* build: upgrade golangci to 1.22.2

* .golangci.yml: don't fail on asset deadcode

travis, build: enable Ubuntu Focal and Go 1.13.6 on PPA

* build: put GOPATH in /tmp on launchpad

* build: don't remove GOPATH from go tool environment

* build: remove env.sh

This removes the dirty symlink-to-self hack we've had for years. The
script was added to enable building without GOPATH and did that job
reliably for all this time. We can remove the workaround because modern
Go supports building without GOPATH natively.

* Makefile: add GO111MODULE=on to environment

core: set max tx size down to 2 slots (64KB)

eth: check propagated block malformation on receiption

* tests for tx size

* alow multiple slots transactions

* tests for tx size limit (32 KB)

* change tx size tests to use addRemoteSync instead of validateTx (requested in pool request).

* core: minor tx slotting polishes, add slot tracking metric

Co-authored-by: Michael Riabzev <RiabzevMichael@gmail.com>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

core/state: add more verbosity to panic

This reverts commit a1bc0e3c.

* internal/testlog: print file+line number of log call in test log

This changes the unit test logger to print the actual file and line
number of the logging call instead of "testlog.go:44".

Output of 'go test -v -run TestServerListen ./p2p' before this change:

    === RUN   TestServerListen
    --- PASS: TestServerListen (0.00s)
        testlog.go:44: DEBUG[01-08|15:16:31.651] UDP listener up         addr=127.0.0.1:62678
        testlog.go:44: DEBUG[01-08|15:16:31.651] TCP listener up         addr=127.0.0.1:62678
        testlog.go:44: TRACE[01-08|15:16:31.652] Accepted connection     addr=127.0.0.1:62679

And after:

    === RUN   TestServerListen
    --- PASS: TestServerListen (0.00s)
        server.go:868: DEBUG[01-08|15:25:35.679] TCP listener up         addr=127.0.0.1:62712
        server.go:557: DEBUG[01-08|15:25:35.679] UDP listener up         addr=127.0.0.1:62712
        server.go:912: TRACE[01-08|15:25:35.680] Accepted connection     addr=127.0.0.1:62713

* internal/testlog: document use of t.Helper

Update copyright from 2013-2019 to 2013-2020

* add node.go unit test file node_test.go

* add node_test.go file license and rollback trie_test.go

* fix unused variable v

* trie: fix license year

Co-authored-by: Péter Szilágyi <peterke@gmail.com>

* les: move the checkpoint oracle into its own package

It's first step of refactor LES package. LES package
basically can be divided into LES client and LES server.
However both sides will use checkpoint package for
status retrieval and verification. So this PR moves
checkpoint oracle into a separate package

* les: address comments

Fixes #19024
Fixes #19332

This commit intents to replicate the DialHTTPWithClient function which allows
creating a RPC Client using a custom dialer but for websockets.

We introduce a new DialWebsocketWithDialer function which allows the caller
to instantiate a new websocket client using a custom dialer.

* Add more functionality to the sim (#5)

* backends: implement more of ethclient in sim

* backends: add BlockByNumber to simulated backend

* backends: make simulated progress function agree with syncprogress interface for client

* backends: add more tests

* backends: add more comments

* backends: fix sim for index in tx and add tests

* backends: add lock back to estimategas

* backends: goimports

* backends: go ci lint

* Add more functionality to the sim (#5)

* backends: implement more of ethclient in sim

* backends: add BlockByNumber to simulated backend

* backends: make simulated progress function agree with syncprogress interface for client

* backends: add more tests

* backends: add more comments

* backends: fix sim for index in tx and add tests

* backends: add lock back to estimategas

* backends: goimports

* backends: go ci lint

* assert errs

* fix parseTopics() and add tests

* remove printf

* add ParseTopicsIntoMap() tests

* fix FixedBytesTy

* fix int and fixed bytes

* golint topics_test.go

The --bench flag uses the testing.B to execute the EVM bytecode many times and get the average exeuction time out of it.

eth, internal/web3ext: add optional first and last arguments to the  `admin_exportChain` RPC. (#20107)

* cmd/abigen: Sanitize vyper's combined json names

* Review feedback: handle full paths

* p2p/dnsdisc: add support for enode.Iterator

This changes the dnsdisc.Client API to support the enode.Iterator
interface.

* p2p/dnsdisc: rate-limit DNS requests

* p2p/dnsdisc: preserve linked trees across root updates

This improves the way links are handled when the link root changes.
Previously, sync would simply remove all links from the current tree and
garbage-collect all unreachable trees before syncing the new list of
links.

This behavior isn't great in certain cases: Consider a structure where
trees A, B, and C reference each other and D links to A. If D's link
root changed, the sync code would first remove trees A, B and C, only to
re-sync them later when the link to A was found again.

The fix for this problem is to track the current set of links in each
clientTree and removing old links only AFTER all links are synced.

* p2p/dnsdisc: deflake iterator test

* cmd/devp2p: adapt dnsClient to new p2p/dnsdisc API

* p2p/dnsdisc: tiny comment fix