This change adds adds an ability to use different source of time for whisper:
when envelope is created it is used to set expiry
to track when envelope needs to be expired
This time is then used to check validity of the envelope when it is received. Currently If we receive an envelope that is sent from future - peer will get disconnected. If envelope that was received has an expiry less then now it will be simply dropped, if expiry is less than now + 10*2 seconds peer will get dropped.
So, it is clear that whisper depends on time. And any time we get a skew with peers that is > 20s reliability will be grealy reduced.
In this change another source of time for whisper will be used. This time source will use ntp servers from pool.ntp.org to compute offset. When whisper queries time - this offset will be added/substracted from current time.
Query is executed every 2 mins, queries 5 different servers, cut offs min and max and the computes mean value. pool.ntp.org is resolved to different servers and according to documentation you will rarely hit the same.
Closes: #687
* Rebase on 1.8.5
* Remove outdated patches and apply all others
* Use shh_post that returns hash
* Use bloom filter for request to mailserver
* Remove tests for sending messages without subbing first
* Fix deadlock in ethdb
* Expect null if receipt is not yet created
* Subscribe to messages before sending them in whisper test
* Update `github.com/ethereum/go-ethereum` package to 1.8.1 branch. Part of #638
* Fix code due to some signature changes. Part of #638
* use upstream for whisper backend
* Add patch to downgrade usage of Whisper v6 to v5 in some geth 1.8.1 vendor files. Part of #638
* Take into account the DNS rebinding protection introduced in 1.8.0 by adding exception for localhost. Part of #638
* Add patches required for cross-compiled builds starting with geth 1.8.0. Only applied during build. Part of #638
* Update expected JSON result in `TestRegressionGetTransactionReceipt()` and `TestCallRawResultGetTransactionReceipt()`. Part of #665
* Fix some failing e2e tests. Part of #638
* Address comments in PR #702. Part of #638
Network disconnect is introduced by removing default gateway, easily reversible condition.
On my local machine it takes 30 seconds for peers to reconnect after connectivity is restored. As you guess this is not an accident, and there is 30 seconds timeout for dial expiration. This dial expiration is used in p2p.Server to guarantee that peers are not dialed too often.
Additionally I added small script to Makefile to run such tests in docker environment, usage example:
```
make docker-test ARGS="./t/destructive/ -v -network=4"
```
Adam Babik
Dmitry Shulyak
Frank Mueller
Igor Mandrigin
Dmitry Shulyak
Pedro Pombeiro
Caner Çıdam
Igor Mandrigin