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-rw-r--r--include/net/checksum.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/net/checksum.h b/include/net/checksum.h
index 10a16b5bd1c7..abffc64e7300 100644
--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -120,6 +120,11 @@ static inline __wsum csum_partial_ext(const void *buff, int len, __wsum sum)
#define CSUM_MANGLED_0 ((__force __sum16)0xffff)
+static inline void csum_replace_by_diff(__sum16 *sum, __wsum diff)
+{
+ *sum = csum_fold(csum_add(diff, ~csum_unfold(*sum)));
+}
+
static inline void csum_replace4(__sum16 *sum, __be32 from, __be32 to)
{
__wsum tmp = csum_sub(~csum_unfold(*sum), (__force __wsum)from);