fix(node): a receive buffer that holds an upload's window

Uploads ran at 6.5 MB/s because the kernel dropped datagrams at the
node's 256 KB socket. Asking for 4 MB gave 19.5 MB/s, no drop.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/transport/webrtc_server.py b/packages/meshbay-node/src/meshbay_node/transport/webrtc_server.py
index 0baaf19..1976ad4 100644
--- a/packages/meshbay-node/src/meshbay_node/transport/webrtc_server.py
+++ b/packages/meshbay-node/src/meshbay_node/transport/webrtc_server.py
@@ -42,6 +42,7 @@ from meshbay_node.indexer import GroupIndex
 from meshbay_node.roots import (
     RootSet,
 )
+from meshbay_node.transport.webrtc import udp_buffer
 from meshbay_node.transport.webrtc.admin import AdminMixin
 from meshbay_node.transport.webrtc.admission import AdmissionMixin
 from meshbay_node.transport.webrtc.apps.music import MusicMixin
@@ -152,6 +153,17 @@ class WebRTCTransport:
         # Above one, the peer connections live in that many processes of their
         # own and the sessions here speak to them (transport/webrtc/workers.py).
         # At one, this process holds them itself and none is started.
+        got = udp_buffer.granted()
+        if got < udp_buffer.WANTED:
+            # Said once, with what to change: nothing else would tell an
+            # operator why uploads to this node stay around 6 MB/s.
+            log.warning(
+                "UDP receive buffer is %d KB per socket, below the %d KB an "
+                "upload needs to run at full speed; raise net.core.rmem_max "
+                "to %d to lift it", got // 1024, udp_buffer.WANTED // 1024,
+                udp_buffer.WANTED)
+        else:
+            log.info("UDP receive buffer: %d KB per socket", got // 1024)
         self._workers = WorkerPool(
             min(max(1, int(connection_processes or 1)), max_processes()),
             self._stun, ice_interfaces)