This PR introduces a new config field SyncFromCheckpoint for light client.

In some special scenarios, it's required to start synchronization from some
arbitrary checkpoint or even from the scratch. So this PR offers this
flexibility to users so that the synchronization start point can be configured.

There are two relevant configs: SyncFromCheckpoint and Checkpoint.

- If the SyncFromCheckpoint is true, the light client will try to sync from the
  specified checkpoint.

- If the Checkpoint is not configured, then the light client will sync from the
  scratch(from the latest header if the database is not empty)

Additional notes: these two configs are not visible in the CLI flags but only
accessable in the config file.

Example Usage:

[Eth]
SyncFromCheckpoint = true

[Eth.Checkpoint]
SectionIndex = 100
SectionHead = "0xabc"
CHTRoot = "0xabc"
BloomRoot = "0xabc"

PS. Historical checkpoint can be retrieved from the synced full node or light
client via les_getCheckpoint API.

Adding warnings of free disk space left and graceful shutdown when there is not enough space left.
This also adds a flag datadir.minfreedisk which can be used to set the trigger for low disk space, and setting it to zero disables the check. 
Co-authored-by: NMartin Holst Swende <martin@swende.se>
Co-authored-by: NFelix Lange <fjl@twurst.com>

* core/state/snapshot: write snapshot generator in batch

* core: refactor the tests

* core: update tests

* core: update tests

* cmd/geth: dump config

* cmd/geth: dump config

* cmd/geth: properly read config again

* cmd/geth: override metrics if flags are set

* cmd/geth: write metrics regardless if enabled

* cmd/geth: renamed to metricsfromcliargs

* metrics: add default configuration

* tests/fuzzers/abi: better test generation

* tests/fuzzers/abi: fixed packing issue

* oss-fuzz: enable abi fuzzer

This PR has two changes in the les protocol:

- the auxRoot is not supported. See ethereum/devp2p#171 for more information
- the empty response will be returned in GetHelperTrieProofsMsg request if the merkle
   proving is failed. note, for backward compatibility, the empty merkle proof as well as
   the request auxiliary data will still be returned in  les2/3 protocol no matter the proving
   is successful or not. the proving failure can happen e.g. request the proving for a
   non-included entry in helper trie (unstable header).

core/state/snapshot: add generation logs to storage too

cmd/faucet: update the embedded website asset

The tests sometimes failed with certain go versions because
the behavior of http.Server.Shutdown changed over time. A bug
that was fixed in Go 1.15 could cause active connections on unrelated
servers to close unexpectedly. This is fixed by avoiding use of the
same port number in all tests.

It seems that the 2 second timeout is not enough for Travis CI:

   --- FAIL: TestTestMode (2.00s)
       ethash_test.go:53: sealing result timeout

This solves an issue in graphql tests:

    graphql_test.go:38: could not create new node: datadir already used by another process

USB enumeration still occured. Make sure it will only occur if --usb is set.
This also deprecates the 'NoUSB' config file option in favor of a new option 'USB'.

* deps: use improved bloom filter implementation

* eth/handler, trie: use 4 keys for syncbloom + minor fixes

* eth/protocols, trie: revert change on syncbloom method signature

Resolves https://github.com/etclabscore/core-geth/issues/273

jsre.JSRE already handles establishing preload
file paths relative to the 'assets' path (aka docroot),
where it joins the assets dir and the file path if relative,
or uses the file path only if absolute.

The duplication of this logic by MakeConsolePreloads
caused preloaded files to have paths which contained
duplicate references to the assets dir path.

Date: 2020-12-30 08:25:01-06:00
Signed-off-by: Nmeows <b5c6@protonmail.com>

This changes the chainID RPC method to return an error when EIP-155 is not yet
active at the current block height. It used to simply return zero in this case, but
that's confusing.

* eth: fixed typos

* eth: fixed log message

common/prque: pull in tests and benchmarks from upstream

* core: persist bad blocks

* core, eth, internal: address comments

* core/rawdb: add badblocks to inspector

* core, eth: update

* internal: revert

* core, eth: only save 10 bad blocks

* core/rawdb: address comments

* core/rawdb: fix

* core: address comments

* downloader: fix race condition in tests

* eth/downloader: fix race condition in tests

* Revert "downloader: fix race condition in tests"

This reverts commit 108033ebc6985de83791d375b6e6647a77d28d5a.

This commit extends the ethclient test suite and increases code coverage of the ethclient
package from ~15% to >55%. These tests act as early smoke tests to signal issues in the
RPC-interface. E.g. if a functionality like eth_chainId or eth_call breaks, the test
will break.

* cmd/faucet: avoid encoding for each client

* cmd/faucet: fix flaw in clearing of txs, avoid sending more than necessary

* cmd/faucet: fix flaw in tx cropping

* cmd/faucet: revert change to not always send tx info

* cmd/faucet: review fixes

* cmd/faucet: revert #22018, fix order in UI

* cmd/faucet: fix lock error

* cmd/faucet: revert json changes

* squashme

cmd/faucet: switch Facebook auth over to mobile site

* eth/protocols/snap: speed up hash checks

* eth/protocols/snap: nit fix
Co-authored-by: NPéter Szilágyi <peterke@gmail.com>

cmd/faucet: fix websocket race regression after switching to gorilla

* eth/protocols/snap: reschedule missed deliveries

* eth/protocols/snap: clarify log message

* eth/protocols/snap: revert failures async and update runloop
Co-authored-by: NPéter Szilágyi <peterke@gmail.com>

cmd/utils, eth/downloader: minor snap nitpicks

* estimateGas, cumulativeGas
* linted
* add test for estimateGas

* crypto/bls12381: fixed ineffectual assignment

* crypto/signify: fix ineffectual assignment