net: introduce skb_transport_header_was_set()

We have skb_mac_header_was_set() helper to tell if mac_header
was set on a skb. We would like the same for transport_header.

__netif_receive_skb() doesn't reset the transport header if already
set by GRO layer.

Note that network stacks usually reset the transport header anyway,
after pulling the network header, so this change only allows
a followup patch to have more precise qdisc pkt_len computation
for GSO packets at ingress side.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 14 insertions, 1 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 320e976d5ab8..8b2256e880e0 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1492,6 +1492,11 @@ static inline void skb_set_inner_network_header(struct sk_buff *skb,
         skb->inner_network_header += offset;
 }
 
+static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
+{
+        return skb->transport_header != ~0U;
+}
+
 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
 {
         return skb->head + skb->transport_header;
@@ -1580,6 +1585,11 @@ static inline void skb_set_inner_network_header(struct sk_buff *skb,
         skb->inner_network_header = skb->data + offset;
 }
 
+static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
+{
+        return skb->transport_header != NULL;
+}
+
 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
 {
         return skb->transport_header;
diff --git a/net/core/dev.c b/net/core/dev.c
index a51ccf46e8b7..2e2448201a76 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3352,7 +3352,8 @@ static int __netif_receive_skb(struct sk_buff *skb)
         orig_dev = skb->dev;
 
         skb_reset_network_header(skb);
-        skb_reset_transport_header(skb);
+        if (!skb_transport_header_was_set(skb))
+                skb_reset_transport_header(skb);
         skb_reset_mac_len(skb);
 
         pt_prev = NULL;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b03fc0c6a952..1e1b9ea0296d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -260,6 +260,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
         skb->end = skb->tail + size;
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
         skb->mac_header = ~0U;
+        skb->transport_header = ~0U;
 #endif
 
         /* make sure we initialize shinfo sequentially */
@@ -328,6 +329,7 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
         skb->end = skb->tail + size;
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
         skb->mac_header = ~0U;
+        skb->transport_header = ~0U;
 #endif
 
         /* make sure we initialize shinfo sequentially */