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authorJeremy Sowden <jeremy@azazel.net>2020-01-19 10:58:01 +0000
committerPablo Neira Ayuso <pablo@netfilter.org>2020-01-22 23:06:56 +0100
commitf833cb3c9ce4174671eb2c55d458221b4c00dd48 (patch)
treebe199f6050d709450bd2f3a888ae8bf1eb7d53dc
parent844ee4cebf45d326890ddbd3d1d124f4fc9b80ad (diff)
include: nf_tables: correct bitwise header comment.HEADmaster
The comment documenting how bitwise expressions work includes a table which summarizes the mask and xor arguments combined to express the supported boolean operations. However, the row for OR: mask xor 0 x is incorrect. dreg = (sreg & 0) ^ x is not equivalent to: dreg = sreg | x What the code actually does is: dreg = (sreg & ~x) ^ x Update the documentation to match. Signed-off-by: Jeremy Sowden <jeremy@azazel.net> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
-rw-r--r--include/linux/netfilter/nf_tables.h7
1 files changed, 4 insertions, 3 deletions
diff --git a/include/linux/netfilter/nf_tables.h b/include/linux/netfilter/nf_tables.h
index c556ccd3..42ed5ca3 100644
--- a/include/linux/netfilter/nf_tables.h
+++ b/include/linux/netfilter/nf_tables.h
@@ -491,15 +491,16 @@ enum nft_immediate_attributes {
* @NFTA_BITWISE_MASK: mask value (NLA_NESTED: nft_data_attributes)
* @NFTA_BITWISE_XOR: xor value (NLA_NESTED: nft_data_attributes)
*
- * The bitwise expression performs the following operation:
+ * The bitwise expression supports boolean and shift operations. It implements
+ * the boolean operations by performing the following operation:
*
* dreg = (sreg & mask) ^ xor
*
- * which allow to express all bitwise operations:
+ * with these mask and xor values:
*
* mask xor
* NOT: 1 1
- * OR: 0 x
+ * OR: ~x x
* XOR: 1 x
* AND: x 0
*/