DoH: Change Network to use try_send

As send() blocks until channel has capacity, Dispatcher gets blocked
at sending commands to a Network object if the Network's mpsc channel
has no capacity. This happens when there are excess DNS requests while
the connection has not been established. Therefore, change all the DoH
code to use try_send() that returns an error immediate if the channel
is full.

If a Network's mpsc channel has no capacity, DNS query threads that
called doh_query() with the associated net_id will get DOH_RESULT_CAN_NOT_SEND
error immediately. Since it's not a timeout error, they will try DoT.

Bug: 207301204
Test: cd packages/modules/DnsResolver && atest
Change-Id: I9575e6f410b8b552c07af15284b67b305ecce6b9
9 files changed
tree: 37c096229bdc769a0d374e4ad8bf1417e3d600bc
  1. aidl_api/
  2. apex/
  3. binder/
  4. doh/
  5. include/
  6. tests/
  7. .editorconfig
  8. Android.bp
  9. cbindgen.toml
  10. Dns64Configuration.cpp
  11. Dns64Configuration.h
  12. DnsProxyListener.cpp
  13. DnsProxyListener.h
  14. DnsQueryLog.cpp
  15. DnsQueryLog.h
  16. DnsQueryLogTest.cpp
  17. DnsResolver.cpp
  18. DnsResolver.h
  19. DnsResolverService.cpp
  20. DnsResolverService.h
  21. DnsStats.cpp
  22. DnsStats.h
  23. DnsStatsTest.cpp
  24. DnsTlsDispatcher.cpp
  25. DnsTlsDispatcher.h
  26. DnsTlsQueryMap.cpp
  27. DnsTlsQueryMap.h
  28. DnsTlsServer.cpp
  29. DnsTlsServer.h
  30. DnsTlsSessionCache.cpp
  31. DnsTlsSessionCache.h
  32. DnsTlsSocket.cpp
  33. DnsTlsSocket.h
  34. DnsTlsSocketFactory.h
  35. DnsTlsTransport.cpp
  36. DnsTlsTransport.h
  37. doh.h
  38. Experiments.cpp
  39. Experiments.h
  40. ExperimentsTest.cpp
  41. getaddrinfo.cpp
  42. getaddrinfo.h
  43. gethnamaddr.cpp
  44. gethnamaddr.h
  45. hostent.h
  46. IDnsTlsSocket.h
  47. IDnsTlsSocketFactory.h
  48. IDnsTlsSocketObserver.h
  49. IPrivateDnsServer.h
  50. libnetd_resolv.map.txt
  51. LockedQueue.h
  52. NOTICE
  53. OperationLimiter.h
  54. OperationLimiterTest.cpp
  55. OWNERS
  56. params.h
  57. PREUPLOAD.cfg
  58. PrivateDnsCommon.h
  59. PrivateDnsConfiguration.cpp
  60. PrivateDnsConfiguration.h
  61. PrivateDnsConfigurationTest.cpp
  62. PrivateDnsValidationObserver.h
  63. README-DoT.md
  64. README.md
  65. res_cache.cpp
  66. res_comp.cpp
  67. res_comp.h
  68. res_debug.cpp
  69. res_debug.h
  70. res_mkquery.cpp
  71. res_query.cpp
  72. res_send.cpp
  73. res_send.h
  74. res_stats.cpp
  75. resolv_cache.h
  76. resolv_private.h
  77. resolv_rust_test_config_template.xml
  78. resolv_test_config_template.xml
  79. ResolverController.cpp
  80. ResolverController.h
  81. ResolverEventReporter.cpp
  82. ResolverEventReporter.h
  83. ResolverStats.h
  84. sethostent.cpp
  85. stats.h
  86. stats.proto
  87. TEST_MAPPING
  88. util.cpp
  89. 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.