net: Handle CHECKSUM_COMPLETE more adequately in pskb_trim_rcsum().
Currently pskb_trim_rcsum() just balks on CHECKSUM_COMPLETE packets
and remarks them as CHECKSUM_NONE, forcing a software checksum
validation later.
We have all of the mechanics available to fixup the skb->csum value,
even for complicated fragmented packets, via the helpers
skb_checksum() and csum_sub().
So just use them.
Based upon a suggestion by Herbert Xu.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 215b5ea..bec1cc7 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2263,24 +2263,6 @@
unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
-/**
- * pskb_trim_rcsum - trim received skb and update checksum
- * @skb: buffer to trim
- * @len: new length
- *
- * This is exactly the same as pskb_trim except that it ensures the
- * checksum of received packets are still valid after the operation.
- */
-
-static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
-{
- if (likely(len >= skb->len))
- return 0;
- if (skb->ip_summed == CHECKSUM_COMPLETE)
- skb->ip_summed = CHECKSUM_NONE;
- return __pskb_trim(skb, len);
-}
-
#define skb_queue_walk(queue, skb) \
for (skb = (queue)->next; \
skb != (struct sk_buff *)(queue); \
@@ -2378,6 +2360,27 @@
__wsum skb_checksum(const struct sk_buff *skb, int offset, int len,
__wsum csum);
+/**
+ * pskb_trim_rcsum - trim received skb and update checksum
+ * @skb: buffer to trim
+ * @len: new length
+ *
+ * This is exactly the same as pskb_trim except that it ensures the
+ * checksum of received packets are still valid after the operation.
+ */
+
+static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
+{
+ if (likely(len >= skb->len))
+ return 0;
+ if (skb->ip_summed == CHECKSUM_COMPLETE) {
+ __wsum adj = skb_checksum(skb, len, skb->len - len, 0);
+
+ skb->csum = csum_sub(skb->csum, adj);
+ }
+ return __pskb_trim(skb, len);
+}
+
static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,
int len, void *buffer)
{