r8152: fix accessing unset transport header

A warning is triggered by commit 66e4c8d9 ("net: warn if transport
header was not set"). The warning is harmless, because the value from
skb_transport_offset() is only used for skb_is_gso() is true or the
skb->ip_summed is equal to CHECKSUM_PARTIAL.

Fixes: 66e4c8d9 ("net: warn if transport header was not set")
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/r8152.c

@@ -2156,7 +2156,7 @@ static inline void rtl_rx_vlan_tag(struct rx_desc *desc, struct sk_buff *skb)
 }
 
 static int r8152_tx_csum(struct r8152 *tp, struct tx_desc *desc,
-			 struct sk_buff *skb, u32 len, u32 transport_offset)
+			 struct sk_buff *skb, u32 len)
 {
 	u32 mss = skb_shinfo(skb)->gso_size;
 	u32 opts1, opts2 = 0;
@@ -2167,6 +2167,8 @@ static int r8152_tx_csum(struct r8152 *tp, struct tx_desc *desc,
 	opts1 = len | TX_FS | TX_LS;
 
 	if (mss) {
+		u32 transport_offset = (u32)skb_transport_offset(skb);
+
 		if (transport_offset > GTTCPHO_MAX) {
 			netif_warn(tp, tx_err, tp->netdev,
 				   "Invalid transport offset 0x%x for TSO\n",
@@ -2197,6 +2199,7 @@ static int r8152_tx_csum(struct r8152 *tp, struct tx_desc *desc,
 		opts1 |= transport_offset << GTTCPHO_SHIFT;
 		opts2 |= min(mss, MSS_MAX) << MSS_SHIFT;
 	} else if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		u32 transport_offset = (u32)skb_transport_offset(skb);
 		u8 ip_protocol;
 
 		if (transport_offset > TCPHO_MAX) {
@@ -2260,7 +2263,6 @@ static int r8152_tx_agg_fill(struct r8152 *tp, struct tx_agg *agg)
 		struct tx_desc *tx_desc;
 		struct sk_buff *skb;
 		unsigned int len;
-		u32 offset;
 
 		skb = __skb_dequeue(&skb_head);
 		if (!skb)
@@ -2276,9 +2278,7 @@ static int r8152_tx_agg_fill(struct r8152 *tp, struct tx_agg *agg)
 		tx_data = tx_agg_align(tx_data);
 		tx_desc = (struct tx_desc *)tx_data;
 
-		offset = (u32)skb_transport_offset(skb);
-
-		if (r8152_tx_csum(tp, tx_desc, skb, skb->len, offset)) {
+		if (r8152_tx_csum(tp, tx_desc, skb, skb->len)) {
 			r8152_csum_workaround(tp, skb, &skb_head);
 			continue;
 		}
@@ -2759,9 +2759,9 @@ rtl8152_features_check(struct sk_buff *skb, struct net_device *dev,
 {
 	u32 mss = skb_shinfo(skb)->gso_size;
 	int max_offset = mss ? GTTCPHO_MAX : TCPHO_MAX;
-	int offset = skb_transport_offset(skb);
 
-	if ((mss || skb->ip_summed == CHECKSUM_PARTIAL) && offset > max_offset)
+	if ((mss || skb->ip_summed == CHECKSUM_PARTIAL) &&
+	    skb_transport_offset(skb) > max_offset)
 		features &= ~(NETIF_F_CSUM_MASK | NETIF_F_GSO_MASK);
 	else if ((skb->len + sizeof(struct tx_desc)) > agg_buf_sz)
 		features &= ~NETIF_F_GSO_MASK;