net: do not read/dump anchors if network is not active #34213

1. 
   brunoerg commented at 9:26 pm on January 6, 2026: contributor

   We currently save 2 block-relay-only (anchor) connections when stopping a node and connect to them right after starting it. However, if you start a node with network disabled (setting -networkactive=0 or disabling using the RPC), it will read the anchors, obviously will not be able to connect to them and then, when stopping the node, considering it will have 0 block-relay-only connections, it will save 0 anchors, basically deleting the previous ones. With this PR, we will only read and write the anchors if the network is active. It will avoid losing the anchors when using the node without network activity and also avoid unecessary actions (like reading the anchors even knowing we have no network activity).
2. DrahtBot added the label P2P on Jan 6, 2026
3. 
   DrahtBot commented at 9:26 pm on January 6, 2026: contributor

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   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/34213.

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   ACK	bensig
   Concept ACK	waketraindev

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4. brunoerg force-pushed on Jan 6, 2026
5. DrahtBot added the label CI failed on Jan 6, 2026
6. 
   DrahtBot commented at 9:31 pm on January 6, 2026: contributor

   🚧 At least one of the CI tasks failed. Task lint: https://github.com/bitcoin/bitcoin/actions/runs/20762589891/job/59621113321 LLM reason (✨ experimental): Linting failed: ruff detected errors (trailing whitespace) in Python code, causing the CI to fail.

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7. net: do not read/dump anchors if network is not active 903a37c1e1
8. brunoerg force-pushed on Jan 6, 2026
9. DrahtBot removed the label CI failed on Jan 6, 2026
10. in src/net.cpp:3348 in 903a37c1e1

    3344@@ -3345,7 +3345,7 @@ bool CConnman::Start(CScheduler& scheduler, const Options& connOptions)
    3345         std::shuffle(seed_nodes.begin(), seed_nodes.end(), FastRandomContext{});
    3346     }
    3347 
    3348-    if (m_use_addrman_outgoing) {
    3349+    if (m_use_addrman_outgoing && fNetworkActive) {
    

    ---

    ---

    

    waketraindev commented at 0:21 am on January 7, 2026:

    I start some nodes with network inactive.

    micro nit (in both cases):

    0    if (fNetworkActive && m_use_addrman_outgoing) {
    

    ---

    

    brunoerg commented at 6:25 pm on January 7, 2026:

    I’ll leave as-is for now.
11. 
    waketraindev commented at 0:22 am on January 7, 2026: contributor

    Concept ACK
12. 
    waketraindev commented at 1:50 am on January 7, 2026: contributor

    Have you considered also adding a DumpAnchors() if anchors_to_dump.size() > 1 when setting network active from true to false?

    That would persist the anchors for nodes that do a setnetworkactive false and after shut down and skip dumping them again at shutdown.

13. 
    brunoerg commented at 6:26 pm on January 7, 2026: contributor

    Have you considered also adding a DumpAnchors() if anchors_to_dump.size() > 1 when setting network active from true to false?

    Yes, but would leave it for a follow-up, it will require more changes than the simple ones to cover the -networkactive behavior.

14. 
    bensig commented at 6:40 pm on January 7, 2026: contributor

    ACK 903a37c1e142b4ee6b83fee99735ab69716084ee

    Tested, feature_anchors.py passes

15. DrahtBot requested review from waketraindev on Jan 7, 2026
16. 
    w0xlt commented at 8:59 pm on January 7, 2026: contributor

    This seems like a reasonable change, but it may be better to document that setting fNetworkActive to false via the setnetworkactive RPC can prevent anchors from being preserved.
17. 
    brunoerg commented at 7:48 pm on January 8, 2026: contributor

    This seems like a reasonable change, but it may be better to document that setting fNetworkActive to false via the setnetworkactive RPC can prevent anchors from being preserved.

    Sounds good, I will add this information in the setnetworkactive RPC.

Contributors
brunoerg DrahtBot waketraindev bensig w0xlt

Review Requested
waketraindev

Labels
P2P