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authorEd Swierk <eswierk@skyportsystems.com>2017-11-16 06:06:06 -0800
committerJason Wang <jasowang@redhat.com>2017-11-20 11:08:00 +0800
commit0dacea92d26c31d453c58de2e99c178fee554166 (patch)
tree5b8fd0c05385e02a586fbc136808821e603ea14f /include/net
parentebc2327f0793deed845e2f7aeddf43b367c5c71c (diff)
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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 <eswierk@skyportsystems.com> Signed-off-by: Jason Wang <jasowang@redhat.com>
Diffstat (limited to 'include/net')
-rw-r--r--include/net/checksum.h6
1 files changed, 6 insertions, 0 deletions
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));