e1000: fix rx accounting for multi-descriptor packets

The receive paths accumulate ri->iri_len across the descriptors making
up a packet, then add that running total to rxr->rx_bytes on every
iteration of the loop.  A packet spanning descriptors of length l1, l2
and l3 thus contributes 3*l1 + 2*l2 + l3 instead of l1 + l2 + l3.

Single descriptor packets, the common case, are accounted correctly,
so this only shows up on jumbo frames.

Add the per descriptor length instead.  iflib memsets the if_rxd_info
before each isc_rxd_pkt_get() call, so summing len gives the same total
as the final iri_len, and the frame error path that returns without
incrementing rx_packets keeps counting bytes exactly as before.

MFC after:	1 week

2 files changed, 3 insertions, 3 deletions

diff --git a/sys/dev/e1000/em_txrx.c b/sys/dev/e1000/em_txrx.c
index b86222e363e9..f2b48d6518f7 100644
--- a/sys/dev/e1000/em_txrx.c
+++ b/sys/dev/e1000/em_txrx.c
@@ -679,7 +679,7 @@ lem_isc_rxd_pkt_get(void *arg, if_rxd_info_t ri)
 
 		len = le16toh(rxd->length);
 		ri->iri_len += len;
-		rxr->rx_bytes += ri->iri_len;
+		rxr->rx_bytes += len;
 
 		eop = (status & E1000_RXD_STAT_EOP) != 0;
 
@@ -745,7 +745,7 @@ em_isc_rxd_pkt_get(void *arg, if_rxd_info_t ri)
 
 		len = le16toh(rxd->wb.upper.length);
 		ri->iri_len += len;
-		rxr->rx_bytes += ri->iri_len;
+		rxr->rx_bytes += len;
 
 		eop = (staterr & E1000_RXD_STAT_EOP) != 0;
 
diff --git a/sys/dev/e1000/igb_txrx.c b/sys/dev/e1000/igb_txrx.c
index e01bc72cdc55..fc690dcfc100 100644
--- a/sys/dev/e1000/igb_txrx.c
+++ b/sys/dev/e1000/igb_txrx.c
@@ -458,7 +458,7 @@ igb_isc_rxd_pkt_get(void *arg, if_rxd_info_t ri)
 		    le32toh(rxd->wb.lower.lo_dword.data) &  IGB_PKTTYPE_MASK;
 
 		ri->iri_len += len;
-		rxr->rx_bytes += ri->iri_len;
+		rxr->rx_bytes += len;
 
 		rxd->wb.upper.status_error = 0;
 		eop = ((staterr & E1000_RXD_STAT_EOP) == E1000_RXD_STAT_EOP);