netfilter: nf_tables: switch registers to 32 bit addressing

Switch the nf_tables registers from 128 bit addressing to 32 bit
addressing to support so called concatenations, where multiple values
can be concatenated over multiple registers for O(1) exact matches of
multiple dimensions using sets.

The old register values are mapped to areas of 128 bits for compatibility.
When dumping register numbers, values are expressed using the old values
if they refer to the beginning of a 128 bit area for compatibility.

To support concatenations, register loads of less than a full 32 bit
value need to be padded. This mainly affects the payload and exthdr
expressions, which both unconditionally zero the last word before
copying the data.

Userspace fully passes the testsuite using both old and new register
addressing.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 30 insertions, 1 deletions

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 05ee1e0804a3..4221a6c3a8a5 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -5,16 +5,45 @@
 #define NFT_CHAIN_MAXNAMELEN	32
 #define NFT_USERDATA_MAXLEN	256
 
+/**
+ * enum nft_registers - nf_tables registers
+ *
+ * nf_tables used to have five registers: a verdict register and four data
+ * registers of size 16. The data registers have been changed to 16 registers
+ * of size 4. For compatibility reasons, the NFT_REG_[1-4] registers still
+ * map to areas of size 16, the 4 byte registers are addressed using
+ * NFT_REG32_00 - NFT_REG32_15.
+ */
 enum nft_registers {
 	NFT_REG_VERDICT,
 	NFT_REG_1,
 	NFT_REG_2,
 	NFT_REG_3,
 	NFT_REG_4,
-	__NFT_REG_MAX
+	__NFT_REG_MAX,
+
+	NFT_REG32_00	= 8,
+	MFT_REG32_01,
+	NFT_REG32_02,
+	NFT_REG32_03,
+	NFT_REG32_04,
+	NFT_REG32_05,
+	NFT_REG32_06,
+	NFT_REG32_07,
+	NFT_REG32_08,
+	NFT_REG32_09,
+	NFT_REG32_10,
+	NFT_REG32_11,
+	NFT_REG32_12,
+	NFT_REG32_13,
+	NFT_REG32_14,
+	NFT_REG32_15,
 };
 #define NFT_REG_MAX	(__NFT_REG_MAX - 1)
 
+#define NFT_REG_SIZE	16
+#define NFT_REG32_SIZE	4
+
 /**
  * enum nft_verdicts - nf_tables internal verdicts
  *