* core/vm: implement AccessListTracer
* eth: implement debug.createAccessList
* core/vm: fixed nil panics in accessListTracer
* eth: better error messages for createAccessList
* eth: some fixes on CreateAccessList
* eth: allow for provided accesslists
* eth: pass accesslist by value
* eth: remove created acocunt from accesslist
* core/vm: simplify access list tracer
* core/vm: unexport accessListTracer
* eth: return best guess if al iteration times out
* eth: return best guess if al iteration times out
* core: docstring, unexport methods
* eth: typo
* internal/ethapi: move createAccessList to eth package
* internal/ethapi: remove reexec from createAccessList
* internal/ethapi: break if al is equal to last run, not if gas is equal
* internal/web3ext: fixed arguments
* core/types: fixed equality check for accesslist
* core/types: no hardcoded vals
* core, internal: simplify access list generation, make it precise
* core/vm: fix typo
Co-authored-by: Martin Holst Swende <martin@swende.se>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>
This removes the duplicated definition of eth_chainID
in package eth and updates the definition in internal/ethapi
to treat chain ID as a bigint.
Co-authored-by: Felix Lange <fjl@twurst.com>
The PR implements the --miner.notify.full flag that enables full pending block
notifications. When this flag is used, the block notifications sent to mining
endpoints contain the complete block header JSON instead of a work package
array.
Co-authored-by: AlexSSD7 <alexandersadovskyi7@protonmail.com>
Co-authored-by: Martin Holst Swende <martin@swende.se>
Fixes the CaptureStart api to include the EVM, thus being able to set the statedb early on. This pr also exposes the struct we used internally in the interpreter to encapsulate the contract, mem, stack, rstack, so we pass it as a single struct to the tracer, and removes the error returns on the capture methods.
This adds support for EIP-2718 typed transactions as well as EIP-2930
access list transactions (tx type 1). These EIPs are scheduled for the
Berlin fork.
There very few changes to existing APIs in core/types, and several new APIs
to deal with access list transactions. In particular, there are two new
constructor functions for transactions: types.NewTx and types.SignNewTx.
Since the canonical encoding of typed transactions is not RLP-compatible,
Transaction now has new methods for encoding and decoding: MarshalBinary
and UnmarshalBinary.
The existing EIP-155 signer does not support the new transaction types.
All code dealing with transaction signatures should be updated to use the
newer EIP-2930 signer. To make this easier for future updates, we have
added new constructor functions for types.Signer: types.LatestSigner and
types.LatestSignerForChainID.
This change also adds support for the YoloV3 testnet.
Co-authored-by: Martin Holst Swende <martin@swende.se>
Co-authored-by: Felix Lange <fjl@twurst.com>
Co-authored-by: Ryan Schneider <ryanleeschneider@gmail.com>
This PR adds a more CLI flag, so that the les-server can serve light clients even the local node is not synced yet.
This functionality is needed in some testing environments(e.g. hive). After launching the les server, no more blocks will be imported so the node is always marked as "non-synced".
This PR prevents users from submitting transactions without EIP-155 enabled. This behaviour can be overridden by specifying the flag --rpc.allow-unprotected-txs=true.
This PR optimizes the broadcast loop. Instead of iterating twice through a given set of transactions to weed out which peers have and which do not have a tx, to send/announce transactions, we do it only once.
Prevents a situation where we (not running snap) connects with a peer running snap, and get stalled waiting for snap registration to succeed (which will never happen), which cause a waitgroup wait to halt shutdown
This moves the eth config definition into a separate package, eth/ethconfig.
Packages eth and les can now import this common package instead of
importing eth from les, reducing dependencies.
Co-authored-by: Felix Lange <fjl@twurst.com>
The PR makes use of the stacktrie, which is is more lenient on resource consumption, than the regular trie, in cases where we only need it for DeriveSha
* remove uneeded convertion type
* remove redundant type in composite literal
* omit explicit type where implicit
* remove unused redundant parenthesis
* remove redundant import alias duktape
Removes the yolov2 definition, adds yolov3, including EIP-2565. This PR also disables some of the erroneously generated blockchain and statetests, and adds the new genesis hash + alloc for yolov3.
This PR disables the CLI switches for yolo, since it's not complete until we merge support for 2930.
This moves the tracing RPC API implementation to package eth/tracers.
By doing so, package eth no longer depends on tracing and the duktape JS engine.
The change also enables tracing using the light client. All tracing methods work with the
light client, but it's a lot slower compared to using a full node.
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.
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.
During the snap and eth refactor, the net_version rpc call was falsely deprecated.
This restores the net_version RPC handler as most eth2 nodes and other software
depend on it.
This commit splits the eth package, separating the handling of eth and snap protocols. It also includes the capability to run snap sync (https://github.com/ethereum/devp2p/blob/master/caps/snap.md) , but does not enable it by default.
Co-authored-by: Marius van der Wijden <m.vanderwijden@live.de>
Co-authored-by: Martin Holst Swende <martin@swende.se>
This PR implements unclean shutdown marker. Every time geth boots, it adds a timestamp to a list of timestamps in the database. This list is capped at 10. At a clean shutdown, the timestamp is removed again.
Thus, when geth exits unclean, the marker remains, and at boot up we show the most recent unclean shutdowns to the user, which makes it easier to diagnose root-causes to certain problems.
Co-authored-by: Nagy Salem <me@muhnagy.com>
In miner/worker.go, there are two goroutine using channel w.newWorkCh: newWorkerLoop() sends to this channel, and mainLoop() receives from this channel. Only the receive operation is in a select.
However, w.exitCh may be closed by another goroutine. This is fine for the receive since receive is in select, but if the send operation is blocking, then it will block forever. This commit puts the send in a select, so it won't block even if w.exitCh is closed.
Similarly, there are two goroutines using channel errc: the parent that runs the test receives from it, and the child created at line 573 sends to it. If the parent goroutine exits too early by calling t.Fatalf() at line 614, then the child goroutine will be blocked at line 574 forever. This commit adds 1 buffer to errc. Now send will not block, and receive is not influenced because receive still needs to wait for the send.
* all: core: split vm.Config into BlockConfig and TxConfig
* core: core/vm: reset EVM between tx in block instead of creating new
* core/vm: added docs
core/types: use stacktrie for derivesha
trie: add stacktrie file
trie: fix linter
core/types: use stacktrie for derivesha
rebased: adapt stacktrie to the newer version of DeriveSha
Co-authored-by: Martin Holst Swende <martin@swende.se>
More linter fixes
review feedback: no key offset for nodes converted to hashes
trie: use EncodeRLP for full nodes
core/types: insert txs in order in derivesha
trie: tests for derivesha with stacktrie
trie: make stacktrie use pooled hashers
trie: make stacktrie reuse tmp slice space
trie: minor polishes on stacktrie
trie/stacktrie: less rlp dancing
core/types: explain the contorsions in DeriveSha
ci: fix goimport errors
trie: clear mem on subtrie hashing
squashme: linter fix
stracktrie: use pooling, less allocs (#3)
trie: in-place hex prefix, reduce allocs and add rawNode.EncodeRLP
Reintroduce the `[]node` method, add the missing `EncodeRLP` implementation for `rawNode` and calculate the hex prefix in place.
Co-authored-by: Martin Holst Swende <martin@swende.se>
Co-authored-by: Martin Holst Swende <martin@swende.se>
This changes how the downloader works, a little bit. Previously, when block sync started,
we immediately started filling up to 8192 blocks. Usually this is fine, blocks are small
in the early numbers. The threshold then is lowered as we measure the size of the blocks
that are filled.
However, if the node is shut down and restarts syncing while we're in a heavy segment,
that might be bad. This PR introduces a more conservative initial threshold of 2K blocks
instead.
* "Downloader queue stats" is now a DEBUG information
I think this info is more a DEBUG related information then an INFO. If it must remains an INFO, maybe it can be slow down to one time every 5 minutes or so.
* Update queue.go
"Downloader queue stats" information is now provided once every minute instead of once every 10 seconds.
This PR significantly changes the APIs for instantiating Ethereum nodes in
a Go program. The new APIs are not backwards-compatible, but we feel that
this is made up for by the much simpler way of registering services on
node.Node. You can find more information and rationale in the design
document: https://gist.github.com/renaynay/5bec2de19fde66f4d04c535fd24f0775.
There is also a new feature in Node's Go API: it is now possible to
register arbitrary handlers on the user-facing HTTP server. In geth, this
facility is used to enable GraphQL.
There is a single minor change relevant for geth users in this PR: The
GraphQL API is no longer available separately from the JSON-RPC HTTP
server. If you want GraphQL, you need to enable it using the
./geth --http --graphql flag combination.
The --graphql.port and --graphql.addr flags are no longer available.
* init
notes
removed some mentions of eth62, bumped protocol err too old to >=63
* remove sanity checks and bump supported protocol version up to 63
* remove 62 tests, still need to add 65
* remove 65 tests
* eth/downloader: refactor downloader + queue
downloader, fetcher: throttle-metrics, fetcher filter improvements, standalone resultcache
downloader: more accurate deliverytime calculation, less mem overhead in state requests
downloader/queue: increase underlying buffer of results, new throttle mechanism
eth/downloader: updates to tests
eth/downloader: fix up some review concerns
eth/downloader/queue: minor fixes
eth/downloader: minor fixes after review call
eth/downloader: testcases for queue.go
eth/downloader: minor change, don't set progress unless progress...
eth/downloader: fix flaw which prevented useless peers from being dropped
eth/downloader: try to fix tests
eth/downloader: verify non-deliveries against advertised remote head
eth/downloader: fix flaw with checking closed-status causing hang
eth/downloader: hashing avoidance
eth/downloader: review concerns + simplify resultcache and queue
eth/downloader: add back some locks, address review concerns
downloader/queue: fix remaining lock flaw
* eth/downloader: nitpick fixes
* eth/downloader: remove the *2*3/4 throttling threshold dance
* eth/downloader: print correct throttle threshold in stats
Co-authored-by: Péter Szilágyi <peterke@gmail.com>
This change introduces garbage collection for the light client. Historical
chain data is deleted periodically. If you want to disable the GC, use
the --light.nopruning flag.
This fixes two issues with state sync restarts:
When sync restarts with a new root, some peers can have in-flight requests.
Since all peers with active requests were marked idle when exiting sync,
the new sync would schedule more requests for those peers. When the
response for the earlier request arrived, the new sync would reject it and
mark the peer idle again, rendering the peer useless until it disconnected.
The other issue was that peers would not be marked idle when they had
delivered a response, but the response hadn't been processed before
restarting the state sync. This also made the peer useless because it
would be permanently marked busy.
Co-authored-by: Felix Lange <fjl@twurst.com>
This PR reduces the bandwidth used by the light client to compute the
recommended gas price. The current mechanism for suggesting the price is:
- retrieve recent 20 blocks
- get the lowest gas price of these blocks
- sort the price array and return the middle(60%) one
This works for full nodes, which have all blocks available locally.
However, this is very expensive for the light client because the light
client needs to retrieve block bodies from the network.
The PR changes the default options for light client. With the new config,
the light client only retrieves the two latest blocks, but in order to
collect more sample transactions, the 3 lowest prices are collected from
each block.
This PR also changes the behavior for empty blocks. If the block is empty,
the lastest price is reused for sampling.
* eth/downloaded: fixed datarace between synchronize and Progress
There was a race condition between `downloader.synchronize()` and `Progress` `syncWithPeer` `fetchHeight` `findAncestors` and `processHeaders`
This PR changes the behavior of the downloader a bit.
Previously the functions `Progress` `syncWithPeer` `fetchHeight` `findAncestors` and `processHeaders` read the syncMode anew within their loops. Now they read the syncMode at the start of their function and don't change it during their runtime.
* eth/downloaded: comment
* eth/downloader: added comment
* core, crypto: various allocation savings regarding tx handling
* core: reduce allocs for gas price comparison
This change reduces the allocations needed for comparing different transactions to each other.
A call to `tx.GasPrice()` copies the gas price as it has to be safe against modifications and
also needs to be threadsafe. For comparing and ordering different transactions we don't need
these guarantees
* core: added tx.GasPriceIntCmp for comparison without allocation
adds a method to remove unneeded allocation in comparison to tx.gasPrice
* core/types: pool legacykeccak256 objects in rlpHash
rlpHash is by far the most used function in core that allocates a legacyKeccak256 object on each call.
Since it is so widely used it makes sense to add pooling here so we relieve the GC.
On my machine these changes result in > 100 MILLION less allocations and > 30 GB less allocated memory.
* reverted some changes
* reverted some changes
* trie: use crypto.KeccakState instead of replicating code
Co-authored-by: Martin Holst Swende <martin@swende.se>
* eth/downloader tests: fix spurious failing test due to race between receipts/headers
* miner tests: fix travis failure on arm64
* eth/downloader: tests - store td in ancients too
* core/vm: use fixed uint256 library instead of big
* core/vm: remove intpools
* core/vm: upgrade uint256, fixes uint256.NewFromBig
* core/vm: use uint256.Int by value in Stack
* core/vm: upgrade uint256 to v1.0.0
* core/vm: don't preallocate space for 1024 stack items (only 16)
Co-authored-by: Martin Holst Swende <martin@swende.se>
This PR makes use of go 1.13 error handling, wrapping errors and using
errors.Is to check a wrapped root-cause. It also removes the travis
builders for go 1.11 and go 1.12.
This adds a new API method on core.BlockChain to allow interrupting
running data inserts, and calls the method before shutting down the
downloader.
The BlockChain interrupt checks are now done through a method instead
of inlining the atomic load everywhere. There is no loss of efficiency from
this and it makes the interrupt protocol a lot clearer because the check is
defined next to the method that sets the flag.
This PR reimplements the light client server pool. It is also a first step
to move certain logic into a new lespay package. This package will contain
the implementation of the lespay token sale functions, the token buying and
selling logic and other components related to peer selection/prioritization
and service quality evaluation. Over the long term this package will be
reusable for incentivizing future protocols.
Since the LES peer logic is now based on enode.Iterator, it can now use
DNS-based fallback discovery to find servers.
This document describes the function of the new components:
https://gist.github.com/zsfelfoldi/3c7ace895234b7b345ab4f71dab102d4
* cmd, core, eth: init tx lookup in background
* core/rawdb: tiny log fixes to make it clearer what's happening
* core, eth: fix rebase errors
* core/rawdb: make reindexing less generic, but more optimal
* rlp: implement rlp list iterator
* core/rawdb: new implementation of tx indexing/unindex using generic tx iterator and hashing rlp-data
* core/rawdb, cmd/utils: fix review concerns
* cmd/utils: fix merge issue
* core/rawdb: add some log formatting polishes
Co-authored-by: rjl493456442 <garyrong0905@gmail.com>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>
* all: seperate consensus error and evm internal error
There are actually two types of error will be returned when
a tranaction/message call is executed: (a) consensus error
(b) evm internal error. The former should be converted to
a consensus issue, e.g. The sender doesn't enough asset to
purchase the gas it specifies. The latter is allowed since
evm itself is a blackbox and internal error is allowed to happen.
This PR emphasizes the difference by introducing a executionResult
structure. The evm error is embedded inside. So if any error
returned, it indicates consensus issue happens.
And also this PR improve the `EstimateGas` API to return the concrete
revert reason if the transaction always fails
* all: polish
* accounts/abi/bind/backends: add tests
* accounts/abi/bind/backends, internal: cleanup error message
* all: address comments
* core: fix lint
* accounts, core, eth, internal: address comments
* accounts, internal: resolve revert reason if possible
* accounts, internal: address comments
This new API allows reading accounts and their content by address range.
Co-authored-by: Martin Holst Swende <martin@swende.se>
Co-authored-by: Felix Lange <fjl@twurst.com>
* eth: improve shutdown synchronization
Most goroutines started by eth.Ethereum didn't have any shutdown sync at
all, which lead to weird error messages when quitting the client.
This change improves the clean shutdown path by stopping all internal
components in dependency order and waiting for them to actually be
stopped before shutdown is considered done. In particular, we now stop
everything related to peers before stopping 'resident' parts such as
core.BlockChain.
* eth: rewrite sync controller
* eth: remove sync start debug message
* eth: notify chainSyncer about new peers after handshake
* eth: move downloader.Cancel call into chainSyncer
* eth: make post-sync block broadcast synchronous
* eth: add comments
* core: change blockchain stop message
* eth: change closeBloomHandler channel type
Prior to this change, eth_call changed the balance of the sender account in the
EVM environment to 2^256 wei to cover the gas cost of the call execution.
We've had this behavior for a long time even though it's super confusing.
This commit sets the default call gasprice to zero instead of updating the balance,
which is better because it makes eth_call semantics less surprising. Removing
the built-in balance assignment also makes balance overrides work as expected.
* node: expose config in service context
* eth: integrate p2p/dnsdisc
* cmd/geth: add some DNS flags
* eth: remove DNS URLs
* cmd/utils: configure DNS names for testnets
* params: update DNS URLs
* cmd/geth: configure mainnet DNS
* cmd/utils: rename DNS flag and fix flag processing
* cmd/utils: remove debug print
* node: fix test
* travis: Enable ARM support
* Include fixes from 20039
* Add a trace to debug the invalid lookup issue
* Try increasing the timeout to see if the arm test passes
* Investigate the resolver issue
* Increase arm64 timeout for clique test
* increase timeout in tests for arm64
* Only test the failing tests
* Review feedback: don't export epsilon
* Remove investigation tricks+include fjl's feeback
* Revert the retry ahead of using the mock resolver
* Fix rebase errors
* core/evm, contracts: avoid copying memory for input in calls + make ecrecover not modify input buffer
* core/vm: optimize mstore a bit
* core/vm: change Get -> GetCopy in vm memory access
When we flush a batch of trie nodes into database during the state
sync, we should guarantee that all children should be flushed before
parent.
Actually the trie nodes commit order is strict by: children -> parent.
But when we flush all ready nodes into db, we don't need the order
anymore since
(1) they are all ready nodes (no more dependency)
(2) underlying database provides write atomicity
The precompile at 0x09 wraps the BLAKE2b F compression function:
https://tools.ietf.org/html/rfc7693#section-3.2
The precompile requires 6 inputs tightly encoded, taking exactly 213
bytes, as explained below.
- `rounds` - the number of rounds - 32-bit unsigned big-endian word
- `h` - the state vector - 8 unsigned 64-bit little-endian words
- `m` - the message block vector - 16 unsigned 64-bit little-endian words
- `t_0, t_1` - offset counters - 2 unsigned 64-bit little-endian words
- `f` - the final block indicator flag - 8-bit word
[4 bytes for rounds][64 bytes for h][128 bytes for m][8 bytes for t_0]
[8 bytes for t_1][1 byte for f]
The boolean `f` parameter is considered as `true` if set to `1`.
The boolean `f` parameter is considered as `false` if set to `0`.
All other values yield an invalid encoding of `f` error.
The precompile should compute the F function as specified in the RFC
(https://tools.ietf.org/html/rfc7693#section-3.2) and return the updated
state vector `h` with unchanged encoding (little-endian).
See EIP-152 for details.
* eth: chain config (genesis + fork) ENR entry
* core/forkid, eth: protocol independent fork ID, update to CRC32 spec
* core/forkid, eth: make forkid a struct, next uint64, enr struct, RLP
* core/forkid: change forkhash rlp encoding from int to [4]byte
* eth: fixup eth entry a bit and update it every block
* eth: fix lint
* eth: fix crash in ethclient tests
This PR adds some hardening in the lower levels of the protocol stack, to bail early on invalid data. Primarily, attacks that this PR protects against are on the "annoyance"-level, which would otherwise write a couple of megabytes of data into the log output, which is a bit resource intensive.
* core/state, cmd/geth: streaming json output dump cmd + optional code+storage
* dump: add option to continue even if preimages are missing
* core, evm: lint nits
* cmd: use local flags for dump, omit empty code/storage
* core/state: fix state dump test
* core, eth: some fixes for freezer
* vendor, core/rawdb, cmd/geth: add db inspector
* core, cmd/utils: check ancient store path forceily
* cmd/geth, common, core/rawdb: a few fixes
* cmd/geth: support windows file rename and fix rename error
* core: support ancient plugin
* core, cmd: streaming file copy
* cmd, consensus, core, tests: keep genesis in leveldb
* core: write txlookup during ancient init
* core: bump database version
* all: freezer style syncing
core, eth, les, light: clean up freezer relative APIs
core, eth, les, trie, ethdb, light: clean a bit
core, eth, les, light: add unit tests
core, light: rewrite setHead function
core, eth: fix downloader unit tests
core: add receipt chain insertion test
core: use constant instead of hardcoding table name
core: fix rollback
core: fix setHead
core/rawdb: remove canonical block first and then iterate side chain
core/rawdb, ethdb: add hasAncient interface
eth/downloader: calculate ancient limit via cht first
core, eth, ethdb: lots of fixes
* eth/downloader: print ancient disable log only for fast sync
* core, eth, trie: bloom filter for trie node dedup during fast sync
* eth/downloader, trie: address review comments
* core, ethdb, trie: restart fast-sync bloom construction now and again
* eth/downloader: initialize fast sync bloom on startup
* eth: reenable eth/62 until we properly remove it
This change makes getBalance, getCode, getStorageAt, getProof,
call, getTransactionCount return an error if the block number in
the request doesn't exist. getHeaderByNumber still returns null
for missing headers.
* cmd, eth, miner: disable advance sealing if user require
* cmd, console, miner, les, eth: wrap the miner config
* eth: remove todo
* cmd, miner: revert noadvance flag
The reason for this is: if the transaction execution is even longer
than block time, then this kind of transactions is DoS attack.
* core/vm: remove function call for stack validation from evm runloop
* core/vm: separate gas calc into static + dynamic
* core/vm: optimize push1
* core/vm: reuse pooled bigints for ADDRESS, ORIGIN and CALLER
* core/vm: use generic error message for jump/jumpi, to avoid string interpolation
* testdata: fix tests for new error message
* core/vm: use 64-bit memory calculations
* core/vm: fix error in memory calculation
* core/vm: address review concerns
* core/vm: avoid unnecessary use of big.Int:BitLen()
This change
- implements concurrent LES request serving even for a single peer.
- replaces the request cost estimation method with a cost table based on
benchmarks which gives much more consistent results. Until now the
allowed number of light peers was just a guess which probably contributed
a lot to the fluctuating quality of available service. Everything related
to request cost is implemented in a single object, the 'cost tracker'. It
uses a fixed cost table with a global 'correction factor'. Benchmark code
is included and can be run at any time to adapt costs to low-level
implementation changes.
- reimplements flowcontrol.ClientManager in a cleaner and more efficient
way, with added capabilities: There is now control over bandwidth, which
allows using the flow control parameters for client prioritization.
Target utilization over 100 percent is now supported to model concurrent
request processing. Total serving bandwidth is reduced during block
processing to prevent database contention.
- implements an RPC API for the LES servers allowing server operators to
assign priority bandwidth to certain clients and change prioritized
status even while the client is connected. The new API is meant for
cases where server operators charge for LES using an off-protocol mechanism.
- adds a unit test for the new client manager.
- adds an end-to-end test using the network simulator that tests bandwidth
control functions through the new API.
Simplifies the transaction presense check to use a function to
determine if the transaction is present in the block provided
to trace, which originally had a redundant parenthesis and used
a `exist` flag to dictate control flow.
This changes default location of the data directory to use the LOCALAPPDATA
environment variable, resolving issues with remote home directories an improving
compatibility with Cygwin.
Fixes#2239Fixes#2237Fixes#16437
* cmd, eth: Added in the flag to step geth once sync based on input
* cmd, eth: 16400 Add an option to stop geth once in sync.
* cmd: 16400 Add an option to stop geth once in sync. WIP
* cmd/geth/main, les/fletcher: added in light mode support
* cmd/geth/main, les/fletcher: Cleaned Comments and code for light mode
* cmd: 16400 Fixed formatting issue and cleaned code
* cmd, eth, les: 16400 Fixed formatting issues
* cmd, eth, les: Performed gofmt to update formatting
* cmd, eth, les: Fixed bugs resulting formatting
* cmd/geth, eth/, les: switched to downloader event
* eth: Fixed styling and gen_config
* eth/: Fix nil error in config file
* cmd/geth: Updated countdown log
* les/fetcher.go: Removed depcreated channel
* eth/downloader.go: Removed deprecated select
* cmd/geth, cmd/utils: Fixed minor issues
* eth: Reverted config files to proper format
* eth: Fixed typo in config file
* cmd/geth, eth/down: Updated code to use header time stamp
* eth/downloader: Changed the time threshold to 10 minutes
* cmd/geth, eth/downloader: Updated downloading event to pass latest header
* cmd/geth: Updated main to use right timer object
* cmd/geth: Removed unused failed event
* cmd/geth: added in correct time field with type assertion
* cmd/geth, cmd/utils: Updated flag to use boolean
* cmd/geth, cmd/utils, eth/downloader: Cleaned up code based on recommendations
* cmd/geth: Removed unneeded import
* cmd/geth, eth/downloader: fixed event field and suggested changes
* cmd/geth, cmd/utils: Updated flag and linting issue
* geth/core/eth: implement constantinople override flag
* les: implemnent constantinople override flag for les clients
* cmd/geth, eth, les: fix typo, move flag to experimentals
