netfilter: nf_tables: Implement fast bitwise expression

A typical use of bitwise expression is to mask out parts of an IP
address when matching on the network part only. Optimize for this common
use with a fast variant for NFT_BITWISE_BOOL-type expressions operating
on 32bit-sized values.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/net/netfilter/nf_tables_core.h b/include/net/netfilter/nf_tables_core.h
index df2d91c814cb35798ec64b2e928e417bdf32ad88..8657e6815b07c5708d66b897cb6db0aa00039a47 100644 (file)
--- a/include/net/netfilter/nf_tables_core.h
+++ b/include/net/netfilter/nf_tables_core.h
@@ -23,6 +23,13 @@ extern struct nft_object_type nft_secmark_obj_type;
 int nf_tables_core_module_init(void);
 void nf_tables_core_module_exit(void);
 
+struct nft_bitwise_fast_expr {
+       u32                     mask;
+       u32                     xor;
+       enum nft_registers      sreg:8;
+       enum nft_registers      dreg:8;
+};
+
 struct nft_cmp_fast_expr {
        u32                     data;
        u32                     mask;
@@ -68,6 +75,8 @@ struct nft_payload_set {
 
 extern const struct nft_expr_ops nft_payload_fast_ops;
 
+extern const struct nft_expr_ops nft_bitwise_fast_ops;
+
 extern struct static_key_false nft_counters_enabled;
 extern struct static_key_false nft_trace_enabled;
 

diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
index e92feacaf55167b75573a2cdc8b53c0f8207c6bd..dbc2e945c98ebce86dd498a093cd693d28030d79 100644 (file)
--- a/net/netfilter/nf_tables_core.c
+++ b/net/netfilter/nf_tables_core.c
@@ -47,6 +47,16 @@ static inline void nft_trace_packet(struct nft_traceinfo *info,
        }
 }
 
+static void nft_bitwise_fast_eval(const struct nft_expr *expr,
+                                 struct nft_regs *regs)
+{
+       const struct nft_bitwise_fast_expr *priv = nft_expr_priv(expr);
+       u32 *src = &regs->data[priv->sreg];
+       u32 *dst = &regs->data[priv->dreg];
+
+       *dst = (*src & priv->mask) ^ priv->xor;
+}
+
 static void nft_cmp_fast_eval(const struct nft_expr *expr,
                              struct nft_regs *regs)
 {
@@ -175,6 +185,8 @@ next_rule:
                nft_rule_for_each_expr(expr, last, rule) {
                        if (expr->ops == &nft_cmp_fast_ops)
                                nft_cmp_fast_eval(expr, &regs);
+                       else if (expr->ops == &nft_bitwise_fast_ops)
+                               nft_bitwise_fast_eval(expr, &regs);
                        else if (expr->ops != &nft_payload_fast_ops ||
                                 !nft_payload_fast_eval(expr, &regs, pkt))
                                expr_call_ops_eval(expr, &regs, pkt);

diff --git a/net/netfilter/nft_bitwise.c b/net/netfilter/nft_bitwise.c
index bc37d6c59db451f98b6756ed745e54e9981a2c75..bbd773d74377350aec367573fe22e1b7267e27e4 100644 (file)
--- a/net/netfilter/nft_bitwise.c
+++ b/net/netfilter/nft_bitwise.c
@@ -163,11 +163,6 @@ static int nft_bitwise_init(const struct nft_ctx *ctx,
        u32 len;
        int err;
 
-       if (!tb[NFTA_BITWISE_SREG] ||
-           !tb[NFTA_BITWISE_DREG] ||
-           !tb[NFTA_BITWISE_LEN])
-               return -EINVAL;
-
        err = nft_parse_u32_check(tb[NFTA_BITWISE_LEN], U8_MAX, &len);
        if (err < 0)
                return err;
@@ -292,9 +287,143 @@ static const struct nft_expr_ops nft_bitwise_ops = {
        .offload        = nft_bitwise_offload,
 };
 
+static int
+nft_bitwise_extract_u32_data(const struct nlattr * const tb, u32 *out)
+{
+       struct nft_data_desc desc;
+       struct nft_data data;
+       int err = 0;
+
+       err = nft_data_init(NULL, &data, sizeof(data), &desc, tb);
+       if (err < 0)
+               return err;
+
+       if (desc.type != NFT_DATA_VALUE || desc.len != sizeof(u32)) {
+               err = -EINVAL;
+               goto err;
+       }
+       *out = data.data[0];
+err:
+       nft_data_release(&data, desc.type);
+       return err;
+}
+
+static int nft_bitwise_fast_init(const struct nft_ctx *ctx,
+                                const struct nft_expr *expr,
+                                const struct nlattr * const tb[])
+{
+       struct nft_bitwise_fast_expr *priv = nft_expr_priv(expr);
+       int err;
+
+       priv->sreg = nft_parse_register(tb[NFTA_BITWISE_SREG]);
+       err = nft_validate_register_load(priv->sreg, sizeof(u32));
+       if (err < 0)
+               return err;
+
+       priv->dreg = nft_parse_register(tb[NFTA_BITWISE_DREG]);
+       err = nft_validate_register_store(ctx, priv->dreg, NULL,
+                                         NFT_DATA_VALUE, sizeof(u32));
+       if (err < 0)
+               return err;
+
+       if (tb[NFTA_BITWISE_DATA])
+               return -EINVAL;
+
+       if (!tb[NFTA_BITWISE_MASK] ||
+           !tb[NFTA_BITWISE_XOR])
+               return -EINVAL;
+
+       err = nft_bitwise_extract_u32_data(tb[NFTA_BITWISE_MASK], &priv->mask);
+       if (err < 0)
+               return err;
+
+       err = nft_bitwise_extract_u32_data(tb[NFTA_BITWISE_XOR], &priv->xor);
+       if (err < 0)
+               return err;
+
+       return 0;
+}
+
+static int
+nft_bitwise_fast_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+       const struct nft_bitwise_fast_expr *priv = nft_expr_priv(expr);
+       struct nft_data data;
+
+       if (nft_dump_register(skb, NFTA_BITWISE_SREG, priv->sreg))
+               return -1;
+       if (nft_dump_register(skb, NFTA_BITWISE_DREG, priv->dreg))
+               return -1;
+       if (nla_put_be32(skb, NFTA_BITWISE_LEN, htonl(sizeof(u32))))
+               return -1;
+       if (nla_put_be32(skb, NFTA_BITWISE_OP, htonl(NFT_BITWISE_BOOL)))
+               return -1;
+
+       data.data[0] = priv->mask;
+       if (nft_data_dump(skb, NFTA_BITWISE_MASK, &data,
+                         NFT_DATA_VALUE, sizeof(u32)) < 0)
+               return -1;
+
+       data.data[0] = priv->xor;
+       if (nft_data_dump(skb, NFTA_BITWISE_XOR, &data,
+                         NFT_DATA_VALUE, sizeof(u32)) < 0)
+               return -1;
+
+       return 0;
+}
+
+static int nft_bitwise_fast_offload(struct nft_offload_ctx *ctx,
+                                   struct nft_flow_rule *flow,
+                                   const struct nft_expr *expr)
+{
+       const struct nft_bitwise_fast_expr *priv = nft_expr_priv(expr);
+       struct nft_offload_reg *reg = &ctx->regs[priv->dreg];
+
+       if (priv->xor || priv->sreg != priv->dreg || reg->len != sizeof(u32))
+               return -EOPNOTSUPP;
+
+       reg->mask.data[0] = priv->mask;
+       return 0;
+}
+
+const struct nft_expr_ops nft_bitwise_fast_ops = {
+       .type           = &nft_bitwise_type,
+       .size           = NFT_EXPR_SIZE(sizeof(struct nft_bitwise_fast_expr)),
+       .eval           = NULL, /* inlined */
+       .init           = nft_bitwise_fast_init,
+       .dump           = nft_bitwise_fast_dump,
+       .offload        = nft_bitwise_fast_offload,
+};
+
+static const struct nft_expr_ops *
+nft_bitwise_select_ops(const struct nft_ctx *ctx,
+                      const struct nlattr * const tb[])
+{
+       int err;
+       u32 len;
+
+       if (!tb[NFTA_BITWISE_LEN] ||
+           !tb[NFTA_BITWISE_SREG] ||
+           !tb[NFTA_BITWISE_DREG])
+               return ERR_PTR(-EINVAL);
+
+       err = nft_parse_u32_check(tb[NFTA_BITWISE_LEN], U8_MAX, &len);
+       if (err < 0)
+               return ERR_PTR(err);
+
+       if (len != sizeof(u32))
+               return &nft_bitwise_ops;
+
+       if (tb[NFTA_BITWISE_OP] &&
+           ntohl(nla_get_be32(tb[NFTA_BITWISE_OP])) != NFT_BITWISE_BOOL)
+               return &nft_bitwise_ops;
+
+       return &nft_bitwise_fast_ops;
+}
+
 struct nft_expr_type nft_bitwise_type __read_mostly = {
        .name           = "bitwise",
-       .ops            = &nft_bitwise_ops,
+       .select_ops     = nft_bitwise_select_ops,
        .policy         = nft_bitwise_policy,
        .maxattr        = NFTA_BITWISE_MAX,
        .owner          = THIS_MODULE,