params,internal/ethapi: add current, next, and last to eth_config

internal/ethapi/api.go

@@ -34,6 +34,7 @@ import (
 	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/consensus/misc/eip1559"
 	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/forkid"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -1157,29 +1158,61 @@ type config struct {
 	ActivationTime  uint64                    `json:"activationTime"`
 	BlobSchedule    *params.BlobConfig        `json:"blobSchedule"`
 	ChainId         *hexutil.Big              `json:"chainId"`
+	ForkId          hexutil.Bytes             `json:"forkId"`
 	Precompiles     map[common.Address]string `json:"precompiles"`
 	SystemContracts map[string]common.Address `json:"systemContracts"`
 }
 
+type configResponse struct {
+	Current *config `json:"current"`
+	Next    *config `json:"next"`
+	Last    *config `json:"last"`
+}
+
 // Config implements the EIP-7910 eth_config method.
-func (api *BlockChainAPI) Config(ctx context.Context) config {
+func (api *BlockChainAPI) Config(ctx context.Context) (*configResponse, error) {
+	genesis, err := api.b.BlockByNumber(ctx, 0)
+	if err != nil {
+		return nil, fmt.Errorf("unable to load genesis: %w", err)
+	}
+	assemble := func(c *params.ChainConfig, ts *uint64) *config {
+		if ts == nil {
+			return nil
+		}
+		t := *ts
+
 		var (
-		c           = api.b.ChainConfig()
-		h           = api.b.CurrentBlock()
-		rules       = c.Rules(h.Number, true, h.Time)
+			rules       = c.Rules(c.LondonBlock, true, t)
 			precompiles = make(map[common.Address]string)
 		)
 		for addr, c := range vm.ActivePrecompiledContracts(rules) {
 			precompiles[addr] = c.Name()
 		}
-	return config{
-		ActivationTime:  c.NextForkTime(h.Time),
-		BlobSchedule:    c.BlobConfig(c.LatestFork(h.Time)),
+		forkid := forkid.NewID(c, genesis, ^uint64(0), t).Hash
+		return &config{
+			ActivationTime:  t,
+			BlobSchedule:    c.BlobConfig(c.LatestFork(t)),
 			ChainId:         (*hexutil.Big)(c.ChainID),
+			ForkId:          forkid[:],
 			Precompiles:     precompiles,
-		SystemContracts: c.ActiveSystemContracts(h.Time),
+			SystemContracts: c.ActiveSystemContracts(t),
 		}
 	}
+	var (
+		c = api.b.ChainConfig()
+		t = api.b.CurrentHeader().Time
+	)
+	resp := configResponse{
+		Next:    assemble(c, c.Timestamp(c.LatestFork(t)+1)),
+		Current: assemble(c, c.Timestamp(c.LatestFork(t))),
+		Last:    assemble(c, c.Timestamp(c.LatestFork(^uint64(0)))),
+	}
+	// Nil out last if no future-fork is configured.
+	if resp.Next == nil {
+		resp.Last = nil
+	}
+	return &resp, nil
+}
 
 // AccessList creates an access list for the given transaction.
 // If the accesslist creation fails an error is returned.

params/config.go

@@ -985,31 +985,6 @@ func (c *ChainConfig) LatestFork(time uint64) forks.Fork {
 	}
 }
 
-// NextFork returns the next fork to activate or nil if the last defined fork is
-// active.
-func (c *ChainConfig) NextForkTime(time uint64) uint64 {
-	// Assume last non-time-based fork has passed.
-	london := c.LondonBlock
-	next := newUint64(0)
-
-	switch {
-	case c.IsOsaka(london, time):
-		next = c.OsakaTime
-	case c.IsPrague(london, time):
-		next = c.OsakaTime
-	case c.IsCancun(london, time):
-		next = c.PragueTime
-	case c.IsShanghai(london, time):
-		next = c.CancunTime
-	default:
-		next = c.ShanghaiTime
-	}
-	if next == nil {
-		return 0
-	}
-	return *next
-}
-
 // BlobConfig returns the blob config associated with the provided fork.
 func (c *ChainConfig) BlobConfig(fork forks.Fork) *BlobConfig {
 	switch fork {