s390/qeth: test RX/TX checksum offload reply

Turning on receive and/or transmit checksum offload support
on the OSA card requires 2 commands:
1. start command which replies with available features
2. enable command to turn on selected features.

The current version does not check the reply of the start
command and simply uses the returned value to enable
offload features. When the start command returns zero, this
leads to a situation where no checksum offload
is turned on by the hardware. Even worse no error
indication is returned. The Linux kernel assumes
the OSA card performs RX/TX checksum offload, but the hardware
does not perform any checksum verification at all.

This patch checks the return of the start and enable
command responses from the hardware and turns off
checksum offloading if the commands fails or does not
respond with the correct bit setting.
Signed-off-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Reviewed-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Reviewed-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core_main.c

@@ -6104,11 +6104,19 @@ static int qeth_ipa_checksum_run_cmd(struct qeth_card *card,
 
 static int qeth_send_checksum_on(struct qeth_card *card, int cstype)
 {
+	const __u32 required_features = QETH_IPA_CHECKSUM_IP_HDR |
+					QETH_IPA_CHECKSUM_UDP |
+					QETH_IPA_CHECKSUM_TCP;
 	struct qeth_checksum_cmd chksum_cb;
 	int rc;
 
 	rc = qeth_ipa_checksum_run_cmd(card, cstype, IPA_CMD_ASS_START, 0,
 				       &chksum_cb);
+	if (!rc) {
+		if ((required_features & chksum_cb.supported) !=
+		    required_features)
+			rc = -EIO;
+	}
 	if (rc) {
 		qeth_send_simple_setassparms(card, cstype, IPA_CMD_ASS_STOP, 0);
 		dev_warn(&card->gdev->dev,
@@ -6118,6 +6126,11 @@ static int qeth_send_checksum_on(struct qeth_card *card, int cstype)
 	}
 	rc = qeth_ipa_checksum_run_cmd(card, cstype, IPA_CMD_ASS_ENABLE,
 				       chksum_cb.supported, &chksum_cb);
+	if (!rc) {
+		if ((required_features & chksum_cb.enabled) !=
+		    required_features)
+			rc = -EIO;
+	}
 	if (rc) {
 		qeth_send_simple_setassparms(card, cstype, IPA_CMD_ASS_STOP, 0);
 		dev_warn(&card->gdev->dev,

drivers/s390/net/qeth_core_mpc.h

@@ -352,6 +352,16 @@ struct qeth_arp_query_info {
 	char *udata;
 };
 
+/* IPA set assist segmentation bit definitions for receive and
+ * transmit checksum offloading.
+ */
+enum qeth_ipa_checksum_bits {
+	QETH_IPA_CHECKSUM_IP_HDR	= 0x0002,
+	QETH_IPA_CHECKSUM_UDP		= 0x0008,
+	QETH_IPA_CHECKSUM_TCP		= 0x0010,
+	QETH_IPA_CHECKSUM_LP2LP		= 0x0020
+};
+
 /* IPA Assist checksum offload reply layout. */
 struct qeth_checksum_cmd {
 	__u32 supported;