REDIRECT (TCP only)

{
  "port": 12345,
  "protocol": "dokodemo-door",
  "settings": {
    "network": "tcp",
    "followRedirect": true
  }
}

# Create new chain
iptables -t nat -N PROXY

# Ignore proxy server address
iptables -t nat -A PROXY -d "ServerIP" -j RETURN

# Ignore local IPv4 address destinations to bypass the proxy
iptables -t nat -A PROXY -d 0.0.0.0/8 -j RETURN
iptables -t nat -A PROXY -d 10.0.0.0/8 -j RETURN
iptables -t nat -A PROXY -d 127.0.0.0/8 -j RETURN
iptables -t nat -A PROXY -d 169.254.0.0/16 -j RETURN
iptables -t nat -A PROXY -d 172.16.0.0/12 -j RETURN
iptables -t nat -A PROXY -d 192.168.0.0/16 -j RETURN
iptables -t nat -A PROXY -d 224.0.0.0/4 -j RETURN
iptables -t nat -A PROXY -d 240.0.0.0/4 -j RETURN

# Anything else should be redirected to Dokodemo-door's local port
iptables -t nat -A PROXY -p tcp -j REDIRECT --to-ports 12345

# Transparent proxy for this machine
iptables -t nat -A OUTPUT -p tcp -j PROXY

# Transparent proxy for other LAN devices
iptables -t nat -A PREROUTING -p tcp -j PROXY

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Transparent Proxy | V2Ray Beginner's Guide

TPROXY (TCP only)

{
  "port": 12345,
  "listen": "127.0.0.1",
  "protocol": "dokodemo-door",
  "settings": {
    "network": "tcp",
    "followRedirect": true
  },
  "streamSettings": {
    "sockopt": {
      "tproxy": "tproxy"
    }
  }
}

# Identify TCP packets with destination address matching a local socket, set the packet mark to 1
iptables -t mangle -N DIVERT
iptables -t mangle -A PREROUTING -p tcp -m socket -j DIVERT
iptables -t mangle -A DIVERT -j MARK --set-mark 1
iptables -t mangle -A DIVERT -j ACCEPT

# Match on packet mark 1 using policy routing to have those packets delivered locally
ip rule add fwmark 1 table 100
ip route add local default dev lo table 100

# Create new chain
iptables -t mangle -N PROXY

# Routed devices won't be able to reach the server with this
# iptables -t mangle -A PROXY -d "ServerIP" -j RETURN

# Set local IPv4 address destinations to bypass the proxy
iptables -t mangle -A PROXY -d 0.0.0.0/8 -j RETURN
iptables -t mangle -A PROXY -d 10.0.0.0/8 -j RETURN
iptables -t mangle -A PROXY -d 127.0.0.0/8 -j RETURN
iptables -t mangle -A PROXY -d 169.254.0.0/16 -j RETURN
iptables -t mangle -A PROXY -d 172.16.0.0/12 -j RETURN
iptables -t mangle -A PROXY -d 192.168.0.0/16 -j RETURN
iptables -t mangle -A PROXY -d 224.0.0.0/4 -j RETURN
iptables -t mangle -A PROXY -d 240.0.0.0/4 -j RETURN

# Anything else should be redirected to the port dokodemo-door listens on
iptables -t mangle -A PROXY -p tcp -j TPROXY --on-ip 127.0.0.1 --on-port 12345 --tproxy-mark 1

# Transparent proxy for routed devices
iptables -t mangle -A PREROUTING -j PROXY

# ---

# Create new chain for proxying the router
iptables -t mangle -N PROXY_LOCAL

# Set proxy server address to bypass the proxy
iptables -t mangle -A PROXY_LOCAL -d "ServerIP" -j RETURN

# Set local IPv4 address destinations to bypass the proxy
iptables -t mangle -A PROXY_LOCAL -d 0.0.0.0/8 -j RETURN
iptables -t mangle -A PROXY_LOCAL -d 10.0.0.0/8 -j RETURN
iptables -t mangle -A PROXY_LOCAL -d 127.0.0.0/8 -j RETURN
iptables -t mangle -A PROXY_LOCAL -d 169.254.0.0/16 -j RETURN
iptables -t mangle -A PROXY_LOCAL -d 172.16.0.0/12 -j RETURN
iptables -t mangle -A PROXY_LOCAL -d 192.168.0.0/16 -j RETURN
iptables -t mangle -A PROXY_LOCAL -d 224.0.0.0/4 -j RETURN
iptables -t mangle -A PROXY_LOCAL -d 240.0.0.0/4 -j RETURN

# Mark anything else as 1
iptables -t mangle -A PROXY_LOCAL -p tcp -j MARK --set-mark 1

# Transparent proxy for the router
iptables -t mangle -A OUTPUT -j PROXY_LOCAL

透明代理(TPROXY) | 新 V2Ray 白话文指南

Transparent proxy support - The Linux Kernel documentation