## Issue Addressed
Relates to https://github.com/sigp/lighthouse/issues/3416
## Proposed Changes
- Add an `OfflineOnFailure` enum to the `first_success` method for querying beacon nodes so that a val registration request failure from the BN -> builder does not result in the BN being marked offline. This seems important because these failures could be coming directly from a connected relay and actually have no bearing on BN health. Other messages that are sent to a relay have a local fallback so shouldn't result in errors
- Downgrade the following log to a `WARN`
```
ERRO Unable to publish validator registrations to the builder network, error: All endpoints failed https://BN_B => RequestFailed(ServerMessage(ErrorMessage { code: 500, message: "UNHANDLED_ERROR: BuilderMissing", stacktraces: [] })), https://XXXX/ => Unavailable(Offline), [omitted]
```
## Additional Info
I think this change at least improves the UX of having a VC connected to some builder and some non-builder beacon nodes. I think we need to balance potentially alerting users that there is a BN <> VC misconfiguration and also allowing this type of fallback to work.
If we want to fully support this type of configuration we may want to consider adding a flag `--builder-beacon-nodes` and track whether a VC should be making builder queries on a per-beacon node basis. But I think the changes in this PR are independent of that type of extension.
PS: Sorry for the big diff here, it's mostly formatting changes after I added a new arg to a bunch of methods calls.
Co-authored-by: realbigsean <sean@sigmaprime.io>
## Issue Addressed
NA
## Proposed Changes
Indicate that local keystores are `readonly: Some(false)` rather than `None` via the `/eth/v1/keystores` method on the VC API.
I'll mark this as backwards-incompat so we remember to mention it in the release notes. There aren't any type-level incompatibilities here, just a change in how Lighthouse responds to responses.
## Additional Info
- Blocked on #3464
## Proposed Changes
Update the merge migration docs to encourage updating mainnet configs _now_!
The docs are also updated to recommend _against_ `--suggested-fee-recipient` on the beacon node (https://github.com/sigp/lighthouse/issues/3432).
Additionally the `--help` for the CLI is updated to match with a few small semantic changes:
- `--execution-jwt` is no longer allowed without `--execution-endpoint`. We've ended up without a default for `--execution-endpoint`, so I think that's fine.
- The flags related to the JWT are only allowed if `--execution-jwt` is provided.
## Issue Addressed
Resolves#3388Resolves#2638
## Proposed Changes
- Return the `BellatrixPreset` on `/eth/v1/config/spec` by default.
- Allow users to opt out of this by providing `--http-spec-fork=altair` (unless there's a Bellatrix fork epoch set).
- Add the Altair constants from #2638 and make serving the constants non-optional (the `http-disable-legacy-spec` flag is deprecated).
- Modify the VC to only read the `Config` and not to log extra fields. This prevents it from having to muck around parsing the `ConfigAndPreset` fields it doesn't need.
## Additional Info
This change is backwards-compatible for the VC and the BN, but is marked as a breaking change for the removal of `--http-disable-legacy-spec`.
I tried making `Config` a `superstruct` too, but getting the automatic decoding to work was a huge pain and was going to require a lot of hacks, so I gave up in favour of keeping the default-based approach we have now.
## Issue Addressed
Fixes#2967
## Proposed Changes
Collect validator indices alongside attestations when creating signed
attestations (and aggregates) for inclusion in the logs.
## Additional Info
This is my first time looking at Lighthouse source code and using Rust, so newbie feedback appreciated!
## Issue Addressed
https://github.com/sigp/lighthouse/issues/3091
Extends https://github.com/sigp/lighthouse/pull/3062, adding pre-bellatrix block support on blinded endpoints and allowing the normal proposal flow (local payload construction) on blinded endpoints. This resulted in better fallback logic because the VC will not have to switch endpoints on failure in the BN <> Builder API, the BN can just fallback immediately and without repeating block processing that it shouldn't need to. We can also keep VC fallback from the VC<>BN API's blinded endpoint to full endpoint.
## Proposed Changes
- Pre-bellatrix blocks on blinded endpoints
- Add a new `PayloadCache` to the execution layer
- Better fallback-from-builder logic
## Todos
- [x] Remove VC transition logic
- [x] Add logic to only enable builder flow after Merge transition finalization
- [x] Tests
- [x] Fix metrics
- [x] Rustdocs
Co-authored-by: Mac L <mjladson@pm.me>
Co-authored-by: realbigsean <sean@sigmaprime.io>
## Issue Addressed
Resolves#3151
## Proposed Changes
When fetching duties for sync committee contributions, check the value of `execution_optimistic` of the head block from the BN and refuse to sign any sync committee messages `if execution_optimistic == true`.
## Additional Info
- Is backwards compatible with older BNs
- Finding a way to add test coverage for this would be prudent. Open to suggestions.
## Issue Addressed
Resolves#3267Resolves#3156
## Proposed Changes
- Move the log for fee recipient checks from proposer cache insertion into block proposal so we are directly checking what we get from the EE
- Only log when there is a discrepancy with the local EE, not when using the builder API. In the `builder-api` branch there is an `info` log when there is a discrepancy, I think it is more likely there will be a difference in fee recipient with the builder api because proposer payments might be made via a transaction in the block. Not really sure what patterns will become commong.
- Upgrade the log from a `warn` to an `error` - not actually sure which we want, but I think this is worth an error because the local EE with default transaction ordering I think should pretty much always use the provided fee recipient
- add a `strict-fee-recipient` flag to the VC so we only sign blocks with matching fee recipients. Falls back from the builder API to the local API if there is a discrepancy .
Co-authored-by: realbigsean <sean@sigmaprime.io>
## Issue Addressed
#3302
## Proposed Changes
Move the `reqwest::Client` from being initialized per-validator, to being initialized per distinct Web3Signer.
This is done by placing the `Client` into a `HashMap` keyed by the definition of the Web3Signer as specified by the `ValidatorDefintion`. This will allow multiple Web3Signers to be used with a single VC and also maintains backwards compatibility.
## Additional Info
This was done to reduce the memory used by the VC when connecting to a Web3Signer.
I set up a local testnet using [a custom script](https://github.com/macladson/lighthouse/tree/web3signer-local-test/scripts/local_testnet_web3signer) and ran a VC with 200 validator keys:
VC with Web3Signer:
- `unstable`: ~200MB
- With fix: ~50MB
VC with Local Signer:
- `unstable`: ~35MB
- With fix: ~35MB
> I'm seeing some fragmentation with the VC using the Web3Signer, but not when using a local signer (this is most likely due to making lots of http requests and dealing with lots of JSON objects). I tested the above using `MALLOC_ARENA_MAX=1` to try to reduce the fragmentation. Without it, the values are around +50MB for both `unstable` and the fix.
## Issue Addressed
Web3signer validators can't produce post-Bellatrix blocks.
## Proposed Changes
Add support for Bellatrix to web3signer validators.
## Additional Info
I am running validators with this code on Ropsten, but it may be a while for them to get a proposal.
## Issue Addressed
Resolves#3276.
## Proposed Changes
Add a timeout for the sync committee contributions at 1/4 the slot length such that we may be able to try backup beacon nodes in the case of contribution post failure.
## Additional Info
1/4 slot length seemed standard for the timeouts, but may want to decrease this to 1/2.
I did not find any timeout related / sync committee related tests, so there are no tests. Happy to write some with a bit of guidance.
## Issue Addressed
* #3173
## Proposed Changes
Moved all `fee_recipient_file` related logic inside the `ValidatorStore` as it makes more sense to have this all together there. I tested this with the validators I have on `mainnet-shadow-fork-5` and everything appeared to work well. Only technicality is that I can't get the method to return `401` when the authorization header is not specified (it returns `400` instead). Fixing this is probably quite difficult given that none of `warp`'s rejections have code `401`.. I don't really think this matters too much though as long as it fails.
## Issue Addressed
Lays the groundwork for builder API changes by implementing the beacon-API's new `register_validator` endpoint
## Proposed Changes
- Add a routine in the VC that runs on startup (re-try until success), once per epoch or whenever `suggested_fee_recipient` is updated, signing `ValidatorRegistrationData` and sending it to the BN.
- TODO: `gas_limit` config options https://github.com/ethereum/builder-specs/issues/17
- BN only sends VC registration data to builders on demand, but VC registration data *does update* the BN's prepare proposer cache and send an updated fcU to a local EE. This is necessary for fee recipient consistency between the blinded and full block flow in the event of fallback. Having the BN only send registration data to builders on demand gives feedback directly to the VC about relay status. Also, since the BN has no ability to sign these messages anyways (so couldn't refresh them if it wanted), and validator registration is independent of the BN head, I think this approach makes sense.
- Adds upcoming consensus spec changes for this PR https://github.com/ethereum/consensus-specs/pull/2884
- I initially applied the bit mask based on a configured application domain.. but I ended up just hard coding it here instead because that's how it's spec'd in the builder repo.
- Should application mask appear in the api?
Co-authored-by: realbigsean <sean@sigmaprime.io>
## Issue Addressed
Following up from https://github.com/sigp/lighthouse/pull/3223#issuecomment-1158718102, it has been observed that the validator client uses vastly more memory in some compilation configurations than others. Compiling with Cross and then putting the binary into an Ubuntu 22.04 image seems to use 3x more memory than compiling with Cargo directly on Debian bullseye.
## Proposed Changes
Enable malloc metrics for the validator client. This will hopefully allow us to see the difference between the two compilation configs and compare heap fragmentation. This PR doesn't enable malloc tuning for the VC because it was found to perform significantly worse. The `--disable-malloc-tuning` flag is repurposed to just disable the metrics.
## Issue Addressed
#3154
## Proposed Changes
Add three new metrics for the VC:
1. `vc_beacon_nodes_synced_count`
2. `vc_beacon_nodes_available_count`
3. `vc_beacon_nodes_total_count`
Their values mirror the values present in the following log line:
```
Apr 08 17:25:17.000 INFO Connected to beacon node(s) synced: 4, available: 4, total: 4, service: notifier
```
## Issue Addressed
This fixes the low-hanging Clippy lints introduced in Rust 1.61 (due any hour now). It _ignores_ one lint, because fixing it requires a structural refactor of the validator client that needs to be done delicately. I've started on that refactor and will create another PR that can be reviewed in more depth in the coming days. I think we should merge this PR in the meantime to unblock CI.
## Issue Addressed
Web3Signer validators do not support client authentication. This means the `--tls-known-clients-file` option on Web3Signer can't be used with Lighthouse.
## Proposed Changes
Add two new fields to Web3Signer validators, `client_identity_path` and `client_identity_password`, which specify the path and password for a PKCS12 file containing a certificate and private key. If `client_identity_path` is present, use the certificate for SSL client authentication.
## Additional Info
I am successfully validating on Prater using client authentication with Web3Signer and client authentication.
## Issue Addressed
#3141
## Proposed Changes
Changes the algorithm for proposing blocks from
```
For each BN (first success):
- Produce a block
- Sign the block and store its root in the slashing protection DB
- Publish the block
```
to
```
For each BN (first success):
- Produce a block
Sign the block and store its root in the slashing protection DB
For each BN (first success):
- Publish the block
```
Separating the producing from the publishing makes sure that we only add a signed block once to the slashing DB.
# Description
Since the `TaskExecutor` currently requires a `Weak<Runtime>`, it's impossible to use it in an async test where the `Runtime` is created outside our scope. Whilst we *could* create a new `Runtime` instance inside the async test, dropping that `Runtime` would cause a panic (you can't drop a `Runtime` in an async context).
To address this issue, this PR creates the `enum Handle`, which supports either:
- A `Weak<Runtime>` (for use in our production code)
- A `Handle` to a runtime (for use in testing)
In theory, there should be no change to the behaviour of our production code (beyond some slightly different descriptions in HTTP 500 errors), or even our tests. If there is no change, you might ask *"why bother?"*. There are two PRs (#3070 and #3175) that are waiting on these fixes to introduce some new tests. Since we've added the EL to the `BeaconChain` (for the merge), we are now doing more async stuff in tests.
I've also added a `RuntimeExecutor` to the `BeaconChainTestHarness`. Whilst that's not immediately useful, it will become useful in the near future with all the new async testing.
Code simplifications using `Option`/`Result` combinators to make pattern-matches a tad simpler.
Opinions on these loosely held, happy to adjust in review.
Tool-aided by [comby-rust](https://github.com/huitseeker/comby-rust).
## Issue Addressed
#3068
## Proposed Changes
Adds support for remote key API.
## Additional Info
Needed to add `is_local_keystore` argument to `delete_definition_and_keystore` to know if we want to delete local or remote key. Previously this wasn't necessary because remotekeys(web3signers) could be deleted.
## Proposed Changes
I did some gardening 🌳 in our dependency tree:
- Remove duplicate versions of `warp` (git vs patch)
- Remove duplicate versions of lots of small deps: `cpufeatures`, `ethabi`, `ethereum-types`, `bitvec`, `nix`, `libsecp256k1`.
- Update MDBX (should resolve#3028). I tested and Lighthouse compiles on Windows 11 now.
- Restore `psutil` back to upstream
- Make some progress updating everything to rand 0.8. There are a few crates stuck on 0.7.
Hopefully this puts us on a better footing for future `cargo audit` issues, and improves compile times slightly.
## Additional Info
Some crates are held back by issues with `zeroize`. libp2p-noise depends on [`chacha20poly1305`](https://crates.io/crates/chacha20poly1305) which depends on zeroize < v1.5, and we can only have one version of zeroize because it's post 1.0 (see https://github.com/rust-lang/cargo/issues/6584). The latest version of `zeroize` is v1.5.4, which is used by the new versions of many other crates (e.g. `num-bigint-dig`). Once a new version of chacha20poly1305 is released we can update libp2p-noise and upgrade everything to the latest `zeroize` version.
I've also opened a PR to `blst` related to zeroize: https://github.com/supranational/blst/pull/111
## Issue Addressed
MEV boost compatibility
## Proposed Changes
See #2987
## Additional Info
This is blocked on the stabilization of a couple specs, [here](https://github.com/ethereum/beacon-APIs/pull/194) and [here](https://github.com/flashbots/mev-boost/pull/20).
Additional TODO's and outstanding questions
- [ ] MEV boost JWT Auth
- [ ] Will `builder_proposeBlindedBlock` return the revealed payload for the BN to propogate
- [ ] Should we remove `private-tx-proposals` flag and communicate BN <> VC with blinded blocks by default once these endpoints enter the beacon-API's repo? This simplifies merge transition logic.
Co-authored-by: realbigsean <seananderson33@gmail.com>
Co-authored-by: realbigsean <sean@sigmaprime.io>
## Issue Addressed
#3103
## Proposed Changes
Parse `http-address` and `metrics-address` as `IpAddr` for both the beacon node and validator client to support IPv6 addresses.
Also adjusts parsing of CORS origins to allow for IPv6 addresses.
## Usage
You can now set `http-address` and/or `metrics-address` flags to IPv6 addresses.
For example, the following:
`lighthouse bn --http --http-address :: --metrics --metrics-address ::1`
will expose the beacon node HTTP server on `[::]` (equivalent of `0.0.0.0` in IPv4) and the metrics HTTP server on `localhost` (the equivalent of `127.0.0.1` in IPv4)
The beacon node API can then be accessed by:
`curl "http://[server-ipv6-address]:5052/eth/v1/some_endpoint"`
And the metrics server api can be accessed by:
`curl "http://localhost:5054/metrics"` or by `curl "http://[::1]:5054/metrics"`
## Additional Info
On most Linux distributions the `v6only` flag is set to `false` by default (see the section for the `IPV6_V6ONLY` flag in https://www.man7.org/linux/man-pages/man7/ipv6.7.html) which means IPv4 connections will continue to function on a IPv6 address (providing it is appropriately mapped). This means that even if the Lighthouse API is running on `::` it is also possible to accept IPv4 connections.
However on Windows, this is not the case. The `v6only` flag is set to `true` so binding to `::` will only allow IPv6 connections.
## Issue Addressed
Presently if the VC is configured with a fee recipient it will error out when sending fee-recipient preparations to a beacon node that doesn't yet support the API:
```
Mar 08 22:23:36.236 ERRO Unable to publish proposer preparation error: All endpoints failed https://eth2-beacon-prater.infura.io/ => RequestFailed(StatusCode(404)), service: preparation
```
This doesn't affect other VC duties, but could be a source of anxiety for users trying to do the right thing and configure their fee recipients in advance.
## Proposed Changes
Change the preparation service to only send preparations if the current slot is later than 2 epochs before the Bellatrix hard fork epoch.
## Additional Info
I've tagged this v2.1.4 as I think it's a small change that's worth having for the next release
## Proposed Changes
Lots of lint updates related to `flat_map`, `unwrap_or_else` and string patterns. I did a little more creative refactoring in the op pool, but otherwise followed Clippy's suggestions.
## Additional Info
We need this PR to unblock CI.
## Issue Addressed
#3020
## Proposed Changes
- Alias the `validators-dir` arg to `validator-dir` in the `validator_client` subcommand.
- Alias the `validator-dir` arg to `validators-dir` in the `account_manager validator` subcommand.
- Add test for the validator_client alias.
## Issue Addressed
Addresses https://github.com/sigp/lighthouse/issues/2926
## Proposed Changes
Appropriated from https://github.com/sigp/lighthouse/issues/2926#issuecomment-1039676768:
When a node returns *any* error we call [`CandidateBeaconNode::set_offline`](c3a793fd73/validator_client/src/beacon_node_fallback.rs (L424)) which sets it's `status` to `CandidateError::Offline`. That node will then be ignored until the routine [`fallback_updater_service`](c3a793fd73/validator_client/src/beacon_node_fallback.rs (L44)) manages to reconnect to it.
However, I believe there was an issue in the [`CanidateBeaconNode::refesh_status`](c3a793fd73/validator_client/src/beacon_node_fallback.rs (L157-L178)) method, which is used by the updater service to see if the node has come good again. It was holding a [write lock on the `status` field](c3a793fd73/validator_client/src/beacon_node_fallback.rs (L165)) whilst it polled the node status. This means a long timeout would hog the write lock and starve other processes.
When a VC is trying to access a beacon node for whatever purpose (getting duties, posting blocks, etc), it performs [three passes](c3a793fd73/validator_client/src/beacon_node_fallback.rs (L432-L482)) through the lists of nodes, trying to run some generic `function` (closure, lambda, etc) on each node:
- 1st pass: only try running `function` on all nodes which are both synced and online.
- 2nd pass: try running `function` on all nodes that are online, but not necessarily synced.
- 3rd pass: for each offline node, try refreshing its status and then running `function` on it.
So, it turns out that if the `CanidateBeaconNode::refesh_status` function from the routine update service is hogging the write-lock, the 1st pass gets blocked whilst trying to read the status of the first node. So, nodes that should be left until the 3rd pass are blocking the process of the 1st and 2nd passes, hence the behaviour described in #2926.
## Additional Info
NA
## Issue Addressed
#2953
## Proposed Changes
Adds empty local validator check.
## Additional Info
Two other options:
- add check inside `local_index` collection. Instead of after collection.
- Move `local_index` collection to the beginning of the `poll_sync_committee_duties` function and combine sync committee with altair fork check.
## Issue Addressed
#2883
## Proposed Changes
* Added `suggested-fee-recipient` & `suggested-fee-recipient-file` flags to validator client (similar to graffiti / graffiti-file implementation).
* Added proposer preparation service to VC, which sends the fee-recipient of all known validators to the BN via [/eth/v1/validator/prepare_beacon_proposer](https://github.com/ethereum/beacon-APIs/pull/178) api once per slot
* Added [/eth/v1/validator/prepare_beacon_proposer](https://github.com/ethereum/beacon-APIs/pull/178) api endpoint and preparation data caching
* Added cleanup routine to remove cached proposer preparations when not updated for 2 epochs
## Additional Info
Changed the Implementation following the discussion in #2883.
Co-authored-by: pk910 <philipp@pk910.de>
Co-authored-by: Paul Hauner <paul@paulhauner.com>
Co-authored-by: Philipp K <philipp@pk910.de>
## Issue Addressed
Implements the standard key manager API from https://ethereum.github.io/keymanager-APIs/, formerly https://github.com/ethereum/beacon-APIs/pull/151
Related to https://github.com/sigp/lighthouse/issues/2557
## Proposed Changes
- [x] Add all of the new endpoints from the standard API: GET, POST and DELETE.
- [x] Add a `validators.enabled` column to the slashing protection database to support atomic disable + export.
- [x] Add tests for all the common sequential accesses of the API
- [x] Add tests for interactions with remote signer validators
- [x] Add end-to-end tests for migration of validators from one VC to another
- [x] Implement the authentication scheme from the standard (token bearer auth)
## Additional Info
The `enabled` column in the validators SQL database is necessary to prevent a race condition when exporting slashing protection data. Without the slashing protection database having a way of knowing that a key has been disabled, a concurrent request to sign a message could insert a new record into the database. The `delete_concurrent_with_signing` test exercises this code path, and was indeed failing before the `enabled` column was added.
The validator client authentication has been modified from basic auth to bearer auth, with basic auth preserved for backwards compatibility.
## Proposed Changes
Remove the check for exact equality on the beacon node spec when polling `/config/spec` from the VC. This check was always overzealous, and mostly served to check that the BN was configured for upcoming forks. I've replaced it by explicit checks of the `altair_fork_epoch` and `bellatrix_fork_epoch` instead.
## Additional Info
We should come back to this and clean it up so that we can retain compatibility while removing the field `default`s we installed.
## Issue Addressed
There was an overeager assert in the import of slashing protection data here:
fff01b24dd/validator_client/slashing_protection/src/slashing_database.rs (L939)
We were asserting that if the import contained any blocks for a validator, then the database should contain only a single block for that validator due to pruning/consolidation. However, we would only prune if the import contained _relevant blocks_ (that would actually change the maximum slot):
fff01b24dd/validator_client/slashing_protection/src/slashing_database.rs (L629-L633)
This lead to spurious failures (in the form of `ConsistencyError`s) when importing an interchange containing no new blocks for any of the validators. This wasn't hard to trigger, e.g. export and then immediately re-import the same file.
## Proposed Changes
This PR fixes the issue by simplifying the import so that it's more like the import for attestations. I.e. we make the assert true by always pruning when the imported file contains blocks.
In practice this doesn't have any downsides: if we import a new block then the behaviour is as before, except that we drop the `signing_root`. If we import an existing block or an old block then we prune the database to a single block. The only time this would be relevant is during extreme clock drift locally _plus_ import of a non-drifted interchange, which should occur infrequently.
## Additional Info
I've also added `Arbitrary` implementations to the slashing protection types so that we can fuzz them. I have a fuzzer sitting in a separate directory which I may or may not commit in a subsequent PR.
There's a new test in the standard interchange tests v5.2.1 that checks for this issue: https://github.com/eth-clients/slashing-protection-interchange-tests/pull/12
## Issue Addressed
New rust lints
## Proposed Changes
- Boxing some enum variants
- removing some unused fields (is the validator lockfile unused? seemed so to me)
## Additional Info
- some error fields were marked as dead code but are logged out in areas
- left some dead fields in our ef test code because I assume they are useful for debugging?
Co-authored-by: realbigsean <seananderson33@gmail.com>
## Issue Addressed
Resolves#2612
## Proposed Changes
Implements both the checks mentioned in the original issue.
1. Verifies the `randao_reveal` in the beacon node
2. Cross checks the proposer index after getting back the block from the beacon node.
## Additional info
The block production time increases by ~10x because of the signature verification on the beacon node (based on the `beacon_block_production_process_seconds` metric) when running on a local testnet.
## Issue Addressed
Part of https://github.com/sigp/lighthouse/issues/2557
## Proposed Changes
Refactor the slashing protection export so that it can export data for a subset of validators.
This is the last remaining building block required for supporting the standard validator API (which I'll start to build atop this branch)
## Additional Info
Built on and requires #2598
## Issue Addressed
Resolves#2262
## Proposed Changes
Add a new CLI flag `--beacon-nodes-tls-certs` which allows the user to specify a path to a certificate file (or a list of files, separated by commas). The VC will then use these certificates (in addition to the existing certificates in the OS trust store) when connecting to a beacon node over HTTPS.
## Additional Info
This only supports certificates in PEM format.
## Issue Addressed
Closes#2419
## Proposed Changes
Address a long-standing issue with the import of slashing protection data where the import would fail due to the data appearing slashable w.r.t the existing database. Importing is now idempotent, and will have no issues importing data that has been handed back and forth between different validator clients, or different implementations.
The implementation works by updating the high and low watermarks if they need updating, and not attempting to check if the input is slashable w.r.t itself or the database. This is a strengthening of the minification that we started to do by default since #2380, and what Teku has been doing since the beginning.
## Additional Info
The only feature we lose by doing this is the ability to do non-minified imports of clock drifted messages (cf. Prysm on Medalla). In theory, with the previous implementation we could import all the messages in case of clock drift and be aware of the "gap" between the real present time and the messages signed in the far future. _However_ for attestations this is close to useless, as the source epoch will advance as soon as justification occurs, which will require us to make slashable attestations with respect to our bogus attestation(s). E.g. if I sign an attestation 100=>200 when the current epoch is 101, then I won't be able to vote in any epochs prior to 101 becoming justified because 101=>102, 101=>103, etc are all surrounded by 100=>200. Seeing as signing attestations gets blocked almost immediately in this case regardless of our import behaviour, there's no point trying to handle it. For blocks the situation is more hopeful due to the lack of surrounds, but losing block proposals from validators who by definition can't attest doesn't seem like an issue (the other block proposers can pick up the slack).
