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 15 out of 16 changed files in this pull request and generated 3 comments.

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

crates/p2p/src/lib.rs

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

crates/p2p/src/lib.rs

Copilot

Pull Request Overview

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

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

crates/p2p/src/lib.rs

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

crates/p2p/src/outgoing.rs

Copilot

Pull Request Overview

Copilot reviewed 15 out of 16 changed files in this pull request and generated 5 comments.

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

crates/p2p/src/lib.rs

crates/p2p/src/outgoing.rs

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

avalonche · 2025-10-17T21:10:38Z

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

+            {
+                let private_key_hex = std::fs::read_to_string(private_key_file)
+                    .wrap_err_with(|| {
+                        format!("failed to read p2p private key file: {private_key_file}")


why not include the error here

avalonche · 2025-10-17T21:12:34Z

crates/op-rbuilder/src/builders/flashblocks/p2p.rs

+pub(super) const AGENT_VERSION: &str = "op-rbuilder/1.0.0";
+pub(super) const FLASHBLOCKS_STREAM_PROTOCOL: p2p::StreamProtocol =
+    p2p::StreamProtocol::new("/flashblocks/1.0.0");


are the versions meant to be updated manually

avalonche · 2025-10-17T21:18:58Z

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

+                Some(payload) = built_rx.recv() => {
+                    let _  = payload_events_handle.send(Events::BuiltPayload(payload.clone()));
+                    // TODO: only broadcast if `!no_tx_pool`?
+                    // ignore error here; if p2p was disabled, the channel will be closed.


hmm what is p2p is enabled and an error occurs here?
we'll still want to broadcast on no_tx_pool because it contains state changes around deposit transactions that other builders need

avalonche · 2025-10-17T21:21:47Z

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

+    pub p2p_enabled: bool,
+
+    /// Port for the p2p node
+    pub p2p_port: u16,
+
+    /// Optional hex-encoded private key file path for the p2p node
+    pub p2p_private_key_file: Option<String>,
+
+    /// Comma-separated list of multiaddresses of known peers to connect to
+    pub p2p_known_peers: Option<String>,


can wrap these into P2PArgs like GasLimiterArgs

avalonche · 2025-10-17T21:23:18Z

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

        flashblocks_block_time: 200,
        flashblocks_leeway_time: 100,
        flashblocks_fixed: false,
+        flashblocks_calculate_state_root: true,


think this is redundant if default is specified

avalonche · 2025-10-17T21:25:49Z

crates/p2p/src/behaviour.rs

+};
+use std::{convert::Infallible, time::Duration};
+
+const DEFAULT_MAX_PEER_COUNT: u32 = 200;


maybe this can be an op-rbuilder arg

avalonche · 2025-10-17T21:30:15Z

crates/p2p/src/lib.rs

+            .map(|addr| {
+                addr.clone()
+                    .with_p2p(self.peer_id)
+                    .expect("can add peer ID to multiaddr")


what are the error cases when peer id can't be added?

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

Copilot AI reviewed Oct 14, 2025

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noot added 2 commits October 14, 2025 18:19

cargo update

1b1f345

fix copilot issues

2b0e5cd

Copilot AI review requested due to automatic review settings October 14, 2025 22:24

Copilot AI reviewed Oct 14, 2025

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noot added 2 commits October 14, 2025 18:27

fix copilot issues

696030a

fix derive_more

9fd7548

Copilot AI review requested due to automatic review settings October 14, 2025 22:29

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noot added 2 commits October 14, 2025 18:42

fix copilot issues

3237890

regenerate Cargo.lock

1badb92

Copilot AI review requested due to automatic review settings October 14, 2025 22:48

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merge w main

1a8fd45

noot mentioned this pull request Oct 15, 2025

feat: implement flashblock sync over p2p #288

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avalonche reviewed Oct 17, 2025

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feat: implement p2p layer and broadcast flashblocks #275

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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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