iflib: clear the deferred TX descriptor state when a queue is stopped

Stopping an interface frees the queued mbufs and zeroes a transmit
queue's descriptor accounting, but the three counters that track
descriptors deferred to a later doorbell write or report-status
request are not cleared there: they only reach zero when the code
that acts on them runs.  After a reset they therefore describe
descriptors that no longer exist, until enough new traffic flushes
them.

The consequences are small - one doorbell written from a stale
count, and a report-status request on the first packet after the
reset - but the state is simply wrong, and the transmit-hang check
in iflib_timer() reads one of them.

MFC after:	1 week
Assisted-by:	Claude Code (Opus 5)

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/net/iflib.c b/sys/net/iflib.c
index f865f2414281..63455fb46d70 100644
--- a/sys/net/iflib.c
+++ b/sys/net/iflib.c
@@ -2701,6 +2701,8 @@ iflib_stop(if_ctx_t ctx)
 		txq->ift_outstanding_prev = 0;
 		txq->ift_wdog_armed = 0;
 		txq->ift_in_use = txq->ift_gen = txq->ift_no_desc_avail = 0;
+		txq->ift_npending = txq->ift_db_pending = 0;
+		txq->ift_rs_pending = 0;
 		if (sctx->isc_flags & IFLIB_PRESERVE_TX_INDICES)
 			txq->ift_cidx = txq->ift_pidx;
 		else