netfilter: nf_tables: add range expression

Inverse ranges != [a,b] are not currently possible because rules are
composites of && operations, and we need to express this:

	data < a || data > b

This patch adds a new range expression. Positive ranges can be already
through two cmp expressions:

	cmp(sreg, data, >=)
	cmp(sreg, data, <=)

This new range expression provides an alternative way to express this.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 146 insertions, 2 deletions

diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 0c8581100ac6..c23c3c84416f 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -71,8 +71,9 @@ obj-$(CONFIG_NF_DUP_NETDEV)	+= nf_dup_netdev.o
 
 # nf_tables
 nf_tables-objs += nf_tables_core.o nf_tables_api.o nf_tables_trace.o
-nf_tables-objs += nft_immediate.o nft_cmp.o nft_lookup.o nft_dynset.o
+nf_tables-objs += nft_immediate.o nft_cmp.o nft_range.o
 nf_tables-objs += nft_bitwise.o nft_byteorder.o nft_payload.o
+nf_tables-objs += nft_lookup.o nft_dynset.o
 
 obj-$(CONFIG_NF_TABLES)         += nf_tables.o
 obj-$(CONFIG_NF_TABLES_INET)    += nf_tables_inet.o
diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
index 67259cefef06..7c94ce0080d5 100644
--- a/net/netfilter/nf_tables_core.c
+++ b/net/netfilter/nf_tables_core.c
@@ -263,8 +263,13 @@ int __init nf_tables_core_module_init(void)
         if (err < 0)
                 goto err7;
 
-        return 0;
+        err = nft_range_module_init();
+        if (err < 0)
+                goto err8;
 
+        return 0;
+err8:
+        nft_dynset_module_exit();
 err7:
         nft_payload_module_exit();
 err6:
diff --git a/net/netfilter/nft_range.c b/net/netfilter/nft_range.c
new file mode 100644
index 000000000000..c6d5358482d1
--- /dev/null
+++ b/net/netfilter/nft_range.c
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2016 Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/netlink.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables_core.h>
+#include <net/netfilter/nf_tables.h>
+
+struct nft_range_expr {
+        struct nft_data         data_from;
+        struct nft_data         data_to;
+        enum nft_registers      sreg:8;
+        u8                      len;
+        enum nft_range_ops      op:8;
+};
+
+static void nft_range_eval(const struct nft_expr *expr,
+                         struct nft_regs *regs,
+                         const struct nft_pktinfo *pkt)
+{
+        const struct nft_range_expr *priv = nft_expr_priv(expr);
+        bool mismatch;
+        int d1, d2;
+
+        d1 = memcmp(&regs->data[priv->sreg], &priv->data_from, priv->len);
+        d2 = memcmp(&regs->data[priv->sreg], &priv->data_to, priv->len);
+        switch (priv->op) {
+        case NFT_RANGE_EQ:
+                mismatch = (d1 < 0 || d2 > 0);
+                break;
+        case NFT_RANGE_NEQ:
+                mismatch = (d1 >= 0 && d2 <= 0);
+                break;
+        }
+
+        if (mismatch)
+                regs->verdict.code = NFT_BREAK;
+}
+
+static const struct nla_policy nft_range_policy[NFTA_RANGE_MAX + 1] = {
+        [NFTA_RANGE_SREG]               = { .type = NLA_U32 },
+        [NFTA_RANGE_OP]                 = { .type = NLA_U32 },
+        [NFTA_RANGE_FROM_DATA]          = { .type = NLA_NESTED },
+        [NFTA_RANGE_TO_DATA]            = { .type = NLA_NESTED },
+};
+
+static int nft_range_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
+                        const struct nlattr * const tb[])
+{
+        struct nft_range_expr *priv = nft_expr_priv(expr);
+        struct nft_data_desc desc_from, desc_to;
+        int err;
+
+        err = nft_data_init(NULL, &priv->data_from, sizeof(priv->data_from),
+                            &desc_from, tb[NFTA_RANGE_FROM_DATA]);
+        if (err < 0)
+                return err;
+
+        err = nft_data_init(NULL, &priv->data_to, sizeof(priv->data_to),
+                            &desc_to, tb[NFTA_RANGE_TO_DATA]);
+        if (err < 0)
+                goto err1;
+
+        if (desc_from.len != desc_to.len) {
+                err = -EINVAL;
+                goto err2;
+        }
+
+        priv->sreg = nft_parse_register(tb[NFTA_RANGE_SREG]);
+        err = nft_validate_register_load(priv->sreg, desc_from.len);
+        if (err < 0)
+                goto err2;
+
+        priv->op  = ntohl(nla_get_be32(tb[NFTA_RANGE_OP]));
+        priv->len = desc_from.len;
+        return 0;
+err2:
+        nft_data_uninit(&priv->data_to, desc_to.type);
+err1:
+        nft_data_uninit(&priv->data_from, desc_from.type);
+        return err;
+}
+
+static int nft_range_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+        const struct nft_range_expr *priv = nft_expr_priv(expr);
+
+        if (nft_dump_register(skb, NFTA_RANGE_SREG, priv->sreg))
+                goto nla_put_failure;
+        if (nla_put_be32(skb, NFTA_RANGE_OP, htonl(priv->op)))
+                goto nla_put_failure;
+
+        if (nft_data_dump(skb, NFTA_RANGE_FROM_DATA, &priv->data_from,
+                          NFT_DATA_VALUE, priv->len) < 0 ||
+            nft_data_dump(skb, NFTA_RANGE_TO_DATA, &priv->data_to,
+                          NFT_DATA_VALUE, priv->len) < 0)
+                goto nla_put_failure;
+        return 0;
+
+nla_put_failure:
+        return -1;
+}
+
+static struct nft_expr_type nft_range_type;
+static const struct nft_expr_ops nft_range_ops = {
+        .type           = &nft_range_type,
+        .size           = NFT_EXPR_SIZE(sizeof(struct nft_range_expr)),
+        .eval           = nft_range_eval,
+        .init           = nft_range_init,
+        .dump           = nft_range_dump,
+};
+
+static struct nft_expr_type nft_range_type __read_mostly = {
+        .name           = "range",
+        .ops            = &nft_range_ops,
+        .policy         = nft_range_policy,
+        .maxattr        = NFTA_RANGE_MAX,
+        .owner          = THIS_MODULE,
+};
+
+int __init nft_range_module_init(void)
+{
+        return nft_register_expr(&nft_range_type);
+}
+
+void nft_range_module_exit(void)
+{
+        nft_unregister_expr(&nft_range_type);
+}