Add attestation gossip pre-verification (#983)

* Add PH & MS slot clock changes

* Account for genesis time

* Add progress on duties refactor

* Add simple is_aggregator bool to val subscription

* Start work on attestation_verification.rs

* Add progress on ObservedAttestations

* Progress with ObservedAttestations

* Fix tests

* Add observed attestations to the beacon chain

* Add attestation observation to processing code

* Add progress on attestation verification

* Add first draft of ObservedAttesters

* Add more tests

* Add observed attesters to beacon chain

* Add observers to attestation processing

* Add more attestation verification

* Create ObservedAggregators map

* Remove commented-out code

* Add observed aggregators into chain

* Add progress

* Finish adding features to attestation verification

* Ensure beacon chain compiles

* Link attn verification into chain

* Integrate new attn verification in chain

* Remove old attestation processing code

* Start trying to fix beacon_chain tests

* Split adding into pools into two functions

* Add aggregation to harness

* Get test harness working again

* Adjust the number of aggregators for test harness

* Fix edge-case in harness

* Integrate new attn processing in network

* Fix compile bug in validator_client

* Update validator API endpoints

* Fix aggreagation in test harness

* Fix enum thing

* Fix attestation observation bug:

* Patch failing API tests

* Start adding comments to attestation verification

* Remove unused attestation field

* Unify "is block known" logic

* Update comments

* Supress fork choice errors for network processing

* Add todos

* Tidy

* Add gossip attn tests

* Disallow test harness to produce old attns

* Comment out in-progress tests

* Partially address pruning tests

* Fix failing store test

* Add aggregate tests

* Add comments about which spec conditions we check

* Dont re-aggregate

* Split apart test harness attn production

* Fix compile error in network

* Make progress on commented-out test

* Fix skipping attestation test

* Add fork choice verification tests

* Tidy attn tests, remove dead code

* Remove some accidentally added code

* Fix clippy lint

* Rename test file

* Add block tests, add cheap block proposer check

* Rename block testing file

* Add observed_block_producers

* Tidy

* Switch around block signature verification

* Finish block testing

* Remove gossip from signature tests

* First pass of self review

* Fix deviation in spec

* Update test spec tags

* Start moving over to hashset

* Finish moving observed attesters to hashmap

* Move aggregation pool over to hashmap

* Make fc attn borrow again

* Fix rest_api compile error

* Fix missing comments

* Fix monster test

* Uncomment increasing slots test

* Address remaining comments

* Remove unsafe, use cfg test

* Remove cfg test flag

* Fix dodgy comment

* Ignore aggregates that are already known.

* Unify aggregator modulo logic

* Fix typo in logs

* Refactor validator subscription logic

* Avoid reproducing selection proof

* Skip HTTP call if no subscriptions

* Rename DutyAndState -> DutyAndProof

* Tidy logs

* Print root as dbg

* Fix compile errors in tests

* Fix compile error in test

beacon_node/beacon_chain/tests/tests.rs

@@ -3,10 +3,12 @@
 #[macro_use]
 extern crate lazy_static;
 
-use beacon_chain::test_utils::{
-    AttestationStrategy, BeaconChainHarness, BlockStrategy, HarnessType, OP_POOL_DB_KEY,
+use beacon_chain::{
+    attestation_verification::Error as AttnError,
+    test_utils::{
+        AttestationStrategy, BeaconChainHarness, BlockStrategy, HarnessType, OP_POOL_DB_KEY,
+    },
 };
-use beacon_chain::{AttestationProcessingOutcome, AttestationType};
 use operation_pool::PersistedOperationPool;
 use state_processing::{
     per_slot_processing, per_slot_processing::Error as SlotProcessingError, EpochProcessingError,
@@ -361,7 +363,7 @@ fn roundtrip_operation_pool() {
 }
 
 #[test]
-fn free_attestations_added_to_fork_choice_some_none() {
+fn unaggregated_attestations_added_to_fork_choice_some_none() {
     let num_blocks_produced = MinimalEthSpec::slots_per_epoch() / 2;
 
     let harness = get_harness(VALIDATOR_COUNT);
@@ -425,7 +427,7 @@ fn attestations_with_increasing_slots() {
         );
 
         attestations.append(
-            &mut harness.get_free_attestations(
+            &mut harness.get_unaggregated_attestations(
                 &AttestationStrategy::AllValidators,
                 &harness.chain.head().expect("should get head").beacon_state,
                 harness
@@ -445,30 +447,31 @@ fn attestations_with_increasing_slots() {
         harness.advance_slot();
     }
 
-    let current_epoch = harness.chain.epoch().expect("should get epoch");
-
-    for attestation in attestations {
-        let attestation_epoch = attestation.data.target.epoch;
+    for attestation in attestations.into_iter().flatten() {
         let res = harness
             .chain
-            .process_attestation(attestation, AttestationType::Aggregated);
+            .verify_unaggregated_attestation_for_gossip(attestation.clone());
 
-        if attestation_epoch + 1 < current_epoch {
+        let current_slot = harness.chain.slot().expect("should get slot");
+        let attestation_slot = attestation.data.slot;
+        let earliest_permissible_slot = current_slot - MinimalEthSpec::slots_per_epoch() - 1;
+
+        if attestation_slot < earliest_permissible_slot {
             assert_eq!(
-                res,
-                Ok(AttestationProcessingOutcome::PastEpoch {
-                    attestation_epoch,
-                    current_epoch,
-                })
+                res.err().unwrap(),
+                AttnError::PastSlot {
+                    attestation_slot,
+                    earliest_permissible_slot,
+                }
             )
         } else {
-            assert_eq!(res, Ok(AttestationProcessingOutcome::Processed))
+            res.expect("should process attestation");
         }
     }
 }
 
 #[test]
-fn free_attestations_added_to_fork_choice_all_updated() {
+fn unaggregated_attestations_added_to_fork_choice_all_updated() {
     let num_blocks_produced = MinimalEthSpec::slots_per_epoch() * 2 - 1;
 
     let harness = get_harness(VALIDATOR_COUNT);