dgb: wire embedded P2P header feed into HeaderChain (live validate_and_append) - #230
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This was referenced Jun 19, 2026
…d_append) wire_header_ingest (coin/header_ingest.hpp) subscribes a HeaderChain to dgb::interfaces::Node::new_headers -- the feed coin/p2p_node.hpp fires from ADD_P2P_HANDLER(headers) -- and routes every announced BlockHeaderType through the make_header_sample SSOT (#227) into HeaderChain::validate_and_append. This is what turns the chain from a unit-test fixture into one that advances on LIVE wire headers, lighting up tip_hash() -> previousblockhash for the embedded work template. The connector adds NO policy: disposition (Scrypt validate / continuity / reject) stays in validate_and_append, the single SSOT. Feeding real-shaped headers surfaced a latent SIGFPE in work_from_target: it divides UINT64_MAX by target.low64(), but a real-difficulty target has its significant bits high in the 256-bit word (genesis target ~2^224 -> low64()==0), an integer div-by-zero. Prior tests only used small uint64-range targets, so it never fired. Guarded: an unrepresentable-in-uint64 target credits 0 proxy work instead of crashing. cumulative_work is unconsumed by any V36 consensus path (retarget demoted to no-op; PPLNS scores shares); true 2^256/(target+1) work lands at the embedded-daemon work-accounting boundary alongside scrypt->pow_hash. dgb_header_ingest_test 5/5 (routing, batch arrival-order, driver-only, reject-delegation, empty-tip); header_chain_test 35/35 (no regression). Test wired into BOTH build.yml --target allowlists (#143 NOT_BUILT trap). Fenced to src/impl/dgb/; no shared-base touch.
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Stacked on #227 (make_header_sample). Retarget to master once #227 lands.
What: wire_header_ingest (coin/header_ingest.hpp) subscribes a HeaderChain to dgb::interfaces::Node::new_headers (fired by coin/p2p_node.hpp ADD_P2P_HANDLER(headers)) and routes each announced header through the make_header_sample SSOT (#227) into HeaderChain::validate_and_append. The live wire path now advances the chain -> tip_hash() -> previousblockhash for the embedded work template. Connector adds NO policy; disposition stays in validate_and_append (the single SSOT).
Latent bug fixed (surfaced by real-shaped headers): work_from_target did UINT64_MAX / target.low64(); a real-difficulty target (~2^224) has low64()==0 -> integer div-by-zero (SIGFPE). Prior tests only used small uint64-range targets. Guarded to credit 0 proxy work; cumulative_work is unconsumed by any V36 consensus path (retarget demoted to no-op, PPLNS scores shares). True 2^256/(target+1) deferred to embedded-daemon work-accounting boundary (with scrypt->pow_hash).
Tests: dgb_header_ingest_test 5/5; header_chain_test 35/35 (no regression). Wired into BOTH build.yml --target allowlists (#143 trap). Fenced to src/impl/dgb/; no shared-base touch. GPG-signed.
HOLD merge (fenced auto-merge on full-matrix green, after #227).