DNS解析第一个失败的情况下不会尝试第二个 #156

darren · 2020-09-03T01:59:09Z

你正在使用哪个版本的 V2Ray？（如果服务器和客户端使用了不同版本，请注明）
d9f50f8
你看到的不正常的现象是什么？（请描述具体现象，比如访问超时，TLS 证书错误等）

配置的域名解析，解析vmwarefusion.github.io 失败

查询v2ray的结果

 dig @127.0.0.1 -p 15354 vmwarefusion.github.io

; <<>> DiG 9.11.5-P4-5.1+deb10u2-Debian <<>> @127.0.0.1 -p 15354 vmwarefusion.github.io
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 31411
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;vmwarefusion.github.io.                IN      A

;; Query time: 4 msec
;; SERVER: 127.0.0.1#15354(127.0.0.1)
;; WHEN: Thu Sep 03 09:55:34 CST 2020
;; MSG SIZE  rcvd: 40

直接查询dns服务器的结果：(status为REFUSED, 即对应日志中rcode=5)

dig @123.123.123.123 vmwarefusion.github.io 

; <<>> DiG 9.11.5-P4-5.1+deb10u2-Debian <<>> @123.123.123.123 vmwarefusion.github.io
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 25360
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 96941fdbbd1d79bd8be6b0c45f5050db298c8357136261de (good)
;; QUESTION SECTION:
;vmwarefusion.github.io.                IN      A

;; Query time: 4 msec
;; SERVER: 123.123.123.123#53(123.123.123.123)
;; WHEN: Thu Sep 03 10:11:39 CST 2020
;; MSG SIZE  rcvd: 79

你期待看到的正确表现是怎样的？

按照配置我理解，当查询第一个dns无返回结果时，应该是不匹配

       "expectIPs": [
          "geoip:cn"
        ]

这个条件的，应该继续往下查询doh。

请附上你的配置（提交 Issue 前请隐藏服务器端IP地址）。

客户端配置:

{
  "log": {
    "loglevel": "info"
  },
  "inbounds": [
    {
      "listen": "127.0.0.1",
      "port": 15354,
      "tag": "dns-in",
      "protocol": "dokodemo-door",
      "settings": {
        "address": "1.1.1.1",
        "port": 53,
        "network": "tcp,udp"
      }
    }
  ],
  "outbounds": [
    {
      "protocol": "dns",
      "tag": "dns-out"
    },
    {
      "protocol": "freedom",
      "settings": {},
      "tag": "direct"
    }
  ],
  "dns": {
    "servers": [
      {
        "address": "123.123.123.123",
        "port": 53,
        "domains": [
          "geosite:cn"
        ],
        "expectIPs": [
          "geoip:cn"
        ]
      },
      "https+local://1.1.1.1/dns-query"
    ],
    "clientIp": "123.121.22.1",
    "tag": "dns-inbound"
  },
  "routing": {
    "strategy": "rules",
    "domainStrategy": "AsIs",
    "rules": [
      {
        "type": "field",
        "inboundTag": [
          "dns-in"
        ],
        "outboundTag": "dns-out"
      },
      {
        "type": "field",
        "inboundTag": [
          "dns-inbound"
        ],
        "outboundTag": "direct"
      }
    ]
  }
}

请附上出错时软件输出的错误日志。在 Linux 中，日志通常在 /var/log/v2ray/error.log 文件中。

客户端错误日志:

2020/09/03 09:44:36 [Info] v2ray.com/core/app/dns: DNS: created udp client inited for 123.123.123.123:53                                                                                                                                            
2020/09/03 09:44:36 [Info] v2ray.com/core/app/dns: DNS: created Local DOH client for https://1.1.1.1/dns-query                                                                                                                                      
2020/09/03 09:44:36 [Info] v2ray.com/core/transport/internet/tcp: listening TCP on 127.0.0.1:15354                                                                                                                                                  
2020/09/03 09:44:36 [Info] v2ray.com/core/transport/internet/udp: listening UDP on 127.0.0.1:15354                                                                                                                                                  
2020/09/03 09:44:36 [Warning] v2ray.com/core: V2Ray 4.27.5 started                                                                                                                                                                                  
2020/09/03 09:44:57 [Info] [4115359556] v2ray.com/core/proxy/dokodemo: received request for 127.0.0.1:39396                                                                                                                                         
2020/09/03 09:44:57 [Info] [4115359556] v2ray.com/core/app/dispatcher: taking detour [dns-out] for [udp:1.1.1.1:53]                                                                                                                                 
2020/09/03 09:44:57 [Info] [4115359556] v2ray.com/core/proxy/dns: handling DNS traffic to udp:1.1.1.1:53                                                                                                                                            
2020/09/03 09:44:57 127.0.0.1:39396 accepted udp:1.1.1.1:53 [dns-out]                                                                                                                                                                               
2020/09/03 09:44:57 [Info] v2ray.com/core/transport/internet/udp: establishing new connection for udp:123.123.123.123:53                                                                                                                            
2020/09/03 09:44:57 [Info] v2ray.com/core/app/dispatcher: taking detour [direct] for [udp:123.123.123.123:53]                                                                                                                                       
2020/09/03 09:44:57 [Info] v2ray.com/core/proxy/freedom: opening connection to udp:123.123.123.123:53                                                                                                                                               
2020/09/03 09:44:57 [Info] v2ray.com/core/app/dns: UDP:123.123.123.123:53 got answer: vmwarefusion.github.io. TypeA -> [] 4.589518ms                                                                                                                
2020/09/03 09:44:57 [Info] v2ray.com/core/app/dns: failed to lookup ip for domain vmwarefusion.github.io at server UDP:123.123.123.123:53 > rcode: 5                                                                                                
2020/09/03 09:45:05 [Info] v2ray.com/core/app/proxyman/outbound: failed to process outbound traffic > v2ray.com/core/proxy/freedom: connection ends > context canceled                                                                              
2020/09/03 09:45:05 [Info] v2ray.com/core/transport/internet/udp: failed to handle UDP input > io: read/write on closed pipe                                                                                                                        
2020/09/03 09:45:21 [Info] [4164880411] v2ray.com/core/proxy/dokodemo: received request for 127.0.0.1:40739

The text was updated successfully, but these errors were encountered:

Fix v2fly#156

Vigilans · 2020-09-03T12:59:32Z

按 #157 (review) ，总结一下目前内置DNS在某个服务器解析失败后，会继续尝试下一个服务器的条件：

1. 使用"domains"字段的优先查询

v2ray-core/app/dns/server.go

Lines 391 to 405 in d2226cb

    
           for _, idx := range indices { 
        
           	clientIdx := int(s.matcherInfos[idx].clientIdx) 
        
           	matchedClient = s.clients[clientIdx] 
        
           	ips, err := s.queryIPTimeout(clientIdx, matchedClient, domain, option) 
        
           	if len(ips) > 0 { 
        
           		return ips, nil 
        
           	} 
        
           	if err == dns.ErrEmptyResponse { 
        
           		return nil, err 
        
           	} 
        
           	if err != nil { 
        
           		newError("failed to lookup ip for domain ", domain, " at server ", matchedClient.Name()).Base(err).WriteToLog() 
        
           		lastErr = err 
        
           	} 
        
           }

398~400行中，只有err为dns.ErrEmptyResponse时，才会中断查询（直接return了）。其余err都将继续DNS查询。这其实是 #94 中的改动带来的一个不合适的遗留问题，这一段的逻辑应该改成与自上而下的默认查询一致。

2. 自上而下的默认查询

v2ray-core/app/dns/server.go

Lines 408 to 426 in d2226cb

    
           for idx, client := range s.clients { 
        
           	if client == matchedClient { 
        
           		newError("domain ", domain, " at server ", client.Name(), " idx:", idx, " already lookup failed, just ignore").AtDebug().WriteToLog() 
        
           		continue 
        
           	} 
        
           	ips, err := s.queryIPTimeout(idx, client, domain, option) 
        
           	if len(ips) > 0 { 
        
           		return ips, nil 
        
           	} 
        
           	if err != nil { 
        
           		newError("failed to lookup ip for domain ", domain, " at server ", client.Name()).Base(err).WriteToLog() 
        
           		lastErr = err 
        
           	} 
        
           	if err != context.Canceled && err != context.DeadlineExceeded && err != errExpectedIPNonMatch { 
        
           		return nil, err 
        
           	} 
        
           }

423~425行中，只有context.Canceled，context.DeadlineExceeded，errExpectedIPNonMatch三种error会继续DNS查询。

#157 的解决方案实质就是将client.QueryIP返回的error（如rcode error），转化成了errExpectedIPNonMatch（因为client.QueryIP有error的时候，返回的ips是空数组），从而使得查询得以继续。

个人觉得相比而言，修改423~425行中允许DNS查询继续的error可能比较合适。如果采用转化到errExpectedIPNonMatch的方案，应该只部分选择应用这种转化的error，而非将诸如context cancelled等error都修改成errExpectedIPNonMatch。#141 中针对DNS服务器返回空解析，@qqqaadd 给出的patch里就有对允许DNS查询继续的error的改动。

client.QueryIP会返回的error

来自ctx.Err():

context.Canceled
context.DeadlineExceeded

来自s.findIPsForDomain():

errRecordNotFound: 被client.QueryIP内部处理了，不会返回
dns_feature.ErrEmptyResponse
dns_feature.RCodeError(r.RCode)

Vigilans · 2020-09-03T13:15:24Z

@Loyalsoldier @Robot-DaneelOlivaw

#94 还带来一个遗留问题：

v2ray-core/app/dns/server.go

Lines 409 to 412 in d2226cb

    
           if client == matchedClient { 
        
           	newError("domain ", domain, " at server ", client.Name(), " idx:", idx, " already lookup failed, just ignore").AtDebug().WriteToLog() 
        
           	continue 
        
           }

由于 #94 之前，优先查询只会做一次，因此matchedClient的本意是如果优先查询失败了，默认的由上自下查询就不尝试用这个client了。但现在优先查询会做多次，matchedClient只会存最后一次的记录，没达成原本的意义，需要修正。

#92 (comment) 中提到，优先查询按 #94 修改后，同一个服务器在优先查询阶段可能会尝试查询多次。当时的想法是保留这个行为，不过如果修正了matchedClient的实现，可以做到同服务器最多只查询一次。

于是选择是，将matchedClient改为适配当前多次优先查询的机制，使得同DNS服务器在一次请求两个阶段中最多只被查询一次，还是去掉这个机制，让同DNS可以被反复查询，从而让超时而没域名缓存的DNS服务器有被重试的机会？

Loyalsoldier · 2020-09-03T13:29:41Z

我倾向于同一个 client 只查询一次。

Robot-DaneelOlivaw · 2020-09-03T18:15:57Z

按照配置我理解，当查询第一个dns无返回结果时，应该是不匹配
       "expectIPs": [
          "geoip:cn"
        ]
这个条件的，应该继续往下查询doh。

似乎与此前 v2fly/domain-list-community#158 (comment) 提到的描述一致。

于是选择是，将matchedClient改为适配当前多次优先查询的机制，使得同DNS服务器在一次请求两个阶段中最多只被查询一次，还是去掉这个机制，让同DNS可以被反复查询，从而让超时而没域名缓存的DNS服务器有被重试的机会？

鉴于DNS服务本身相较稳定，再次查询相同DNS可能依然返回空解析，换一个DNS进行查询比较高效，所以我的想法与@Loyalsoldier相同，同一个client只查询一次。

k79e · 2020-10-24T08:23:42Z

我过来问问 dns乱尝试的那个 bug现在还在不在了.
就是retry查询打破了分流规则的限制问题.

qqqaadd · 2020-10-25T07:03:25Z

允许所有错误都继续查询吧，我从9月开始用还没察觉到问题
（有几次把系统设置成alidns[223.5.5.5 / 223.6.6.6]后，超时导致连不上网，不过本来超时就不应该可以连，但是希望v2ray不是直接断开连接，浏览器显示断开连接(?)，而是让浏览器显示dns错误，不过之前看了一下好像改起来挺麻烦，也就不再理会了）
相关 #141

https://github.com/v2fly/v2ray-core/blob/master/app/dns/server.go#L422-L443

//v2ray-core/app/dns/server.go 
...
	for idx, client := range s.clients {
		if client == matchedClient {
			newError("domain ", domain, " at server ", client.Name(), " idx:", idx, " already lookup failed, just ignore").AtDebug().WriteToLog()
			continue
		}

		ips, err := s.queryIPTimeout(idx, client, domain, option)
		if len(ips) > 0 {
			return ips, nil
		}

		if err != nil {
			newError("failed to lookup ip for domain ", domain, " at server ", client.Name()).Base(err).WriteToLog()
			lastErr = err
		}
	}
	
	newError("returning nil for domain ", domain).Base(lastErr).WriteToLog()

	return nil, lastErr
}

https://github.com/v2fly/v2ray-core/blob/master/app/dns/dohdns.go#L302-L316

// app/dns/dohdns.go
func (s *DoHNameServer) findIPsForDomain(domain string, option IPOption) ([]net.IP, error) {
...
-	if option.IPv6Enable && record.AAAA != nil && record.AAAA.RCode == dnsmessage.RCodeSuccess {
+	if option.IPv6Enable && record.AAAA != nil {
		aaaa, err := record.AAAA.getIPs()
		if err != nil {
			lastErr = err
		}
		ips = append(ips, aaaa...)
	}

-	if option.IPv4Enable && record.A != nil && record.A.RCode == dnsmessage.RCodeSuccess {
+	if option.IPv4Enable && record.A != nil {
		a, err := record.A.getIPs()
		if err != nil {
			lastErr = err
		}
		ips = append(ips, a...)
	}

	if len(ips) > 0 {
		return toNetIP(ips), nil
	}
...

github-actions · 2021-02-23T02:05:15Z

This issue is stale because it has been open 120 days with no activity. Remove stale label or comment or this will be closed in 5 days

darren mentioned this issue Sep 3, 2020

Do not check err while match dns query result darren/v2ray-core#1

Closed

darren added a commit to darren/v2ray-core that referenced this issue Sep 3, 2020

Do not check err while match dns query result

fcd1153

Fix v2fly#156

darren mentioned this issue Sep 3, 2020

Match ip first before return original error #157

Closed

darren added a commit to darren/v2ray-core that referenced this issue Sep 3, 2020

Match ip first before return original error

a3ce4c0

Fix v2fly#156

Vigilans mentioned this issue Sep 8, 2020

Refactoring: DNS App #169

Merged

github-actions bot added the Stale label Feb 23, 2021

github-actions bot closed this as completed Feb 28, 2021

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DNS解析第一个失败的情况下不会尝试第二个 #156

DNS解析第一个失败的情况下不会尝试第二个 #156

darren commented Sep 3, 2020 •

edited

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Vigilans commented Sep 3, 2020 •

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Vigilans commented Sep 3, 2020 •

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Loyalsoldier commented Sep 3, 2020

Robot-DaneelOlivaw commented Sep 3, 2020

k79e commented Oct 24, 2020

qqqaadd commented Oct 25, 2020 •

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github-actions bot commented Feb 23, 2021

DNS解析第一个失败的情况下不会尝试第二个 #156

DNS解析第一个失败的情况下不会尝试第二个 #156

Comments

darren commented Sep 3, 2020 • edited Loading

Vigilans commented Sep 3, 2020 • edited Loading

1. 使用"domains"字段的优先查询

2. 自上而下的默认查询

client.QueryIP会返回的error

Vigilans commented Sep 3, 2020 • edited Loading

Loyalsoldier commented Sep 3, 2020

Robot-DaneelOlivaw commented Sep 3, 2020

k79e commented Oct 24, 2020

qqqaadd commented Oct 25, 2020 • edited Loading

github-actions bot commented Feb 23, 2021

darren commented Sep 3, 2020 •

edited

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Vigilans commented Sep 3, 2020 •

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Vigilans commented Sep 3, 2020 •

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qqqaadd commented Oct 25, 2020 •

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