net: fix checksum on big endian CPUs

With current code, the checksum of odd-length buffers is wrong on
big endian CPUs: the last byte is not properly summed to the
accumulator.

Fix this by left-shifting the remaining byte by 8. For instance,
if the last byte is 0x42, we should add 0x4200 to the accumulator
on big endian CPUs.

This change is similar to what is suggested in Errata 3133 of
RFC 1071.

Fixes: 6006818cfb26("net: new checksum functions")
Cc: stable@dpdk.org
Signed-off-by: Hongzhi Guo <guohongzhi1@huawei.com>
Reviewed-by: Morten Brørup <mb@smartsharesystems.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>

diff --git a/lib/librte_net/rte_ip.h b/lib/librte_net/rte_ip.h
index a9ffc33..fcd1eb3 100644 (file)
--- a/lib/librte_net/rte_ip.h
+++ b/lib/librte_net/rte_ip.h
@@ -139,8 +139,11 @@ __rte_raw_cksum(const void *buf, size_t len, uint32_t sum)
        }
 
        /* if length is in odd bytes */
-       if (len == 1)
-               sum += *((const uint8_t *)u16_buf);
+       if (len == 1) {
+               uint16_t left = 0;
+               *(uint8_t *)&left = *(const uint8_t *)u16_buf;
+               sum += left;
+       }
 
        return sum;
 }