common: allow specifying eip-7840 blobSchedule via geth genesis

config/cspell-md.json

@@ -321,6 +321,7 @@
     "beaconroot",
     "Grandine",
     "EVMBN",
-    "kaust"
+    "kaust",
+    "blobschedule"
   ]
 }

packages/common/src/common.ts

@@ -66,8 +66,9 @@ export class Common {
     // Assign hardfork changes in the sequence of the applied hardforks
     this.HARDFORK_CHANGES = this.hardforks().map((hf) => [
       hf.name,
-      hardforksDict[hf.name] ??
-        (this._chainParams.customHardforks && this._chainParams.customHardforks[hf.name]),
+      // Allow to even override an existing hardfork specification
+      (this._chainParams.customHardforks && this._chainParams.customHardforks[hf.name]) ?? 
+      hardforksDict[hf.name],
     ])
     this._hardfork = this.DEFAULT_HARDFORK
     this._params = opts.params ? JSON.parse(JSON.stringify(opts.params)) : {} // copy
@@ -322,7 +323,7 @@ export class Common {
           this._mergeWithParamsCache(this._params[eip] ?? {})
         }
       }
-      // Parameter-inlining HF config (e.g. for istanbul)
+      // Parameter-inlining HF config (e.g. for istanbul or custom blobSchedule)
       this._mergeWithParamsCache(hfChanges[1].params ?? {})
       if (hfChanges[0] === hardfork) break
     }

packages/common/src/utils.ts

@@ -2,9 +2,12 @@
 
 import { Goerli, Holesky, Kaustinen6, Mainnet, Sepolia } from './chains.js'
 import { Hardfork } from './enums.js'
+import { hardforksDict } from './hardforks.js'
 
+import type { HardforksDict } from './types.js'
 import type { PrefixedHexString } from '@ethereumjs/util'
 
+
 type ConfigHardfork =
   | { name: string; block: null; timestamp: number }
   | { name: string; block: number; timestamp?: number }
@@ -93,6 +96,33 @@
     throw new Error('nonzero terminal total difficulty is not supported')
   }
 
+  let customHardforks: HardforksDict | undefined = undefined;
+  if (config.blobSchedule !== undefined) {
+    customHardforks = {};
+    const blobGasPerBlob = 131072;
+    for (const [hfKey, hfSchedule] of Object.entries(config.blobSchedule)) {
+      const hfConfig = hardforksDict[hfKey];
+      if (hfConfig === undefined) {
+        throw new Error(`unknown hardfork=${hfKey} specified in blobSchedule`);
+      }
+      const { target, max, baseFeeUpdateFraction: blobGasPriceUpdateFraction } = hfSchedule as { target?: number, max?: number, baseFeeUpdateFraction?: undefined };
+      if (target === undefined || max === undefined) {
+        throw new Error(`undefined target or max specified in blobSchedule for hardfork=${hfKey}`);
+      }
+
+
+      // copy current hardfork info to custom and add blob config
+      const customHfConfig = JSON.parse(JSON.stringify(hfConfig));
+      customHfConfig.params = {
+        ...customHardforks.params,
+        // removes blobGasPriceUpdateFraction key to prevent undefined overriding if undefined
+        ...{ targetBlobGasPerBlock: blobGasPerBlob * target, maxBlobGasPerBlock: blobGasPerBlob * max, blobGasPriceUpdateFraction }
+      }
+
+      customHardforks[hfKey] = customHfConfig;
+    }
+  }
+
   const params = {
     name,
     chainId,
@@ -111,25 +141,26 @@
     },
     hardfork: undefined as string | undefined,
     hardforks: [] as ConfigHardfork[],
+    customHardforks,
     bootstrapNodes: [],
     consensus:
       config.clique !== undefined
         ? {
-            type: 'poa',
-            algorithm: 'clique',
-            clique: {
-              // The recent geth genesis seems to be using blockperiodseconds // cspell:disable-line
-              // and epochlength for clique specification
-              // see: https://hackmd.io/PqZgMpnkSWCWv5joJoFymQ
-              period: config.clique.period ?? config.clique.blockperiodseconds, // cspell:disable-line
-              epoch: config.clique.epoch ?? config.clique.epochlength,
-            },
-          }
-        : {
-            type: 'pow',
-            algorithm: 'ethash',
-            ethash: {},
+          type: 'poa',
+          algorithm: 'clique',
+          clique: {
+            // The recent geth genesis seems to be using blockperiodseconds // cspell:disable-line
+            // and epochlength for clique specification
+            // see: https://hackmd.io/PqZgMpnkSWCWv5joJoFymQ
+            period: config.clique.period ?? config.clique.blockperiodseconds, // cspell:disable-line
+            epoch: config.clique.epoch ?? config.clique.epochlength,
           },
+        }
+        : {
+          type: 'pow',
+          algorithm: 'ethash',
+          ethash: {},
+        },
   }
 
   const forkMap: { [key: string]: { name: string; postMerge?: boolean; isTimestamp?: boolean } } = {

packages/common/test/utils.spec.ts

@@ -91,7 +91,7 @@ describe('[Utils/Parse]', () => {
 
   it('should correctly parse deposit contract address', async () => {
     // clone json out to not have side effects
-    const customData = postMergeHardforkData
+    const customData = JSON.parse(JSON.stringify(postMergeHardforkData))
     Object.assign(customData.config, {
       depositContractAddress: '0x4242424242424242424242424242424242424242',
     })
@@ -108,4 +108,83 @@ describe('[Utils/Parse]', () => {
       'should parse correct address',
     )
   })
+
+  it('should assign correct blob schedule', async () => {
+    // clone json out to not have side effects
+    const customData = JSON.parse(JSON.stringify(postMergeHardforkData))
+    Object.assign(customData.config, {
+      "chainId": 3151908,
+      "homesteadBlock": 0,
+      "eip150Block": 0,
+      "eip155Block": 0,
+      "eip158Block": 0,
+      "byzantiumBlock": 0,
+      "constantinopleBlock": 0,
+      "petersburgBlock": 0,
+      "istanbulBlock": 0,
+      "berlinBlock": 0,
+      "londonBlock": 0,
+      "mergeNetsplitBlock": 0,
+      "depositContractAddress": "0x4242424242424242424242424242424242424242",
+      "terminalTotalDifficulty": 0,
+      "terminalTotalDifficultyPassed": true,
+      "shanghaiTime": 0,
+      "cancunTime": 0,
+      "blobSchedule": {
+        "prague": {
+          "target": 61,
+          "max": 91,
+          "baseFeeUpdateFraction": 13338477
+        },
+      },
+      "pragueTime": 1736942378,
+    });
+
+    const common = createCommonFromGethGenesis(customData, {
+      chain: 'customChain',
+    });
+    const paramsTx = {
+      4844: {
+        blobCommitmentVersionKzg: 1, // The number indicated a versioned hash is a KZG commitment
+        blobGasPerBlob: 131072, // The base fee for blob gas per blob
+        maxBlobGasPerBlock: 786432, // The max blob gas allowable per block
+        blobGasPriceUpdateFraction: 3338477,
+        targetBlobGasPerBlock: 393216,
+      },
+      7691: {
+        maxBlobGasPerBlock: 1179648, // The max blob gas allowable per block
+      },
+    }
+    common.updateParams(paramsTx);
+
+    const testCases = [
+      // should be picked from eip params
+      [Hardfork.Cancun, 393216n, 786432n, 3338477n],
+      // from the genesis blobschedule
+      [Hardfork.Prague, 7995392, 11927552, 13338477],
+    ]
+    for (const [testHf, testTarget, testMax, testUpdateFraction] of testCases) {
+      common.setHardfork(testHf as Hardfork);
+
+      const targetBlobGasPerBlock = common.param("targetBlobGasPerBlock");
+      const maxBlobGasPerBlock = common.param("maxBlobGasPerBlock");
+      const blobGasPriceUpdateFraction = common.param("blobGasPriceUpdateFraction");
+
+      assert.equal(
+        targetBlobGasPerBlock,
+        testTarget,
+        'target blob gas should match',
+      )
+      assert.equal(
+        maxBlobGasPerBlock,
+        testMax,
+        'max blob gas should match',
+      )
+      assert.equal(
+        blobGasPriceUpdateFraction,
+        testUpdateFraction,
+        'update fraction should match',
+      )
+    }
+  })
 })