืืขื ืงืขื ืืขื ืึทื ืืขืจ ืงืืืขื ื ืืึธื ืฆืืืื ืืึธื ืืขืฉืืงื ืึท SYN ืคึผืึทืงืึทื, ืืื ืืขืจ ืกืขืจืืืขืจ ืืึธื ืฆืืืื ืืึธื ืืขืฉืืงื ืึท SYN/ACK.
ืืื ืึทืืืฉืึทื ืฆื ืึท ืงืขืกืืืืขืจืืืง ืืืขืจื, ืื ืคืึทืจืืึทืืื ืงืขื ืขื ืืืื ืืึทืฉืืืื ืฆื ืึท ืืืืืืืืฉืึทื, ืึท ืคืึทืจืฉืคึผืจืืืืื ื ืคึฟืื ืงืฆืืข ืืื ืึท ืงืึธืจืึทืืืืฉืึทื (ืืื ืื ืืืขืจื ืคึฟืึทืจ ืื ืคืจืืขืจืืืงืข ืคึผืึทืงืึทื). ืืึธืก ืืื ืืขืืื ืืื ืืืื:
tc qdisc change dev lo root netem delay 500ms 400ms 50 distribution normal
ืืึธ ืืืจ ืืึธืื ืืึทืฉืืืื ืื ืคืึทืจืืึทืืื ืฆืืืืฉื 100 ืืื 900 ืืืืืกืขืงืึทื ืื, ืื ืืืึทืืืขืก ืืืขื ืืืื ืืืืกืืขืงืืืื ืืืื ืึท ื ืึธืจืืึทื ืคืึทืจืฉืคึผืจืืืืื ื ืืื ืขืก ืืืขื ืืืื ืึท 50% ืงืึธืจืึทืืืืฉืึทื ืืื ืื ืคืึทืจืืึทืืื ืืืขืจื ืคึฟืึทืจ ืื ืคืจืืขืจืืืงืข ืคึผืึทืงืึทื.
ืืืจ ืงืขื ืืึธืื ืืืืขืจืงื ืึทื ืืื ืืขืจ ืขืจืฉืืขืจ ืืึทืคึฟืขื ืืื ืืขืืืืื ื ืฆืืืขืื, ืืื ืืื ืืืืฉื. ืืขืจ ืืืึทืืฉ ืคืื ืื ืงืึทืืึทื ืื ืืื ืงืืึธืจ ืืื ืืขืจ ืืึธื, ืึทืืื ืืื ืืืขื ื ืึธืจ ืืืืื ืึทื ืขืก ืืื ืืขืจ ืืขื, ืืืึธืก ืงืขื ืขื ืืืื ืืขืืืืื ื ืฆื ืืึทืืืึทืืืงื ืื ืงืึทื ืคืืืืขืจืืืฉืึทื.
ืคึผืึทืงืึทื ืืึธืก
ืืื ืก ืืืฆื ืคึผืจืืืืจื ืฆื ืืึธื ืคึผืึทืงืึทื ืึธื ืืืขืจ. ืืื ืงืขื ืขื ืืืื ืืขืืขื ืคืื ืื ืืึทืงืืืืขื ืืืืฉืึทื, ืืึธืก ืงืขื ืขื ืืืื ืืขืืื ืืื ืืจืื ืืืขืื: ืจืึทื ืืึทืืื ืืืืื ื ืคึผืึทืงืืฅ ืืื ืขืืืขืืข ืืึทืฉืืึธืขืก, ื ืืฆื ืึท ืืึทืจืงืึธืื ืงืืื ืคืื 2, 3 ืึธืืขืจ 4 ืฉืืึทืื ืฆื ืจืขืืขื ืขื ืคึผืึทืงืึทื ืึธื ืืืขืจ, ืึธืืขืจ ื ืืฆื ืื Elliott-Gilbert ืืึธืืขื. ืืื ืืขื ืึทืจืืืงื ืืื ืืืขื ืืึทืืจืึทืืื ืื ืขืจืฉืืขืจ (ืกืืืคึผืึทืกื ืืื ืืขืจืกื ืงืืึธืจ ืืื ืืขืจ ืืึธื) ืืืคึฟื, ืืื ืืืจ ืงืขื ืขื ืืืืขื ืขื ืืืขืื ืื ืืขืจืข .
ืืึธืืืจ ืืึทืื ืื ืึธื ืืืขืจ ืคืื 50% ืคืื ืคึผืึทืงืืฅ ืืื ืึท ืงืึธืจืึทืืืืฉืึทื ืคืื 25%:
tc qdisc add dev lo root netem loss 50% 25%
ืืืืืขืจ, ืืงืคึผืืืืคึผ ืืืขื ื ืืฉื ืงืขื ืขื ืงืืืจ ืืืืึทืื ืืื ืื ืื ืึธื ืืืขืจ ืคืื ืคึผืึทืงืืฅ, ืืืจ ืืืขืื ื ืึธืจ ืืืขืจื ืขืืขื ืึทื ืขืก ืืึทืงืข ืึทืจืืขื. ืืื ืื ืืขืืืืงืกื ืืื ืึทื ืกืืืืืึทื ืคืืืกื ืืืง ืฆืืื ืคืื ืื ืฉืจืืคื ืืืขื ืืขืืคึฟื ืืื ืื ืืึทืฉืืขืืืงื ืืขื. client.py (ืงืขื ืขื ืืืื ืืขืขื ืืืงื ืืืืงืขืฃ, ืึธืืขืจ ืืคึฟืฉืจ ืืื 20 ืกืขืงืื ืืขืก), ืืื ืืขืืื ื ืืื ืึท ืืขืืืืงืกื ื ืืืขืจ ืคืื ืจืืืจืึทื ืกืืืืืขื ืคึผืึทืงืืฅ:
[user@host ~]# netstat -s | grep retransmited; sleep 10; netstat -s | grep retransmited
17147 segments retransmited
17185 segments retransmited
ืึทืืื ื ืจืึทืฉ ืฆื ืคึผืึทืงืืฅ
ืืื ืึทืืืฉืึทื ืฆื ืคึผืึทืงืึทื ืึธื ืืืขืจ, ืืืจ ืงืขื ืขื ืกืืืืืืจื ืคึผืึทืงืึทื ืฉืขืืืงื: ืจืึทืฉ ืืืขื ืืขืจืฉืืึทื ืขื ืืื ืึท ืืจืึทืค - ืคึผืึทืงืึทื ืฉืืขืืข. ืืึธืืืจ ืืึทืื ืคึผืึทืงืึทื ืฉืขืืืงื ืืื ืึท 50% ืืึทืฉืืึธืขืก ืืื ืึธื ืงืึธืจืึทืืืืฉืึทื:
tc qdisc change dev lo root netem corrupt 50%
ืืืจ ืืืืคื ืืขื ืงืืืขื ื ืฉืจืืคื (ืืึธืจื ืืฉื ืืฉืืงืึทืืืข ืืึธืจื, ืึธืืขืจ ืขืก ืืขื ืืืขื 2 ืกืขืงืื ืืขืก ืฆื ืคืึทืจืขื ืืืงื), ืงืืง ืืื ืื ืคืึทืจืงืขืจ:
ืคืึทืจืงืขืจ ืืึทืืคึผ
[user@host ~]# tcpdump -i lo -nn port 12345
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
10:20:54.812434 IP 127.0.0.1.43666 > 127.0.0.1.12345: Flags [S], seq 2023663770, win 43690, options [mss 65495,sackOK,TS val 1037001049 ecr 0,nop,wscale 7], length 0
10:20:54.812449 IP 127.0.0.1.12345 > 127.0.0.1.43666: Flags [S.], seq 2104268044, ack 2023663771, win 43690, options [mss 65495,sackOK,TS val 1037001049 ecr 1037001049,nop,wscale 7], length 0
10:20:54.812458 IP 127.0.0.1.43666 > 127.0.0.1.12345: Flags [.], ack 1, win 342, options [nop,nop,TS val 1037001049 ecr 1037001049], length 0
10:20:54.812509 IP 127.0.0.1.43666 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 1037001049 ecr 1037001049], length 5
10:20:55.013093 IP 127.0.0.1.43666 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 1037001250 ecr 1037001049], length 5
10:20:55.013122 IP 127.0.0.1.12345 > 127.0.0.1.43666: Flags [.], ack 6, win 342, options [nop,nop,TS val 1037001250 ecr 1037001250], length 0
10:20:55.014681 IP 127.0.0.1.12345 > 127.0.0.1.43666: Flags [P.], seq 1:15, ack 6, win 342, options [nop,nop,TS val 1037001251 ecr 1037001250], length 14
10:20:55.014745 IP 127.0.0.1.43666 > 127.0.0.1.12345: Flags [.], ack 15, win 340, options [nop,nop,TS val 1037001251 ecr 1037001251], length 0
10:20:55.014823 IP 127.0.0.1.43666 > 127.0.0.5.12345: Flags [F.], seq 2023663776, ack 2104268059, win 342, options [nop,nop,TS val 1037001251 ecr 1037001251], length 0
10:20:55.214088 IP 127.0.0.1.12345 > 127.0.0.1.43666: Flags [P.], seq 1:15, ack 6, win 342, options [nop,unknown-65 0x0a3dcf62eb3d,[bad opt]>
10:20:55.416087 IP 127.0.0.1.43666 > 127.0.0.1.12345: Flags [F.], seq 6, ack 15, win 342, options [nop,nop,TS val 1037001653 ecr 1037001251], length 0
10:20:55.416804 IP 127.0.0.1.12345 > 127.0.0.1.43666: Flags [F.], seq 15, ack 7, win 342, options [nop,nop,TS val 1037001653 ecr 1037001653], length 0
10:20:55.416818 IP 127.0.0.1.43666 > 127.0.0.1.12345: Flags [.], ack 16, win 343, options [nop,nop,TS val 1037001653 ecr 1037001653], length 0
10:20:56.147086 IP 127.0.0.1.12345 > 127.0.0.1.43666: Flags [F.], seq 15, ack 7, win 342, options [nop,nop,TS val 1037002384 ecr 1037001653], length 0
10:20:56.147101 IP 127.0.0.1.43666 > 127.0.0.1.12345: Flags [.], ack 16, win 342, options [nop,nop,TS val 1037002384 ecr 1037001653], length 0
ืขืก ืงืขื ืขื ืืืื ืืขืืขื ืึทื ืขืืืขืืข ืคึผืึทืงืืฅ ืืขื ืขื ืจืืคึผืืืืืื ืืขืฉืืงื ืืื ืขืก ืืื ืืืื ืคึผืึทืงืึทื ืืื ืฆืขืืจืืื ืืขืืึทืืึทืืึท: ืึธืคึผืฆืืขืก [nop,unknown-65 0x0a3dcf62eb3d, [ืฉืืขืื ืึธืคึผื]>. ืืืขืจ ืื ืืืืคึผื ืืึทื ืืื ืึทื ืืื ืื ืกืืฃ ืึทืืฅ ืืขืืจืืขื ืจืืืืืง - ืืงืคึผ ืงืึธืืคึผื ืืื ืืืึทื ืึทืจืืขื.
ืคึผืึทืงืึทื ืืืคึผืืืงืึทืืืึธื
ืืืึธืก ืึทื ืืขืจืฉ ืงืขื ืขื ืืืจ ืืึธื ืืื ื ืขืืขื? ืคึฟืึทืจ ืืืึทืฉืคึผืื, ืกืืืืืืจื ืื ืคืึทืจืงืขืจื ืกืืืืึทืฆืืข ืคืื โโืคึผืึทืงืึทื ืึธื ืืืขืจ - ืคึผืึทืงืึทื ืืืคึผืืืงืืืฉืึทื. ืืขืจ ืืึทืคึฟืขื ืืืื ื ืขืื 2 ืึทืจืืืืขื ืื: ืืึทืฉืืึธืขืก ืืื ืงืึธืจืึทืืืืฉืึทื.
tc qdisc change dev lo root netem duplicate 50% 25%
ืืฉืึทื ืืื ื ืื ืกืืจ ืคืื ืคึผืึทืงืึทืืืฉืึทื
ืืืจ ืงืขื ืขื ืืืฉื ืื ืืึทืืก ืืื ืฆืืืื ืืืขืื.
ืืื ืืขืจ ืขืจืฉืืขืจ, ืขืืืขืืข ืคึผืึทืงืืฅ ืืขื ืขื ืืขืฉืืงื ืืื, ืื ืื ืืื ืืื ืึท ืกืคึผืขืกืืคืืขื ืคืึทืจืืึทืืื. ืืืึทืฉืคึผืื ืคืื ืื ืืึทืงืืืืขื ืืืืฉืึทื:
tc qdisc change dev lo root netem delay 10ms reorder 25% 50%
ืืื ืึท ืืึทืฉืืึธืขืก ืคืื 25% (ืืื ืึท ืงืึธืจืึทืืืืฉืึทื ืคืื 50%) ืื ืคึผืึทืงืึทื ืืืขื ืืืื ืืขืฉืืงื ืืื, ืื ืื ืืื ืืืขื ืืืื ืืขืฉืืงื ืืื ืึท ืคืึทืจืืึทืืื ืคืื 10 ืืืืืกืขืงืึทื ืื.
ืื ืฆืืืืืืข ืืืคึฟื ืืื ืืืขื ืืขืืขืจ ื ื ืคึผืึทืงืึทื ืืื ืืขืฉืืงื ืืืืงืขืฃ ืืื ืึท ืืขืืขืื ืืึทืฉืืึธืขืก (ืืื ืงืึธืจืึทืืืืฉืึทื), ืืื ืื ืื ืืื ืืื ืึท ืืขืืขืื ืคืึทืจืืึทืืื. ืืืึทืฉืคึผืื ืคืื ืื ืืึทืงืืืืขื ืืืืฉืึทื:
tc qdisc change dev lo root netem delay 10ms reorder 25% 50% gap 5
ืืขืืขืจ ืคืื ืคื ืคึผืขืงื ืืื ืึท 25% ืืขืืขืื ืืืึทื ืฆื ืืืื ืืขืฉืืงื ืึธื ืคืึทืจืืึทืืื.
ืืฉืึทื ืืื ื ืืึทื ืืืืืื
ืืกืืึทืืื ืืืืขืืื ืืื ืึธืคึผืฉืืงื ืฆื , ืึธืืขืจ ืืื ืืขืจ ืืืืฃ ื ืขืืขื ืืืจ ืงืขื ืขื ืืืื ืืืืฉื ืื ืฆืืืื ื ืืึทื ืืืืืื:
tc qdisc change dev lo root netem rate 56kbit
ืืขื ืงืึธืืขืงืืืื ืืืขื ืืึทืื ืืจืขืงืก ืึทืจืื ืืึธืงืึทืืืึธืกื ืืื ืืืืืืืงืืืง ืืื ืกืขืจืคืื ื ืื ืืื ืืขืจื ืขื ืืืจื ืึท ืจืขืื-ืึทืจืืืฃ ืืึธืืขื. ืืื ืึทืืืฉืึทื ืฆื ืืึทืฉืืขืืืงื ืื ืืืืจืึทืืข, ืืืจ ืงืขื ืขื ืืืื ืขืืืึทืืืื ืื ืืื ืง ืฉืืืืข ืคึผืจืึธืืึธืงืึธื ืืึธืืขื: ืฉืืขืื ืื ืึธืืืืขืจืืขื ืคึฟืึทืจ ืื ืคึผืึทืงืึทื, ืื ืฆืขื ืืจืืืก ืืื ืื ืึธืืืืขืจืืขื ืคึฟืึทืจ ืื ืฆืขื. ืคึฟืึทืจ ืืืึทืฉืคึผืื, ืืึธืก ืงืขื ืขื ืืืื ืกืืืืึทืืืืืื ืืื ืืืืจืึทืืข 56 ืงืืื / ืกืขืง:
tc qdisc change dev lo root netem rate 56kbit 0 48 5
ืกืืืืืึทืืื ื ืงืฉืจ ืืืืืึทืื
ืื ืื ืืขืจ ืืืืืืืง ืคืื ื ืืื ืื ืคึผืจืึธืืข ืคึผืืึทื ืืืขื ืึทืงืกืขืคึผืืื ื ืืืืืืืืืจื ืืื ืืืืืึทืืฅ. ืืึธืก ืืื ืืืืืืืง ืืืืึทื ืืื ืคืื ืื ืืขืจืืขืืืืื ืกืืกืืขืืขื, ืืืขื ืืืื ืขืจ ืคืื ืื ืกืขืจืืืืกืขืก ืืื ืคืึทืจืงืจืืคึผืื, ืื ืื ืืขืจืข ืืืื ืคืึทืื ืฆืืจืืง ืฆื ืื ืื ืืขืจืข ืืื ืฆืืื ืึธืืขืจ ืฆืืจืืงืงืืืขื ืึท ืืขืืช ืฆื ืืขื ืงืืืขื ื, ืืื ืืื ืงืืื ืคืึทื ืืึธื ืืื ืคืฉืื ืืขื ืืขื, ืืืืจืื ืคึฟืึทืจ ืึท ืขื ืืคืขืจ ืึธืืขืจ ืึท ืงืฉืจ ืฆื ืืืื ืืขืืจืื ืืขื.
ืขืก ืืขื ืขื ืขืืืขืืข ืืืขืื ืฆื ืืึธื ืืึธืก: ืคึฟืึทืจ ืืืึทืฉืคึผืื, ื ืืฆื ืึท ืฉืคึผืึธื ืืืึธืก ืืื ื ืืฉื ืจืืกืคึผืึทื ื, ืึธืืขืจ ืคืึทืจืืื ืื ืฆื ืืขื ืคึผืจืึธืฆืขืก ื ืืฆื ืึท ืืขืืืืืขืจ, ืฉืืขืื ืึท ืืจืืืงืคึผืืื ื ืืื ืื ืจืขืื ืึธืจื ืืื ืืึทืืื ืืขื ืคึผืจืึธืฆืขืก (ืืึธืก ืืื ืืืกืืึธืืข ืื ืืขืจืกื ืคึผืขืจืืืขืจืืื ืืืขื). ืึธืืขืจ ืืืื ืขืจ ืคืื ืื ืืขืจืกื ืงืืึธืจ ืืื ืืขืจ ืืึธื ืืื ืฆื ืคืืจืขืืืึทืื ืคึผืึธืจืฅ ืึธืืขืจ ืืื ืืช. ืขืก ืืืขื ืืื ืื ืืขืืคื ืืื ืืขื .
ืคึฟืึทืจ ืืขืืึทื ืกืืจืืืฉืึทื, ืืืจ ืืืขืื ืคืืืจืืืึทื ืคึผืึธืจื 12345 ืืื ืืืืคื ืืื ืืืขืจ ืงืืืขื ื ืฉืจืืคื. ืืืจ ืงืขื ืขื ืคืืจืขืืืึทืื ืึทืืืืึธืืื ื ืคึผืึทืงืืฅ ืฆื ืืขื ืคึผืึธืจื ืืื ืื ืกืขื ืืขืจ ืึธืืขืจ ืื ืงืึทืืื ื ืคึผืึทืงืืฅ ืืื ืื ืืคื ืขืืขืจ. ืืื ืืืื ืืืืฉืคืืื, ืื ืงืึทืืื ื ืคึผืึทืงืืฅ ืืืขื ืืืื ืคืืืจืืืึทืื (ืืืจ ื ืืฆื ืงืืื INPUT ืืื ืื ืึธืคึผืฆืืข --ืืคึผืึธืจื). ืึทืืึท ืคึผืึทืงืืฅ ืงืขื ืขื ืืืื DROP, REJECT ืึธืืขืจ REJECT ืืื ืื TCP ืคืึธื RST, ืึธืืขืจ ืืื ICMP ืืึทืืขืืึธืก ืึทื ืจืืึทืืฉืึทืืึทื (ืืื ืคืึทืงื, ืื ืคืขืืืงืืึทื ื ืึทืืืจ ืืื icmp-port-unreachable, ืืื ืขืก ืืื ืืืื ืื ืืขืืขืื ืืืื ืฆื ืฉืืงื ืึท ืขื ืืคืขืจ icmp-net-unreachable, icmp-proto-unreachable, icmp-net-prohibited ะธ icmp-host-prohibited).
ืคืึทืื
ืืืื ืขืก ืืื ืึท ืืขืจืฉื ืืื DROP, ืคึผืึทืงืืฅ ืืืขื ืคืฉืื "ืคืึทืจืฉืืืื ืื".
iptables -A INPUT -p tcp --dport 12345 -j DROP
ืืืจ ืงืึทืืขืจ ืืขื ืงืืืขื ื ืืื ืืขื ืึทื ืขืก ืคืจืืืื ืืื ืืขืจ ืืื ืข ืคืื โโืงืึทื ืขืงืืื ื ืฆื ืื ืกืขืจืืืขืจ. ืืื ืก ืงืืง ืืื ืื ืคืึทืจืงืขืจ:
ืคืึทืจืงืขืจ ืืึทืืคึผ
[user@host ~]# tcpdump -i lo -nn port 12345
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
08:28:20.213506 IP 127.0.0.1.32856 > 127.0.0.1.12345: Flags [S], seq 3019694933, win 43690, options [mss 65495,sackOK,TS val 1203046450 ecr 0,nop,wscale 7], length 0
08:28:21.215086 IP 127.0.0.1.32856 > 127.0.0.1.12345: Flags [S], seq 3019694933, win 43690, options [mss 65495,sackOK,TS val 1203047452 ecr 0,nop,wscale 7], length 0
08:28:23.219092 IP 127.0.0.1.32856 > 127.0.0.1.12345: Flags [S], seq 3019694933, win 43690, options [mss 65495,sackOK,TS val 1203049456 ecr 0,nop,wscale 7], length 0
08:28:27.227087 IP 127.0.0.1.32856 > 127.0.0.1.12345: Flags [S], seq 3019694933, win 43690, options [mss 65495,sackOK,TS val 1203053464 ecr 0,nop,wscale 7], length 0
08:28:35.235102 IP 127.0.0.1.32856 > 127.0.0.1.12345: Flags [S], seq 3019694933, win 43690, options [mss 65495,sackOK,TS val 1203061472 ecr 0,nop,wscale 7], length 0
ืขืก ืงืขื ืขื ืืืื ืืขืืขื ืึทื ืืขืจ ืงืืืขื ื ืกืขื ืื SYN ืคึผืึทืงืืฅ ืืื ืึท ืขืงืกืคึผืึธืื ืขื ืฉืึทืื ืื ืงืจืืกืื ื ืืืืืึทืื. ืึทืืื ืืืจ ืืขืคึฟืื ืขื ืึท ืงืืืื ืืฉืืง ืืื ืืขื ืงืืืขื ื: ืืืจ ืืึทืจืคึฟื ืฆื ื ืืฆื ืืขื ืืืคึฟื settimeout ()ืฆื ืืึทืืจืขื ืขืฆื ืื ืฆืืื ืืขืฉืึทืก ืืืึธืก ืืขืจ ืงืืืขื ื ืืืขื ืคึผืจืืืืจื ืฆื ืคืึทืจืืื ืื ืฆื ืื ืกืขืจืืืขืจ.
ืืืจ ืืื ืึทืจืึธืคึผื ืขืืขื ืื ืืขืจืฉื:
iptables -D INPUT -p tcp --dport 12345 -j DROPืืืจ ืงืขื ืขื ืืืกืืขืงื ืึทืืข ืึผืืืื ืืื ืึทืืึธื:
iptables -F
ืืืื ืืืจ ื ืืฆื ืืึธืงืขืจ ืืื ืืืจ ืืึทืจืคึฟื ืฆื ืคืืจืขืืืึทืื ืึทืืข ืคืึทืจืงืขืจ ืฆื ืืขื ืงืึทื ืืืื ืขืจ, ืืืจ ืงืขื ืขื ืืึธื ืืึธืก ืืื ืืืื:
iptables -I DOCKER-USER -p tcp -d CONTAINER_IP -j DROP
ืึธืคึผืืืึทืจืคื
ืืืฆื ืืึธืื ืก ืืืืื ืึท ืขื ืืขื ืืขืจืฉื, ืึธืืขืจ ืืื REJECT:
iptables -A INPUT -p tcp --dport 12345 -j REJECT
ืืขืจ ืงืืืขื ื ืืืื ืึทืจืืืก ื ืึธื ืึท ืจืืข ืืื ืึท ืืขืืช [ืขืจื ืึธ 111] ืงืฉืจ ืืคืืขืืืื. ืืื ืก ืงืืง ืืื ืื ICMP ืคืึทืจืงืขืจ:
[user@host ~]# tcpdump -i lo -nn icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
08:45:32.871414 IP 127.0.0.1 > 127.0.0.1: ICMP 127.0.0.1 tcp port 12345 unreachable, length 68
08:45:33.873097 IP 127.0.0.1 > 127.0.0.1: ICMP 127.0.0.1 tcp port 12345 unreachable, length 68
ืขืก ืงืขื ืขื ืืืื ืืขืืขื ืึทื ืืขืจ ืงืืืขื ื ืืืงืืืขื ืฆืืืื ืืึธื ืคึผืึธืจื ืึทื ืจืืืฉืึทืืึทื ืืื ืืขืืึธืื ืืขืขื ืืืงื ืืื ืึท ืืขืืช.
ืึธืคึผืืืึทืจืคื ืืื tcp-ืืึทืฉืืขืืืง
ืืื ืก ืคึผืจืืืืจื ืฆื ืืืืื ืื ืึธืคึผืฆืืข - ืึธืคึผืืืึทืจืคื-ืืื tcp-ืืึทืฉืืขืืืง:
iptables -A INPUT -p tcp --dport 12345 -j REJECT --reject-with tcp-reset
ืืื ืืขื ืคืึทื, ืืขืจ ืงืืืขื ื ืืืืื ืึทืจืืืก ืืื ืึท ืืขืืช, ืืืืึทื ืืขืจ ืขืจืฉืืขืจ ืืขืื ืืืงืืืขื ืึท RST ืคึผืึทืงืึทื:
[user@host ~]# tcpdump -i lo -nn port 12345
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
09:02:52.766175 IP 127.0.0.1.60658 > 127.0.0.1.12345: Flags [S], seq 1889460883, win 43690, options [mss 65495,sackOK,TS val 1205119003 ecr 0,nop,wscale 7], length 0
09:02:52.766184 IP 127.0.0.1.12345 > 127.0.0.1.60658: Flags [R.], seq 0, ack 1889460884, win 0, length 0
ืึธืคึผืืืึทืจืคื ืืื icmp-host-unreachable
ืืึธืืืจ ืคึผืจืืืืจื ืื ืื ืืขืจ ืึธืคึผืฆืืข ืคึฟืึทืจ ื ืืฆื REJECT:
iptables -A INPUT -p tcp --dport 12345 -j REJECT --reject-with icmp-host-unreachable
ืืขืจ ืงืืืขื ื ืืืื ืึทืจืืืก ื ืึธื ืึท ืจืืข ืืื ืึท ืืขืืช [ืขืจืจื ืึธ 113] ืงืืื ืืึทืจืฉืจืื ืฆื ืืึทืืขืืึธืก, ืืืจ ืืขื ืืื ICMP ืคืึทืจืงืขืจ ICMP ืืึธืกื 127.0.0.1 ื ืื ืจืืืฉืึทืืึทื.
ืืืจ ืงืขื ื ืืืื ืคึผืจืืืืจื ืื ืื ืืขืจืข ืึธืคึผืืืึทืจืคื ืคึผืึทืจืึทืืขืืขืจืก, ืืื ืืื ืืืขื ืคืึธืงืืก ืืืืฃ ืื :)
ืกืืืืืึทืืื ื ืืขืื ืืืืืึทืื
ืื ืื ืืขืจ ืกืืืืึทืฆืืข ืืื ืืืขื ืืขืจ ืงืืืขื ื ืืื ืืืืืืช ืฆื ืคืึทืจืืื ืื ืฆื ืื ืกืขืจืืืขืจ, ืึธืืขืจ ืงืขื ื ืืฉื ืฉืืงื ืึท ืืงืฉื ืฆื ืืื. ืืื ืฆื ืคืืืืขืจ ืคึผืึทืงืืฅ ืึทืืื ืึทื ืคืืืืขืจืื ื ืืื ื ืืฉื ืึธื ืืืืื ืืื? ืืืื ืืืจ ืงืืง ืืื ืื ืคืึทืจืงืขืจ ืคืื ืงืืื ืงืึธืืื ืืงืึทืฆืืข ืฆืืืืฉื ืืขื ืงืืืขื ื ืืื ืื ืกืขืจืืืขืจ, ืืืจ ืืืขื ืืึทืืขืจืงื ืึทื ืืืขื ืืจืื ืื ืึท ืคึฟืึทืจืืื ืืื ื, ืืืืื ืื SYN ืืื ACK ืคืืึทืืก ืืขื ืขื ืืขื ืืฆื, ืึธืืขืจ ืืืขื ืื ืืงืกืืฉืืื ืืืฉืื ื ืืึทืื, ืื ืืขืฆืืข ืืขืื ืคึผืึทืงืึทื ืืืขื ืึทื ืืืึทืืื ืื PSH ืคืึธื. ืขืก ืื ืกืืึธืื ืืืืืึธืืึทืืืฉ ืฆื ืืืกืืืืื ืืึทืคืขืจืื ื. ืืืจ ืงืขื ืขื ื ืืฆื ืืขื ืืื ืคึฟืึธืจืืึทืฆืืข ืฆื ืฉืึทืคึฟื ืึท ืคืืืืขืจ: ืขืก ืืืขื ืืึธืื ืึทืืข ืคึผืึทืงืืฅ ืึทืืืฅ ืื ืืื ืื PSH ืคืึธื. ืืืื, ืืขืจ ืงืฉืจ ืืืขื ืืืื ืืขืืจืื ืืขื, ืึธืืขืจ ืืขืจ ืงืืืขื ื ืืืขื ื ืืฉื ืงืขื ืขื ืฆื ืฉืืงื ืืึทืื ืฆื ืื ืกืขืจืืืขืจ.
ืคืึทืื
ืคึฟืึทืจ DROP ืื ืืึทืคึฟืขื ืืืขื ืงืืงื ืืื ืืึธืก:
iptables -A INPUT -p tcp --tcp-flags PSH PSH --dport 12345 -j DROP
ืงืึทืืขืจ ืืขื ืงืืืขื ื ืืื ืืืื ืื ืคืึทืจืงืขืจ:
ืคืึทืจืงืขืจ ืืึทืืคึผ
[user@host ~]# tcpdump -i lo -nn port 12345
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
10:02:47.549498 IP 127.0.0.1.49594 > 127.0.0.1.12345: Flags [S], seq 2166014137, win 43690, options [mss 65495,sackOK,TS val 1208713786 ecr 0,nop,wscale 7], length 0
10:02:47.549510 IP 127.0.0.1.12345 > 127.0.0.1.49594: Flags [S.], seq 2341799088, ack 2166014138, win 43690, options [mss 65495,sackOK,TS val 1208713786 ecr 1208713786,nop,wscale 7], length 0
10:02:47.549520 IP 127.0.0.1.49594 > 127.0.0.1.12345: Flags [.], ack 1, win 342, options [nop,nop,TS val 1208713786 ecr 1208713786], length 0
10:02:47.549568 IP 127.0.0.1.49594 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 1208713786 ecr 1208713786], length 5
10:02:47.750084 IP 127.0.0.1.49594 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 1208713987 ecr 1208713786], length 5
10:02:47.951088 IP 127.0.0.1.49594 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 1208714188 ecr 1208713786], length 5
10:02:48.354089 IP 127.0.0.1.49594 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 1208714591 ecr 1208713786], length 5
ืืืจ ืืขื ืึทื ืืขืจ ืงืฉืจ ืืื ืืขืืจืื ืืขื ืืื ืืขืจ ืงืืืขื ื ืงืขื ื ืืฉื ืฉืืงื ืืึทืื ืฆื ืื ืกืขืจืืืขืจ.
ืึธืคึผืืืึทืจืคื
ืืื ืืขื ืคืึทื, ืื ื ืึทืืืจ ืืืขื ืืืื ืื ืืขืืืข: ืืขืจ ืงืืืขื ื ืืืขื ื ืืฉื ืงืขื ืขื ืฆื ืฉืืงื ืื ืืงืฉื, ืึธืืขืจ ืืืขื ืืึทืงืืืขื ICMP 127.0.0.1 tcp ืคึผืึธืจื 12345 ืึทื ืจืืึทืืฉืึทืืึทื ืืื ืคืึทืจืืจืขืกืขืจื ืื ืฆืืื ืฆืืืืฉื ืจืืกืืืื ื ืืขืื ืขืงืกืคึผืึธืื ืขื ืฉืึทืื. ืืขืจ ืืึทืคึฟืขื ืงืืงื ืืื ืืึธืก:
iptables -A INPUT -p tcp --tcp-flags PSH PSH --dport 12345 -j REJECT
ืึธืคึผืืืึทืจืคื ืืื tcp-ืืึทืฉืืขืืืง
ืืขืจ ืืึทืคึฟืขื ืงืืงื ืืื ืืึธืก:
iptables -A INPUT -p tcp --tcp-flags PSH PSH --dport 12345 -j REJECT --reject-with tcp-reset
ืืืจ ืฉืืื ืืืืกื ืึทื ืืืขื ื ืืฆื - ืึธืคึผืืืึทืจืคื-ืืื tcp-ืืึทืฉืืขืืืง ืืขืจ ืงืืืขื ื ืืืขื ืืึทืงืืืขื ืึท RST ืคึผืึทืงืึทื ืืื ืขื ืืคืขืจ, ืึทืืื ืื ื ืึทืืืจ ืงืขื ืขื ืืืื ืคึผืจืขืืืงืืขื: ืจืืกืืืืื ื ืึท RST ืคึผืึทืงืึทื ืืฉืขืช ืื ืคึฟืึทืจืืื ืืื ื ืืื ืืขืืจืื ืืขื ืืืื ืึทื ืื ืืึธืืขื ืืื ืืืืืขืจืืื ืคึฟืึทืจืืึทืื ืืืืฃ ืื ืื ืืขืจืข ืืืึทื, ืืืึธืก ืืืื ืึทื ืืขืจ ืงืืืขื ื ืืึธื ืืึทืงืืืขื ืงืฉืจ ืืึทืฉืืขืืืง ืืืจื ืืึทื ืงืืงื . ืืึธืืืจ ืืืืคื ืืื ืืืขืจ ืฉืจืืคื ืืื ืืึทืื ืืืืขืจ ืคืื ืืขื. ืืื ืืึธืก ืืื ืืืึธืก ืืขืจ ืคืึทืจืงืขืจ ืืืขื ืงืืงื ืืื:
ืคืึทืจืงืขืจ ืืึทืืคึผ
[user@host ~]# tcpdump -i lo -nn port 12345
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
10:22:14.186269 IP 127.0.0.1.52536 > 127.0.0.1.12345: Flags [S], seq 2615137531, win 43690, options [mss 65495,sackOK,TS val 1209880423 ecr 0,nop,wscale 7], length 0
10:22:14.186284 IP 127.0.0.1.12345 > 127.0.0.1.52536: Flags [S.], seq 3999904809, ack 2615137532, win 43690, options [mss 65495,sackOK,TS val 1209880423 ecr 1209880423,nop,wscale 7], length 0
10:22:14.186293 IP 127.0.0.1.52536 > 127.0.0.1.12345: Flags [.], ack 1, win 342, options [nop,nop,TS val 1209880423 ecr 1209880423], length 0
10:22:14.186338 IP 127.0.0.1.52536 > 127.0.0.1.12345: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 1209880423 ecr 1209880423], length 5
10:22:14.186344 IP 127.0.0.1.12345 > 127.0.0.1.52536: Flags [R], seq 3999904810, win 0, length 0
ืึธืคึผืืืึทืจืคื ืืื icmp-host-unreachable
ืืื ืืจืึทืืื ืขืก ืืื ืฉืืื ืงืืึธืจ ืืื ืืขืจ ืืึธื ืคึฟืึทืจ ืึทืืขืืขื ืืื ืื ืืึทืคึฟืขื ืืืขื ืงืืงื ืืื :) ืืขืจ ืึธืคึผืคืืจืื ื ืคืื ืืขื ืงืืืขื ื ืืื ืืขื ืคืึทื ืืืขื ืืืื ืึท ืืืกื ืึทื ืืขืจืฉ ืคืื ืืขื ืืื ืึท ืคึผืฉืื ืึธืคึผืืืึทืจืคื: ืืขืจ ืงืืืขื ื ืืืขื ื ืืฉื ืคืึทืจืืจืขืกืขืจื ืื ืืืืืึทืื ืฆืืืืฉื ืคืจืืืื ืฆื ืฉืืงื ืื ืคึผืึทืงืึทื ืืืืืขืจ.
[user@host ~]# tcpdump -i lo -nn icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
10:29:56.149202 IP 127.0.0.1 > 127.0.0.1: ICMP host 127.0.0.1 unreachable, length 65
10:29:56.349107 IP 127.0.0.1 > 127.0.0.1: ICMP host 127.0.0.1 unreachable, length 65
10:29:56.549117 IP 127.0.0.1 > 127.0.0.1: ICMP host 127.0.0.1 unreachable, length 65
10:29:56.750125 IP 127.0.0.1 > 127.0.0.1: ICMP host 127.0.0.1 unreachable, length 65
10:29:56.951130 IP 127.0.0.1 > 127.0.0.1: ICMP host 127.0.0.1 unreachable, length 65
10:29:57.152107 IP 127.0.0.1 > 127.0.0.1: ICMP host 127.0.0.1 unreachable, length 65
10:29:57.353115 IP 127.0.0.1 > 127.0.0.1: ICMP host 127.0.0.1 unreachable, length 65
ืจืขืืืืืึทื
ืขืก ืืื ื ืื ื ืืืืืง ืฆื ืฉืจืืึทืื ืึท ืจืืืฆื ืฆื ืคึผืจืืืืจื ืื ืื ืืขืจืึทืงืฉืึทื ืคืื ืึท ืืื ืกื ืืื ืึท ืืขืืื ืืขื ืงืืืขื ื ืึธืืขืจ ืกืขืจืืืขืจ; ืืื ืขืก ืืื ืืขื ืื ืฆื ื ืืฆื ื ืึธืจืืึทื ืืืืืืึทืืื ืืขืคึฟืื ืขื ืืื ืืื ืืงืก.
ืื ืืืืืืึทืืื ืืืกืงืึทืกื ืืื ืืขื ืึทืจืืืงื ืืึธืื ืืคืืื ืืขืจ ืงืืืคึผืึทืืืืึทืืื ืืื ืืืกืงืจืืืื, ืึทืืื ืืืจ ืงืขื ืขื ืงืืืขื ืึทืจืืืฃ ืืื ืขืืืขืืข ืคืื โโืืืื ืืืืืขื ืข ืึธืคึผืฆืืขืก ืคึฟืึทืจ ื ืืฆื ืืื. ืคึผืขืจืกื ืึทืื, ืืื ืฉืืขื ืืืง ืืึธืื ืืขื ืื ืคืื ืืืึธืก ืืื ืืขืฉืจืืื ืืืขืื (ืืื ืคืึทืงื, ืืคืืื ืืืืื ืืงืขืจ). ืืืื ืืืจ ื ืืฆื ืื ืึธืืขืจ ืขื ืืขื ืืืืืืึทืืื ืืื ืืขืกืืื ื ืืื ืืืื ืคืืจืืข, ืืืืข ืฉืจืืึทืื ืืื ืคึผืื ืงื. ืืืื ื ืืฉื, ืืื ืืึธืคึฟื ืึทื ืืืื ืืืืืืืืืจื ืืืขื ืืืื ืืขืกืขืจ ืืืื ืืืจ ืืึทืฉืืืกื ืฆื ืคึผืจืืืืจื ืขืก ืืื ืืขืจืืื ืขื ืคืื ื ืขืฅ ืคึผืจืึธืืืขืืก ืืื ืื ืกืึทืืืืฉืขืกืืื ืืขืืืึธืืก.
ืืงืืจ: www.habr.com