Revert "net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends"

This reverts commit 88078d9.

Author: popcornmix

include/linux/skbuff.h

@@ -3143,7 +3143,6 @@ static inline void *skb_push_rcsum(struct sk_buff *skb, unsigned int len)
 	return skb->data;
 }
 
-int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len);
 /**
  *	pskb_trim_rcsum - trim received skb and update checksum
  *	@skb: buffer to trim
@@ -3157,7 +3156,9 @@ static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
 {
 	if (likely(len >= skb->len))
 		return 0;
-	return pskb_trim_rcsum_slow(skb, len);
+	if (skb->ip_summed == CHECKSUM_COMPLETE)
+		skb->ip_summed = CHECKSUM_NONE;
+	return __pskb_trim(skb, len);
 }
 
 static inline int __skb_trim_rcsum(struct sk_buff *skb, unsigned int len)

net/core/skbuff.c

@@ -1839,20 +1839,6 @@ int ___pskb_trim(struct sk_buff *skb, unsigned int len)
 }
 EXPORT_SYMBOL(___pskb_trim);
 
-/* Note : use pskb_trim_rcsum() instead of calling this directly
- */
-int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len)
-{
-	if (skb->ip_summed == CHECKSUM_COMPLETE) {
-		int delta = skb->len - len;
-
-		skb->csum = csum_sub(skb->csum,
-				     skb_checksum(skb, len, delta, 0));
-	}
-	return __pskb_trim(skb, len);
-}
-EXPORT_SYMBOL(pskb_trim_rcsum_slow);
-
 /**
  *	__pskb_pull_tail - advance tail of skb header
  *	@skb: buffer to reallocate