X520 live as the product NIC: rate buckets re-keyed to read time (one shared clock, one commit per drained batch) with the backward smear as a settled window — each completed bucket enters once, donates excess to the nearest earlier deficits once, locks for display when nothing later can refill it (per-sample recompute double-counted excess and read >20G on a 20G wire); timestamp machinery deleted (ts.go, SO_TIMESTAMPING, rx_filter=ALL check) after the audit confirmed the buckets were its sole consumer; testDriver ixgbe; RollBall mailbox hardened against orphaned-command completions (never sample status before a poll gap, value from the same block read, devad/reg echo required — a killed session's 7.60 read answered a PHY ID as 0x0006); full hardware pass: 20.00G flat both directions, zero errors, ECD 42m, SNR +7.4dB

sock.go

@@ -101,22 +101,6 @@ func newMmsghdrs(bufs [][]byte) ([]mmsghdr, []unix.Iovec) {
 	return hdrs, iovs
 }
 
-// Room for one SCM_TIMESTAMPING and its three timespecs.
-const cmsgLen = 128
-
-// Receive headers carry a control buffer each, so the mac's receive stamp comes
-// back alongside every frame.
-func newRxMmsghdrs(bufs [][]byte) ([]mmsghdr, [][]byte) {
-	hdrs, _ := newMmsghdrs(bufs)
-	oob := make([][]byte, len(bufs))
-	for i := range bufs {
-		oob[i] = make([]byte, cmsgLen)
-		hdrs[i].hdr.Control = &oob[i][0]
-		hdrs[i].hdr.Controllen = cmsgLen
-	}
-	return hdrs, oob
-}
-
 func packetDrops(fd int) uint64 {
 	st, err := unix.GetsockoptTpacketStats(fd, unix.SOL_PACKET, unix.PACKET_STATISTICS)
 	if err != nil {