lib/checksum.c: fix carry in csum_tcpudp_nofold

The carry from the 64->32bits folding was dropped, e.g with: saddr=0xFFFFFFFF daddr=0xFF0000FF len=0xFFFF proto=0 sum=1, csum_tcpudp_nofold returned 0 instead of 1. Signed-off-by: Karl Beldan <[email protected]> Cc: Al Viro <[email protected]> Cc: Eric Dumazet <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Mike Frysinger <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Signed-off-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]>
penberg · Jan 29, 2015 · 150ae0e · 150ae0e
1 parent 59ccaaa
commit 150ae0e
Showing 1 changed file with 10 additions and 2 deletions.
diff --git a/lib/checksum.c b/lib/checksum.c
@@ -47,6 +47,15 @@ static inline unsigned short from32to16(unsigned int x)
 	return x;
 }
 
+static inline u32 from64to32(u64 x)
+{
+	/* add up 32-bit and 32-bit for 32+c bit */
+	x = (x & 0xffffffff) + (x >> 32);
+	/* add up carry.. */
+	x = (x & 0xffffffff) + (x >> 32);
+	return (u32)x;
+}
+
 static unsigned int do_csum(const unsigned char *buff, int len)
 {
 	int odd;
@@ -195,8 +204,7 @@ __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
 #else
 	s += (proto + len) << 8;
 #endif
-	s += (s >> 32);
-	return (__force __wsum)s;
+	return (__force __wsum)from64to32(s);
 }
 EXPORT_SYMBOL(csum_tcpudp_nofold);
 #endif