#35940 net: allow selecting BIP152 high-bandwidth peers with `-addnode`

• Let node operators guarantee immediate compact block announcements over dedicated low-latency links
• Allows manually specifying high-bandwidth peers outside the automatic three-peer limit

Adds an opt-in `=bip152-hb` suffix to `-addnode` configuration values, instructing the node to immediately send a high-bandwidth `SENDCMPCT(1)` request to that outbound peer upon connection and reconnection. Configured peers operate outside the default three-peer limit and automatic block-announcement rotation.

Problem: Bitcoin Core automatically chooses up to three BIP152 high-bandwidth peers based on which peers deliver blocks first, preventing operators with dedicated low-latency peering links from guaranteeing immediate compact block announcements.

P3 · new feature

• P3 because it helps operators with custom peering setups guarantee fast compact block relay
• Provides an opt-in CLI configuration rather than resolving network-wide relay bottlenecks

Clear operational use case for node runners with known network topology, but deferrable as it introduces an opt-in CLI enhancement rather than addressing network-wide relay bottlenecks or security risks.

Membership: Modifies outbound peer compact block announcement negotiation and connection tracking in net and net_processing.

Factors: security/stability 0, bug 0, performance 1, user value 2, leverage 0

• Ready for review
• Applies cleanly with passing CI and previous feedback addressed

The branch applies cleanly, CI is passing, and previous reviewer feedback has been addressed.

Author status: active

Resolved concerns:

• Release note naming convention addressed in a push.

• Concept support for allowing explicit operator override of the three-peer cap (jeanpablojp)
• No objections raised

Concept ACK from jeanpablojp supporting explicit operator override; no objections.

jeanpablojp explicitly supported overriding the BIP152 three-peer limit via operator opt-in and agreed with reusing -addnode.

• jeanpablojp: 'The opt-in override of the BIP152 three-peer cap seems fine to me, since it's an explicit operator choice, not a default, and it's disclosed upfront.'

Review verdicts (DrahtBot): 0

• Concept ACK: jeanpablojp

109 lines under test/bench/ci.

• src/test/net_peer_connection_tests.cpp +48/-0
• test/functional/p2p_compactblocks_hb.py +39/-1
• src/init.cpp +23/-3
• src/net.cpp +25/-0
• test/functional/feature_config_args.py +21/-0
• src/net_processing.cpp +14/-5
• src/net.h +7/-7
• doc/release-notes-35940.md +12/-0

Adds an opt-in `=bip152-hb` suffix to `-addnode` to request BIP152 high-bandwidth compact block announcements from specific outbound peers. Solves the inability of node operators with dedicated low-latency peering links or multi-node clusters to ensure immediate compact block relay without waiting for automatic rotation. It has received a Concept ACK endorsing the approach, with no open objections or blocking dependencies.