src: allow binop expressions with variable right-hand operands

Hitherto, the kernel has required constant values for the `xor` and
`mask` attributes of boolean bitwise expressions.  This has meant that
the right-hand operand of a boolean binop must be constant.  Now the
kernel has support for AND, OR and XOR operations with right-hand
operands passed via registers, we can relax this restriction.  Allow
non-constant right-hand operands if the left-hand operand is not
constant, e.g.:

  ct mark & 0xffff0000 | meta mark & 0xffff

The kernel now supports performing AND, OR and XOR operations directly,
on one register and an immediate value or on two registers, so we need
to be able to generate and parse bitwise boolean expressions of this
form.

If a boolean operation has a constant RHS, we continue to send a
mask-and-xor expression to the kernel.

Add tests for {ct,meta} mark with variable RHS operands.

JSON support is also included.

This requires Linux kernel >= 6.13-rc.

[ Originally posted as patch 1/8 and 6/8 which has been collapsed and
  simplified to focus on initial {ct,meta} mark support. Tests have
  been extracted from 8/8 including a tests/py fix to payload output
  due to incorrect output in original patchset. JSON support has been
  extracted from patch 7/8 --pablo]

Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 16 insertions, 3 deletions

diff --git a/include/linux/netfilter/nf_tables.h b/include/linux/netfilter/nf_tables.h
index c62e6ac5..f57963e8 100644
--- a/include/linux/netfilter/nf_tables.h
+++ b/include/linux/netfilter/nf_tables.h
@@ -557,16 +557,27 @@ enum nft_immediate_attributes {
 /**
  * enum nft_bitwise_ops - nf_tables bitwise operations
  *
- * @NFT_BITWISE_BOOL: mask-and-xor operation used to implement NOT, AND, OR and
- *                    XOR boolean operations
+ * @NFT_BITWISE_MASK_XOR: mask-and-xor operation used to implement NOT, AND, OR
+ *                        and XOR boolean operations
  * @NFT_BITWISE_LSHIFT: left-shift operation
  * @NFT_BITWISE_RSHIFT: right-shift operation
+ * @NFT_BITWISE_AND: and operation
+ * @NFT_BITWISE_OR: or operation
+ * @NFT_BITWISE_XOR: xor operation
  */
 enum nft_bitwise_ops {
-	NFT_BITWISE_BOOL,
+	NFT_BITWISE_MASK_XOR,
 	NFT_BITWISE_LSHIFT,
 	NFT_BITWISE_RSHIFT,
+	NFT_BITWISE_AND,
+	NFT_BITWISE_OR,
+	NFT_BITWISE_XOR,
 };
+/*
+ * Old name for NFT_BITWISE_MASK_XOR, predating the addition of NFT_BITWISE_AND,
+ * NFT_BITWISE_OR and NFT_BITWISE_XOR.  Retained for backwards-compatibility.
+ */
+#define NFT_BITWISE_BOOL NFT_BITWISE_MASK_XOR
 
 /**
  * enum nft_bitwise_attributes - nf_tables bitwise expression netlink attributes
@@ -579,6 +590,7 @@ enum nft_bitwise_ops {
  * @NFTA_BITWISE_OP: type of operation (NLA_U32: nft_bitwise_ops)
  * @NFTA_BITWISE_DATA: argument for non-boolean operations
  *                     (NLA_NESTED: nft_data_attributes)
+ * @NFTA_BITWISE_SREG2: second source register (NLA_U32: nft_registers)
  *
  * The bitwise expression supports boolean and shift operations.  It implements
  * the boolean operations by performing the following operation:
@@ -602,6 +614,7 @@ enum nft_bitwise_attributes {
 	NFTA_BITWISE_XOR,
 	NFTA_BITWISE_OP,
 	NFTA_BITWISE_DATA,
+	NFTA_BITWISE_SREG2,
 	__NFTA_BITWISE_MAX
 };
 #define NFTA_BITWISE_MAX	(__NFTA_BITWISE_MAX - 1)