chunk: Fix internet checksum calculation on big-endian systems

ntohs() might be defined as noop (#define ntohs(x) (x)) so we have
to manually shorten the negated value (gets promoted to an int).

Fixes #747.

diff --git a/src/libstrongswan/utils/chunk.c b/src/libstrongswan/utils/chunk.c
index 4b24b37c25b03f2c8d9be78021832444fb74c357..c4471be707302d699c01fe531152631eed9494e7 100644 (file)
--- a/src/libstrongswan/utils/chunk.c
+++ b/src/libstrongswan/utils/chunk.c
@@ -992,7 +992,7 @@ u_int32_t chunk_hash_static(chunk_t chunk)
  */
 u_int16_t chunk_internet_checksum_inc(chunk_t data, u_int16_t checksum)
 {
-       u_int32_t sum = ntohs(~checksum);
+       u_int32_t sum = ntohs((u_int16_t)~checksum);
 
        while (data.len > 1)
        {