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cname bug #1886

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zhengqwe opened this issue Dec 30, 2024 · 8 comments
Open

cname bug #1886

zhengqwe opened this issue Dec 30, 2024 · 8 comments

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@zhengqwe
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问题现象
查询cname target域名，软件没有任何回应，这种情况最初是在路由器上的smartdns上发现的，之后在ubuntu 24.04虚拟机上测试也能复现

运行环境

  1. 固件型号

  2. 运营商

  3. smartdns来源以及版本
    https://github.com/pymumu/smartdns/releases/download/Release46/smartdns-x86_64

  4. 涉及的配置(注意去除个人相关信息)

bind :5354
server 223.5.5.5
server 2400:3200::1
server 180.184.1.1
server 119.29.29.29
server 8.8.8.8
speed-check-mode ping,tcp:443
response-mode fastest-ip
log-file /var/log/smartdns/smartdns.log
log-level debug

cname /cloudfront.net/d2e1asnsl7br7b.cloudfront.net

重现步骤

  1. 上游DNS配置。

  2. 访问的域名。
    d2e1asnsl7br7b.cloudfront.net

信息收集

  1. 将/var/log/smrtdns.log日志作为附件上传(注意去除个人相关信息)。
[2024-12-30 11:36:59,928][NOTICE][       smartdns.c:640 ] smartdns starting...(Copyright (C) Nick Peng <[email protected]>, build: 1.2024.06.12-2222 (Release46))
[2024-12-30 11:36:59,931][ INFO][     dns_server.c:9013] bind ip :5354, type 0
[2024-12-30 11:36:59,931][DEBUG][      fast_ping.c:1454] ping 2001::, id = 1
[2024-12-30 11:36:59,932][DEBUG][      fast_ping.c:678 ] ping 2001:: end, id 1
[2024-12-30 11:36:59,932][ INFO][     dns_server.c:9330] IPV6 is ready, enable IPV6 features
[2024-12-30 11:36:59,933][ INFO][     dns_client.c:1272] add server 223.5.5.5:53, type: udp
[2024-12-30 11:36:59,933][ INFO][     dns_client.c:1272] add server 2400:3200::1:53, type: udp
[2024-12-30 11:36:59,933][ INFO][     dns_client.c:1272] add server 180.184.1.1:53, type: udp
[2024-12-30 11:36:59,933][ INFO][     dns_client.c:1272] add server 119.29.29.29:53, type: udp
[2024-12-30 11:36:59,933][ INFO][     dns_client.c:1272] add server 8.8.8.8:53, type: udp
[2024-12-30 11:37:02,157][DEBUG][     dns_server.c:7155] recv query packet from 127.0.0.1, len = 47, type = 0
[2024-12-30 11:37:02,157][DEBUG][     dns_server.c:7171] request qdcount = 1, ancount = 0, nscount = 0, nrcount = 0, len = 47, id = 52079, tc = 0, rd = 1, ra = 0, rcode = 0
[2024-12-30 11:37:02,157][DEBUG][     dns_server.c:7196] query d2e1asnsl7br7b.cloudfront.net from 127.0.0.1, qtype: 1, id: 52079, query-num: 1
[2024-12-30 11:37:02,157][ INFO][     dns_server.c:5264] RULE-MATCH, type: 12, domain: d2e1asnsl7br7b.cloudfront.net, rule: cloudfront.net.
[2024-12-30 11:37:02,157][ INFO][     dns_server.c:5908] query d2e1asnsl7br7b.cloudfront.net with cname d2e1asnsl7br7b.cloudfront.net
[2024-12-30 11:37:02,157][ INFO][     dns_server.c:5264] RULE-MATCH, type: 12, domain: d2e1asnsl7br7b.cloudfront.net, rule: cloudfront.net.
[2024-12-30 11:37:16,742][ INFO][       smartdns.c:724 ] stop smartdns by signal 15
[2024-12-30 11:37:16,842][ INFO][       smartdns.c:1219] smartdns exit...
[2024-12-30 11:37:16,843][DEBUG][      dns_cache.c:832 ] write cache file /var/cache/smartdns/smartdns.cache
[2024-12-30 11:37:16,844][DEBUG][      dns_cache.c:875 ] wrote total 0 records.
  1. 如进程异常，请将coredump功能开启，上传coredump信息文件，同时上传配套的smartdns进程文件。
    在自定义界面，开启设置->自定义设置->生成coredump配置，重现问题后提交coredump文件
    coredump文件在/tmp目录下
@PikuZheng
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PikuZheng commented Dec 30, 2024 •
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cloudfront.net 包含 d2e1asnsl7br7b.cloudfront.net ，你这样配置不会导致查询死循环吗

大致测了一下这个是可以的，但可能你的缓存里已经有了记录，所以这样设置不生效。删缓存或等缓存过期后再试试？

@zhengqwe
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大致测了一下这个是可以的，但可能你的缓存里已经有了记录，所以这样设置不生效。删缓存或等缓存过期后再试试？

就是删缓存测的，并且这种没有响应的查询也根本没有缓存
q是和nslookup功能相似的工具，原版的nslookup不支持非标端口
image
image

@PikuZheng
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bind :5354
server 2400:3200::1

speed-check-mode ping,tcp:443
response-mode fastest-ip
log-file /userdata/smartdns/smartdns-test.log
log-level debug

cname /cloudfront.net/d2e1asnsl7br7b.cloudfront.net

cache-persist no

测试

localhost:~# kdig cloudfront.net @127.0.0.1:5354
;; ->>HEADER<<- opcode: QUERY; status: NOERROR; id: 40100
;; Flags: qr rd ra; QUERY: 1; ANSWER: 3; AUTHORITY: 0; ADDITIONAL: 0

;; QUESTION SECTION:
;; cloudfront.net.              IN      A

;; ANSWER SECTION:
cloudfront.net.         600     IN      CNAME   d2e1asnsl7br7b.cloudfront.net.
d2e1asnsl7br7b.cloudfront.net.  600     IN      A       18.172.50.20
d2e1asnsl7br7b.cloudfront.net.  600     IN      A       18.172.50.75

;; Received 93 B
;; Time 2024-12-30 16:23:07 CST
;; From 127.0.0.1@5354(UDP) in 143.0 ms
localhost:~# kdig something.cloudfront.net @127.0.0.1:5354
;; ->>HEADER<<- opcode: QUERY; status: NOERROR; id: 26143
;; Flags: qr rd ra; QUERY: 1; ANSWER: 3; AUTHORITY: 0; ADDITIONAL: 0

;; QUESTION SECTION:
;; something.cloudfront.net.            IN      A

;; ANSWER SECTION:
something.cloudfront.net.       589     IN      CNAME   d2e1asnsl7br7b.cloudfront.net.
d2e1asnsl7br7b.cloudfront.net.  589     IN      A       18.172.50.20
d2e1asnsl7br7b.cloudfront.net.  589     IN      A       18.172.50.75

;; Received 103 B
;; Time 2024-12-30 16:23:18 CST
;; From 127.0.0.1@5354(UDP) in 0.3 ms

看起来没问题

@PikuZheng
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还有一种可能是你配置的5个上游中有3个都对d2e1asnsl7br7b.cloudfront.net返回soa

@zhengqwe
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zhengqwe commented Dec 30, 2024 •
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按这个顺序试试：启动smrtdns后先请求something.cloudfront.net有结果，再请求d2e1asnsl7br7b.cloudfront.net也有结果；一旦启动smrtdns后先请求d2e1asnsl7br7b.cloudfront.net就直接GG，之后再请求something.cloudfront.net也无响应（每次启动smrtdns前都清掉缓存），触发条件比较苛刻
也就是在没有请求其他*.cloudfront.net做铺垫的情况下，直接请求d2e1asnsl7br7b.cloudfront.net（cname中的配置本身）就直接GG

aaa@aaa-VMware20-1:~$ sudo smartdns
aaa@aaa-VMware20-1:~$ q A AAAA something.cloudfront.net @127.0.0.1:5354
d2e1asnsl7br7b.cloudfront.net. 10m A 3.165.84.120
d2e1asnsl7br7b.cloudfront.net. 10m A 3.165.84.185
d2e1asnsl7br7b.cloudfront.net. 10m A 3.165.84.50
d2e1asnsl7br7b.cloudfront.net. 10m A 3.165.84.87
something.cloudfront.net. 10m CNAME d2e1asnsl7br7b.cloudfront.net.
d2e1asnsl7br7b.cloudfront.net. 10m AAAA 2600:9000:271a:3e00:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 10m AAAA 2600:9000:271a:4200:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 10m AAAA 2600:9000:271a:5000:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 10m AAAA 2600:9000:271a:600:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 10m AAAA 2600:9000:271a:6200:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 10m AAAA 2600:9000:271a:7800:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 10m AAAA 2600:9000:271a:b800:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 10m AAAA 2600:9000:271a:e000:d:172e:5dc0:21
aaa@aaa-VMware20-1:~$ q A AAAA d2e1asnsl7br7b.cloudfront.net @127.0.0.1:5354
d2e1asnsl7br7b.cloudfront.net. 9m51s A 3.165.84.120
d2e1asnsl7br7b.cloudfront.net. 9m51s A 3.165.84.185
d2e1asnsl7br7b.cloudfront.net. 9m51s A 3.165.84.50
d2e1asnsl7br7b.cloudfront.net. 9m51s A 3.165.84.87
d2e1asnsl7br7b.cloudfront.net. 9m51s AAAA 2600:9000:271a:3e00:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 9m51s AAAA 2600:9000:271a:4200:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 9m51s AAAA 2600:9000:271a:5000:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 9m51s AAAA 2600:9000:271a:600:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 9m51s AAAA 2600:9000:271a:6200:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 9m51s AAAA 2600:9000:271a:7800:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 9m51s AAAA 2600:9000:271a:b800:d:172e:5dc0:21
d2e1asnsl7br7b.cloudfront.net. 9m51s AAAA 2600:9000:271a:e000:d:172e:5dc0:21

aaa@aaa-VMware20-1:~$ sudo smartdns
aaa@aaa-VMware20-1:~$ q A AAAA d2e1asnsl7br7b.cloudfront.net @127.0.0.1:5354
FATA[0010] read udp 127.0.0.1:52020->127.0.0.1:5354: i/o timeout 
aaa@aaa-VMware20-1:~$ q A AAAA something.cloudfront.net @127.0.0.1:5354
FATA[0010] read udp 127.0.0.1:41580->127.0.0.1:5354: i/o timeout

还有一种可能是你配置的5个上游中有3个都对d2e1asnsl7br7b.cloudfront.net返回soa

这种情况应该不输出任何东西，而不是没有响应直到超时i/o timeout

@PikuZheng
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确实。
先查询 d2e1asnsl7br7b.cloudfront.net ，会匹配到规则 /cloudfront.net/d2e1asnsl7br7b.cloudfront.net 导致死循环
如果只需要将 cloudfront.net 映射到 d2e1asnsl7br7b.cloudfront.net ，可以设置
cname /-.cloudfront.net/d2e1asnsl7br7b.cloudfront.net

@cresky-github
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根域名映射到子域名？
难道不应该是子域名映射到根域名？

@PikuZheng
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根域名映射到子域名？ 难道不应该是子域名映射到根域名？

子到根，子到子都没问题。但是泛子到子、根到子都会有问题 @pymumu

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@PikuZheng @cresky-github @zhengqwe