Loop detection breaks transparent proxying

[linnaea]

trafficserver/proxy/http/HttpTransact.cc

Line 6541 in 926dd71

if (dst_port == local_port && (ats_ip_addr_eq(s->host_db_info.ip(), &Machine::instance()->ip.sa) ||

By the very definition of transparent proxying, this will detect a loop when it's trying to connect to origin server.

Diag traces captured:

Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpTransact.cc:3239 (HandleCacheOpenReadMiss)> (http_seq) [633] [HttpTransact::HandleCacheOpenReadMiss] Miss in cache
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpTransact.cc:5182 (get_ka_info_from_config)> (http_trans) [633] get_ka_info_from_config, server_info->http_version 65537, check_hostdb 0
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpTransact.cc:7821 (build_request)> (http_trans) [633] [build_request] removing host name from url
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpTransact.cc:7834 (build_request)> (http_trans) [633] [build_request] request like cacheable and conditional headers removed
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpTransact.cc:7863 (build_request)> (http_trans) [633] [build_request] request_sent_time: 1613411433
Feb 16 01:50:33 hub traffic_manager[1043]: +++++++++ Proxy's Request +++++++++
Feb 16 01:50:33 hub traffic_manager[1043]: -- State Machine Id: 633
Feb 16 01:50:33 hub traffic_manager[1043]: GET / HTTP/1.1
Feb 16 01:50:33 hub traffic_manager[1043]: Host: lab.linnaea.local
Feb 16 01:50:33 hub traffic_manager[1043]: User-Agent: curl/7.66.0
Feb 16 01:50:33 hub traffic_manager[1043]: Accept: */*
Feb 16 01:50:33 hub traffic_manager[1043]: Via: http/1.1 traffic_server[745d2a80-67e3-4654-8bdd-49ee740d488c] (ApacheTrafficServer/9.0.0)
Feb 16 01:50:33 hub traffic_manager[1043]:
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpSM.cc:7319 (call_transact_and_set_next_state)> (http) [633] State Transition: SM_ACTION_CACHE_LOOKUP -> SM_ACTION_CACHE_ISSUE_WRITE
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpSM.cc:4715 (do_cache_prepare_action)> (http_cache_write) [633] writing to cache with URL http://lab.linnaea.local/
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpCacheSM.cc:160 (state_cache_open_write)> (http_cache) [633] [&HttpCacheSM::state_cache_open_write, CACHE_EVENT_OPEN_WRITE/TS_EVENT_CACHE_OPEN_WRITE]
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpSM.cc:2611 (main_handler)> (http) [633] [HttpSM::main_handler, CACHE_EVENT_OPEN_WRITE/TS_EVENT_CACHE_OPEN_WRITE]
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpSM.cc:2423 (state_cache_open_write)> (http) [633] [&HttpSM : state_cache_open_write, CACHE_EVENT_OPEN_WRITE/TS_EVENT_CACHE_OPEN_WRITE]
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpTransact.cc:3207 (handle_cache_write_lock)> (http_trans) Next action next; nullptr
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpSM.cc:7319 (call_transact_and_set_next_state)> (http) [633] State Transition: SM_ACTION_CACHE_ISSUE_WRITE -> SM_ACTION_ORIGIN_SERVER_OPEN
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpSM.cc:4820 (do_http_server_open)> (http_track) entered inside do_http_server_open ][ipv4]
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpSM.cc:4852 (do_http_server_open)> (http) [633] open connection to lab.linnaea.local: 10.141.0.2:80
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpSM.cc:4864 (do_http_server_open)> (http_seq) [HttpSM::do_http_server_open] Sending request to server
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpTransact.cc:6667 (will_this_request_self_loop)> (http_transact) [633] host ip and port same as local ip and port - bailing
Feb 16 01:50:33 hub traffic_manager[1043]: +++++++++ Proxy's Response 2 +++++++++
Feb 16 01:50:33 hub traffic_manager[1043]: -- State Machine Id: 633
Feb 16 01:50:33 hub traffic_manager[1043]: HTTP/1.1 400 Cycle Detected
Feb 16 01:50:33 hub traffic_manager[1043]: Date: Mon, 15 Feb 2021 17:50:33 GMT
Feb 16 01:50:33 hub traffic_manager[1043]: Connection: close
Feb 16 01:50:33 hub traffic_manager[1043]: Via: http/1.1 traffic_server (ATS [uEcMs f p eH:t cCMp s ] [http/1.1])
Feb 16 01:50:33 hub traffic_manager[1043]:
Feb 16 01:50:33 hub traffic_manager[1043]: [Feb 16 01:50:33.718] [ET_NET 3] DEBUG: <HttpTransact.cc:801 (SelfLoop)> (http_trans) [633] [Loop]Request will selfloop.

[shinrich]

I just ran into this as well in the 9.1.1 codebase. Found a fix. Putting PR #8586 to address the issue. Basically if the transaction is outbound transparent, there is no sense in performing the self loop check.