This PR implements the new LES protocol version extensions:
* new and more efficient Merkle proofs reply format (when replying to
a multiple Merkle proofs request, we just send a single set of trie
nodes containing all necessary nodes)
* BBT (BloomBitsTrie) works similarly to the existing CHT and contains
the bloombits search data to speed up log searches
* GetTxStatusMsg returns the inclusion position or the
pending/queued/unknown state of a transaction referenced by hash
* an optional signature of new block data (number/hash/td) can be
included in AnnounceMsg to provide an option for "very light
clients" (mobile/embedded devices) to skip expensive Ethash check
and accept multiple signatures of somewhat trusted servers (still a
lot better than trusting a single server completely and retrieving
everything through RPC). The new client mode is not implemented in
this PR, just the protocol extension.
This commit does various code refactorings:
- generalizes and moves the request retrieval/timeout/resend logic out of LesOdr
(will be used by a subsequent PR)
- reworks the peer management logic so that all services can register with
peerSet to get notified about added/dropped peers (also gets rid of the ugly
getAllPeers callback in requestDistributor)
- moves peerSet, LesOdr, requestDistributor and retrieveManager initialization
out of ProtocolManager because I believe they do not really belong there and the
whole init process was ugly and ad-hoc
There is no need to depend on the old context package now that the
minimum Go version is 1.7. The move to "context" eliminates our weird
vendoring setup. Some vendored code still uses golang.org/x/net/context
and it is now vendored in the normal way.
This change triggered new vet checks around context.WithTimeout which
didn't fire with golang.org/x/net/context.
