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review.blissroms.org / platform_packages_modules_DnsResolver / 3c07ec67d152e200ad708e12db97800430378572
commit3c07ec67d152e200ad708e12db97800430378572[log] [tgz]
authorMike Yu <yumike@google.com>Wed Jul 01 12:02:14 2020 +0800
committerMike Yu <yumike@google.com>Thu Jul 02 14:04:23 2020 +0800
treef10678933ef32ccaeb08734a89d0164d63d0c927
parentc35b4541c3c7e7e7bd339a036ebe1ad9e94a10eb [diff]
Fix private DNS not working due to getConnectCounter() stuck

This call is not necessary to be protected by DnsTlsDispatcher::sLock.
The lock aims at protecting the creation/deletion of DnsTlsTransport.
Since the call is used only for the metrics, this change doesn't impact
on the functionality of private DNS.

Bug description:
When a thread gets stuck in TLS handshake, it might lead to another
thread blocking in the call getConnectCounter(). This results in
other DNS requests get stuck in the call getOrderedServerList()
because they are awaiting a lock hold by the second thread which
is also awaiting another lock hold by the first thread.

An example scenario is: In DNS strict mode, a private DNS server
used to be available in mobile data but becomes unresponsive.
Then, a new DNS request triggers the DnsResolver to do handshaking.
Before the handshake finishes, wifi can't work.

How to reproduce the bug:
  1) Set DNS strict mode, turn on mobile data
  2) Wait 20s for TLS connection disconnected. It can be check by:
       - ps -AT $(pidof netd) | grep "TlsListen"
  3) Drop DoT traffic by the command:
       - iptables -A OUTPUT -p tcp --dport 853 -o rmnet_data1 -j DROP
  4) Turn on wifi. Wifi shows no internet

Bug: 160027328
Test: not reproducible by the above steps
Test: cd packages/modules/DnsResolver && atest

Change-Id: I050ce8f13c19f706d58bac44c0e5a269481cb0c0
1 file changed
tree: f10678933ef32ccaeb08734a89d0164d63d0c927
  1. aidl_api/
  2. apex/
  3. binder/
  4. include/
  5. tests/
  6. .clang-format ⇨ ../../../build/soong/scripts/system-clang-format
  7. .editorconfig
  8. Android.bp
  9. Dns64Configuration.cpp
  10. Dns64Configuration.h
  11. DnsProxyListener.cpp
  12. DnsProxyListener.h
  13. DnsQueryLog.cpp
  14. DnsQueryLog.h
  15. DnsQueryLogTest.cpp
  16. DnsResolver.cpp
  17. DnsResolver.h
  18. DnsResolverService.cpp
  19. DnsResolverService.h
  20. DnsStats.cpp
  21. DnsStats.h
  22. DnsStatsTest.cpp
  23. DnsTlsDispatcher.cpp
  24. DnsTlsDispatcher.h
  25. DnsTlsQueryMap.cpp
  26. DnsTlsQueryMap.h
  27. DnsTlsServer.cpp
  28. DnsTlsServer.h
  29. DnsTlsSessionCache.cpp
  30. DnsTlsSessionCache.h
  31. DnsTlsSocket.cpp
  32. DnsTlsSocket.h
  33. DnsTlsSocketFactory.h
  34. DnsTlsTransport.cpp
  35. DnsTlsTransport.h
  36. Experiments.cpp
  37. Experiments.h
  38. ExperimentsTest.cpp
  39. getaddrinfo.cpp
  40. getaddrinfo.h
  41. gethnamaddr.cpp
  42. gethnamaddr.h
  43. hostent.h
  44. IDnsTlsSocket.h
  45. IDnsTlsSocketFactory.h
  46. IDnsTlsSocketObserver.h
  47. libnetd_resolv.map.txt
  48. LockedQueue.h
  49. NOTICE
  50. OWNERS
  51. params.h
  52. PREUPLOAD.cfg
  53. PrivateDnsConfiguration.cpp
  54. PrivateDnsConfiguration.h
  55. README-DoT.md
  56. README.md
  57. res_cache.cpp
  58. res_comp.cpp
  59. res_comp.h
  60. res_debug.cpp
  61. res_debug.h
  62. res_init.cpp
  63. res_init.h
  64. res_mkquery.cpp
  65. res_query.cpp
  66. res_send.cpp
  67. res_send.h
  68. res_stats.cpp
  69. resolv_cache.h
  70. resolv_cache_unit_test.cpp
  71. resolv_callback_unit_test.cpp
  72. resolv_private.h
  73. resolv_test_config_template.xml
  74. resolv_tls_unit_test.cpp
  75. resolv_unit_test.cpp
  76. ResolverController.cpp
  77. ResolverController.h
  78. ResolverEventReporter.cpp
  79. ResolverEventReporter.h
  80. ResolverStats.h
  81. sethostent.cpp
  82. stats.h
  83. stats.proto
  84. TEST_MAPPING
  85. util.cpp
  86. util.h
README.md

Logging

This code uses LOG(X) for logging. Log levels are VERBOSE,DEBUG,INFO,WARNING and ERROR. The default setting is WARNING and logs relate to WARNING and ERROR will be shown. If you want to enable the DEBUG level logs, using following command. adb shell service call dnsresolver 10 i32 1 VERBOSE 0 DEBUG 1 INFO 2 WARNING 3 ERROR 4 Verbose resolver logs could contain PII -- do NOT enable in production builds.