This is an implementation of a slasher that lives inside the BN and can be enabled via `lighthouse bn --slasher`.
Features included in this PR:
- [x] Detection of attester slashing conditions (double votes, surrounds existing, surrounded by existing)
- [x] Integration into Lighthouse's attestation verification flow
- [x] Detection of proposer slashing conditions
- [x] Extraction of attestations from blocks as they are verified
- [x] Compression of chunks
- [x] Configurable history length
- [x] Pruning of old attestations and blocks
- [x] More tests
Future work:
* Focus on a slice of history separate from the most recent N epochs (e.g. epochs `current - K` to `current - M`)
* Run out-of-process
* Ingest attestations from the chain without a resync
Design notes are here https://hackmd.io/@sproul/HJSEklmPL
## Issue Addressed
Closes#1719
## Proposed Changes
Lift the internal `RwLock`s and `Mutex`es from the `Observed*` data structures to resolve the race conditions described in #1719.
Most of this work was done by @paulhauner on his `lift-locks` branch, I merely updated it for the current `master` and checked over it.
## Additional Info
I think it would be prudent to test this on a testnet or two before mainnet launch, just to be sure that the extra lock contention doesn't negatively impact performance.
## Issue Addressed
Closes#800Closes#1713
## Proposed Changes
Implement the temporary state storage algorithm described in #800. Specifically:
* Add `DBColumn::BeaconStateTemporary`, for storing 0-length temporary marker values.
* Store intermediate states immediately as they are created, marked temporary. Delete the temporary flag if the block is processed successfully.
* Add a garbage collection process to delete leftover temporary states on start-up.
* Bump the database schema version to 2 so that a DB with temporary states can't accidentally be used with older versions of the software. The auto-migration is a no-op, but puts in place some infra that we can use for future migrations (e.g. #1784)
## Additional Info
There are two known race conditions, one potentially causing permanent faults (hopefully rare), and the other insignificant.
### Race 1: Permanent state marked temporary
EDIT: this has been fixed by the addition of a lock around the relevant critical section
There are 2 threads that are trying to store 2 different blocks that share some intermediate states (e.g. they both skip some slots from the current head). Consider this sequence of events:
1. Thread 1 checks if state `s` already exists, and seeing that it doesn't, prepares an atomic commit of `(s, s_temporary_flag)`.
2. Thread 2 does the same, but also gets as far as committing the state txn, finishing the processing of its block, and _deleting_ the temporary flag.
3. Thread 1 is (finally) scheduled again, and marks `s` as temporary with its transaction.
4.
a) The process is killed, or thread 1's block fails verification and the temp flag is not deleted. This is a permanent failure! Any attempt to load state `s` will fail... hope it isn't on the main chain! Alternatively (4b) happens...
b) Thread 1 finishes, and re-deletes the temporary flag. In this case the failure is transient, state `s` will disappear temporarily, but will come back once thread 1 finishes running.
I _hope_ that steps 1-3 only happen very rarely, and 4a even more rarely. It's hard to know
This once again begs the question of why we're using LevelDB (#483), when it clearly doesn't care about atomicity! A ham-fisted fix would be to wrap the hot and cold DBs in locks, which would bring us closer to how other DBs handle read-write transactions. E.g. [LMDB only allows one R/W transaction at a time](https://docs.rs/lmdb/0.8.0/lmdb/struct.Environment.html#method.begin_rw_txn).
### Race 2: Temporary state returned from `get_state`
I don't think this race really matters, but in `load_hot_state`, if another thread stores a state between when we call `load_state_temporary_flag` and when we call `load_hot_state_summary`, then we could end up returning that state even though it's only a temporary state. I can't think of any case where this would be relevant, and I suspect if it did come up, it would be safe/recoverable (having data is safer than _not_ having data).
This could be fixed by using a LevelDB read snapshot, but that would require substantial changes to how we read all our values, so I don't think it's worth it right now.
## Issue Addressed
Solution 2 proposed here: https://github.com/sigp/lighthouse/issues/1435#issuecomment-692317639
## Proposed Changes
- Adds an optional `--wss-checkpoint` flag that takes a string `root:epoch`
- Verify that the given checkpoint exists in the chain, or that the the chain syncs through this checkpoint. If not, shutdown and prompt the user to purge state before restarting.
## Additional Info
Co-authored-by: Paul Hauner <paul@paulhauner.com>
## Issue Addressed
- Resolves#1616
## Proposed Changes
Fixes a bug where we are unable to read the finalized block from fork choice.
## Detail
I had made an assumption that the finalized block always has a parent root of `None`:
e5fc6bab48/consensus/fork_choice/src/fork_choice.rs (L749-L752)
This was a faulty assumption, we don't set parent *roots* to `None`. Instead we *sometimes* set parent *indices* to `None`, depending if this pruning condition is satisfied:
e5fc6bab48/consensus/proto_array/src/proto_array.rs (L229-L232)
The bug manifested itself like this:
1. We attempt to get the finalized block from fork choice
1. We try to check that the block is descendant of the finalized block (note: they're the same block).
1. We expect the parent root to be `None`, but it's actually the parent root of the finalized root.
1. We therefore end up checking if the parent of the finalized root is a descendant of itself. (note: it's an *ancestor* not a *descendant*).
1. We therefore declare that the finalized block is not a descendant of (or eq to) the finalized block. Bad.
## Additional Info
In reflection, I made a poor assumption in the quest to obtain a probably negligible performance gain. The performance gain wasn't worth the risk and we got burnt.
## Issue Addressed
NA
## Proposed Changes
- Fixes a mistake I made in #1530 which resulted us in *not* rejecting attestations that we intended to reject.
- Adds skip-slot checks for blocks earlier in import process, so it rejects gossip and RPC blocks.
## Additional Info
NA
## Proposed Changes
To mitigate the impact of minority forks on RAM and disk usage, this change rejects blocks whose parent lies more than 320 slots (10 epochs, ~1 hour) in the past. The behaviour is configurable via `lighthouse bn --max-skip-slots N`, and can be turned off entirely using `--max-skip-slots none`.
Co-authored-by: Paul Hauner <paul@paulhauner.com>
## Issue Addressed
NA
## Proposed Changes
- Adds a new function to allow getting a state with a bad state root history for attestation verification. This reduces unnecessary tree hashing during attestation processing, which accounted for 23% of memory allocations (by bytes) in a recent `heaptrack` observation.
- Don't clone caches on intermediate epoch-boundary states during block processing.
- Reject blocks that are known to fork choice earlier during gossip processing, instead of waiting until after state has been loaded (this only happens in edge-case).
- Avoid multiple re-allocations by creating a "forced" exact size iterator.
## Additional Info
NA
## Issue Addressed
- Resolves#1451
## Proposed Changes
- Restricts the `contains_block` and `contains_block` so they only indicate a block is present if it descends from the finalized root. This helps to ensure that fork choice never points to a block that has been pruned from the database.
- Resolves#1451
- Before importing a block, double-check that its parent is known and a descendant of the finalized root.
- Split a big, monolithic block verification test into smaller tests.
## Additional Notes
I suspect there would be a craftier way to do the `is_descendant_of_finalized` check, but we're a bit tight on time now and we can optimize later if it starts showing in benches.
## TODO
- [x] Tests
## Issue Addressed
#1028
A bit late, but I think if `BlockError` had a kind (the current `BlockError` minus everything on the variants that comes directly from the block) and the original block, more clones could be removed
* Port eth1 lib to use stable futures
* Port eth1_test_rig to stable futures
* Port eth1 tests to stable futures
* Port genesis service to stable futures
* Port genesis tests to stable futures
* Port beacon_chain to stable futures
* Port lcli to stable futures
* Fix eth1_test_rig (#1014)
* Fix lcli
* Port timer to stable futures
* Fix timer
* Port websocket_server to stable futures
* Port notifier to stable futures
* Add TODOS
* Update hashmap hashset to stable futures
* Adds panic test to hashset delay
* Port remote_beacon_node to stable futures
* Fix lcli merge conflicts
* Non rpc stuff compiles
* protocol.rs compiles
* Port websockets, timer and notifier to stable futures (#1035)
* Fix lcli
* Port timer to stable futures
* Fix timer
* Port websocket_server to stable futures
* Port notifier to stable futures
* Add TODOS
* Port remote_beacon_node to stable futures
* Partial eth2-libp2p stable future upgrade
* Finished first round of fighting RPC types
* Further progress towards porting eth2-libp2p adds caching to discovery
* Update behaviour
* RPC handler to stable futures
* Update RPC to master libp2p
* Network service additions
* Fix the fallback transport construction (#1102)
* Correct warning
* Remove hashmap delay
* Compiling version of eth2-libp2p
* Update all crates versions
* Fix conversion function and add tests (#1113)
* Port validator_client to stable futures (#1114)
* 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
* Revert "Update hashmap hashset to stable futures"
This reverts commit d432378a3c.
* Revert "Adds panic test to hashset delay"
This reverts commit 281502396f.
* Ported attestation_service
* Ported duties_service
* Ported fork_service
* More ports
* Port block_service
* Minor fixes
* VC compiles
* Update TODOS
* Borrow self where possible
* 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
* Re-Fix attestation and duties service
* Minor fixes
Co-authored-by: Paul Hauner <paul@paulhauner.com>
* Network crate update to stable futures
* Port account_manager to stable futures (#1121)
* Port account_manager to stable futures
* Run async fns in tokio environment
* Port rest_api crate to stable futures (#1118)
* Port rest_api lib to stable futures
* Reduce tokio features
* Update notifier to stable futures
* Builder update
* Further updates
* Convert self referential async functions
* stable futures fixes (#1124)
* Fix eth1 update functions
* Fix genesis and client
* Fix beacon node lib
* Return appropriate runtimes from environment
* Fix test rig
* Refactor eth1 service update
* Upgrade simulator to stable futures
* Lighthouse compiles on stable futures
* Remove println debugging statement
* Update libp2p service, start rpc test upgrade
* Update network crate for new libp2p
* Update tokio::codec to futures_codec (#1128)
* Further work towards RPC corrections
* Correct http timeout and network service select
* Use tokio runtime for libp2p
* Revert "Update tokio::codec to futures_codec (#1128)"
This reverts commit e57aea924a.
* Upgrade RPC libp2p tests
* Upgrade secio fallback test
* Upgrade gossipsub examples
* Clean up RPC protocol
* Test fixes (#1133)
* Correct websocket timeout and run on os thread
* Fix network test
* Clean up PR
* Correct tokio tcp move attestation service tests
* Upgrade attestation service tests
* Correct network test
* Correct genesis test
* Test corrections
* Log info when block is received
* Modify logs and update attester service events
* Stable futures: fixes to vc, eth1 and account manager (#1142)
* Add local testnet scripts
* Remove whiteblock script
* Rename local testnet script
* Move spawns onto handle
* Fix VC panic
* Initial fix to block production issue
* Tidy block producer fix
* Tidy further
* Add local testnet clean script
* Run cargo fmt
* Tidy duties service
* Tidy fork service
* Tidy ForkService
* Tidy AttestationService
* Tidy notifier
* Ensure await is not suppressed in eth1
* Ensure await is not suppressed in account_manager
* Use .ok() instead of .unwrap_or(())
* RPC decoding test for proto
* Update discv5 and eth2-libp2p deps
* Fix lcli double runtime issue (#1144)
* Handle stream termination and dialing peer errors
* Correct peer_info variant types
* Remove unnecessary warnings
* Handle subnet unsubscription removal and improve logigng
* Add logs around ping
* Upgrade discv5 and improve logging
* Handle peer connection status for multiple connections
* Improve network service logging
* Improve logging around peer manager
* Upgrade swarm poll centralise peer management
* Identify clients on error
* Fix `remove_peer` in sync (#1150)
* remove_peer removes from all chains
* Remove logs
* Fix early return from loop
* Improved logging, fix panic
* Partially correct tests
* Stable futures: Vc sync (#1149)
* Improve syncing heuristic
* Add comments
* Use safer method for tolerance
* Fix tests
* Stable futures: Fix VC bug, update agg pool, add more metrics (#1151)
* Expose epoch processing summary
* Expose participation metrics to prometheus
* Switch to f64
* Reduce precision
* Change precision
* Expose observed attesters metrics
* Add metrics for agg/unagg attn counts
* Add metrics for gossip rx
* Add metrics for gossip tx
* Adds ignored attns to prom
* Add attestation timing
* Add timer for aggregation pool sig agg
* Add write lock timer for agg pool
* Add more metrics to agg pool
* Change map lock code
* Add extra metric to agg pool
* Change lock handling in agg pool
* Change .write() to .read()
* Add another agg pool timer
* Fix for is_aggregator
* Fix pruning bug
Co-authored-by: pawan <pawandhananjay@gmail.com>
Co-authored-by: Paul Hauner <paul@paulhauner.com>
* 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
* Remove ping protocol
* Initial renaming of network services
* Correct rebasing relative to latest master
* Start updating types
* Adds HashMapDelay struct to utils
* Initial network restructure
* Network restructure. Adds new types for v0.2.0
* Removes build artefacts
* Shift validation to beacon chain
* Temporarily remove gossip validation
This is to be updated to match current optimisation efforts.
* Adds AggregateAndProof
* Begin rebuilding pubsub encoding/decoding
* Signature hacking
* Shift gossipsup decoding into eth2_libp2p
* Existing EF tests passing with fake_crypto
* Shifts block encoding/decoding into RPC
* Delete outdated API spec
* All release tests passing bar genesis state parsing
* Update and test YamlConfig
* Update to spec v0.10 compatible BLS
* Updates to BLS EF tests
* Add EF test for AggregateVerify
And delete unused hash2curve tests for uncompressed points
* Update EF tests to v0.10.1
* Use optional block root correctly in block proc
* Use genesis fork in deposit domain. All tests pass
* Fast aggregate verify test
* Update REST API docs
* Fix unused import
* Bump spec tags to v0.10.1
* Add `seconds_per_eth1_block` to chainspec
* Update to timestamp based eth1 voting scheme
* Return None from `get_votes_to_consider` if block cache is empty
* Handle overflows in `is_candidate_block`
* Revert to failing tests
* Fix eth1 data sets test
* Choose default vote according to spec
* Fix collect_valid_votes tests
* Fix `get_votes_to_consider` to choose all eligible blocks
* Uncomment winning_vote tests
* Add comments; remove unused code
* Reduce seconds_per_eth1_block for simulation
* Addressed review comments
* Add test for default vote case
* Fix logs
* Remove unused functions
* Meter default eth1 votes
* Fix comments
* Progress on attestation service
* Address review comments; remove unused dependency
* Initial work on removing libp2p lock
* Add LRU caches to store (rollup)
* Update attestation validation for DB changes (WIP)
* Initial version of should_forward_block
* Scaffold
* Progress on attestation validation
Also, consolidate prod+testing slot clocks so that they share much
of the same implementation and can both handle sub-slot time changes.
* Removes lock from libp2p service
* Completed network lock removal
* Finish(?) attestation processing
* Correct network termination future
* Add slot check to block check
* Correct fmt issues
* Remove Drop implementation for network service
* Add first attempt at attestation proc. re-write
* Add version 2 of attestation processing
* Minor fixes
* Add validator pubkey cache
* Make get_indexed_attestation take a committee
* Link signature processing into new attn verification
* First working version
* Ensure pubkey cache is updated
* Add more metrics, slight optimizations
* Clone committee cache during attestation processing
* Update shuffling cache during block processing
* Remove old commented-out code
* Fix shuffling cache insert bug
* Used indexed attestation in fork choice
* Restructure attn processing, add metrics
* Add more detailed metrics
* Tidy, fix failing tests
* Fix failing tests, tidy
* Address reviewers suggestions
* Disable/delete two outdated tests
* Modification of validator for subscriptions
* Add slot signing to validator client
* Further progress on validation subscription
* Adds necessary validator subscription functionality
* Add new Pubkeys struct to signature_sets
* Refactor with functional approach
* Update beacon chain
* Clean up validator <-> beacon node http types
* Add aggregator status to ValidatorDuty
* Impl Clone for manual slot clock
* Fix minor errors
* Further progress validator client subscription
* Initial subscription and aggregation handling
* Remove decompressed member from pubkey bytes
* Progress to modifying val client for attestation aggregation
* First draft of validator client upgrade for aggregate attestations
* Add hashmap for indices lookup
* Add state cache, remove store cache
* Only build the head committee cache
* Removes lock on a network channel
* Partially implement beacon node subscription http api
* Correct compilation issues
* Change `get_attesting_indices` to use Vec
* Fix failing test
* Partial implementation of timer
* Adds timer, removes exit_future, http api to op pool
* Partial multiple aggregate attestation handling
* Permits bulk messages accross gossipsub network channel
* Correct compile issues
* Improve gosispsub messaging and correct rest api helpers
* Added global gossipsub subscriptions
* Update validator subscriptions data structs
* Tidy
* Re-structure validator subscriptions
* Initial handling of subscriptions
* Re-structure network service
* Add pubkey cache persistence file
* Add more comments
* Integrate persistence file into builder
* Add pubkey cache tests
* Add HashSetDelay and introduce into attestation service
* Handles validator subscriptions
* Add data_dir to beacon chain builder
* Remove Option in pubkey cache persistence file
* Ensure consistency between datadir/data_dir
* Fix failing network test
* Peer subnet discovery gets queued for future subscriptions
* Reorganise attestation service functions
* Initial wiring of attestation service
* First draft of attestation service timing logic
* Correct minor typos
* Tidy
* Fix todos
* Improve tests
* Add PeerInfo to connected peers mapping
* Fix compile error
* Fix compile error from merge
* Split up block processing metrics
* Tidy
* Refactor get_pubkey_from_state
* Remove commented-out code
* Rename state_cache -> checkpoint_cache
* Rename Checkpoint -> Snapshot
* Tidy, add comments
* Tidy up find_head function
* Change some checkpoint -> snapshot
* Add tests
* Expose max_len
* Remove dead code
* Tidy
* Fix bug
* Add sync-speed metric
* Add first attempt at VerifiableBlock
* Start integrating into beacon chain
* Integrate VerifiableBlock
* Rename VerifableBlock -> PartialBlockVerification
* Add start of typed methods
* Add progress
* Add further progress
* Rename structs
* Add full block verification to block_processing.rs
* Further beacon chain integration
* Update checks for gossip
* Add todo
* Start adding segement verification
* Add passing chain segement test
* Initial integration with batch sync
* Minor changes
* Tidy, add more error checking
* Start adding chain_segment tests
* Finish invalid signature tests
* Include single and gossip verified blocks in tests
* Add gossip verification tests
* Start adding docs
* Finish adding comments to block_processing.rs
* Rename block_processing.rs -> block_verification
* Start removing old block processing code
* Fixes beacon_chain compilation
* Fix project-wide compile errors
* Remove old code
* Correct code to pass all tests
* Fix bug with beacon proposer index
* Fix shim for BlockProcessingError
* Only process one epoch at a time
* Fix loop in chain segment processing
* Correct tests from master merge
* Add caching for state.eth1_data_votes
* Add BeaconChain::validator_pubkey
* Revert "Add caching for state.eth1_data_votes"
This reverts commit cd73dcd643.
Co-authored-by: Grant Wuerker <gwuerker@gmail.com>
Co-authored-by: Michael Sproul <michael@sigmaprime.io>
Co-authored-by: Michael Sproul <micsproul@gmail.com>
Co-authored-by: pawan <pawandhananjay@gmail.com>
Co-authored-by: Paul Hauner <paul@paulhauner.com>
