{"id":95716,"date":"2020-10-02T01:42:50","date_gmt":"2020-10-01T23:42:50","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/inicziativa-dns-flag-day-2020-dlya-resheniya-problem-s-fragmentacziej-i-podderzhkoj-tcp"},"modified":"2020-10-02T01:42:50","modified_gmt":"2020-10-01T23:42:50","slug":"inicziativa-dns-flag-day-2020-dlya-resheniya-problem-s-fragmentacziej-i-podderzhkoj-tcp","status":"publish","type":"post","link":"https:\/\/prohoster.info\/hu\/blog\/news\/inicziativa-dns-flag-day-2020-dlya-resheniya-problem-s-fragmentacziej-i-podderzhkoj-tcp","title":{"rendered":"A DNS flag day 2020 kezdem\u00e9nyez\u00e9s a fragment\u00e1ci\u00f3s probl\u00e9m\u00e1k \u00e9s a TCP t\u00e1mogat\u00e1s megold\u00e1s\u00e1ra","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Ma sz\u00e1mos nagy DNS-szolg\u00e1ltat\u00f3 \u00e9s DNS-szerver gy\u00e1rt\u00f3 k\u00f6z\u00f6s esem\u00e9nyt tart DNS flag day 2020<\/a><\/noindex>, amely a figyelmet a megold\u00e1sra<\/a><\/noindex> probl\u00e9m\u00e1kra<\/a><\/noindex> IP-fragment\u00e1ci\u00f3 DNS \u00fczenetek nagy m\u00e9ret\u0171 feldolgoz\u00e1sa sor\u00e1n. Ez a m\u00e1sodik hasonl\u00f3 esem\u00e9ny, tavaly t\u00f6rt\u00e9nt a «DNS flag day». a helyes EDNS-k\u00e9relmek feldolgoz\u00e1s\u00e1ra \u00f6sszpontos\u00edtott.<\/a><\/noindex> A DNS flag day 2020 kezdem\u00e9nyez\u00e9s r\u00e9sztvev\u0151i arra k\u00e9rik, hogy r\u00f6gz\u00edts\u00e9k az EDNS-hez aj\u00e1nlott pufferm\u00e9reteket 1232 byte-ra (az MTU 1280 minusz 48 byte a fejl\u00e9cekhez), \u00e9s <\/p>\n

tegy\u00e9k k\u00f6telez\u0151v\u00e9 a TCP-n kereszt\u00fcli k\u00e9relmek feldolgoz\u00e1s\u00e1t a szerverek sz\u00e1m\u00e1ra. Az<\/a><\/noindex> RFC 1035 csak az UDP-k\u00e9relmek feldolgoz\u00e1s\u00e1nak t\u00e1mogat\u00e1s\u00e1t jel\u00f6li k\u00f6telez\u0151nek, m\u00edg a TCP-t k\u00edv\u00e1natosnak, de nem k\u00f6telez\u0151nek tekinti a m\u0171k\u00f6d\u00e9shez. Az \u00faj<\/a><\/noindex> RFC 7766 RFC 5966<\/a><\/noindex> \u00e9s kifejezetten a TCP-t az DNS helyes m\u0171k\u00f6d\u00e9s\u00e9hez sz\u00fcks\u00e9ges k\u00f6telez\u0151 funkci\u00f3k k\u00f6z\u00e9 sorolj\u00e1k. A kezdem\u00e9nyez\u00e9s keretein bel\u00fcl azt javasolj\u00e1k, hogy k\u00e9nyszer\u00edts\u00e9k a UDP-n k\u00fcld\u00f6tt k\u00e9relmekr\u0151l a TCP haszn\u00e1lat\u00e1ra val\u00f3 \u00e1tt\u00e9r\u00e9st, ha az EDNS pufferm\u00e9rete nem elegend\u0151.<\/a><\/noindex> A javasolt v\u00e1ltoz\u00e1sok megsz\u00fcntetik a z\u0171rzavart az EDNS pufferm\u00e9ret\u00e9nek megv\u00e1laszt\u00e1s\u00e1val kapcsolatban, \u00e9s megoldj\u00e1k a nagy UDP-\u00fczenetek fragment\u00e1l\u00e1s\u00e1nak probl\u00e9m\u00e1it, amelyek sok esetben csomagveszt\u00e9shez \u00e9s id\u0151t\u00fall\u00e9p\u00e9shez vezetnek az \u00fcgyf\u00e9l oldal\u00e1n. Az \u00fcgyf\u00e9ln\u00e9l az EDNS pufferm\u00e9ret \u00e1lland\u00f3 lesz, \u00e9s a nagy v\u00e1laszok azonnal TCP-n kereszt\u00fcl ker\u00fclnek elk\u00fcld\u00e9sre az \u00fcgyf\u00e9lnek. A nagy \u00fczenetek UDP-n val\u00f3 k\u00fcld\u00e9s\u00e9nek kiz\u00e1r\u00e1sa szint\u00e9n megoldja a nagy csomagok egyes t\u0171zfalakon t\u00f6rt\u00e9n\u0151 eldob\u00e1s\u00e1val kapcsolatos probl\u00e9m\u00e1kat, \u00e9s lehet\u0151v\u00e9 teszi a DNS-gyors\u00edt\u00f3t\u00e1r-t\u00f6lt\u00e9s t\u00e1mad\u00e1sok blokkol\u00e1s\u00e1t, amelyek fragment\u00e1lt UDP-csomagok manipul\u00e1ci\u00f3j\u00e1n alapulnak (a fragment\u00e1ci\u00f3n\u00e1l a m\u00e1sodik fragmentum nem tartalmazza az azonos\u00edt\u00f3t, \u00edgy hamis\u00edthat\u00f3, el\u00e9g, ha a checksum egyezik).<\/p>\n

A kezdem\u00e9nyez\u00e9sben r\u00e9szt vev\u0151 DNS-szolg\u00e1ltat\u00f3k, bele\u00e9rtve a CloudFlaret, Quad 9-et, a Cisco-t (OpenDNS) \u00e9s a Google-t, kezdve a mai napt\u00f3l fokozatosan v\u00e1ltanak U1.1.9.6. A t\u00e1mad\u00f3k a hiteles\u00edt\u0151 adatok billenty\u0171zeten val\u00f3 be\u00edr\u00e1s\u00e1t a billenty\u0171k megnyom\u00e1s\u00e1nak hangj\u00e1nak elemz\u00e9s\u00e9vel figyelt\u00e9k meg.<\/a><\/noindex> DNS gyors\u00edt\u00f3t\u00e1r\u00e1nak megfert\u0151z\u00e9s\u00e9r\u0151l, amely a fragment\u00e1lt UDP-csomagok manipul\u00e1l\u00e1s\u00e1n alapul (fragment\u00e1l\u00e1s sor\u00e1n a m\u00e1sodik fragment nem tartalmazza az azonos\u00edt\u00f3 fejl\u00e9cet, ez\u00e9rt hamis\u00edtani lehet, csak a checksumnak kell egyeznie).<\/p>\n

A DNS-kezdem\u00e9nyez\u00e9s r\u00e9sztvev\u0151i m\u00e1ra k\u00f6z\u00f6s esem\u00e9nyt tartanak, amelyen a Cloudflare, Quad 9, Cisco (OpenDNS) \u00e9s Google fokozatosan v\u00e1ltanak \u00e1t<\/a><\/noindex> Az EDNS pufferm\u00e9ret cs\u00f6kkent\u00e9se 4096 b\u00e1jr\u00f3l 1232 b\u00e1jtra a DNS-kiszolg\u00e1l\u00f3ikon (az EDNS m\u00f3dos\u00edt\u00e1sa 4-6 h\u00e9t alatt t\u00f6rt\u00e9nik, \u00e9s id\u0151vel egyre t\u00f6bb lek\u00e9rdez\u00e9st \u00e9rint). A UDP lek\u00e9rdez\u00e9sek v\u00e1lasza, amelyek nem felelnek meg az \u00faj korl\u00e1toz\u00e1snak, TCP-n kereszt\u00fcl ker\u00fclnek elk\u00fcld\u00e9sre. A DNS-kiszolg\u00e1l\u00f3 gy\u00e1rt\u00f3k, bele\u00e9rtve a BIND, Unbound, Knot, NSD \u00e9s PowerDNS-t, friss\u00edt\u00e9seket bocs\u00e1tanak ki az EDNS pufferm\u00e9ret\u00e9nek alap\u00e9rtelmezett cs\u00f6kkent\u00e9s\u00e9r\u0151l 4096 b\u00e1jr\u00f3l 1232 b\u00e1jtra. <\/p>\n

V\u00e9gs\u0151 soron a bevezetett v\u00e1ltoz\u00e1sok probl\u00e9m\u00e1khoz vezethetnek a DNS-szerverek el\u00e9r\u00e9s\u00e9ben, amelyek UDP-n kereszt\u00fcl 1232 b\u00e1jtot meghalad\u00f3 DNS-v\u00e1laszokat k\u00fcldenek, \u00e9s nem tudj\u00e1k a v\u00e1laszt TCP-n kereszt\u00fcl elk\u00fcldeni. A Google \u00e1ltal v\u00e9gzett k\u00eds\u00e9rlet azt mutatta, hogy az EDNS buffer m\u00e9ret\u00e9nek megv\u00e1ltoztat\u00e1sa gyakorlatilag nem befoly\u00e1solja a hib\u00e1k szintj\u00e9t \u2014 4096 b\u00e1jtos buffer mellett az UDP k\u00e9rd\u00e9sek lev\u00e1g\u00e1s\u00e1nak sz\u00e1ma 0,345%, m\u00edg a TCP-n kereszt\u00fcl el\u00e9rhetetlen \u00fajb\u00f3li v\u00e1laszok sz\u00e1ma 0,115%. 1232 b\u00e1jtos buffer mellett ezek az ar\u00e1nyok 0,367% \u00e9s 0,116%. A TCP k\u00f6telez\u0151 k\u00e9pess\u00e9gek k\u00f6z\u00e9 sorol\u00e1sa a DNS-ben probl\u00e9m\u00e1kat okoz k\u00f6r\u00fclbel\u00fcl 0,1% DNS-szerverrel val\u00f3 interakci\u00f3kor. Megjegyzend\u0151, hogy a jelenlegi k\u00f6r\u00fclm\u00e9nyek k\u00f6z\u00f6tt TCP n\u00e9lk\u00fcli m\u0171k\u00f6d\u00e9s eset\u00e9n ezeknek a szervereknek a m\u0171k\u00f6d\u00e9se am\u00fagy is instabil.<\/p>\n

Az authoritative DNS-kiszolg\u00e1l\u00f3k adminisztr\u00e1torainak biztos\u00edtaniuk kell, hogy kiszolg\u00e1l\u00f3juk TCP-n v\u00e1laszol a 53-as h\u00e1l\u00f3zati porton, \u00e9s hogy ez a TCP-port ne legyen blokkolva az t\u0171zfal \u00e1ltal. Az authoritative DNS-kiszolg\u00e1l\u00f3nak nem szabad UDP-v\u00e1laszokat k\u00fcldenie, amelyek m\u00e9rete meghaladja
\naz EDNS buffer k\u00e9rt m\u00e9rete. A szerveren az EDNS buffer m\u00e9ret\u00e9nek 1232 b\u00e1jtnak kell lennie. A resolver \u00e1ltal t\u00e1masztott k\u00f6vetelm\u00e9nyek hasonl\u00f3ak \u2014 k\u00f6telez\u0151 TCP-n v\u00e1laszolni, k\u00f6telez\u0151 t\u00e1mogat\u00e1s a TCP-n kereszt\u00fcli \u00fajb\u00f3li k\u00e9rd\u00e9sek k\u00fcld\u00e9s\u00e9re lev\u00e1gott UDP v\u00e1lasz eset\u00e9n, \u00e9s az EDNS buffer 1232 b\u00e1jton t\u00f6rt\u00e9n\u0151 be\u00e1ll\u00edt\u00e1sa.<\/p>\n

Az EDNS pufferm\u00e9ret\u00e9nek be\u00e1ll\u00edt\u00e1s\u00e1\u00e9rt a k\u00fcl\u00f6nb\u00f6z\u0151 DNS-kiszolg\u00e1l\u00f3kon a k\u00f6vetkez\u0151 param\u00e9terek felelnek:<\/p>\n

  • BIND\n

    options {
    \n edns-udp-size 1232;
    \n max-udp-size 1232;
    \n };<\/p>\n

  • Knot DNS\n

    max-udp-payload: 1232<\/p>\n

  • Knot Resolver\n

    net.bufsize(1232)<\/p>\n

  • PowerDNS Authoritative\n

    udp-truncation-threshold=1232<\/p>\n

  • PowerDNS Recursor\n

    edns-outgoing-bufsize=1232
    \n udp-truncation-threshold=1232<\/p>\n

  • Unbound\n

    edns-buffer-size: 1232<\/p>\n

  • NSD\n

    ipv4-edns-size: 1232
    \n ipv6-edns-size: 1232<\/p>\n

    <\/a><\/noindex><\/p>\n

    Forr\u00e1s: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

    \u0421\u0435\u0433\u043e\u0434\u043d\u044f \u0440\u044f\u0434 \u043a\u0440\u0443\u043f\u043d\u044b\u0445 DNS-\u0441\u0435\u0440\u0432\u0438\u0441\u043e\u0432 \u0438 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u0435\u0439 DNS-\u0441\u0435\u0440\u0432\u0435\u0440\u043e\u0432 \u043f\u0440\u043e\u0432\u0435\u0434\u0443\u0442 \u0441\u043e\u0432\u043c\u0435\u0441\u0442\u043d\u043e\u0435 \u043c\u0435\u0440\u043e\u043f\u0440\u0438\u044f\u0442\u0438\u0435 DNS flag day 2020, \u043f\u0440\u0438\u0437\u0432\u0430\u043d\u043d\u043e\u0435 \u0441\u0444\u043e\u043a\u0443\u0441\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u0432\u043d\u0438\u043c\u0430\u043d\u0438\u0435 \u043d\u0430 \u0440\u0435\u0448\u0435\u043d\u0438\u0438 \u043f\u0440\u043e\u0431\u043b\u0435\u043c \u0441 IP-\u0444\u0440\u0430\u0433\u043c\u0435\u043d\u0442\u0430\u0446\u0438\u0435\u0439 \u043f\u0440\u0438 \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u043a\u0435 DNS-\u0441\u043e\u043e\u0431\u0449\u0435\u043d\u0438\u0439 \u0431\u043e\u043b\u044c\u0448\u043e\u0433\u043e \u0440\u0430\u0437\u043c\u0435\u0440\u0430. \u042d\u0442\u043e \u0432\u0442\u043e\u0440\u043e\u0435 \u043f\u043e\u0434\u043e\u0431\u043d\u043e\u0435 \u043c\u0435\u0440\u043e\u043f\u0440\u0438\u044f\u0442\u0438\u0435, \u0432 \u043f\u0440\u043e\u0448\u043b\u043e\u043c \u0433\u043e\u0434\u0443 «DNS flag day» \u0431\u044b\u043b \u0441\u043e\u0441\u0440\u0435\u0434\u043e\u0442\u043e\u0447\u0435\u043d \u043d\u0430 \u043a\u043e\u0440\u0440\u0435\u043a\u0442\u043d\u043e\u0439 \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u043a\u0435 \u0437\u0430\u043f\u0440\u043e\u0441\u043e\u0432 EDNS. \u0423\u0447\u0430\u0441\u0442\u043d\u0438\u043a\u0438 \u0438\u043d\u0438\u0446\u0438\u0430\u0442\u0438\u0432\u044b DNS flag day 2020 \u043f\u0440\u0438\u0437\u044b\u0432\u0430\u044e\u0442 \u0437\u0430\u0444\u0438\u043a\u0441\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u0440\u0435\u043a\u043e\u043c\u0435\u043d\u0434\u043e\u0432\u0430\u043d\u043d\u044b\u0435 \u0440\u0430\u0437\u043c\u0435\u0440\u044b \u0431\u0443\u0444\u0435\u0440\u043e\u0432 […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-95716","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47A DNS Flag Day 2020 kezdem\u00e9nyez\u00e9s a t\u00f6redezetts\u00e9g \u00e9s a TCP t\u00e1mogat\u00e1si probl\u00e9m\u00e1k megold\u00e1s\u00e1ra | ProHoster","description":"Ma sz\u00e1mos nagy DNS-szolg\u00e1ltat\u00f3 \u00e9s DNS-kiszolg\u00e1l\u00f3 gy\u00e1rt\u00f3 k\u00f6z\u00f6s esem\u00e9nyt tart a DNS flag day 2020 keret\u00e9ben, amelynek c\u00e9lja a f\u00f3kusz\u00e1l\u00e1s.","canonical_url":"https:\/\/prohoster.info\/hu\/blog\/news\/inicziativa-dns-flag-day-2020-dlya-resheniya-problem-s-fragmentacziej-i-podderzhkoj-tcp","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"hu_HU","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47\u0418\u043d\u0438\u0446\u0438\u0430\u0442\u0438\u0432\u0430 DNS flag day 2020 \u0434\u043b\u044f \u0440\u0435\u0448\u0435\u043d\u0438\u044f \u043f\u0440\u043e\u0431\u043b\u0435\u043c \u0441 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