Skip to content

Limit outbound gossip buffer by size, rather than length#4096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
TheBlueMatt merged 1 commit into from
Sep 23, 2025
Merged

Limit outbound gossip buffer by size, rather than length #4096

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions lightning/src/ln/peer_channel_encryptor.rs
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -641,6 +641,11 @@ impl PeerChannelEncryptor {
/// padding to allow for future encryption/MACing.
pub struct MessageBuf(Vec<u8>);
impl MessageBuf {
/// The total allocated space for this message
pub fn capacity(&self) -> usize {
self.0.capacity()
}

/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
/// the message contents).
///
Expand Down
59 changes: 34 additions & 25 deletions lightning/src/ln/peer_handler.rs
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -718,19 +718,11 @@ enum MessageBatchImpl {
CommitmentSigned(Vec<msgs::CommitmentSigned>),
}

/// The ratio between buffer sizes at which we stop sending initial sync messages vs when we stop
/// forwarding gossip messages to peers altogether.
const FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO: usize = 2;

/// When the outbound buffer has this many messages, we'll stop reading bytes from the peer until
/// we have fewer than this many messages in the outbound buffer again.
/// We also use this as the target number of outbound gossip messages to keep in the write buffer,
/// refilled as we send bytes.
const OUTBOUND_BUFFER_LIMIT_READ_PAUSE: usize = 12;
/// When the outbound buffer has this many messages, we'll simply skip relaying gossip messages to
/// the peer.
const OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP: usize =
OUTBOUND_BUFFER_LIMIT_READ_PAUSE * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO;

/// If we've sent a ping, and are still awaiting a response, we may need to churn our way through
/// the socket receive buffer before receiving the ping.
Expand All@@ -754,10 +746,20 @@ const MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER: i8 = 4;
/// process before the next ping.
///
/// Note that we continue responding to other messages even after we've sent this many messages, so
/// it's more of a general guideline used for gossip backfill (and gossip forwarding, times
/// [`FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO`]) than a hard limit.
/// this really limits gossip broadcast, gossip backfill, and onion message relay.
const BUFFER_DRAIN_MSGS_PER_TICK: usize = 32;

/// The maximum number of bytes which we allow in a peer's outbound buffers before we start
/// dropping outbound gossip forwards.
///
/// This is currently 128KiB, or two messages at the maximum message size (though in practice we
/// refuse to forward gossip messages which are substantially larger than we expect, so this is
/// closer to ~85 messages if all queued messages are maximum-sized channel announcements).
///
/// Note that as we always drain the gossip forwarding queue before continuing gossip backfill,
/// the equivalent maximum buffer size for gossip backfill is zero.
const OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP: usize = 64 * 1024 * 2;

struct Peer {
channel_encryptor: PeerChannelEncryptor,
/// We cache a `NodeId` here to avoid serializing peers' keys every time we forward gossip
Expand DownExpand Up@@ -889,12 +891,11 @@ impl Peer {

/// Returns whether this peer's outbound buffers are full and we should drop gossip broadcasts.
fn buffer_full_drop_gossip_broadcast(&self) -> bool {
let total_outbound_buffered =
self.gossip_broadcast_buffer.len() + self.pending_outbound_buffer.len();
let total_outbound_buffered: usize =
self.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>()
+ self.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>();

total_outbound_buffered > OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP
|| self.msgs_sent_since_pong
> BUFFER_DRAIN_MSGS_PER_TICK * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO
total_outbound_buffered > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP
}

fn set_their_node_id(&mut self, node_id: PublicKey) {
Expand DownExpand Up@@ -4693,22 +4694,27 @@ mod tests {
let secp_ctx = Secp256k1::new();
let key = SecretKey::from_slice(&[1; 32]).unwrap();
let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
// The message bufer size is the message length plus two 16-byte MACs plus a 2-byte length
// and 2-byte type.
let encoded_size = msg.serialized_length() + 16 * 2 + 2 + 2;
let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement { msg, update_msg: None };

fd_a.hang_writes.store(true, Ordering::Relaxed);

// Now push an arbitrarily large number of messages and check that only
// `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
// `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP` message bytes end up in the queue.
for _ in 0..OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size {
cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
peers[0].process_events();
}
Comment on lines +4706 to 4709

@tankyleotankyleoSep 23, 2025

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should have raised this earlier sorry, looks like increasing the number of iterations here breaks the test is that expected ?

@TheBlueMattTheBlueMattSep 23, 2025

Copy link
Copy Markdown
CollaboratorAuthor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, absolutely. This loop pushes exactly the new buffer limit worth of messages into the gossip_broadcast_buffer and then we test the correct handling of that later in the test.


{
let peer_a_lock = peers[0].peers.read().unwrap();
let buf_len =
peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
+ peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP - encoded_size);
Comment thread
TheBlueMatt marked this conversation as resolved.
assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
}

// Check that if a broadcast message comes in from the channel handler (i.e. it is an
Expand All@@ -4718,14 +4724,17 @@ mod tests {

{
let peer_a_lock = peers[0].peers.read().unwrap();
let buf_len =
peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
+ peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + encoded_size);
}

// Finally, deliver all the messages and make sure we got the right count. Note that there
// was an extra message that had already moved from the broadcast queue to the encrypted
// message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
// message queue so we actually receive `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + 2`
// message bytes.
fd_a.hang_writes.store(false, Ordering::Relaxed);
cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
Expand All@@ -4740,7 +4749,7 @@ mod tests {

assert_eq!(
cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2
OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size + 1
);
}

Expand Down
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
Limit outbound gossip buffer by size, rather than length by TheBlueMatt · Pull Request #4096 · lightningdevkit/rust-lightning · GitHub
Skip to content
Limit outbound gossip buffer by size, rather than length#4096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

TheBlueMatt
merged 1 commit into

from

Sep 23, 2025
 Merged


Limit outbound gossip buffer by size, rather than length
#4096
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


1 commit


Select commit


File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


5 changes: 5 additions & 0 deletions
lightning/src/ln/peer_channel_encryptor.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -641,6 +641,11 @@ impl PeerChannelEncryptor {
/// padding to allow for future encryption/MACing.
pub struct MessageBuf(Vec<u8>);
impl MessageBuf {
	/// The total allocated space for this message
	pub fn capacity(&self) -> usize {
 self.0.capacity()
	}

	/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
	/// the message contents).
	///
Expand Down

59 changes: 34 additions & 25 deletions
lightning/src/ln/peer_handler.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -718,19 +718,11 @@ enum MessageBatchImpl {
	CommitmentSigned(Vec<msgs::CommitmentSigned>),
}

/// The ratio between buffer sizes at which we stop sending initial sync messages vs when we stop
/// forwarding gossip messages to peers altogether.
const FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO: usize = 2;

/// When the outbound buffer has this many messages, we'll stop reading bytes from the peer until
/// we have fewer than this many messages in the outbound buffer again.
/// We also use this as the target number of outbound gossip messages to keep in the write buffer,
/// refilled as we send bytes.
const OUTBOUND_BUFFER_LIMIT_READ_PAUSE: usize = 12;
/// When the outbound buffer has this many messages, we'll simply skip relaying gossip messages to
/// the peer.
const OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP: usize =
	OUTBOUND_BUFFER_LIMIT_READ_PAUSE * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO;

/// If we've sent a ping, and are still awaiting a response, we may need to churn our way through
/// the socket receive buffer before receiving the ping.
Expand All@@ -754,10 +746,20 @@ const MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER: i8 = 4;
/// process before the next ping.
///
/// Note that we continue responding to other messages even after we've sent this many messages, so
/// it's more of a general guideline used for gossip backfill (and gossip forwarding, times
/// [`FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO`]) than a hard limit.
/// this really limits gossip broadcast, gossip backfill, and onion message relay.
const BUFFER_DRAIN_MSGS_PER_TICK: usize = 32;

/// The maximum number of bytes which we allow in a peer's outbound buffers before we start
/// dropping outbound gossip forwards.
///
/// This is currently 128KiB, or two messages at the maximum message size (though in practice we
/// refuse to forward gossip messages which are substantially larger than we expect, so this is
/// closer to ~85 messages if all queued messages are maximum-sized channel announcements).
///
/// Note that as we always drain the gossip forwarding queue before continuing gossip backfill,
/// the equivalent maximum buffer size for gossip backfill is zero.
const OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP: usize = 64 * 1024 * 2;

struct Peer {
	channel_encryptor: PeerChannelEncryptor,
	/// We cache a `NodeId` here to avoid serializing peers' keys every time we forward gossip
Expand DownExpand Up@@ -889,12 +891,11 @@ impl Peer {

	/// Returns whether this peer's outbound buffers are full and we should drop gossip broadcasts.
	fn buffer_full_drop_gossip_broadcast(&self) -> bool {
 let total_outbound_buffered =
 self.gossip_broadcast_buffer.len() + self.pending_outbound_buffer.len();
 let total_outbound_buffered: usize =
 self.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + self.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>();

 total_outbound_buffered > OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP
 || self.msgs_sent_since_pong
 > BUFFER_DRAIN_MSGS_PER_TICK * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO
 total_outbound_buffered > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP
	}

	fn set_their_node_id(&mut self, node_id: PublicKey) {
Expand DownExpand Up@@ -4693,22 +4694,27 @@ mod tests {
 let secp_ctx = Secp256k1::new();
 let key = SecretKey::from_slice(&[1; 32]).unwrap();
 let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
 // The message bufer size is the message length plus two 16-byte MACs plus a 2-byte length
 // and 2-byte type.
 let encoded_size = msg.serialized_length() + 16 * 2 + 2 + 2;
 let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement { msg, update_msg: None };

 fd_a.hang_writes.store(true, Ordering::Relaxed);

 // Now push an arbitrarily large number of messages and check that only
 // `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
 // `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP` message bytes end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size {
 cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
 peers[0].process_events();
 }

Comment on lines

+4706
 to 
4709

@tankyleotankyleoSep 23, 2025

Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should have raised this earlier sorry, looks like increasing the number of iterations here breaks the test is that expected ?
@TheBlueMattTheBlueMattSep 23, 2025

Copy link


Copy Markdown

CollaboratorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, absolutely. This loop pushes exactly the new buffer limit worth of messages into the gossip_broadcast_buffer and then we test the correct handling of that later in the test.

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP - encoded_size);
Comment thread
TheBlueMatt marked this conversation as resolved.

 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 }

 // Check that if a broadcast message comes in from the channel handler (i.e. it is an
Expand All@@ -4718,14 +4724,17 @@ mod tests {

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + encoded_size);
 }

 // Finally, deliver all the messages and make sure we got the right count. Note that there
 // was an extra message that had already moved from the broadcast queue to the encrypted
 // message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
 // message queue so we actually receive `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + 2`
 // message bytes.
 fd_a.hang_writes.store(false, Ordering::Relaxed);
 cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
 peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
Expand All@@ -4740,7 +4749,7 @@ mod tests {

 assert_eq!(
 cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2
OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size + 1
 );
	}

Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Limit outbound gossip buffer by size, rather than length by TheBlueMatt · Pull Request #4096 · lightningdevkit/rust-lightning · GitHub
Skip to content
Limit outbound gossip buffer by size, rather than length#4096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

TheBlueMatt
merged 1 commit into

from

Sep 23, 2025
 Merged


Limit outbound gossip buffer by size, rather than length
#4096
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


1 commit


Select commit


File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


5 changes: 5 additions & 0 deletions
lightning/src/ln/peer_channel_encryptor.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -641,6 +641,11 @@ impl PeerChannelEncryptor {
/// padding to allow for future encryption/MACing.
pub struct MessageBuf(Vec<u8>);
impl MessageBuf {
	/// The total allocated space for this message
	pub fn capacity(&self) -> usize {
 self.0.capacity()
	}

	/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
	/// the message contents).
	///
Expand Down

59 changes: 34 additions & 25 deletions
lightning/src/ln/peer_handler.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -718,19 +718,11 @@ enum MessageBatchImpl {
	CommitmentSigned(Vec<msgs::CommitmentSigned>),
}

/// The ratio between buffer sizes at which we stop sending initial sync messages vs when we stop
/// forwarding gossip messages to peers altogether.
const FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO: usize = 2;

/// When the outbound buffer has this many messages, we'll stop reading bytes from the peer until
/// we have fewer than this many messages in the outbound buffer again.
/// We also use this as the target number of outbound gossip messages to keep in the write buffer,
/// refilled as we send bytes.
const OUTBOUND_BUFFER_LIMIT_READ_PAUSE: usize = 12;
/// When the outbound buffer has this many messages, we'll simply skip relaying gossip messages to
/// the peer.
const OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP: usize =
	OUTBOUND_BUFFER_LIMIT_READ_PAUSE * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO;

/// If we've sent a ping, and are still awaiting a response, we may need to churn our way through
/// the socket receive buffer before receiving the ping.
Expand All@@ -754,10 +746,20 @@ const MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER: i8 = 4;
/// process before the next ping.
///
/// Note that we continue responding to other messages even after we've sent this many messages, so
/// it's more of a general guideline used for gossip backfill (and gossip forwarding, times
/// [`FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO`]) than a hard limit.
/// this really limits gossip broadcast, gossip backfill, and onion message relay.
const BUFFER_DRAIN_MSGS_PER_TICK: usize = 32;

/// The maximum number of bytes which we allow in a peer's outbound buffers before we start
/// dropping outbound gossip forwards.
///
/// This is currently 128KiB, or two messages at the maximum message size (though in practice we
/// refuse to forward gossip messages which are substantially larger than we expect, so this is
/// closer to ~85 messages if all queued messages are maximum-sized channel announcements).
///
/// Note that as we always drain the gossip forwarding queue before continuing gossip backfill,
/// the equivalent maximum buffer size for gossip backfill is zero.
const OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP: usize = 64 * 1024 * 2;

struct Peer {
	channel_encryptor: PeerChannelEncryptor,
	/// We cache a `NodeId` here to avoid serializing peers' keys every time we forward gossip
Expand DownExpand Up@@ -889,12 +891,11 @@ impl Peer {

	/// Returns whether this peer's outbound buffers are full and we should drop gossip broadcasts.
	fn buffer_full_drop_gossip_broadcast(&self) -> bool {
 let total_outbound_buffered =
 self.gossip_broadcast_buffer.len() + self.pending_outbound_buffer.len();
 let total_outbound_buffered: usize =
 self.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + self.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>();

 total_outbound_buffered > OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP
 || self.msgs_sent_since_pong
 > BUFFER_DRAIN_MSGS_PER_TICK * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO
 total_outbound_buffered > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP
	}

	fn set_their_node_id(&mut self, node_id: PublicKey) {
Expand DownExpand Up@@ -4693,22 +4694,27 @@ mod tests {
 let secp_ctx = Secp256k1::new();
 let key = SecretKey::from_slice(&[1; 32]).unwrap();
 let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
 // The message bufer size is the message length plus two 16-byte MACs plus a 2-byte length
 // and 2-byte type.
 let encoded_size = msg.serialized_length() + 16 * 2 + 2 + 2;
 let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement { msg, update_msg: None };

 fd_a.hang_writes.store(true, Ordering::Relaxed);

 // Now push an arbitrarily large number of messages and check that only
 // `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
 // `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP` message bytes end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size {
 cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
 peers[0].process_events();
 }

Comment on lines

+4706
 to 
4709

@tankyleotankyleoSep 23, 2025

Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should have raised this earlier sorry, looks like increasing the number of iterations here breaks the test is that expected ?
@TheBlueMattTheBlueMattSep 23, 2025

Copy link


Copy Markdown

CollaboratorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, absolutely. This loop pushes exactly the new buffer limit worth of messages into the gossip_broadcast_buffer and then we test the correct handling of that later in the test.

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP - encoded_size);
Comment thread
TheBlueMatt marked this conversation as resolved.

 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 }

 // Check that if a broadcast message comes in from the channel handler (i.e. it is an
Expand All@@ -4718,14 +4724,17 @@ mod tests {

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + encoded_size);
 }

 // Finally, deliver all the messages and make sure we got the right count. Note that there
 // was an extra message that had already moved from the broadcast queue to the encrypted
 // message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
 // message queue so we actually receive `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + 2`
 // message bytes.
 fd_a.hang_writes.store(false, Ordering::Relaxed);
 cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
 peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
Expand All@@ -4740,7 +4749,7 @@ mod tests {

 assert_eq!(
 cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2
OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size + 1
 );
	}

Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Limit outbound gossip buffer by size, rather than length by TheBlueMatt · Pull Request #4096 · lightningdevkit/rust-lightning · GitHub
Skip to content
Limit outbound gossip buffer by size, rather than length#4096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

TheBlueMatt
merged 1 commit into

from

Sep 23, 2025
 Merged


Limit outbound gossip buffer by size, rather than length
#4096
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


1 commit


Select commit


File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


5 changes: 5 additions & 0 deletions
lightning/src/ln/peer_channel_encryptor.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -641,6 +641,11 @@ impl PeerChannelEncryptor {
/// padding to allow for future encryption/MACing.
pub struct MessageBuf(Vec<u8>);
impl MessageBuf {
	/// The total allocated space for this message
	pub fn capacity(&self) -> usize {
 self.0.capacity()
	}

	/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
	/// the message contents).
	///
Expand Down

59 changes: 34 additions & 25 deletions
lightning/src/ln/peer_handler.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -718,19 +718,11 @@ enum MessageBatchImpl {
	CommitmentSigned(Vec<msgs::CommitmentSigned>),
}

/// The ratio between buffer sizes at which we stop sending initial sync messages vs when we stop
/// forwarding gossip messages to peers altogether.
const FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO: usize = 2;

/// When the outbound buffer has this many messages, we'll stop reading bytes from the peer until
/// we have fewer than this many messages in the outbound buffer again.
/// We also use this as the target number of outbound gossip messages to keep in the write buffer,
/// refilled as we send bytes.
const OUTBOUND_BUFFER_LIMIT_READ_PAUSE: usize = 12;
/// When the outbound buffer has this many messages, we'll simply skip relaying gossip messages to
/// the peer.
const OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP: usize =
	OUTBOUND_BUFFER_LIMIT_READ_PAUSE * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO;

/// If we've sent a ping, and are still awaiting a response, we may need to churn our way through
/// the socket receive buffer before receiving the ping.
Expand All@@ -754,10 +746,20 @@ const MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER: i8 = 4;
/// process before the next ping.
///
/// Note that we continue responding to other messages even after we've sent this many messages, so
/// it's more of a general guideline used for gossip backfill (and gossip forwarding, times
/// [`FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO`]) than a hard limit.
/// this really limits gossip broadcast, gossip backfill, and onion message relay.
const BUFFER_DRAIN_MSGS_PER_TICK: usize = 32;

/// The maximum number of bytes which we allow in a peer's outbound buffers before we start
/// dropping outbound gossip forwards.
///
/// This is currently 128KiB, or two messages at the maximum message size (though in practice we
/// refuse to forward gossip messages which are substantially larger than we expect, so this is
/// closer to ~85 messages if all queued messages are maximum-sized channel announcements).
///
/// Note that as we always drain the gossip forwarding queue before continuing gossip backfill,
/// the equivalent maximum buffer size for gossip backfill is zero.
const OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP: usize = 64 * 1024 * 2;

struct Peer {
	channel_encryptor: PeerChannelEncryptor,
	/// We cache a `NodeId` here to avoid serializing peers' keys every time we forward gossip
Expand DownExpand Up@@ -889,12 +891,11 @@ impl Peer {

	/// Returns whether this peer's outbound buffers are full and we should drop gossip broadcasts.
	fn buffer_full_drop_gossip_broadcast(&self) -> bool {
 let total_outbound_buffered =
 self.gossip_broadcast_buffer.len() + self.pending_outbound_buffer.len();
 let total_outbound_buffered: usize =
 self.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + self.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>();

 total_outbound_buffered > OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP
 || self.msgs_sent_since_pong
 > BUFFER_DRAIN_MSGS_PER_TICK * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO
 total_outbound_buffered > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP
	}

	fn set_their_node_id(&mut self, node_id: PublicKey) {
Expand DownExpand Up@@ -4693,22 +4694,27 @@ mod tests {
 let secp_ctx = Secp256k1::new();
 let key = SecretKey::from_slice(&[1; 32]).unwrap();
 let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
 // The message bufer size is the message length plus two 16-byte MACs plus a 2-byte length
 // and 2-byte type.
 let encoded_size = msg.serialized_length() + 16 * 2 + 2 + 2;
 let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement { msg, update_msg: None };

 fd_a.hang_writes.store(true, Ordering::Relaxed);

 // Now push an arbitrarily large number of messages and check that only
 // `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
 // `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP` message bytes end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size {
 cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
 peers[0].process_events();
 }

Comment on lines

+4706
 to 
4709

@tankyleotankyleoSep 23, 2025

Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should have raised this earlier sorry, looks like increasing the number of iterations here breaks the test is that expected ?
@TheBlueMattTheBlueMattSep 23, 2025

Copy link


Copy Markdown

CollaboratorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, absolutely. This loop pushes exactly the new buffer limit worth of messages into the gossip_broadcast_buffer and then we test the correct handling of that later in the test.

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP - encoded_size);
Comment thread
TheBlueMatt marked this conversation as resolved.

 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 }

 // Check that if a broadcast message comes in from the channel handler (i.e. it is an
Expand All@@ -4718,14 +4724,17 @@ mod tests {

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + encoded_size);
 }

 // Finally, deliver all the messages and make sure we got the right count. Note that there
 // was an extra message that had already moved from the broadcast queue to the encrypted
 // message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
 // message queue so we actually receive `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + 2`
 // message bytes.
 fd_a.hang_writes.store(false, Ordering::Relaxed);
 cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
 peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
Expand All@@ -4740,7 +4749,7 @@ mod tests {

 assert_eq!(
 cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2
OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size + 1
 );
	}

Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
Limit outbound gossip buffer by size, rather than length by TheBlueMatt · Pull Request #4096 · lightningdevkit/rust-lightning · GitHub
Skip to content
Limit outbound gossip buffer by size, rather than length#4096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

TheBlueMatt
merged 1 commit into

from

Sep 23, 2025
 Merged


Limit outbound gossip buffer by size, rather than length
#4096
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


1 commit


Select commit


File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


5 changes: 5 additions & 0 deletions
lightning/src/ln/peer_channel_encryptor.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -641,6 +641,11 @@ impl PeerChannelEncryptor {
/// padding to allow for future encryption/MACing.
pub struct MessageBuf(Vec<u8>);
impl MessageBuf {
	/// The total allocated space for this message
	pub fn capacity(&self) -> usize {
 self.0.capacity()
	}

	/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
	/// the message contents).
	///
Expand Down

59 changes: 34 additions & 25 deletions
lightning/src/ln/peer_handler.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -718,19 +718,11 @@ enum MessageBatchImpl {
	CommitmentSigned(Vec<msgs::CommitmentSigned>),
}

/// The ratio between buffer sizes at which we stop sending initial sync messages vs when we stop
/// forwarding gossip messages to peers altogether.
const FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO: usize = 2;

/// When the outbound buffer has this many messages, we'll stop reading bytes from the peer until
/// we have fewer than this many messages in the outbound buffer again.
/// We also use this as the target number of outbound gossip messages to keep in the write buffer,
/// refilled as we send bytes.
const OUTBOUND_BUFFER_LIMIT_READ_PAUSE: usize = 12;
/// When the outbound buffer has this many messages, we'll simply skip relaying gossip messages to
/// the peer.
const OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP: usize =
	OUTBOUND_BUFFER_LIMIT_READ_PAUSE * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO;

/// If we've sent a ping, and are still awaiting a response, we may need to churn our way through
/// the socket receive buffer before receiving the ping.
Expand All@@ -754,10 +746,20 @@ const MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER: i8 = 4;
/// process before the next ping.
///
/// Note that we continue responding to other messages even after we've sent this many messages, so
/// it's more of a general guideline used for gossip backfill (and gossip forwarding, times
/// [`FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO`]) than a hard limit.
/// this really limits gossip broadcast, gossip backfill, and onion message relay.
const BUFFER_DRAIN_MSGS_PER_TICK: usize = 32;

/// The maximum number of bytes which we allow in a peer's outbound buffers before we start
/// dropping outbound gossip forwards.
///
/// This is currently 128KiB, or two messages at the maximum message size (though in practice we
/// refuse to forward gossip messages which are substantially larger than we expect, so this is
/// closer to ~85 messages if all queued messages are maximum-sized channel announcements).
///
/// Note that as we always drain the gossip forwarding queue before continuing gossip backfill,
/// the equivalent maximum buffer size for gossip backfill is zero.
const OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP: usize = 64 * 1024 * 2;

struct Peer {
	channel_encryptor: PeerChannelEncryptor,
	/// We cache a `NodeId` here to avoid serializing peers' keys every time we forward gossip
Expand DownExpand Up@@ -889,12 +891,11 @@ impl Peer {

	/// Returns whether this peer's outbound buffers are full and we should drop gossip broadcasts.
	fn buffer_full_drop_gossip_broadcast(&self) -> bool {
 let total_outbound_buffered =
 self.gossip_broadcast_buffer.len() + self.pending_outbound_buffer.len();
 let total_outbound_buffered: usize =
 self.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + self.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>();

 total_outbound_buffered > OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP
 || self.msgs_sent_since_pong
 > BUFFER_DRAIN_MSGS_PER_TICK * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO
 total_outbound_buffered > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP
	}

	fn set_their_node_id(&mut self, node_id: PublicKey) {
Expand DownExpand Up@@ -4693,22 +4694,27 @@ mod tests {
 let secp_ctx = Secp256k1::new();
 let key = SecretKey::from_slice(&[1; 32]).unwrap();
 let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
 // The message bufer size is the message length plus two 16-byte MACs plus a 2-byte length
 // and 2-byte type.
 let encoded_size = msg.serialized_length() + 16 * 2 + 2 + 2;
 let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement { msg, update_msg: None };

 fd_a.hang_writes.store(true, Ordering::Relaxed);

 // Now push an arbitrarily large number of messages and check that only
 // `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
 // `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP` message bytes end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size {
 cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
 peers[0].process_events();
 }

Comment on lines

+4706
 to 
4709

@tankyleotankyleoSep 23, 2025

Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should have raised this earlier sorry, looks like increasing the number of iterations here breaks the test is that expected ?
@TheBlueMattTheBlueMattSep 23, 2025

Copy link


Copy Markdown

CollaboratorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, absolutely. This loop pushes exactly the new buffer limit worth of messages into the gossip_broadcast_buffer and then we test the correct handling of that later in the test.

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP - encoded_size);
Comment thread
TheBlueMatt marked this conversation as resolved.

 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 }

 // Check that if a broadcast message comes in from the channel handler (i.e. it is an
Expand All@@ -4718,14 +4724,17 @@ mod tests {

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + encoded_size);
 }

 // Finally, deliver all the messages and make sure we got the right count. Note that there
 // was an extra message that had already moved from the broadcast queue to the encrypted
 // message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
 // message queue so we actually receive `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + 2`
 // message bytes.
 fd_a.hang_writes.store(false, Ordering::Relaxed);
 cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
 peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
Expand All@@ -4740,7 +4749,7 @@ mod tests {

 assert_eq!(
 cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2
OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size + 1
 );
	}

Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Limit outbound gossip buffer by size, rather than length by TheBlueMatt · Pull Request #4096 · lightningdevkit/rust-lightning · GitHub
Skip to content
Limit outbound gossip buffer by size, rather than length#4096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

TheBlueMatt
merged 1 commit into

from

Sep 23, 2025
 Merged


Limit outbound gossip buffer by size, rather than length
#4096
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


1 commit


Select commit


File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


5 changes: 5 additions & 0 deletions
lightning/src/ln/peer_channel_encryptor.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -641,6 +641,11 @@ impl PeerChannelEncryptor {
/// padding to allow for future encryption/MACing.
pub struct MessageBuf(Vec<u8>);
impl MessageBuf {
	/// The total allocated space for this message
	pub fn capacity(&self) -> usize {
 self.0.capacity()
	}

	/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
	/// the message contents).
	///
Expand Down

59 changes: 34 additions & 25 deletions
lightning/src/ln/peer_handler.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -718,19 +718,11 @@ enum MessageBatchImpl {
	CommitmentSigned(Vec<msgs::CommitmentSigned>),
}

/// The ratio between buffer sizes at which we stop sending initial sync messages vs when we stop
/// forwarding gossip messages to peers altogether.
const FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO: usize = 2;

/// When the outbound buffer has this many messages, we'll stop reading bytes from the peer until
/// we have fewer than this many messages in the outbound buffer again.
/// We also use this as the target number of outbound gossip messages to keep in the write buffer,
/// refilled as we send bytes.
const OUTBOUND_BUFFER_LIMIT_READ_PAUSE: usize = 12;
/// When the outbound buffer has this many messages, we'll simply skip relaying gossip messages to
/// the peer.
const OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP: usize =
	OUTBOUND_BUFFER_LIMIT_READ_PAUSE * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO;

/// If we've sent a ping, and are still awaiting a response, we may need to churn our way through
/// the socket receive buffer before receiving the ping.
Expand All@@ -754,10 +746,20 @@ const MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER: i8 = 4;
/// process before the next ping.
///
/// Note that we continue responding to other messages even after we've sent this many messages, so
/// it's more of a general guideline used for gossip backfill (and gossip forwarding, times
/// [`FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO`]) than a hard limit.
/// this really limits gossip broadcast, gossip backfill, and onion message relay.
const BUFFER_DRAIN_MSGS_PER_TICK: usize = 32;

/// The maximum number of bytes which we allow in a peer's outbound buffers before we start
/// dropping outbound gossip forwards.
///
/// This is currently 128KiB, or two messages at the maximum message size (though in practice we
/// refuse to forward gossip messages which are substantially larger than we expect, so this is
/// closer to ~85 messages if all queued messages are maximum-sized channel announcements).
///
/// Note that as we always drain the gossip forwarding queue before continuing gossip backfill,
/// the equivalent maximum buffer size for gossip backfill is zero.
const OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP: usize = 64 * 1024 * 2;

struct Peer {
	channel_encryptor: PeerChannelEncryptor,
	/// We cache a `NodeId` here to avoid serializing peers' keys every time we forward gossip
Expand DownExpand Up@@ -889,12 +891,11 @@ impl Peer {

	/// Returns whether this peer's outbound buffers are full and we should drop gossip broadcasts.
	fn buffer_full_drop_gossip_broadcast(&self) -> bool {
 let total_outbound_buffered =
 self.gossip_broadcast_buffer.len() + self.pending_outbound_buffer.len();
 let total_outbound_buffered: usize =
 self.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + self.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>();

 total_outbound_buffered > OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP
 || self.msgs_sent_since_pong
 > BUFFER_DRAIN_MSGS_PER_TICK * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO
 total_outbound_buffered > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP
	}

	fn set_their_node_id(&mut self, node_id: PublicKey) {
Expand DownExpand Up@@ -4693,22 +4694,27 @@ mod tests {
 let secp_ctx = Secp256k1::new();
 let key = SecretKey::from_slice(&[1; 32]).unwrap();
 let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
 // The message bufer size is the message length plus two 16-byte MACs plus a 2-byte length
 // and 2-byte type.
 let encoded_size = msg.serialized_length() + 16 * 2 + 2 + 2;
 let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement { msg, update_msg: None };

 fd_a.hang_writes.store(true, Ordering::Relaxed);

 // Now push an arbitrarily large number of messages and check that only
 // `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
 // `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP` message bytes end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size {
 cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
 peers[0].process_events();
 }

Comment on lines

+4706
 to 
4709

@tankyleotankyleoSep 23, 2025

Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should have raised this earlier sorry, looks like increasing the number of iterations here breaks the test is that expected ?
@TheBlueMattTheBlueMattSep 23, 2025

Copy link


Copy Markdown

CollaboratorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, absolutely. This loop pushes exactly the new buffer limit worth of messages into the gossip_broadcast_buffer and then we test the correct handling of that later in the test.

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP - encoded_size);
Comment thread
TheBlueMatt marked this conversation as resolved.

 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 }

 // Check that if a broadcast message comes in from the channel handler (i.e. it is an
Expand All@@ -4718,14 +4724,17 @@ mod tests {

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + encoded_size);
 }

 // Finally, deliver all the messages and make sure we got the right count. Note that there
 // was an extra message that had already moved from the broadcast queue to the encrypted
 // message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
 // message queue so we actually receive `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + 2`
 // message bytes.
 fd_a.hang_writes.store(false, Ordering::Relaxed);
 cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
 peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
Expand All@@ -4740,7 +4749,7 @@ mod tests {

 assert_eq!(
 cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2
OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size + 1
 );
	}

Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Limit outbound gossip buffer by size, rather than length by TheBlueMatt · Pull Request #4096 · lightningdevkit/rust-lightning · GitHub
Skip to content
Limit outbound gossip buffer by size, rather than length#4096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

TheBlueMatt
merged 1 commit into

from

Sep 23, 2025
 Merged


Limit outbound gossip buffer by size, rather than length
#4096
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


1 commit


Select commit


File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


5 changes: 5 additions & 0 deletions
lightning/src/ln/peer_channel_encryptor.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -641,6 +641,11 @@ impl PeerChannelEncryptor {
/// padding to allow for future encryption/MACing.
pub struct MessageBuf(Vec<u8>);
impl MessageBuf {
	/// The total allocated space for this message
	pub fn capacity(&self) -> usize {
 self.0.capacity()
	}

	/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
	/// the message contents).
	///
Expand Down

59 changes: 34 additions & 25 deletions
lightning/src/ln/peer_handler.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -718,19 +718,11 @@ enum MessageBatchImpl {
	CommitmentSigned(Vec<msgs::CommitmentSigned>),
}

/// The ratio between buffer sizes at which we stop sending initial sync messages vs when we stop
/// forwarding gossip messages to peers altogether.
const FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO: usize = 2;

/// When the outbound buffer has this many messages, we'll stop reading bytes from the peer until
/// we have fewer than this many messages in the outbound buffer again.
/// We also use this as the target number of outbound gossip messages to keep in the write buffer,
/// refilled as we send bytes.
const OUTBOUND_BUFFER_LIMIT_READ_PAUSE: usize = 12;
/// When the outbound buffer has this many messages, we'll simply skip relaying gossip messages to
/// the peer.
const OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP: usize =
	OUTBOUND_BUFFER_LIMIT_READ_PAUSE * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO;

/// If we've sent a ping, and are still awaiting a response, we may need to churn our way through
/// the socket receive buffer before receiving the ping.
Expand All@@ -754,10 +746,20 @@ const MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER: i8 = 4;
/// process before the next ping.
///
/// Note that we continue responding to other messages even after we've sent this many messages, so
/// it's more of a general guideline used for gossip backfill (and gossip forwarding, times
/// [`FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO`]) than a hard limit.
/// this really limits gossip broadcast, gossip backfill, and onion message relay.
const BUFFER_DRAIN_MSGS_PER_TICK: usize = 32;

/// The maximum number of bytes which we allow in a peer's outbound buffers before we start
/// dropping outbound gossip forwards.
///
/// This is currently 128KiB, or two messages at the maximum message size (though in practice we
/// refuse to forward gossip messages which are substantially larger than we expect, so this is
/// closer to ~85 messages if all queued messages are maximum-sized channel announcements).
///
/// Note that as we always drain the gossip forwarding queue before continuing gossip backfill,
/// the equivalent maximum buffer size for gossip backfill is zero.
const OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP: usize = 64 * 1024 * 2;

struct Peer {
	channel_encryptor: PeerChannelEncryptor,
	/// We cache a `NodeId` here to avoid serializing peers' keys every time we forward gossip
Expand DownExpand Up@@ -889,12 +891,11 @@ impl Peer {

	/// Returns whether this peer's outbound buffers are full and we should drop gossip broadcasts.
	fn buffer_full_drop_gossip_broadcast(&self) -> bool {
 let total_outbound_buffered =
 self.gossip_broadcast_buffer.len() + self.pending_outbound_buffer.len();
 let total_outbound_buffered: usize =
 self.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + self.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>();

 total_outbound_buffered > OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP
 || self.msgs_sent_since_pong
 > BUFFER_DRAIN_MSGS_PER_TICK * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO
 total_outbound_buffered > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP
	}

	fn set_their_node_id(&mut self, node_id: PublicKey) {
Expand DownExpand Up@@ -4693,22 +4694,27 @@ mod tests {
 let secp_ctx = Secp256k1::new();
 let key = SecretKey::from_slice(&[1; 32]).unwrap();
 let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
 // The message bufer size is the message length plus two 16-byte MACs plus a 2-byte length
 // and 2-byte type.
 let encoded_size = msg.serialized_length() + 16 * 2 + 2 + 2;
 let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement { msg, update_msg: None };

 fd_a.hang_writes.store(true, Ordering::Relaxed);

 // Now push an arbitrarily large number of messages and check that only
 // `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
 // `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP` message bytes end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size {
 cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
 peers[0].process_events();
 }

Comment on lines

+4706
 to 
4709

@tankyleotankyleoSep 23, 2025

Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should have raised this earlier sorry, looks like increasing the number of iterations here breaks the test is that expected ?
@TheBlueMattTheBlueMattSep 23, 2025

Copy link


Copy Markdown

CollaboratorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, absolutely. This loop pushes exactly the new buffer limit worth of messages into the gossip_broadcast_buffer and then we test the correct handling of that later in the test.

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP - encoded_size);
Comment thread
TheBlueMatt marked this conversation as resolved.

 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 }

 // Check that if a broadcast message comes in from the channel handler (i.e. it is an
Expand All@@ -4718,14 +4724,17 @@ mod tests {

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + encoded_size);
 }

 // Finally, deliver all the messages and make sure we got the right count. Note that there
 // was an extra message that had already moved from the broadcast queue to the encrypted
 // message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
 // message queue so we actually receive `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + 2`
 // message bytes.
 fd_a.hang_writes.store(false, Ordering::Relaxed);
 cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
 peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
Expand All@@ -4740,7 +4749,7 @@ mod tests {

 assert_eq!(
 cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2
OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size + 1
 );
	}

Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
Limit outbound gossip buffer by size, rather than length by TheBlueMatt · Pull Request #4096 · lightningdevkit/rust-lightning · GitHub
Skip to content
Limit outbound gossip buffer by size, rather than length#4096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

TheBlueMatt
merged 1 commit into

from

Sep 23, 2025
 Merged


Limit outbound gossip buffer by size, rather than length
#4096
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


1 commit


Select commit


File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


5 changes: 5 additions & 0 deletions
lightning/src/ln/peer_channel_encryptor.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -641,6 +641,11 @@ impl PeerChannelEncryptor {
/// padding to allow for future encryption/MACing.
pub struct MessageBuf(Vec<u8>);
impl MessageBuf {
	/// The total allocated space for this message
	pub fn capacity(&self) -> usize {
 self.0.capacity()
	}

	/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
	/// the message contents).
	///
Expand Down

59 changes: 34 additions & 25 deletions
lightning/src/ln/peer_handler.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -718,19 +718,11 @@ enum MessageBatchImpl {
	CommitmentSigned(Vec<msgs::CommitmentSigned>),
}

/// The ratio between buffer sizes at which we stop sending initial sync messages vs when we stop
/// forwarding gossip messages to peers altogether.
const FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO: usize = 2;

/// When the outbound buffer has this many messages, we'll stop reading bytes from the peer until
/// we have fewer than this many messages in the outbound buffer again.
/// We also use this as the target number of outbound gossip messages to keep in the write buffer,
/// refilled as we send bytes.
const OUTBOUND_BUFFER_LIMIT_READ_PAUSE: usize = 12;
/// When the outbound buffer has this many messages, we'll simply skip relaying gossip messages to
/// the peer.
const OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP: usize =
	OUTBOUND_BUFFER_LIMIT_READ_PAUSE * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO;

/// If we've sent a ping, and are still awaiting a response, we may need to churn our way through
/// the socket receive buffer before receiving the ping.
Expand All@@ -754,10 +746,20 @@ const MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER: i8 = 4;
/// process before the next ping.
///
/// Note that we continue responding to other messages even after we've sent this many messages, so
/// it's more of a general guideline used for gossip backfill (and gossip forwarding, times
/// [`FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO`]) than a hard limit.
/// this really limits gossip broadcast, gossip backfill, and onion message relay.
const BUFFER_DRAIN_MSGS_PER_TICK: usize = 32;

/// The maximum number of bytes which we allow in a peer's outbound buffers before we start
/// dropping outbound gossip forwards.
///
/// This is currently 128KiB, or two messages at the maximum message size (though in practice we
/// refuse to forward gossip messages which are substantially larger than we expect, so this is
/// closer to ~85 messages if all queued messages are maximum-sized channel announcements).
///
/// Note that as we always drain the gossip forwarding queue before continuing gossip backfill,
/// the equivalent maximum buffer size for gossip backfill is zero.
const OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP: usize = 64 * 1024 * 2;

struct Peer {
	channel_encryptor: PeerChannelEncryptor,
	/// We cache a `NodeId` here to avoid serializing peers' keys every time we forward gossip
Expand DownExpand Up@@ -889,12 +891,11 @@ impl Peer {

	/// Returns whether this peer's outbound buffers are full and we should drop gossip broadcasts.
	fn buffer_full_drop_gossip_broadcast(&self) -> bool {
 let total_outbound_buffered =
 self.gossip_broadcast_buffer.len() + self.pending_outbound_buffer.len();
 let total_outbound_buffered: usize =
 self.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + self.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>();

 total_outbound_buffered > OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP
 || self.msgs_sent_since_pong
 > BUFFER_DRAIN_MSGS_PER_TICK * FORWARD_INIT_SYNC_BUFFER_LIMIT_RATIO
 total_outbound_buffered > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP
	}

	fn set_their_node_id(&mut self, node_id: PublicKey) {
Expand DownExpand Up@@ -4693,22 +4694,27 @@ mod tests {
 let secp_ctx = Secp256k1::new();
 let key = SecretKey::from_slice(&[1; 32]).unwrap();
 let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
 // The message bufer size is the message length plus two 16-byte MACs plus a 2-byte length
 // and 2-byte type.
 let encoded_size = msg.serialized_length() + 16 * 2 + 2 + 2;
 let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement { msg, update_msg: None };

 fd_a.hang_writes.store(true, Ordering::Relaxed);

 // Now push an arbitrarily large number of messages and check that only
 // `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
 // `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP` message bytes end up in the queue.
 for _ in 0..OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size {
 cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
 peers[0].process_events();
 }

Comment on lines

+4706
 to 
4709

@tankyleotankyleoSep 23, 2025

Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should have raised this earlier sorry, looks like increasing the number of iterations here breaks the test is that expected ?
@TheBlueMattTheBlueMattSep 23, 2025

Copy link


Copy Markdown

CollaboratorAuthor
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, absolutely. This loop pushes exactly the new buffer limit worth of messages into the gossip_broadcast_buffer and then we test the correct handling of that later in the test.

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP - encoded_size);
Comment thread
TheBlueMatt marked this conversation as resolved.

 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 }

 // Check that if a broadcast message comes in from the channel handler (i.e. it is an
Expand All@@ -4718,14 +4724,17 @@ mod tests {

 {
 let peer_a_lock = peers[0].peers.read().unwrap();
 let buf_len =
 peer_a_lock.get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len();
 assert_eq!(buf_len, OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
 let peer = peer_a_lock.get(&fd_a).unwrap().lock().unwrap();
 let buf_len = peer.pending_outbound_buffer.iter().map(|m| m.capacity()).sum::<usize>()
 + peer.gossip_broadcast_buffer.iter().map(|m| m.capacity()).sum::<usize>();
 assert!(buf_len > OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP);
 assert!(buf_len < OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + encoded_size);
 }

 // Finally, deliver all the messages and make sure we got the right count. Note that there
 // was an extra message that had already moved from the broadcast queue to the encrypted
 // message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
 // message queue so we actually receive `OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP + 2`
 // message bytes.
 fd_a.hang_writes.store(false, Ordering::Relaxed);
 cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
 peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
Expand All@@ -4740,7 +4749,7 @@ mod tests {

 assert_eq!(
 cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2
OUTBOUND_BUFFER_SIZE_LIMIT_DROP_GOSSIP / encoded_size + 1
 );
	}

Expand Down
Loading