From 0dacea92d26c31d453c58de2e99c178fee554166 Mon Sep 17 00:00:00 2001 From: Ed Swierk Date: Thu, 16 Nov 2017 06:06:06 -0800 Subject: net: Transmit zero UDP checksum as 0xFFFF The checksum algorithm used by IPv4, TCP and UDP allows a zero value to be represented by either 0x0000 and 0xFFFF. But per RFC 768, a zero UDP checksum must be transmitted as 0xFFFF because 0x0000 is a special value meaning no checksum. Substitute 0xFFFF whenever a checksum is computed as zero when modifying a UDP datagram header. Doing this on IPv4 and TCP checksums is unnecessary but legal. Add a wrapper for net_checksum_finish() that makes the substitution. (We can't just change net_checksum_finish(), as that function is also used by receivers to verify checksums, and in that case the expected value is always 0x0000.) Signed-off-by: Ed Swierk Signed-off-by: Jason Wang --- include/net/checksum.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/net') diff --git a/include/net/checksum.h b/include/net/checksum.h index 7df472c..05a0d27 100644 --- a/include/net/checksum.h +++ b/include/net/checksum.h @@ -34,6 +34,12 @@ net_checksum_add(int len, uint8_t *buf) } static inline uint16_t +net_checksum_finish_nozero(uint32_t sum) +{ + return net_checksum_finish(sum) ?: 0xFFFF; +} + +static inline uint16_t net_raw_checksum(uint8_t *data, int length) { return net_checksum_finish(net_checksum_add(length, data)); -- cgit v1.1