Tarmoq - IP, portlar va DNS

"Sayt ochilmayapti" - bu bitta muammo emas, oltita mumkin bo'lgan muammo. Ularni bir-biridan ajratish uchun tarmoq qatlamlarini bilish kerak.

So'rov qanday yo'l bosadi #

Interfeyslar va manzillar #

ip -o link show | awk '{print $2}' | tr -d ':' | sort | head -2

eth0
lo

ip -4 -o addr show lo | awk '{print $2, $4}'

lo 127.0.0.1/8

Kim qaysi portni tinglayapti #

Bu serverdagi eng ko'p ishlatiladigan tarmoq buyrug'i.

echo "<h1>Salom</h1>" > index.html

python3 -m http.server 8099 --bind 127.0.0.1 >/dev/null 2>&1 &
SRV=$!
sleep 1
ss -tln 'sport = :8099' | tail -1 | awk '{print $1, $4}'
kill "$SRV"

LISTEN 127.0.0.1:8099

Eslab qolish uchun: ss -tlnp - "TCP, tinglayotgan, raqamli, jarayon bilan".

127.0.0.1 va 0.0.0.0 - eng ko'p uchraydigan xato #

python3 -m http.server 8097 --bind 0.0.0.0 >/dev/null 2>&1 & A=$!
python3 -m http.server 8096 --bind 127.0.0.1 >/dev/null 2>&1 & B=$!
sleep 1
ss -tln 'sport = :8097 or sport = :8096' | tail -n +2 | awk '{print $4}' | sort
kill "$A" "$B" 2>/dev/null

0.0.0.0:8097
127.0.0.1:8096

sudo ss -tlnp | grep -E ':(3306|5432|6379|27017)'

Ulanishni sinash #

python3 -m http.server 8099 --bind 127.0.0.1 >/dev/null 2>&1 &
SRV=$!
sleep 1
nc -z -w 2 127.0.0.1 8099 && echo "8099 ochiq"
nc -z -w 2 127.0.0.1 8098 || echo "8098 yopiq"
kill "$SRV"

8099 ochiq
8098 yopiq

nc -zv sayt.uz 443

HTTP javobini o'qish #

python3 -m http.server 8099 --bind 127.0.0.1 >/dev/null 2>&1 &
SRV=$!
sleep 1
curl -s -o /dev/null -w '%{http_code}\n' http://127.0.0.1:8099/index.html
curl -s http://127.0.0.1:8099/index.html
curl -s -o /dev/null -w '%{http_code}\n' http://127.0.0.1:8099/mavjud-emas
kill "$SRV"

200
<h1>Salom</h1>
404

Xizmat umuman yo'q bo'lsa, curl HTTP kod bermaydi:

curl -s -o /dev/null -w '%{http_code}\n' --max-time 2 http://127.0.0.1:8098/
echo "curl chiqish kodi: $?"

000
curl chiqish kodi: 7

Foydali curl bayroqlari:

curl -I --resolve sayt.uz:443:203.0.113.99 https://sayt.uz/

DNS - nom qanday yechiladi #

getent hosts localhost | awk '{print $2}'

localhost

Yechish tartibi /etc/nsswitch.conf da belgilanadi:

hosts: files dns

203.0.113.99  sayt.uz www.sayt.uz

Portlar va xizmatlar #

getent services ssh https

ssh                   22/tcp
https                 443/tcp

Ulanishlar statistikasi #

ss -s | head -1 | grep -c 'Total:'

1

python3 -m http.server 8099 --bind 127.0.0.1 >/dev/null 2>&1 &
SRV=$!
sleep 1
curl -s -o /dev/null http://127.0.0.1:8099/
ss -tan 'sport = :8099 or dport = :8099' | tail -n +2 | awk '{print $1}' | sort -u
kill "$SRV"

LISTEN
TIME-WAIT

Bitta curl so'rovidan keyin ikkita holat qoldi: port hali ham tinglayapti, va yopilgan ulanish TIME-WAIT da turibdi.

"Sayt ochilmayapti" - tartib bilan #

Xulosa #

• ifconfig/netstat emas - ip/ss; ular tezroq va hamma joyda bor.
• ss -tlnp - serverdagi eng ko'p kerak bo'ladigan tarmoq buyrug'i.
• 127.0.0.1 - faqat server o'zi; 0.0.0.0 - hamma.
• Nginx orqasidagi ilova uchun 127.0.0.1 to'g'ri tanlov.
• Ma'lumotlar bazasi hech qachon 0.0.0.0 da turmasin.
• ping bloklangan bo'lishi mumkin - portni nc bilan tekshiring.
• curl chiqish kodi: 6 - DNS, 7 - port yopiq, 28 - paket yutilgan.
• --resolve DNS ni chetlab o'tadi - ko'chirishni sinash uchun ideal.
• /etc/hosts DNS dan ustun; unutilgan yozuv soatlab vaqt yeydi.
• CLOSE-WAIT ko'p bo'lsa - ilova soketlarni yopmayapti.

Keyingi bo'limda xavfsizlik devorini sozlaymiz: nftables, ufw va serverga qaysi portlar ochiq bo'lishi kerakligini.