Extension Points

Modifications to upstream go-ethereum files that wire in ETC/PoW code. Each point is a hook, field, conditional, call, or function added to a file that originally existed in upstream.

Metric	Value
Total extension points	95
Files touched	36

Points by kind

Kind	Count
field	30
conditional	31
call	21
function	9
const	2
import	2

Struct Fields

#	File	Name	Lines	Description	Wires To
1	params/config.go	ChainConfig ETC fields	497-507	ECIP fork blocks (1017/1041/1099/Spiral), era rounds, DieHard bomb pause, MESS (ECBP-1100) activation/deactivation	params/config_etc.go
2	params/config.go	Rules.IsEIP160	1410	EIP-160 activation flag in Rules struct — ETC activates EIP-160 independently of EIP-158	—
3	params/config.go	Rules.IsSpiral	1418	Spiral hard fork activation flag in Rules struct — ETC equivalent of Shanghai	—
4	eth/handler.go	handler.isPow	124	Flag for perpetual PoW chains — gates TD-based sync, block fetcher, chain syncer	eth/handler_pow.go
5	eth/handler.go	handler.forkFilter	121	Fork ID filter for ETC chain identity — rejects incompatible peers	core/forkid
6	eth/handler.go	handler.messForceEnable/Disable	126-127	MESS emergency override flags propagated from ethconfig	eth/sync_mess.go
7	eth/handler.go	handler.blockFetcher	136	Block fetcher instance for PoW chains (nil on PoS)	eth/handler_pow.go
8	eth/handler.go	handler.chainSync	139	PoW chain syncer managing TD-based sync loop (nil on PoS)	eth/sync_pow.go
9	eth/handler.go	handler.minedBlockSub	144	PoW mined block subscription — subscribed in Start(), unsubscribed in Stop()	eth/handler_mining_pow.go
10	eth/peer.go	ethPeerInfo.Difficulty	32	Total difficulty field in peer info — exposed in admin_peers for PoW diagnostics	—
11	eth/downloader/queue.go	queue.revokeHook	153	Callback for header request revocation on peer drop	eth/downloader/queue_pow.go
12	eth/downloader/downloader.go	Downloader.cancelPeer	158	Tracks the master peer for cancellation on stalling — used by concurrent fetchers	eth/downloader/downloader_pow.go
13	core/blockchain.go	BlockChain.forker	367	ETC PoW fork choice engine (nil for non-PoW) — replaces upstream hc.td comparison	core/forkchoice_pow.go
14	core/headerchain.go	HeaderChain.tdCache	68	LRU cache for total difficulty values, keyed by block hash	core/headerchain_pow.go
15	eth/protocols/eth/peer.go	Peer.powExt	86	PoW-specific peer state (TD, head info) — nil for PoS peers	eth/protocols/eth/peer_pow.go
16	eth/ethconfig/config.go	Config.MESSForceEnable/Disable	226-227	Emergency MESS overrides — force enable or force disable regardless of chain config	eth/sync_mess.go
17	eth/ethconfig/config.go	Config.Ethash	230	Ethash configuration for ETC PoW mining	consensus/ethash
18	ethstats/ethstats.go	nodeStats.Mining/Hashrate	818-819	Mining flag and hashrate in the periodic node stats report — restored from the #28623 removal	miner/miner_pow.go

Conditional Blocks

#	File	Name	Lines	Description	Wires To
19	core/genesis.go	chainConfigOrDefault Classic guard	463	Prefers a stored Classic/Mordor config over the ETH/ETC shared genesis hash, so a Classic datadir opened without an explicit genesis isn't misresolved to Ethereum mainnet	params/config_etc.go
20	eth/handler.go	isPow dispatch in runEthPeer	263-281	Routes to Handshake68PoW (with TD) for PoW peers, standard Handshake for PoS	eth/protocols/eth/handshake_pow.go
21	eth/handler.go	isPow notify chainSync	330-332	Notifies PoW chain syncer about new peer for TD-based sync	eth/sync_pow.go
22	eth/handler.go	isPow in Start (txFetcher guard)	468-470	Skips txFetcher.Start() for PoW — lifecycle managed by chainSyncer.loop()	eth/sync_pow.go
23	eth/handler.go	isPow in Start (PoW syncer)	473-486	Starts chainSyncer, block fetcher, and MESS safety loop for PoW chains	eth/handler_pow.go, eth/sync_pow.go
24	eth/handler.go	isPow in Stop	502-508	Skips manual fetcher/downloader stop for PoW — defers handle teardown	eth/sync_pow.go
25	eth/handler_eth.go	NewBlockHashesPacket PoW dispatch	62-64	Dispatches NewBlockHashes to block fetcher for PoW announcement-based propagation	eth/handler_pow.go
26	eth/handler_eth.go	NewBlockPacket PoW dispatch	66-67	Dispatches NewBlock to block fetcher for PoW block propagation	eth/handler_pow.go
27	eth/peer.go	PoW block in ethPeer.info()	54-56	Adds difficulty and head hash to peer info when TD is available	—
28	core/evm.go	London-without-EIP1559 baseFee=0	59-61	Sets baseFee to 0 when London is active but EIP-1559 is not — ETC decouples these	—
29	core/vm/evm.go	IsSpiral instruction set	164-165	Selects Spiral instruction set — ETC equivalent of Shanghai EVM rules	—
30	core/vm/evm.go	IsEIP160 activation	192,194-195	Deep-copies jump table and enables EIP-160 (increased gas for EXP) independently	—
31	consensus/misc/eip1559/eip1559.go	IsEIP1559 guard	66	Guards EIP-1559 base fee verification — skips when chain has London without 1559	—
32	core/blockchain.go	forker in writeKnownBlock	1689-1697	Uses ForkChoice.ReorgNeeded() to decide reorg for known blocks	core/forkchoice_pow.go
33	core/blockchain.go	forker in writeBlockAndSetHead	1835-1843	Uses ForkChoice.ReorgNeeded() to decide reorg for new blocks	core/forkchoice_pow.go
34	core/blockchain.go	IsPow in NewBlockChain	438-439	Initializes ForkChoice with MESS for PoW chains	core/forkchoice_pow.go
35	eth/downloader/queue.go	revokeHook in Revoke	498-500	Calls revokeHook callback (if set) to also revoke in-flight header requests	eth/downloader/queue_pow.go
36	eth/downloader/fetchers_concurrent.go	errNoPeers check	131	Returns errNoPeers when no peers available — triggers master peer cancel flow	eth/downloader/downloader_pow.go
37	eth/downloader/fetchers_concurrent.go	master peer cancel	317-322	Detects master peer drop and triggers download cancellation via cancelPeer	eth/downloader/downloader_pow.go
38	eth/downloader/fetchers.go	cancelCh case	48	Listens on cancelCh to abort header fetching when master peer drops	eth/downloader/downloader_pow.go
39	eth/backend.go	Conditional NewPoW miner creation	383-389	Creates miner with PoW support (miner.NewPoW) for IsPow chains, standard miner.New for PoS	miner/miner_pow.go

Function Calls

#	File	Name	Lines	Description	Wires To
40	params/config.go	checkCompatible → checkCompatibleETC	1157	Guards the ETC fork blocks (ECIP-1017/1041/1099, Spiral) against incompatible changes; upstream's enumerated checkCompatible omits them although they enter the fork ID	params/config_etc.go
41	params/config.go	CheckConfigForkOrder → checkConfigForkOrderETC	945	Validates ETC fork ordering (Gotham/DieHard/Etchash/Spiral interleaved with the shared forks)	params/config_etc.go
42	core/rawdb/accessors_chain.go	DeleteTd in DeleteBlock	825	Deletes TD when deleting a block (PoS doesn't have TD)	core/rawdb/accessors_chain_pow.go
43	core/rawdb/accessors_chain.go	DeleteTd in DeleteBlockWithoutNumber	835	Deletes TD in the variant without number lookup	core/rawdb/accessors_chain_pow.go
44	core/blockchain.go	WriteTd in SetHead reset	1239	Writes genesis TD during chain head reset	core/rawdb/accessors_chain_pow.go
45	core/blockchain.go	WriteTd for sidechain block	1671-1674	Calculates and writes TD for sidechain (non-canonical) blocks	core/rawdb/accessors_chain_pow.go
46	core/blockchain.go	WriteTd for canonical block	1722-1725	Calculates and writes TD for blocks inserted into the canonical chain	core/rawdb/accessors_chain_pow.go
47	core/headerchain.go	TD write in WriteHeaders	228-242	Accumulates TD for every header and writes rawdb.WriteTd/cache for newly inserted headers during header-chain insertion	core/rawdb/accessors_pow.go
48	core/rawdb/chain_freezer.go	AppendRaw TD in freezeRange	354-361	Appends TD to ancient freezer store during block freezing	core/rawdb/ancient_scheme.go
49	core/genesis.go	WriteTd in Commit	599	Writes genesis block total difficulty during chain database commit	core/rawdb/accessors_chain_pow.go
50	ethstats/ethstats.go	GetTd in assembleBlockStats	701,712	Fetches total difficulty for block stats reporting to ethstats server	eth/api_backend_pow.go
51	ethstats/ethstats.go	Miner Mining/Hashrate in reportStats	837-839	Queries the PoW miner for mining state and hashrate when the backend satisfies miningNodeBackend — verbatim restore of the pre-#28623 hunks	eth/api_backend_pow.go
52	internal/ethapi/api.go	rpcMarshalHeader in GetHeaderByNumber	497	Calls rpcMarshalHeader to inject totalDifficulty in header response	internal/ethapi/api_pow.go
53	internal/ethapi/api.go	rpcMarshalHeader in GetHeaderByHash	513	Calls rpcMarshalHeader to inject totalDifficulty in header response	internal/ethapi/api_pow.go
54	internal/ethapi/api.go	rpcMarshalBlock in GetBlockByNumber	528	Calls rpcMarshalBlock to inject totalDifficulty in block response	internal/ethapi/api_pow.go
55	internal/ethapi/api.go	rpcMarshalBlock in GetBlockByHash	548	Calls rpcMarshalBlock to inject totalDifficulty in block response	internal/ethapi/api_pow.go
56	internal/ethapi/api.go	rpcMarshalBlock in GetUncleByBlockNumberAndIndex	563	Calls rpcMarshalBlock to inject totalDifficulty in uncle response	internal/ethapi/api_pow.go
57	internal/ethapi/api.go	rpcMarshalBlock in GetUncleByBlockHashAndIndex	578	Calls rpcMarshalBlock to inject totalDifficulty in uncle response	internal/ethapi/api_pow.go
58	eth/backend.go	ResolvePath for ethash CacheDir	201	Resolves ethash cache directory relative to datadir — pre-purge3 did this in CreateConsensusEngine, we do it before CreateConsensusEngineWithConfig. Without this, CacheDir 'etchash' is created relative to CWD (e.g. / under systemd), causing permission errors and OOM from in-memory cache regeneration.	—
59	eth/backend.go	minerUpdate goroutine	386	Launches minerUpdate goroutine for PoW chains — coordinates mining pause/resume with downloader sync events	eth/backend_mining_pow.go
60	eth/backend.go	CloseMining in Stop	635	Closes PoW mining goroutines before stopping other subsystems	miner/miner_pow.go

EIP-1559 Decoupling

#	File	Name	Lines	Description	Wires To
61	core/chain_makers.go	IsEIP1559 in GenerateChain header	246,248	Uses IsEIP1559 instead of IsLondon for base fee initialization in test chain generation	—
62	core/chain_makers.go	IsEIP1559 in makeHeader	518,520	Uses IsEIP1559 instead of IsLondon for base fee calculation in test header construction	—
63	core/state_transition.go	IsEIP1559 in gas price	528	Uses IsEIP1559 instead of IsLondon to determine effective gas price calculation	—
64	core/txpool/legacypool/legacypool.go	IsEIP1559 in pool reset	1263	Uses IsEIP1559 instead of IsLondon for base fee tracking in transaction pool	—
65	eth/gasprice/feehistory.go	IsEIP1559 in fee history	92	Uses IsEIP1559 instead of IsLondon for fee history base fee resolution	—
66	graphql/graphql.go	IsEIP1559 in GraphQL baseFee	785	Uses IsEIP1559 instead of IsLondon for GraphQL base fee next-block estimation	—
67	internal/ethapi/simulate.go	IsEIP1559 in simulation	263	Uses IsEIP1559 instead of IsLondon for base fee in block simulation	—
68	internal/ethapi/transaction_args.go	IsEIP1559 in tx args	215	Uses IsEIP1559 instead of IsLondon for gas tip cap defaults in transaction arguments	—
69	miner/worker.go	IsEIP1559 in miner	290,292	Uses IsEIP1559 instead of IsLondon for base fee initialization in block preparation	—

Constants & Variables

#	File	Name	Lines	Description	Wires To
70	core/rawdb/ancient_scheme.go	ChainFreezerDifficultyTable	43-44	Declares 'diffs' freezer table for storing total difficulty in ancient store	—
71	core/rawdb/ancient_scheme.go	Difficulty table in freezer schema	71	Registers the diffs (total-difficulty) table in chainFreezerTableConfigs — uncompressed (noSnappy: true, same as core-geth), non-prunable	—
72	core/headerchain.go	tdCacheLimit	39	LRU cache size constant (1024) for TD values	—
73	eth/downloader/downloader.go	errStallingPeer etc.	74	Error variables for PoW sync — errStallingPeer, errNoPeers, errCanceled	—
74	eth/downloader/metrics.go	headerDropMeter	28	Meter tracking dropped headers during PoW sync	—
75	params/bootnodes_etc.go	ClassicBootnodes, MordorBootnodes	19-34	Bootstrap node lists for ETC mainnet and Mordor testnet	—
76	params/bootnodes_etc.go	etcDNSPrefix + DNS discovery	37,45-46,47-48	DNS discovery prefix and tree URLs for ETC mainnet and Mordor	—

Added Functions

#	File	Name	Lines	Description	Wires To
77	eth/ethconfig/config.go	CreateConsensusEngineWithConfig	246-268	Consensus engine routing by config shape — any perpetual PoW config (IsPow) gets the ETCEngine, merge-track configs get the beacon wrapper	consensus/etc
78	eth/peer.go	KnownBlock, AsyncSendNewBlock, AsyncSendNewBlockHash	72-73,78-79,84-85	PoW block propagation helpers — track known blocks and async broadcast to peers	eth/handler_pow.go
79	core/vm/eips.go	enable160	171-175	Enables EIP-160 (EXP gas increase) independently — ETC activates separately from EIP-158	—

Interface Additions

#	File	Name	Lines	Description	Wires To
80	eth/downloader/downloader.go	BlockChain.GetTd	191-192	GetTd method added to BlockChain interface — required for TD-based PoW sync	core/blockchain_pow.go
81	eth/downloader/peer.go	Peer.Head()	60	Head() method in Peer interface — returns head hash and TD for PoW peer selection	eth/protocols/eth/peer_pow.go
82	ethstats/ethstats.go	backend.GetTd	70	GetTd method added to ethstats backend interface — used for block stats reporting	eth/api_backend_pow.go
83	ethstats/ethstats.go	miningNodeBackend	86-89	Mining-node backend interface (fullNodeBackend + Miner) — restored from the #28623 removal, satisfied by EthAPIBackend via the revived Miner accessor	eth/api_backend_pow.go
84	internal/ethapi/backend.go	GetTd in Backend interface	74	Interface method for fetching total difficulty by block hash — removed in PR #30386, restored for ETC	eth/api_backend_pow.go

Import Additions

#	File	Name	Lines	Description	Wires To
85	eth/ethconfig/config.go	consensus/etc and consensus/ethash imports	28-29	Adds imports for ETC consensus engine and Ethash configuration	consensus/etc, consensus/ethash
86	ethstats/ethstats.go	miner import	42	Adds the miner package import for the restored miningNodeBackend interface	miner/miner_pow.go

Config Plumbing

#	File	Name	Lines	Description	Wires To
87	eth/handler.go	handlerConfig.IsPow	113	Config field that propagates IsPow flag from ethconfig to handler	eth/backend.go
88	eth/handler.go	isPow initialization	173-175	Copies config.IsPow into handler struct during construction	—
89	eth/backend.go	IsPow passthrough	374	Passes IsPow from blockchain config to handler config	eth/handler.go
90	eth/backend.go	MESS flags passthrough	375-376	Passes MESSForceEnable/Disable from ethconfig to handler config	eth/handler.go
91	eth/backend.go	etherbase seed in New	384	Seeds the mining etherbase from Miner.PendingFeeRecipient at backend construction — restored from the #28623 removal (etherbase: config.Miner.Etherbase); without it --mine dies at startup with 'etherbase missing'	eth/backend_mining_pow.go
92	eth/backend.go	isPow to MakeProtocols	490	Passes isPow flag to eth.MakeProtocols for protocol version selection	eth/protocols/eth/handler.go
93	eth/protocols/eth/handler.go	MakeProtocols versions param	108	MakeProtocols accepts versions []uint param to select protocol versions for PoW	eth/protocols/eth/protocol_pow.go
94	eth/protocols/eth/handler.go	versionHandlers registry	175-177	Map[uint]map[uint64]msgHandler{} — runtime registry for version-specific message handlers (ETH68 PoW handlers registered via init())	eth/protocols/eth/handlers_pow.go
95	eth/protocols/eth/handler.go	versionHandlers dispatch	245-246	Fallback dispatch in handleMessage — checks versionHandlers map for version-specific handlers (ETH68 PoW messages)	eth/protocols/eth/handlers_pow.go