net: switch to use skb_probe_transport_header()

Switch to use the new help skb_probe_transport_header() to do the l4 header
probing for untrusted sources. For packets with partial csum, the header should
already been set by skb_partial_csum_set().

Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index acf6450..59e9605 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -21,7 +21,6 @@
 #include <net/rtnetlink.h>
 #include <net/sock.h>
 #include <linux/virtio_net.h>
-#include <net/flow_keys.h>
 
 /*
  * A macvtap queue is the central object of this driver, it connects
@@ -646,7 +645,6 @@
 	int vnet_hdr_len = 0;
 	int copylen = 0;
 	bool zerocopy = false;
-	struct flow_keys keys;
 
 	if (q->flags & IFF_VNET_HDR) {
 		vnet_hdr_len = q->vnet_hdr_sz;
@@ -727,12 +725,7 @@
 			goto err_kfree;
 	}
 
-	if (skb->ip_summed == CHECKSUM_PARTIAL)
-		skb_set_transport_header(skb, skb_checksum_start_offset(skb));
-	else if (skb_flow_dissect(skb, &keys))
-		skb_set_transport_header(skb, keys.thoff);
-	else
-		skb_set_transport_header(skb, ETH_HLEN);
+	skb_probe_transport_header(skb, ETH_HLEN);
 
 	rcu_read_lock_bh();
 	vlan = rcu_dereference_bh(q->vlan);