cmd/devp2p/internal/ethtest: add 'large announcement' tests (#21792)

* cmd/devp2p/internal/ethtest: added large announcement tests

* cmd/devp2p/internal/ethtest: added large announcement tests

* cmd/devp2p/internal/ethtest: refactored stuff a bit

* cmd/devp2p/internal/ethtest: added TestMaliciousStatus/Handshake

* cmd/devp2p/internal/ethtest: fixed rebasing issue

* happy linter, happy life

* cmd/devp2p/internal/ethtest: used readAndServe

* stuff

* cmd/devp2p/internal/ethtest: fixed test cases

cmd/devp2p/internal/ethtest/large.go

@@ -0,0 +1,80 @@
+// Copyright 2020 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ethtest
+
+import (
+	"crypto/rand"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+// largeNumber returns a very large big.Int.
+func largeNumber(megabytes int) *big.Int {
+	buf := make([]byte, megabytes*1024*1024)
+	rand.Read(buf)
+	bigint := new(big.Int)
+	bigint.SetBytes(buf)
+	return bigint
+}
+
+// largeBuffer returns a very large buffer.
+func largeBuffer(megabytes int) []byte {
+	buf := make([]byte, megabytes*1024*1024)
+	rand.Read(buf)
+	return buf
+}
+
+// largeString returns a very large string.
+func largeString(megabytes int) string {
+	buf := make([]byte, megabytes*1024*1024)
+	rand.Read(buf)
+	return hexutil.Encode(buf)
+}
+
+func largeBlock() *types.Block {
+	return types.NewBlockWithHeader(largeHeader())
+}
+
+// Returns a random hash
+func randHash() common.Hash {
+	var h common.Hash
+	rand.Read(h[:])
+	return h
+}
+
+func largeHeader() *types.Header {
+	return &types.Header{
+		MixDigest:   randHash(),
+		ReceiptHash: randHash(),
+		TxHash:      randHash(),
+		Nonce:       types.BlockNonce{},
+		Extra:       []byte{},
+		Bloom:       types.Bloom{},
+		GasUsed:     0,
+		Coinbase:    common.Address{},
+		GasLimit:    0,
+		UncleHash:   randHash(),
+		Time:        1337,
+		ParentHash:  randHash(),
+		Root:        randHash(),
+		Number:      largeNumber(2),
+		Difficulty:  largeNumber(2),
+	}
+}