s390/qeth: drop unwanted packets earlier in RX path

Packets with an unexpected HW format are currently first extracted from
the RX buffer, passed upwards to the layer-specific driver and only then
finally dropped.

Enhance the RX path so that we can drop such packets before even
allocating an skb. For this, add some additional logic so that when a
packet is meant to be dropped, we can still walk along the packet's data
chunks in the RX buffer. This allows us to extract the following
packet(s) from the buffer.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core_main.c

@@ -5072,6 +5072,7 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 	int headroom = 0;
 	int use_rx_sg = 0;
 
+next_packet:
 	/* qeth_hdr must not cross element boundaries */
 	while (element->length < offset + sizeof(struct qeth_hdr)) {
 		if (qeth_is_last_sbale(element))
@@ -5088,10 +5089,22 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 		break;
 	case QETH_HEADER_TYPE_LAYER3:
 		skb_len = (*hdr)->hdr.l3.length;
+		if (!IS_LAYER3(card)) {
+			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
+			skb = NULL;
+			goto walk_packet;
+		}
+
 		headroom = ETH_HLEN;
 		break;
 	case QETH_HEADER_TYPE_OSN:
 		skb_len = (*hdr)->hdr.osn.pdu_length;
+		if (!IS_OSN(card)) {
+			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
+			skb = NULL;
+			goto walk_packet;
+		}
+
 		headroom = sizeof(struct qeth_hdr);
 		break;
 	default:
@@ -5100,7 +5113,8 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 		else
 			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
 
-		break;
+		/* Can't determine packet length, drop the whole buffer. */
+		return NULL;
 	}
 
 	if (!skb_len)
@@ -5126,10 +5140,12 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 	if (headroom)
 		skb_reserve(skb, headroom);
 
+walk_packet:
 	data_ptr = element->addr + offset;
 	while (skb_len) {
 		data_len = min(skb_len, (int)(element->length - offset));
-		if (data_len) {
+
+		if (skb && data_len) {
 			if (use_rx_sg)
 				qeth_create_skb_frag(element, skb, offset,
 						     data_len);
@@ -5141,8 +5157,11 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 			if (qeth_is_last_sbale(element)) {
 				QETH_CARD_TEXT(card, 4, "unexeob");
 				QETH_CARD_HEX(card, 2, buffer, sizeof(void *));
-				dev_kfree_skb_any(skb);
-				QETH_CARD_STAT_INC(card, rx_length_errors);
+				if (skb) {
+					dev_kfree_skb_any(skb);
+					QETH_CARD_STAT_INC(card,
+							   rx_length_errors);
+				}
 				return NULL;
 			}
 			element++;
@@ -5152,6 +5171,11 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 			offset += data_len;
 		}
 	}
+
+	/* This packet was skipped, go get another one: */
+	if (!skb)
+		goto next_packet;
+
 	*__element = element;
 	*__offset = offset;
 	if (use_rx_sg) {

drivers/s390/net/qeth_l2_main.c

@@ -315,30 +315,19 @@ static int qeth_l2_process_inbound_buffer(struct qeth_card *card,
 			*done = 1;
 			break;
 		}
-		switch (hdr->hdr.l2.id) {
-		case QETH_HEADER_TYPE_LAYER2:
+
+		if (hdr->hdr.l2.id == QETH_HEADER_TYPE_LAYER2) {
 			skb->protocol = eth_type_trans(skb, skb->dev);
 			qeth_rx_csum(card, skb, hdr->hdr.l2.flags[1]);
 			len = skb->len;
 			napi_gro_receive(&card->napi, skb);
-			break;
-		case QETH_HEADER_TYPE_OSN:
-			if (IS_OSN(card)) {
-				skb_push(skb, sizeof(struct qeth_hdr));
-				skb_copy_to_linear_data(skb, hdr,
-						sizeof(struct qeth_hdr));
-				len = skb->len;
-				card->osn_info.data_cb(skb);
-				break;
-			}
-			/* Else, fall through */
-		default:
-			dev_kfree_skb_any(skb);
-			QETH_CARD_TEXT(card, 3, "inbunkno");
-			QETH_DBF_HEX(CTRL, 3, hdr, sizeof(*hdr));
-			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
-			continue;
+		} else {
+			skb_push(skb, sizeof(*hdr));
+			skb_copy_to_linear_data(skb, hdr, sizeof(*hdr));
+			len = skb->len;
+			card->osn_info.data_cb(skb);
 		}
+
 		work_done++;
 		budget--;
 		QETH_CARD_STAT_INC(card, rx_packets);

drivers/s390/net/qeth_l3_main.c

@@ -1366,7 +1366,6 @@ static int qeth_l3_process_inbound_buffer(struct qeth_card *card,
 	int work_done = 0;
 	struct sk_buff *skb;
 	struct qeth_hdr *hdr;
-	unsigned int len;
 
 	*done = 0;
 	WARN_ON_ONCE(!budget);
@@ -1378,26 +1377,17 @@ static int qeth_l3_process_inbound_buffer(struct qeth_card *card,
 			*done = 1;
 			break;
 		}
-		switch (hdr->hdr.l3.id) {
-		case QETH_HEADER_TYPE_LAYER3:
+
+		if (hdr->hdr.l3.id == QETH_HEADER_TYPE_LAYER3)
 			qeth_l3_rebuild_skb(card, skb, hdr);
-			/* fall through */
-		case QETH_HEADER_TYPE_LAYER2: /* for HiperSockets sniffer */
-			skb->protocol = eth_type_trans(skb, skb->dev);
-			len = skb->len;
-			napi_gro_receive(&card->napi, skb);
-			break;
-		default:
-			dev_kfree_skb_any(skb);
-			QETH_CARD_TEXT(card, 3, "inbunkno");
-			QETH_DBF_HEX(CTRL, 3, hdr, sizeof(*hdr));
-			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
-			continue;
-		}
+
+		skb->protocol = eth_type_trans(skb, skb->dev);
+		QETH_CARD_STAT_INC(card, rx_packets);
+		QETH_CARD_STAT_ADD(card, rx_bytes, skb->len);
+
+		napi_gro_receive(&card->napi, skb);
 		work_done++;
 		budget--;
-		QETH_CARD_STAT_INC(card, rx_packets);
-		QETH_CARD_STAT_ADD(card, rx_bytes, len);
 	}
 	return work_done;
 }