D60217.diff
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	diff --git a/sys/net/iflib.c b/sys/net/iflib.c
	--- a/sys/net/iflib.c
	+++ b/sys/net/iflib.c
	@@ -1205,6 +1205,34 @@
	uint64_t paddr;
	void *addr = PNMB(na, slot, &paddr);

	+ /*
	+ * An empty packet still takes its descriptor, as netmap
	+ * slots and NIC descriptors go in step. A VALE switch
	+ * fills the slots it has leased in a destination ring
	+ * and then not used with empty packets. Passing them
	+ * on with no segment makes the drivers' txd_encap write
	+ * through a NULL descriptor pointer, and not every NIC
	+ * accepts a descriptor of length 0. Send a minimum size
	+ * frame from the interface's address to itself instead:
	+ * a switch that has learned the address on this port
	+ * filters it, and no other host takes it for its own.
	+ */
	+ if (__predict_false(len == 0 && seg_idx == 0 &&
	+ !(slot->flags & NS_MOREFRAG) &&
	+ offset + ETHER_MIN_LEN - ETHER_CRC_LEN <=
	+ NETMAP_BUF_SIZE(na))) {
	+ uint8_t f = (uint8_t )addr + offset;
	+
	+ len = ETHER_MIN_LEN - ETHER_CRC_LEN;
	+ memset(f, 0, len);
	+ memcpy(f, if_getlladdr(ifp), ETHER_ADDR_LEN);
	+ memcpy(f + ETHER_ADDR_LEN, if_getlladdr(ifp),
	+ ETHER_ADDR_LEN);
	+ /* IEEE Std 802 Local Experimental Ethertype 1 */
	+ f[2 * ETHER_ADDR_LEN] = 0x88;
	+ f[2 * ETHER_ADDR_LEN + 1] = 0xb5;
	+ }
	+
	flags \|= (slot->flags & NS_REPORT \|\|
	nic_i == 0 \|\| nic_i == report_frequency) ?
	IPI_TX_INTR : 0;