1000+ uBridge processes share a single UDP marker.sink endpoint. The
default kernel receive buffer (~208 KB) holds ~1000 datagrams — a
traffic burst can overflow it before the event loop drains them. Grow
it to 8 MB via setsockopt(SO_RCVBUF) so the kernel absorbs bursts
without silent packet loss. UDP is unordered — buffer size does not
affect per-datagram latency, only burst-loss resilience.
a699383933