sing-box/docs/examples/dns-hijack.md

Sniff Mode

{
  "inbounds": [
    {
      "type": "tun",
      "inet4_address": "172.19.0.1/30",
      "auto_route": true,
      "sniff": true // required
    }
  ],
  "outbounds": [
    {
      "type": "direct"
    },
    {
      "type": "dns",
      "tag": "dns-out"
    }
  ],
  "route": {
    "rules": [
      {
        "protocol": "dns",
        "outbound": "dns-out"
      }
    ],
    "auto_detect_interface": true
  }
}

Port Mode

{
  "inbounds": [
    {
      "type": "tun",
      "inet4_address": "172.19.0.1/30",
      "auto_route": true,
      "sniff": true // not required
    }
  ],
  "outbounds": [
    {
      "type": "direct"
    },
    {
      "type": "dns",
      "tag": "dns-out"
    }
  ],
  "route": {
    "rules": [
      {
        "port": 53,
        "outbound": "dns-out"
      }
    ],
    "auto_detect_interface": true
  }
}