feat: implement p2p layer and broadcast flashblocks #275

noot · 2025-09-24T22:29:39Z

📝 Summary

implement p2p crate which implements a simple libp2p node
p2p node has the ability to support various stream protocols and broadcasting to all peers on a protocol
note: this is not gossip; messages will only be sent to directly-connected peers. we currently assume a very small builder network (<10 nodes) so direct connectivity is okay, but for larger networks, this will need to be extended.
update flashblocks payload builder to broadcast newly built flashblock payloads over p2p
implement payload handler to handle incoming flashblock payloads from peers
NOTE: syncing and execution of flashblocks is not yet implemented; it will be added to the payload handler in a follow up PR.

future extensions:

connection management/max peer count/peer persistence
flashblock sync and execution
test fallback building (if one builder fails in the middle of a block after building some flashblocks, can another builder take over flashblock building?) be out of scope for this PR, as the main goal of this PR is to ensure flashblock sync over p2p.

💡 Motivation and Context

see https://hackmd.io/@nZ-twauPRISEa6G9zg3XRw/H1fekrwolx

✅ I have completed the following steps:

Run make lint
Run make test
Added tests (if applicable)

akundaz

How are you handling the race conditions p2p introduces? Like if two builder build different flashblocks or something like that.

Not really sure what's happening in the p2p crate, please make sure it's documented well so that others can contribute easily

crates/p2p/src/behaviour.rs

crates/p2p/src/lib.rs

akundaz · 2025-09-30T18:41:51Z

crates/p2p/src/lib.rs

+    loop {
+        match reader.next().await {
+            Some(Ok(str)) => {
+                let payload: M = serde_json::from_str(&str)


Shouldn't deserialization happen in op-rbuilder code?

i originally had it there, i was debating if the serialization format should be internal or external to the p2p layer. i'm going to refactor this to not be json anyways. could change the p2p layer back to just handle Bytes instead of Message if you prefer that

sounds good, i'll look again after you refactor

looks better now that it's over Message, just fix the error messages about flashblocks

noot · 2025-09-30T20:21:56Z

How are you handling the race conditions p2p introduces? Like if two builder build different flashblocks or something like that.

out of scope for this PR, i am assuming the high availability setup will be used where op-conductor will manage which party is building at a specific time.

Not really sure what's happening in the p2p crate, please make sure it's documented well so that others can contribute easily

yes will add! PR is still draft, not ready for review yet tbh, will ping you again when it's fully ready.

avalonche · 2025-10-03T17:43:30Z

crates/op-rbuilder/src/builders/flashblocks/ctx.rs

+        &self.evm_config
+    }
+
+    pub(super) fn into_op_payload_builder_ctx(


why not for conversions between the types?

i'm probably going to remove this function after cleanup

Copilot

Pull Request Overview

This PR implements a P2P layer for flashblocks using libp2p to enable broadcasting and receiving flashblock payloads between builder nodes. The implementation adds a new p2p crate with basic networking capabilities and integrates it into the flashblocks payload builder to broadcast newly built payloads.

Implements P2P crate with libp2p node supporting stream protocols and broadcasting
Updates flashblocks payload builder to broadcast payloads over P2P instead of just WebSocket
Adds payload handler to manage incoming P2P flashblock messages and route them to the payload builder service

Reviewed Changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
`crates/p2p/src/lib.rs`	Core P2P node implementation with libp2p networking, message handling, and stream management
`crates/p2p/src/outgoing.rs`	Outgoing stream handler for broadcasting messages to connected peers
`crates/p2p/src/behaviour.rs`	libp2p network behavior configuration with protocols like identify, ping, mDNS
`crates/op-rbuilder/src/builders/flashblocks/service.rs`	Integration of P2P node into flashblocks service with payload handler
`crates/op-rbuilder/src/builders/flashblocks/payload_handler.rs`	Handler for routing built payloads and incoming P2P messages
`crates/op-rbuilder/src/builders/flashblocks/payload.rs`	Updated payload builder to send payloads via channel instead of direct engine calls
`crates/op-rbuilder/src/builders/flashblocks/p2p.rs`	P2P message types and conversions for flashblock payloads
`crates/op-rbuilder/src/args/op.rs`	Added CLI arguments for P2P configuration

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crates/op-rbuilder/src/args/op.rs

crates/p2p/src/lib.rs

Copilot

Pull Request Overview

Copilot reviewed 17 out of 18 changed files in this pull request and generated 1 comment.

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crates/op-rbuilder/src/builders/flashblocks/service.rs

akundaz · 2025-10-20T15:26:50Z

crates/op-rbuilder/src/builders/flashblocks/payload.rs

    pub client: Client,
+    /// Sender for sending built payloads to [`PayloadHandler`],
+    /// which broadcasts outgoing payloads via p2p.
+    pub payload_tx: mpsc::Sender<OpBuiltPayload>,


Can you clean up the naming a bit since there are also "payload_tx" metrics that are unrelated to this?

it's standard for channels to have _tx or _rx at the end, so i renamed the metrics, let me know if that's okay

akundaz · 2025-10-23T14:46:26Z

crates/op-rbuilder/src/flashtestations/builder_tx.rs

 use alloy_evm::Database;
 use alloy_op_evm::OpEvm;
-use alloy_primitives::{Address, B256, Bytes, TxKind, U256, keccak256, map::foldhash::HashMap};
+use alloy_primitives::{Address, B256, Bytes, TxKind, U256, keccak256, map::DefaultHashBuilder};


What is this change for? It looks like we're only using the alloy hashmap in this file

i'm not sure exactly why but the previous version doesn't compile for me, even though i didn't make changes:

error[E0308]: mismatched types --> crates/op-rbuilder/src/builders/builder_tx.rs:373:36 | 373 | state_changes: state, | ^^^^^ expected `HashMap<Address, Account, RandomState>`, found `HashMap<Address, Account, DefaultHashBuilder>` | = note: expected struct `HashMap<_, _, alloy_primitives::map::foldhash::fast::RandomState>` found struct `HashMap<_, _, DefaultHashBuilder>` error[E0308]: mismatched types --> crates/op-rbuilder/src/flashtestations/builder_tx.rs:232:29 | 232 | evm.db_mut().commit(state_changes); | ------ ^^^^^^^^^^^^^ expected `HashMap<Address, Account, DefaultHashBuilder>`, found `HashMap<Address, Account, RandomState>` | | | arguments to this method are incorrect | = note: expected struct `HashMap<_, _, DefaultHashBuilder>` found struct `HashMap<_, _, alloy_primitives::map::foldhash::fast::RandomState>` note: method defined here --> /home/e/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/revm-database-interface-7.0.5/src/lib.rs:72:8 | 72 | fn commit(&mut self, changes: HashMap<Address, Account>); | ^^^^^^ For more information about this error, try `rustc --explain E0308`. error: could not compile `op-rbuilder` (lib) due to 2 previous errors

i'm still trying to debug this but this was a stopgap change just so i can have the PR up still

Copilot

Pull Request Overview

Copilot reviewed 17 out of 18 changed files in this pull request and generated 7 comments.

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crates/p2p/src/lib.rs

crates/op-rbuilder/src/builders/flashblocks/wspub.rs

crates/op-rbuilder/src/tests/flashblocks.rs

crates/op-rbuilder/src/builders/flashblocks/service.rs

crates/op-rbuilder/src/builders/flashblocks/payload.rs

SozinM · 2025-10-27T18:50:45Z

crates/op-rbuilder/src/builders/flashblocks/payload_handler.rs

+        loop {
+            tokio::select! {
+                Some(payload) = built_rx.recv() => {
+                    let _ = payload_events_handle.send(Events::BuiltPayload(payload.clone()));


Add some logging around this errors pls

SozinM · 2025-10-27T18:56:47Z

crates/op-rbuilder/src/tests/flashblocks.rs

        flashblocks_leeway_time: 100,
-        flashblocks_fixed: false,
-        ..Default::default()
+        flashblocks_fixed: false,        ..Default::default()


Let's change it back? Is it rustfmt that formatted it that way?

i think it wasn't formatted by rustfmt since it's in a macro, fixed it

SozinM · 2025-10-27T18:57:09Z

crates/op-rbuilder/src/tests/flashblocks.rs

    flashblocks: FlashblocksArgs {
-        flashblocks_number_contract_address: Some(FLASHBLOCKS_NUMBER_ADDRESS),
-        ..Default::default()
+        flashblocks_number_contract_address: Some(FLASHBLOCKS_NUMBER_ADDRESS),        ..Default::default()


SozinM · 2025-10-27T18:58:34Z

crates/op-rbuilder/src/builders/builder_tx.rs

    pub gas_used: u64,
    pub output: T::Return,
-    pub state_changes: HashMap<Address, Account>,
+    pub state_changes: HashMap<Address, Account, DefaultHashBuilder>,


Wow, this looks strange, what's reason for this?

see https://github.com/flashbots/op-rbuilder/actions/runs/18853582189/job/53795775017?pr=275 and #275 (comment)

i have no idea why this is happening, thought it was maybe a local issue but it's happening on CI also.

SozinM · 2025-10-27T19:09:23Z

General Q:
should we make params like trusted peers to make sure that only out builder would be able to link and send events?

Copilot

Pull Request Overview

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Pull Request Overview

Copilot reviewed 19 out of 20 changed files in this pull request and generated 3 comments.

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crates/op-rbuilder/Cargo.toml

crates/p2p/src/lib.rs

crates/op-rbuilder/src/builders/flashblocks/payload_handler.rs

noot · 2025-10-27T19:47:20Z

should we make params like trusted peers to make sure that only out builder would be able to link and send events?

do you mean so that only trusted peers are able to form connections? that could definitely be added as a flag, i plan to do a follow-up with more connection management features. i would say it's out of scope for this PR as it's already large, and is its own feature

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Copilot reviewed 19 out of 20 changed files in this pull request and generated 2 comments.

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crates/p2p/src/lib.rs

crates/op-rbuilder/src/builders/flashblocks/service.rs

noot added 13 commits September 18, 2025 16:33

initial p2p node impl in p2p crate

7914369

update args and add p2p node to flashblocks service

a082367

send built flashblocks to p2p layer

960ecf7

implement generic message in p2p crate, concrete message in builder

c03416d

implement incoming streams handler

5428121

implement PayloadHandler for handling incoming p2p payloads

847180e

support multiple stream protocols

fa98c77

make agent version configurable

590927c

merge w main

192340d

fmt

7ae5778

clippy

5b77ff1

add known peers flag

3b66510

update error handling for better logging in payload builder

380a5c1

akundaz reviewed Sep 30, 2025

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avalonche reviewed Oct 3, 2025

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noot force-pushed the noot/p2p branch from e98cd34 to 380a5c1 Compare October 5, 2025 23:18

noot added 2 commits October 5, 2025 19:27

merge w main

f522f4f

change p2p hex string to file path; add documentation for p2p crate

2ee1855

noot marked this pull request as ready for review October 6, 2025 00:15

noot requested review from SozinM and karim-agha as code owners October 6, 2025 00:15

noot changed the title ~~feat: implement p2p layer for flashblocks~~ feat: implement p2p layer and broadcast flashblocks Oct 6, 2025

noot requested review from akundaz and avalonche October 6, 2025 00:22

noot added 2 commits October 5, 2025 20:49

fix optional flags

b20f773

update Message trait to have custom to/from string

35715c7

Copilot AI review requested due to automatic review settings October 14, 2025 22:17

noot requested a review from 0x416e746f6e as a code owner October 14, 2025 22:17

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lint

9ebf706

noot requested a review from avalonche October 21, 2025 20:11

akundaz reviewed Oct 23, 2025

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noot added 2 commits October 27, 2025 12:09

merge wip

31c527c

temp fix

7bb5c80

Copilot AI review requested due to automatic review settings October 27, 2025 16:32

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rename metrics with payload_tx_ to payload_transaction_

5313e7d

noot requested a review from akundaz October 27, 2025 16:36

SozinM reviewed Oct 27, 2025

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address comments

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noot added 2 commits October 27, 2025 15:32

revert builder_tx to see if it compiles on ci

669507a

re-add builder_tx changes

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SozinM approved these changes Oct 27, 2025

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noot added 2 commits October 27, 2025 16:20

fix formatting

6c28ec4

use alloy_primitives::map::HashMap

9bbc4a4

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noot merged commit 8f08b2e into main Oct 27, 2025
4 checks passed

noot deleted the noot/p2p branch October 27, 2025 21:04

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feat: implement p2p layer and broadcast flashblocks #275

feat: implement p2p layer and broadcast flashblocks #275

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noot commented Sep 24, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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📝 Summary

💡 Motivation and Context

✅ I have completed the following steps:

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noot commented Sep 30, 2025

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noot commented Sep 24, 2025 •

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