Fix slot check in proposer preferences gossip - #5191
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Oops. The wording here was confusing & it was previously correct.
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**What type of PR is this?**
Bug fix
**What does this PR do? Why is it needed?**
The proposer preference cache was keyed by slot only
(`map[Slot]ProposerPreference`) with first-write-wins semantics. During
a reorg that changes the proposer shuffling (different RANDAO at epoch
boundary), a new proposer's preferences for the same slot would be
rejected because the slot already had an entry. This caused:
- Gossip dedup blocking the new proposer's preferences
- Bid validation using the wrong validator's fee recipient and gas limit
- Payload attributes using the wrong fee recipient
Makes the proposer preferences cache reorg-safe by re-keying from `slot`
to `(slot, validatorIndex)`. After a reorg that changes the proposer
shuffling, the correct proposer's preferences are resolved dynamically
from the head state's proposer lookahead.
## Reproducing reorg testing with Kurtosis
To validate this change under real reorgs, add a temporary broadcast
delay flag that is NOT part of this PR. Apply the following patch
locally, build new images, and run with the kurtosis config below.
### 1. Patch `config/features/flags.go`
Add a flag variable before `DisableDutiesV2`:
```go
reorgTestBroadcastDelay = &cli.DurationFlag{
Name: "reorg-test-broadcast-delay",
Usage: "(Testing): Delays P2P block broadcast by this duration while processing the block locally first.",
}
```
Add `reorgTestBroadcastDelay,` to the `BeaconChainFlags` slice.
### 2. Patch `config/features/config.go`
Add a field to the `Flags` struct:
```go
ReorgTestBroadcastDelay time.Duration
```
Add to `ConfigureBeaconChain()` before `Init(cfg)`:
```go
if ctx.IsSet(reorgTestBroadcastDelay.Name) {
cfg.ReorgTestBroadcastDelay = ctx.Duration(reorgTestBroadcastDelay.Name)
}
```
### 3. Patch `beacon-chain/rpc/prysm/v1alpha1/validator/proposer.go`
Add `"github.com/OffchainLabs/prysm/v7/config/features"` to imports.
Replace `broadcastReceiveBlock` with:
```go
func (vs *Server) broadcastReceiveBlock(ctx context.Context, wg *sync.WaitGroup, block interfaces.SignedBeaconBlock, root [fieldparams.RootLength]byte) error {
delay := features.Get().ReorgTestBroadcastDelay
if delay > 0 {
// Receive locally first, then delay broadcast — creates a divergent fork.
vs.BlockNotifier.BlockFeed().Send(&feed.Event{
Type: blockfeed.ReceivedBlock,
Data: &blockfeed.ReceivedBlockData{SignedBlock: block},
})
if err := vs.BlockReceiver.ReceiveBlock(ctx, block, root, nil); err != nil {
return errors.Wrap(err, "receive block")
}
time.Sleep(delay)
if err := vs.broadcastBlock(ctx, wg, block, root); err != nil {
return errors.Wrap(err, "broadcast block")
}
return nil
}
if err := vs.broadcastBlock(ctx, wg, block, root); err != nil {
return errors.Wrap(err, "broadcast block")
}
vs.BlockNotifier.BlockFeed().Send(&feed.Event{
Type: blockfeed.ReceivedBlock,
Data: &blockfeed.ReceivedBlockData{SignedBlock: block},
})
if err := vs.BlockReceiver.ReceiveBlock(ctx, block, root, nil); err != nil {
return errors.Wrap(err, "receive block")
}
return nil
}
```
### 4. Kurtosis config (`gloas-config-4node-reorg.yml`)
```yaml
participants:
el:
el_type: geth
el_image: ethpandaops/geth:glamsterdam-devnet-0
cl:
cl_type: prysm
cl_image: gcr.io/offchainlabs/prysm/beacon-chain:latest
vc_image: gcr.io/offchainlabs/prysm/validator:latest
supernode: true
count: 2
vc_extra_params:
- "--verbosity=debug"
- el_type: geth
el_image: ethpandaops/geth:epbs-devnet-0
cl_type: prysm
cl_image: gcr.io/offchainlabs/prysm/beacon-chain:latest
vc_image: gcr.io/offchainlabs/prysm/validator:latest
supernode: true
count: 2
cl_extra_params:
- "--reorg-test-broadcast-delay=5s"
vc_extra_params:
- "--verbosity=debug"
network_params:
fulu_fork_epoch: 0
gloas_fork_epoch: 2
seconds_per_slot: 4
genesis_delay: 40
additional_services:
- dora
global_log_level: debug
dora_params:
image: ethpandaops/dora:gloas-support
```
### 5. Run and monitor
```bash
kurtosis run --enclave gloas-reorg github.com/ethpandaops/ethereum-package \
--args-file gloas-config-4node-reorg.yml
# Check for reorgs (delayed nodes experience them)
kurtosis service logs gloas-reorg cl-3-prysm-geth --all 2>&1 | grep "Chain reorg occurred"
# Check proposer preferences are flowing
kurtosis service logs gloas-reorg cl-1-prysm-geth --all 2>&1 | grep "Processed signed proposer"
# Key log: cache accepted a different validator's preference for a slot that already had one.
# This is the reorg-safety signal — proves the (slot, validatorIndex) keying works.
kurtosis service logs gloas-reorg cl-3-prysm-geth --all 2>&1 | grep "possible reorg"
```
With 4-second slots and a 5-second delay, the delayed nodes' blocks
arrive after the next slot begins, reliably triggering reorgs (depth
2-3).
### Logs to look for
| Log message | Source | Meaning |
|---|---|---|
| `Chain reorg occurred` | `blockchain` | A reorg happened on this node
|
| `New proposer preference for slot that already has a different
validator (possible reorg)` | `cache` | The cache accepted a second
validator's preference for the same slot — proves the reorg-safe keying
works |
| `Processed signed proposer preferences` | `rpc/validator` | VC
submitted preferences via RPC (shows broadcast/duplicate/total counts) |
**Which issues(s) does this PR fix?**
Fixes #OffchainLabs#16616
related specs
ethereum/consensus-specs#5196
ethereum/consensus-specs#5190
ethereum/consensus-specs#5191
**Other notes for review**
**Acknowledgements**
- [x] I have read
[CONTRIBUTING.md](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md).
- [x] I have included a uniquely named [changelog fragment
file](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md#maintaining-changelogmd).
- [x] I have added a description with sufficient context for reviewers
to understand this PR.
- [x] I have tested that my changes work as expected and I added a
testing plan to the PR description (if applicable).
---------
Co-authored-by: terence <terence@prysmaticlabs.com>
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We wanna check if
proposal_slotis greater than thecurrent_slot, ie. not in the past, in #5190 this check was mistakenly inverted.