v2ray内置dns无法查询到vps server的IPv4地址，导致无法连接VPS

[koiiok]

你好，我在openwrt上搭建了v2ray (v4.34.0)，使用TPROXY做透明代理，v2ray使用内置dns。vps server仅有ipv4地址。

现遇到一个问题：v2ray的内置dns在查询vps地址时（直连）收到的dns response 总是AAAA （很少时候会有A）类型，因为vps没有ipv6地址，因此dns response一直是empty response，导致v2ray无法连接vps。

我试了以下操作：

1. 在openwrt的shell里面用nslookup和dig查询vps地址，是可以得到A类型response的
2. 把openwrt的ipv6功能关闭，但仍然解决不了上述问题

在/etc/sysctl.conf里面添加两行：
net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.default.disable_ipv6=1
SSH执行 sysctl -p 生效

另外，v2ray的内置dns在查询其他domain的时候，好像会同时请求A和AAAA类型，并一直更新收到的response进缓存，由于AAAA一般回来的慢，导致v2ray的dns 缓存都是AAAA类型，由于openwrt和vps都没有ipv6地址，导致根本无法连接。

type IPOption struct {
	IPv4Enable bool
	IPv6Enable bool
}

看到代码里面好像有一个IPOption控制发出的dns请求是A还是AAAA类型，请问在我所描述的问题场景下，是否可以让v2ray的内置dns只请求A类型的地址？

我还观察到，v2ray的内置dns list应该是会按照sort后的顺序依次请求，但是在我描述的场景下，第一个dns收到AAAA的empty response后，v2ray好像就不再用其他的dns了。

实在被这个问题折腾了很久，很期待能够得到解答。谢谢

config.json

{
  "inbounds": [
    {
      "tag":"transparent",
      "port": 12345,
      "protocol": "dokodemo-door",
      "settings": {
        "network": "tcp,udp",
        "followRedirect": true
      },
      "sniffing": {
        "enabled": true,
        "destOverride": [
          "http",
          "tls"
        ]
      },
      "streamSettings": {
        "sockopt": {
          "tproxy": "tproxy" 
        }
      }
    },
    {
      "port": 1080, 
      "protocol": "socks", 
      "sniffing": {
        "enabled": true,
        "destOverride": ["http", "tls"]
      },
      "settings": {
        "auth": "noauth"
      }
    }
  ],
  "outbounds": [
    {
      "tag": "proxy",
      "protocol": "vmess",
      "settings": {
        "vnext": [
          ...
        ]
      },
      "streamSettings": {
        "sockopt": {
          "mark": 255
        }
      },
      "mux": {
        "enabled": false
      }
    },
    {
      "tag": "direct",
      "protocol": "freedom",
      "settings": {
        "domainStrategy": "UseIPv4"
      },
      "streamSettings": {
        "sockopt": {
          "mark": 255
        }
      }      
    },
    {
      "tag": "block",
      "protocol": "blackhole",
      "settings": {
        "response": {
          "type": "http"
        }
      }
    },
    {
      "tag": "dns-out",
      "protocol": "dns",
      "streamSettings": {
        "sockopt": {
          "mark": 255
        }
      }  
    }
  ],
  "dns": {
    "servers": [
      "8.8.8.8", 
      "1.1.1.1", 
      "114.114.114.114", 
      {
        "address": "223.5.5.5", 
        "port": 53,
        "domains": [
          "geosite:cn",
          "ntp.org",  
          "$myserver.address" 
        ]
      }
    ]
  },
  "routing": {
    "domainStrategy": "IPOnDemand",
    "rules": [
      { 
        "type": "field",
        "inboundTag": [
          "transparent"
        ],
        "port": 53,
        "network": "udp",
        "outboundTag": "dns-out" 
      },    
      { 
        "type": "field",
        "inboundTag": [
          "transparent"
        ],
        "port": 123,
        "network": "udp",
        "outboundTag": "direct" 
      },    
      {
        "type": "field", 
        "ip": [ 
          "223.5.5.5",
          "114.114.114.114"
        ],
        "outboundTag": "direct"
      },
      {
        "type": "field",
        "ip": [ 
          "8.8.8.8",
          "1.1.1.1"
        ],
        "outboundTag": "proxy" 
      },
      { 
        "type": "field", 
        "domain": [
          "geosite:category-ads-all"
        ],
        "outboundTag": "block"
      },
      { 
        "type": "field",
        "protocol":["bittorrent"], 
        "outboundTag": "direct"
      },
      { 
        "type": "field", 
        "ip": [
          "geoip:private",
          "geoip:cn"
        ],
        "outboundTag": "direct"
      },
      { 
        "type": "field", 
        "domain": [
          "geosite:cn"
        ],
        "outboundTag": "direct"
      }
    ]
  }
}

error.log

2021/01/10 07:50:56 [Debug] v2ray.com/core/app/log: Logger started
2021/01/10 07:50:56 [Info] v2ray.com/core/app/dns: DNS: created UDP client inited for 8.8.8.8:53
2021/01/10 07:50:56 [Info] v2ray.com/core/app/dns: DNS: created UDP client inited for 1.1.1.1:53
2021/01/10 07:50:56 [Info] v2ray.com/core/app/dns: DNS: created UDP client inited for 114.114.114.114:53
2021/01/10 07:50:56 [Info] v2ray.com/core/app/dns: DNS: created UDP client inited for 223.5.5.5:53
2021/01/10 07:50:56 [Debug] v2ray.com/core/app/proxyman/inbound: creating stream worker on 0.0.0.0:12345
2021/01/10 07:50:56 [Debug] v2ray.com/core/app/proxyman/inbound: creating stream worker on 0.0.0.0:1080
2021/01/10 07:50:56 [Info] v2ray.com/core/transport/internet/tcp: listening TCP on 0.0.0.0:12345
2021/01/10 07:50:56 [Info] v2ray.com/core/transport/internet/udp: listening UDP on 0.0.0.0:12345
2021/01/10 07:50:56 [Info] v2ray.com/core/transport/internet/tcp: listening TCP on 0.0.0.0:1080
2021/01/10 07:50:56 [Warning] v2ray.com/core: V2Ray 4.34.0 started
2021/01/10 07:51:00 [Debug] [2436073808] v2ray.com/core/proxy/dokodemo: processing connection from: 192.168.50.15:54500
2021/01/10 07:51:00 [Info] [2436073808] v2ray.com/core/proxy/dokodemo: received request for 192.168.50.15:54500
2021/01/10 07:51:00 [Info] [2436073808] v2ray.com/core/app/dispatcher: sniffed domain: p27-buy.itunes.apple.com
2021/01/10 07:51:00 [Debug] v2ray.com/core/app/dns: domain p27-buy.itunes.apple.com will use DNS in order: [UDP:8.8.8.8:53 UDP:1.1.1.1:53 UDP:114.114.114.114:53 UDP:223.5.5.5:53]
2021/01/10 07:51:00 [Debug] v2ray.com/core/app/dns: UDP:8.8.8.8:53 querying DNS for: p27-buy.itunes.apple.com.
2021/01/10 07:51:00 [Debug] v2ray.com/core/transport/internet/udp: dispatch request to: udp:8.8.8.8:53
2021/01/10 07:51:00 [Info] v2ray.com/core/transport/internet/udp: establishing new connection for udp:8.8.8.8:53
2021/01/10 07:51:00 [Debug] v2ray.com/core/transport/internet/udp: dispatch request to: udp:8.8.8.8:53
2021/01/10 07:51:00 [Info] v2ray.com/core/app/dispatcher: taking detour [proxy] for [udp:8.8.8.8:53]
2021/01/10 07:51:00 [Info] v2ray.com/core/transport/internet/tcp: dialing TCP to tcp:my.server.domain:443
2021/01/10 07:51:00 [Debug] v2ray.com/core/transport/internet/udp: UDP original destination: udp:192.168.50.1:53
2021/01/10 07:51:00 [Debug] [1858709342] v2ray.com/core/proxy/dokodemo: processing connection from: 192.168.50.178:42472
2021/01/10 07:51:00 [Info] [1858709342] v2ray.com/core/proxy/dokodemo: received request for 192.168.50.178:42472
2021/01/10 07:51:00 [Info] [1858709342] v2ray.com/core/app/dispatcher: taking detour [dns-out] for [udp:192.168.50.1:53]
2021/01/10 07:51:00 [Info] [1858709342] v2ray.com/core/proxy/dns: handling DNS traffic to udp:192.168.50.1:53
2021/01/10 07:51:00 [Debug] v2ray.com/core/app/dns: domain my.server.domain matches following rules: [my.server.domain(DNS idx:3)]
2021/01/10 07:51:00 [Debug] v2ray.com/core/app/dns: domain my.server.domain will use DNS in order: [UDP:223.5.5.5:53 UDP:8.8.8.8:53 UDP:1.1.1.1:53 UDP:114.114.114.114:53]
2021/01/10 07:51:00 [Debug] v2ray.com/core/app/dns: UDP:223.5.5.5:53 querying DNS for: my.server.domain.
2021/01/10 07:51:00 [Debug] v2ray.com/core/transport/internet/udp: dispatch request to: udp:223.5.5.5:53
2021/01/10 07:51:00 [Info] v2ray.com/core/transport/internet/udp: establishing new connection for udp:223.5.5.5:53
2021/01/10 07:51:00 [Info] v2ray.com/core/app/dispatcher: taking detour [direct] for [udp:223.5.5.5:53]
2021/01/10 07:51:00 [Info] v2ray.com/core/proxy/freedom: opening connection to udp:223.5.5.5:53
2021/01/10 07:51:00 [Info] v2ray.com/core/app/dns: UDP:223.5.5.5:53 got answer: my.server.domain. TypeAAAA -> [] 10.004202ms
2021/01/10 07:51:00 [Debug] v2ray.com/core/app/dns: UDP:223.5.5.5:53 updating IP records for domain:my.server.domain.
2021/01/10 07:51:00 [Info] v2ray.com/core/app/dns: failed to lookup ip for domain my.server.domain at server UDP:223.5.5.5:53 > empty response
2021/01/10 07:51:00 [Info] v2ray.com/core/proxy/vless/outbound: tunneling request to udp:8.8.8.8:53 via tcp:my.server.domain:443
2021/01/10 07:51:01 [Info] v2ray.com/core/app/dns: UDP:8.8.8.8:53 got answer: p27-buy.itunes.apple.com. TypeA -> [17.120.254.57] 512.271547ms
2021/01/10 07:51:01 [Debug] v2ray.com/core/app/dns: UDP:8.8.8.8:53 updating IP records for domain:p27-buy.itunes.apple.com.
2021/01/10 07:51:01 [Info] v2ray.com/core/app/dns: UDP:8.8.8.8:53 got answer: p27-buy.itunes.apple.com. TypeAAAA -> [] 655.685201ms
2021/01/10 07:51:01 [Debug] v2ray.com/core/app/dns: UDP:8.8.8.8:53 updating IP records for domain:p27-buy.itunes.apple.com.

...

2021/01/10 07:51:03 [Info] [162439825] v2ray.com/core/transport/internet/tcp: dialing TCP to tcp:my.server.domain:443
2021/01/10 07:51:03 [Info] [953917434] v2ray.com/core/transport/internet/tcp: dialing TCP to tcp:my.server.domain:443  
2021/01/10 07:51:03 [Debug] v2ray.com/core/transport/internet/udp: UDP original destination: udp:192.168.50.1:53
2021/01/10 07:51:03 [Debug] [1158215340] v2ray.com/core/proxy/dokodemo: processing connection from: 192.168.50.178:5778             
2021/01/10 07:51:03 [Info] [1158215340] v2ray.com/core/proxy/dokodemo: received request for 192.168.50.178:5778                                                            
2021/01/10 07:51:03 [Info] [1158215340] v2ray.com/core/app/dispatcher: taking detour [dns-out] for [udp:192.168.50.1:53]
2021/01/10 07:51:03 [Info] [1158215340] v2ray.com/core/proxy/dns: handling DNS traffic to udp:192.168.50.1:53
2021/01/10 07:51:03 [Debug] v2ray.com/core/app/dns: domain my.server.domain matches following rules: [my.server.domain(DNS idx:3)]
2021/01/10 07:51:03 [Debug] v2ray.com/core/app/dns: domain my.server.domain will use DNS in order: [UDP:223.5.5.5:53 UDP:8.8.8.8:53 UDP:1.1.1.1:53 UDP:114.114.114.114:53]
2021/01/10 07:51:03 [Info] v2ray.com/core/app/dns: UDP:223.5.5.5:53 cache HIT my.server.domain -> [] > empty response
2021/01/10 07:51:03 [Info] v2ray.com/core/app/dns: failed to lookup ip for domain my.server.domain at server UDP:223.5.5.5:53 > empty response

[CalmLong]

这种情况应该是优先使用 IPv6 导致的，看看固件里面有没有设置，或者换个固件试试