1 files changed, 34 insertions, 0 deletions
diff --git a/packages/meshbay-node/src/meshbay_node/transport/webrtc/udp_buffer.py b/packages/meshbay-node/src/meshbay_node/transport/webrtc/udp_buffer.py
new file mode 100644
index 0000000..8a2db31
--- /dev/null
+++ b/packages/meshbay-node/src/meshbay_node/transport/webrtc/udp_buffer.py
@@ -0,0 +1,34 @@
+"""A larger receive buffer on the node's ICE sockets, applied on import.
+
+aioice asks the kernel for 256 KB per socket. The node reads its sockets from
+Python, more slowly than a line delivers, and a browser sending a file keeps up
+to 1.5 MB in flight (32 chunks of 48 KB, `transport-upload.js`). What does not
+fit in the buffer is dropped by the kernel of the node's own machine
+(`UdpRcvbufErrors`), the browser's SCTP sender takes each drop for congestion,
+and an upload settles around 6.5 MB/s on a line that carries 47
+(docs/MESHBAY_DESIGN.md §5.5).
+
+The buffer has to hold what one upload may have in flight, counted the way the
+kernel counts it, which is about twice the bytes for packets of this size. The
+kernel grants no more than `net.core.rmem_max` allows, and on a machine where
+that is left at its default of 208 KB this changes nothing: `granted()` says
+what a socket really gets, and the node logs it once.
+"""
+
+import socket
+
+import aioice.turn
+
+WANTED = 4 * 1024 * 1024
+
+aioice.turn.UDP_SOCKET_BUFFER_SIZE = WANTED
+
+
+def granted() -> int:
+    """What the kernel gives a socket that asks for `WANTED`, in bytes."""
+    with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sock:
+        try:
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, WANTED)
+        except OSError:
+            pass
+        return sock.getsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF)