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AdguardTeam / dnsproxy

Simple DNS proxy with DoH, DoT, DoQ and DNSCrypt support
Apache License 2.0
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dnsproxy report error when dnsmasq uses use-stale-cache option #328

Closed cattyhouse closed 1 year ago

cattyhouse commented 1 year ago

i feel like this is still an issue worth reporting:

client definition:

the client who uses gateway's dns services, not the client who runs dnsproxy or dnsmasq

gateway definition:

the machine runs dnsproxy and dnsmasq, to provide dns services

only reproducable from macOS client

linux client does not have this issue

on gateway 192.168.1.1 (debian)

  1. start dnsmasq on 5353, upstream set to dnsproxy 9999

    dnsmasq --port=5353 --server='127.0.0.1#9999' --use-stale-cache --no-daemon --filter-AAAA --no-resolv --no-poll --domain-needed --log-queries=extra --log-async  --log-debug --log-facility=- --fast-dns-retry --edns-packet-max=1232

  2. start dnsproxy on 9999

dnsproxy -l 127.0.0.1 -p 9999 -u https://1.1.1.1/dns-query -u https://8.8.8.8/dns-query --ipv6-disabled --all-servers

on macOS client

while true ; do dig @192.168.1.1 -p 5353 api.github.com +short ; sleep 10 ; done

# we sleep 10 because api.github.com ttl is around 70s

when dnsmasq report after ttl (70s for apt.github.com) expired : 

cached-stale api.github.com is 192.30.255.116
forwarded api.github.com to 127.0.0.1#9999
forwarded api.github.com to 127.0.0.1#9999
forwarded api.github.com to 127.0.0.1#9999

# no reply any more

dnsproxy report :

dnsproxy: unpacking udp packet: dns: overflowing header size
dnsproxy: unpacking udp packet: dns: overflowing header size
dnsproxy: unpacking udp packet: dns: overflowing header size
dnsproxy: unpacking udp packet: dns: overflowing header size

my conclusion

on Linux client and gateway itself

same command while true ; do dig @192.168.1.1 -p 5353 api.github.com +short ; sleep 10 ; done

no issue found on dnsmasq and dnsproxy.

dig output difference

macOS client vs Linux client after gateway stale-cache query

macOS : 

; EDNS: version: 0, flags:; udp: 1232
; OPT=15: 00 03 ("..")

Linux : 


; EDNS: version: 0, flags:; udp: 1232
; EDE: 3 (Stale Answer)

Questions

cattyhouse commented 1 year ago

the error message is from this project?

https://github.com/miekg/dns/blob/f07f1e694f394f5b205b224f7abdd30d433d8019/msg_helpers.go#L141

cattyhouse commented 1 year ago

tcpdump command on gateway (debian)

tcpdump -nn -s0 -vvv -i lo udp dst port 9999 -T domain
tcpdump: listening on lo, link-type EN10MB (Ethernet), snapshot length 262144 bytes

query from macOS client

query from Linux client (no issue query from linux client, just here for compare)

20:44:15.658298 IP (tos 0x0, ttl 64, id 25923, offset 0, flags [DF], proto UDP (17), length 83)
    127.0.0.1.35265 > 127.0.0.1.9999: 15747+ [1au] A? api.github.com. ar: . OPT UDPsize=1232 [COOKIE b2285511cf13d8ae] (55)
20:45:16.328696 IP (tos 0x0, ttl 64, id 31246, offset 0, flags [DF], proto UDP (17), length 83)
    127.0.0.1.50230 > 127.0.0.1.9999: 16837+ [1au] A? api.github.com. ar: . OPT UDPsize=1232 [Opt15 0003] (55)
cattyhouse commented 1 year ago

query from macOS client (tcpdump on gateway with showing hex)

first query , dnsmasq -> dnsproxy

21:13:23.275378 IP (tos 0x0, ttl 64, id 31750, offset 0, flags [DF], proto UDP (17), length 71)
    127.0.0.1.13590 > 127.0.0.1.9999: 16382+ [1au] A? api.github.com. ar: . OPT UDPsize=1232 (43)
        0x0000:  0000 0000 0000 0000 0000 0000 0800 4500  ..............E.
        0x0010:  0047 7c06 4000 4011 c09d 7f00 0001 7f00  .G|.@.@.........
        0x0020:  0001 3516 270f 0033 fe46 3ffe 0120 0001  ..5.'..3.F?.....
        0x0030:  0000 0000 0001 0361 7069 0667 6974 6875  .......api.githu
        0x0040:  6203 636f 6d00 0001 0001 0000 2904 d000  b.com.......)...
        0x0050:  0000 0000 00                             .....

query after stale-cache dnsmasq -> dnsproxy


21:13:44.072807 IP (tos 0x0, ttl 64, id 35421, offset 0, flags [DF], proto UDP (17), length 71)
    127.0.0.1.63375 > 127.0.0.1.9999: 28918+ [1au] A? api.github.com. ar: . OPT [|domain]
        0x0000:  0000 0000 0000 0000 0000 0000 0800 4500  ..............E.
        0x0010:  0047 8a5d 4000 4011 b246 7f00 0001 7f00  .G.]@.@..F......
        0x0020:  0001 f78f 270f 0033 fe46 70f6 0120 0001  ....'..3.Fp.....
        0x0030:  0000 0000 0001 0361 7069 0667 6974 6875  .......api.githu
        0x0040:  6203 636f 6d00 0001 0001 0000 2904 d000  b.com.......)...
        0x0050:  0000 0000 06                             .....
cattyhouse commented 1 year ago

dnsmasq has fixed the issue

https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=d774add784d01c8346b271e8fb5cbedc44d7ed08

/close

ameshkov commented 1 year ago

thank you for reporting this to us and dnsmasq, glad it got resolved