Mhoroi mose, zita rangu ndinonzi Sasha, ndinotungamira kuyedza kumashure kuFunCorp. Isu, sevamwe vazhinji, takaita architecture yakanangana nebasa. Kune rimwe divi, izvi zvinorerutsa basa, nekuti... Zviri nyore kuyedza sevhisi yega yega, asi kune rumwe rutivi, pane kudikanwa kwekuyedza kudyidzana kwesevhisi kune mumwe nemumwe, izvo zvinowanzoitika pane network.
Muchikamu chino, ini ndichataura nezve maviri ekushandisa anogona kushandiswa kutarisa ekutanga mamiriro anotsanangura kushanda kwechikumbiro pamberi pematambudziko etiweki.
Kutevedzera matambudziko etiweki
Kazhinji, software inoedzwa pamaseva ebvunzo ane yakanaka Internet yekubatanidza. Munzvimbo dzakaomarara dzekugadzira, zvinhu zvinogona kunge zvisiri kutsetseka, saka dzimwe nguva unofanirwa kuyedza zvirongwa mumamiriro asina kunaka ekubatanidza. PaLinux, iyo yekushandisa ichabatsira nebasa rekuenzanisa mamiriro akadaro tc.
tc(abbr. kubva kuTraffic Control) inobvumidza iwe kugadzirisa kutapurirana kwetiweki mapaketi muhurongwa. Ichi chishandiso chine kugona kukuru, unogona kuverenga zvakawanda nezvavo . Pano ini ndichafunga zvishoma zvacho: isu tinofarira kurongeka kwetraffic, kwatinoshandisa qdisc, uye sezvo tichida kutevedzera network isina kugadzikana, isu tichashandisa classless qdisc .
Ngatitangei echo server pane server (ndakashandisa ):
ncat -l 127.0.0.1 12345 -k -c 'xargs -n1 -i echo "Response: {}"'
Kuti ndiratidze zvakadzama matimestamps pane imwe neimwe nhanho yekudyidzana pakati pemutengi neserver, ndakanyora iri nyore Python script inotumira chikumbiro. bvunzo kune yedu echo server.
Client source code
#!/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
Ngatitangei uye titarise traffic pane iyo interface lo uye port 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
Traffic dump
[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
Zvese zvakajairwa: kubatwa kwemaoko-matatu, PSH/ACK uye ACK mukupindura kaviri - uku ndiko kuchinjana kwekukumbira uye mhinduro pakati pemutengi neserver, uye FIN/ACK uye ACK kaviri - kupedzisa kubatana.
Packet kunonoka
Zvino ngatiise kunonoka ku500 milliseconds:
tc qdisc add dev lo root netem delay 500ms
Isu tinovhura mutengi uye toona kuti script ikozvino inomhanya kwemasekonzi maviri:
[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
Chii chiri mumotokari? Ngatitarisei:
Traffic dump
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
Iwe unogona kuona kuti iyo inotarisirwa lag yehafu yechipiri yakaonekwa mukudyidzana pakati pemutengi neserver. Iyo sisitimu inoita zvakanyanya kunakidza kana iyo lag yakakura: iyo kernel inotanga kutumira mamwe TCP mapaketi. Ngatichinje kunonoka kuita 1 sekondi uye titarise traffic (ini handisi kuzoratidza kuburitswa kwemutengi, pane zvinotarisirwa masekonzi mana muhuwandu hwenguva):
tc qdisc change dev lo root netem delay 1s
Traffic dump
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
Zvinogona kuoneka kuti mutengi akatumira SYN pakiti kaviri, uye sevha yakatumira SYN/ACK kaviri.
Mukuwedzera kune kukosha kwekugara, kunonoka kunogona kuiswa kune kutsauka, basa rekugovera, uye kuwirirana (nekukosha kwepakiti yapfuura). Izvi zvinoitwa sezvinotevera:
tc qdisc change dev lo root netem delay 500ms 400ms 50 distribution normal
Pano takaisa kunonoka pakati pe100 ne900 milliseconds, kukosha kuchasarudzwa zvichienderana nekugoverwa kwakajairika uye pachave ne50% kuwirirana nekunonoka kukosha kwepakeji yapfuura.
Iwe unogona kunge wakacherechedza kuti mumurairo wekutanga wandakashandisa wedzera, ndokuzo chinja. Zvinorehwa nemirairo iyi zviri pachena, saka ini ndinongowedzera kuti pane zvimwe Del, iyo inogona kushandiswa kubvisa kugadzirisa.
Packet Loss
Ngatiedzei kuita kurasikirwa kwepaketi. Sezvinoonekwa kubva muzvinyorwa, izvi zvinogona kuitwa nenzira nhatu: kurasikirwa mapaketi zvisina tsarukano neimwe mukana, uchishandisa Markov cheni ye2, 3 kana 4 inoti kuverenga kurasikirwa kwepaketi, kana kushandisa Elliott-Gilbert modhi. Muchinyorwa ini ndichafunga yekutanga (yakapusa uye yakajeka) nzira, uye iwe unogona kuverenga nezve vamwe .
Ngatiitei kurasikirwa kwe50% yemapaketi ane kuwirirana kwe25%:
tc qdisc add dev lo root netem loss 50% 25%
Nhamo, tcpdump hazvizokwanisi kutiratidza zvakajeka kurasikirwa kwepakiti, isu tichangofunga kuti inoshanda chaizvo. Uye iyo yakawedzera uye isina kugadzikana yekumhanya nguva yescript ichatibatsira kuona izvi. client.py (inogona kupedzwa ipapo ipapo, kana pamwe mumasekonzi makumi maviri), pamwe nenhamba yakawedzera yemapaketi anotumirwazve:
[user@host ~]# netstat -s | grep retransmited; sleep 10; netstat -s | grep retransmited
17147 segments retransmited
17185 segments retransmited
Kuwedzera ruzha kumapakiti
Pamusoro pekurasikirwa kwepaketi, unogona kutevedzera kukuvadzwa kwepaketi: ruzha ruchaonekwa panzvimbo isina kujairika packet. Ngatiitei kukuvara kwepaketi ne50% mukana uye pasina kuwirirana:
tc qdisc change dev lo root netem corrupt 50%
Isu tinomhanyisa script yemutengi (hapana chinonakidza ipapo, asi zvakatora masekondi maviri kuti apedze), tarisa traffic:
Traffic dump
[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
Zvinogona kuoneka kuti mamwe mapaketi akatumirwa kakawanda uye kune imwe pakiti ine metadata yakaputsika: sarudzo [nop, isingazivikanwe-65 0x0a3dcf62eb3d,[yakaipa opt]>. Asi chinhu chikuru ndechokuti pakupedzisira zvose akashanda zvakanaka - TCP kutsungirira basa rayo.
Packet kudzokorodza
Chii chimwe chaungaita nacho netem? Semuyenzaniso, tevedzera mamiriro ekudzokera kumashure ekurasikirwa kwepaketi- kudzokorora kwepaketi. Uyu murairo unotorawo nharo mbiri: mukana uye kuwirirana.
tc qdisc change dev lo root netem duplicate 50% 25%
Kuchinja kurongeka kwemapakeji
Iwe unogona kusanganisa mabhegi nenzira mbiri.
Mukutanga, mamwe mapaketi anotumirwa pakarepo, mamwe acho nekunonoka kwakataurwa. Muenzaniso kubva pane zvinyorwa:
tc qdisc change dev lo root netem delay 10ms reorder 25% 50%
Nekukwanisa kwe25% (uye kuwirirana kwe50%) pakiti ichatumirwa pakarepo, mamwe ose achatumirwa nekunonoka kwe10 milliseconds.
Yechipiri nzira ndeye apo yega yega pakiti yeNth inotumirwa ipapo paine mukana wakapihwa (uye kuwirirana), uye imwe yese nekunonoka kwakapihwa. Muenzaniso kubva pane zvinyorwa:
tc qdisc change dev lo root netem delay 10ms reorder 25% 50% gap 5
Yese yechishanu package ine 25% mukana wekutumirwa pasina kunonoka.
Kuchinja Bandwidth
Kazhinji kwese kwavanoreva , asi norubatsiro netem Iwe unogona zvakare kushandura iyo interface bandwidth:
tc qdisc change dev lo root netem rate 56kbit
Chikwata ichi chichafamba nzendo localhost zvinorwadza sekusevha paInternet uchishandisa dial-up modem. Pamusoro pekuseta bitrate, iwe unogona zvakare kutevedzera iyo link layer protocol modhi: isa iyo yepamusoro yepaketi, saizi yesero, uye pamusoro pesero. Somuenzaniso, izvi zvinogona kuenzaniswa uye bitrate 56 kbit/sec:
tc qdisc change dev lo root netem rate 56kbit 0 48 5
Simulating yekubatanidza nguva
Imwe pfungwa yakakosha muchirongwa chekuyedza kana uchigamuchira software ndeye nguva yekubuda. Izvi zvakakosha nekuti mumasevhisi akagoverwa, kana rimwe remasevhisi rakaremara, mamwe anofanirwa kudzokera kune mamwe nenguva kana kudzorera kukanganisa kune mutengi, uye hapana kana mhosva vangangorembera, vakamirira mhinduro kana kubatana. kusimbiswa.
Pane nzira dzakati wandei dzekuita izvi: semuenzaniso, shandisa chiseko chisingapindure, kana kubatanidza kune iyo nzira uchishandisa debugger, isa nzvimbo yekutyora panzvimbo chaiyo uye kumisa maitiro (iyi ingangove nzira yakatsveyama). Asi imwe yeanonyanya kujeka ndeye firewall ports kana mauto. Zvichatibatsira izvi .
Nekuratidzira, isu tichava firewall port 12345 uye tomhanyisa mutengi script. Iwe unogona firewall inobuda mapaketi kune ino chiteshi kune anotumira kana mapakeji anouya pane anogamuchira. Mumienzaniso yangu, mapakeji anouya achave akadzimwa moto (tinoshandisa cheni INPUT uye sarudzo --dport) Mapaketi akadai anogona kuDHARA, KURAMBA kana KURAMBA neTCP mureza RST, kana neICMP host isingasvikike (chaizvoizvo, maitiro akasarudzika ndeaya. icmp-port-isingasvikike, uye panewo mukana wekutumira mhinduro icmp-net-isingasvikike, icmp-proto-isingasvikike, icmp-net-inorambidzwa ΠΈ icmp-host-yakarambidzwa).
DONHEDZA
Kana paine mutemo une DROP, mapaketi anongo "nyangarika".
iptables -A INPUT -p tcp --dport 12345 -j DROP
Isu tinovhura mutengi uye tinoona kuti inotonhora padanho rekubatanidza kune server. Ngatitarisei traffic:
Traffic dump
[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
Zvinogona kuoneka kuti mutengi anotumira SYN mapaketi ane exponentially inowedzera nguva yekubuda. Saka isu takawana diki bug mumutengi: unofanirwa kushandisa nzira settimeout()kuderedza nguva iyo mutengi achaedza kubatanidza kune server.
Isu tinobva tabvisa mutemo:
iptables -D INPUT -p tcp --dport 12345 -j DROPUnogona kudzima mitemo yese kamwechete:
iptables -F
Kana iwe uri kushandisa Docker uye iwe unofanirwa firewall traffic yese inoenda kumudziyo, saka unogona kuzviita seinotevera:
iptables -I DOCKER-USER -p tcp -d CONTAINER_IP -j DROP
RUDZA
Zvino ngatiwedzerei mutemo wakafanana, asi neREJECT:
iptables -A INPUT -p tcp --dport 12345 -j REJECT
Mutengi anobuda mushure mesekondi aine chikanganiso [Errno 111] Kubatana kwaramba. Ngatitarisei iyo ICMP traffic:
[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
Zvinogona kuonekwa kuti mutengi akagamuchira kaviri chiteshi hachisvikiki ndokuzopedzisira nekukanganisa.
RAMBA ne tcp-reset
Ngatiedzei kuwedzera sarudzo --ramba-ne tcp-reset:
iptables -A INPUT -p tcp --dport 12345 -j REJECT --reject-with tcp-reset
Muchiitiko ichi, mutengi anobva angobuda nekukanganisa, nekuti chikumbiro chekutanga chakagamuchira RST packet:
[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
RAMBA ne icmp-host-isingasvikike
Ngatiedze imwe sarudzo yekushandisa REJECT:
iptables -A INPUT -p tcp --dport 12345 -j REJECT --reject-with icmp-host-unreachable
Mutengi anobuda mushure mesekondi aine chikanganiso [Errno 113] Hapana nzira yekugamuchira, tinoona mu ICMP traffic ICMP host 127.0.0.1 isingasvikike.
Iwe unogona zvakare kuedza mamwe RAVA paramita, uye ini ndichatarisa pane izvi :)
Kutevedzera nguva yekukumbira
Imwe mamiriro ndeye apo mutengi akakwanisa kubatana neserver, asi haakwanise kutumira chikumbiro kwairi. Maitiro ekusefa mapaketi kuitira kuti kusefa kusatanga nekukasira? Kana iwe ukatarisa traffic yechero kutaurirana pakati pemutengi uye sevha, iwe uchaona kuti kana uchigadzira kubatana, chete SYN uye ACK mireza inoshandiswa, asi kana uchitsinhana data, yekupedzisira chikumbiro packet ichava nePSH mureza. Inoisa otomatiki kudzivirira kubhafa. Iwe unogona kushandisa ruzivo urwu kugadzira sefa: inobvumira ese mapaketi kunze kweaya ane PSH mureza. Nokudaro, kubatana kuchasimbiswa, asi mutengi haazokwanisi kutumira data kune server.
DONHEDZA
Kune DROP murairo waizotaridzika seizvi:
iptables -A INPUT -p tcp --tcp-flags PSH PSH --dport 12345 -j DROP
Vhura mutengi uye tarisa traffic:
Traffic dump
[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
Isu tinoona kuti kubatana kwakasimbiswa uye mutengi haakwanise kutumira data kune server.
RUDZA
Muchiitiko ichi maitiro achave akafanana: mutengi haazokwanisi kutumira chikumbiro, asi achagamuchira ICMP 127.0.0.1 tcp port 12345 isingasvikiki uye wedzera nguva pakati pekukumbirazve kutumirwa zvakare exponentially. Murairo unotaridzika seizvi:
iptables -A INPUT -p tcp --tcp-flags PSH PSH --dport 12345 -j REJECT
RAMBA ne tcp-reset
Murairo unotaridzika seizvi:
iptables -A INPUT -p tcp --tcp-flags PSH PSH --dport 12345 -j REJECT --reject-with tcp-reset
Isu tinotoziva izvozvo kana tichishandisa --ramba-ne tcp-reset mutengi anogashira RST packet mukupindura, saka maitiro anogona kufanotaurwa: kugamuchira RST packet apo kubatana kwasimbiswa zvinoreva socket yakavharwa zvisingatarisirwi kune rimwe divi, zvinoreva kuti mutengi anofanira kugamuchira. Kubatana kwakagadziriswazve nevezera. Ngatimhanyei script yedu uye tive nechokwadi cheizvi. Uye izvi ndizvo zvichange zvakaita traffic:
Traffic dump
[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
RAMBA ne icmp-host-isingasvikike
Ndinofunga kuti zvatove pachena kune wese kuti murairo uchaita sei :) Muitiro wemutengi munyaya iyi uchave wakasiyana zvishoma kubva kune iyo iri nyore REJECT: mutengi haazowedzera nguva pakati pekuedza kutumirazve pakiti.
[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
mhedziso
Izvo hazvifanirwe kunyora kunyomba kuti uedze kudyidzana kwesevhisi neakarembera mutengi kana sevha; dzimwe nguva zvakakwana kushandisa zvakajairwa zvinoshandiswa zvinowanikwa muLinux.
Zvishandiso zvinokurukurwa muchinyorwa zvinotonyanya kugona kupfuura zvakatsanangurwa, saka unogona kuunza dzimwe sarudzo dzako dzekuzvishandisa. Ini pachangu, ndinogara ndine zvakakwana pane zvandakanyora nezvazvo (chaizvoizvo, kunyange zvishoma). Kana iwe ukashandisa izvi kana zvakafanana zvinoshandiswa mukuyedza mukambani yako, ndapota nyora kuti sei chaizvo. Kana zvisina kudaro, saka ndinovimba kuti software yako ichaita nani kana ukafunga kuiyedza mumamiriro ematambudziko etiweki uchishandisa nzira dzakakurudzirwa.
Source: www.habr.com