test: avoid non-loopback network traffic from node_init_tests/init_test #35193

1. 
   vasild commented at 11:05 AM on May 1, 2026: contributor

   The test node_init_tests/init_test calls: AppInitMain() -> StartMapPort() -> StartThreadMapPort() -> ThreadMapPort() -> ProcessPCP() -> PCPRequestPortMap() -> CreateSock() and on the returned value from CreateSock() it calls the Connect() method.

   Thus, change BasicTestingSetup::BasicTestingSetup() to set -natpmp to 0. This way node_init_tests/init_test or other tests will not do network activity due to ThreadMapPort().

   Also add a comment about natpmp=0 in test/functional/test_framework/util.py.

   Also set -dnsseed=0 in BasicTestingSetup::BasicTestingSetup() to avoid DNS queries.

2. DrahtBot added the label Tests on May 1, 2026
3. 
   DrahtBot commented at 11:05 AM on May 1, 2026: contributor

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   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/35193.

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   ACK	ryanofsky, fjahr

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4. 
   vasild commented at 11:18 AM on May 1, 2026: contributor

   @fjahr, @ryanofsky, maybe you would be interested in reviewing this PR because it is part of #31349 which you ACKed before in #31349 (comment) and #31349#pullrequestreview-3589303104

5. 
   fjahr commented at 10:58 AM on May 2, 2026: contributor

   ACK 7545f8dfd3012eff018b31110daee227cb87fe85

   Verified this is just the same commit pulled out of https://github.com/bitcoin/bitcoin/pull/31349

6. 
   ferminquant commented at 4:28 PM on May 8, 2026: none

   I tested this with strace -f -e trace=network and confirmed that the patch does stop the NAT-PMP/PCP ThreadMapPort() traffic described in the PR body.

   However, given the PR title and the link to #31349 / #31339, I expected node_init_tests/init_test to avoid non-loopback traffic more generally. The test still performs DNS lookups for x9.dummySeed.invalid through the system resolver. In my environment that resolver is local-routed, but #31349 discusses cases where this same DNS lookup goes to non-loopback resolvers such as 8.8.8.8 or 1111:1111::1.

   As a control, rerunning the test with -dnsseed=0 removed those DNS queries, leaving only the expected 127.0.0.1 Tor-control attempt.

   So I think the NAT-PMP part works, but either BasicTestingSetup should also force -dnsseed=0, or the PR title/description should make clear that this only addresses the ThreadMapPort() source of traffic rather than all non-loopback traffic from node_init_tests/init_test.

7. ryanofsky approved
8. 
   ryanofsky commented at 10:50 PM on May 13, 2026: contributor

   Code review ACK 7545f8dfd3012eff018b31110daee227cb87fe85

9. 
   vasild commented at 9:20 AM on May 15, 2026: contributor

   The test still performs DNS lookups ... -dnsseed=0 removed those DNS queries

   Oh, looks like you figured out the unexplained local failures reported on #31349 plus proposed a fix!

10. test: avoid non-loopback network traffic from node_init_tests/init_test

    The test calls:
    `AppInitMain()` -> `StartMapPort()` -> `StartThreadMapPort()` ->
    `ThreadMapPort()` -> `ProcessPCP()` -> `PCPRequestPortMap()` ->
    `CreateSock()` and on the returned value from `CreateSock()` it calls
    the `Connect()` method.
    
    Thus, change `BasicTestingSetup::BasicTestingSetup()` to set `-natpmp`
    to 0. This way `node_init_tests/init_test` or other tests will not do
    network activity due to `ThreadMapPort()`.
    
    Also add a comment about `natpmp=0` in
    `test/functional/test_framework/util.py`.
    
    Also set `-dnsseed=0` in `BasicTestingSetup::BasicTestingSetup()` to
    avoid DNS queries.

    1c500b1709
11. vasild force-pushed on May 15, 2026
12. 
    vasild commented at 10:17 AM on May 15, 2026: contributor

    7545f8dfd3012eff018b31110daee227cb87fe85...1c500b17098e2c65129a1dda7345b9961f4a951f: added -dnsseed=0 as per #35193 (comment)

13. ryanofsky approved
14. 
    ryanofsky commented at 5:39 PM on May 18, 2026: contributor

    Code review ACK 1c500b17098e2c65129a1dda7345b9961f4a951f, just disabling -dnsseed since previous review, which makes sense.

    Curious if it also makes sense to disable dnsseed in test/functional/test_framework/util.py?

15. DrahtBot requested review from fjahr on May 18, 2026
16. 
    fjahr commented at 5:52 PM on May 18, 2026: contributor

    re-ACK 1c500b17098e2c65129a1dda7345b9961f4a951f

17. fanquake merged this on May 19, 2026
18. fanquake closed this on May 19, 2026

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Review Requested
fjahr