[nf-next PATCH] netfilter: nf_tables: add support for inverted login in nft_lookup

[Arturo Borrero Gonzalez]

Introduce a new configuration option for this expression, which allows users
to invert the logic of set lookups.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.g...@gmail.com>
---
 include/uapi/linux/netfilter/nf_tables.h |    6 ++++++
 net/netfilter/nft_lookup.c               |   15 ++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/netfilter/nf_tables.h 
b/include/uapi/linux/netfilter/nf_tables.h
index 6a4dbe0..01751fa 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -546,6 +546,10 @@ enum nft_cmp_attributes {
 };
 #define NFTA_CMP_MAX           (__NFTA_CMP_MAX - 1)
 
+enum nft_lookup_flags {
+       NFT_LOOKUP_F_INV = (1 << 0),
+};
+
 /**
  * enum nft_lookup_attributes - nf_tables set lookup expression netlink 
attributes
  *
@@ -553,6 +557,7 @@ enum nft_cmp_attributes {
  * @NFTA_LOOKUP_SREG: source register of the data to look for (NLA_U32: 
nft_registers)
  * @NFTA_LOOKUP_DREG: destination register (NLA_U32: nft_registers)
  * @NFTA_LOOKUP_SET_ID: uniquely identifies a set in a transaction (NLA_U32)
+ * @NFTA_LOOKUP_FLAGS: flags (NLA_U32: enum nft_lookup_flags)
  */
 enum nft_lookup_attributes {
        NFTA_LOOKUP_UNSPEC,
@@ -560,6 +565,7 @@ enum nft_lookup_attributes {
        NFTA_LOOKUP_SREG,
        NFTA_LOOKUP_DREG,
        NFTA_LOOKUP_SET_ID,
+       NFTA_LOOKUP_FLAGS,
        __NFTA_LOOKUP_MAX
 };
 #define NFTA_LOOKUP_MAX                (__NFTA_LOOKUP_MAX - 1)
diff --git a/net/netfilter/nft_lookup.c b/net/netfilter/nft_lookup.c
index b3c31ef..4a9ee78 100644
--- a/net/netfilter/nft_lookup.c
+++ b/net/netfilter/nft_lookup.c
@@ -23,6 +23,7 @@ struct nft_lookup {
        enum nft_registers              sreg:8;
        enum nft_registers              dreg:8;
        struct nft_set_binding          binding;
+       bool                            invert;
 };
 
 static void nft_lookup_eval(const struct nft_expr *expr,
@@ -33,7 +34,8 @@ static void nft_lookup_eval(const struct nft_expr *expr,
        const struct nft_set *set = priv->set;
        const struct nft_set_ext *ext;
 
-       if (set->ops->lookup(set, &regs->data[priv->sreg], &ext)) {
+       if (set->ops->lookup(set, &regs->data[priv->sreg], &ext) ^
+           priv->invert) {
                if (set->flags & NFT_SET_MAP)
                        nft_data_copy(&regs->data[priv->dreg],
                                      nft_set_ext_data(ext), set->dlen);
@@ -47,6 +49,7 @@ static const struct nla_policy 
nft_lookup_policy[NFTA_LOOKUP_MAX + 1] = {
        [NFTA_LOOKUP_SET_ID]    = { .type = NLA_U32 },
        [NFTA_LOOKUP_SREG]      = { .type = NLA_U32 },
        [NFTA_LOOKUP_DREG]      = { .type = NLA_U32 },
+       [NFTA_LOOKUP_FLAGS]     = { .type = NLA_U32 },
 };
 
 static int nft_lookup_init(const struct nft_ctx *ctx,
@@ -55,6 +58,7 @@ static int nft_lookup_init(const struct nft_ctx *ctx,
 {
        struct nft_lookup *priv = nft_expr_priv(expr);
        struct nft_set *set;
+       u32 flags;
        int err;
 
        if (tb[NFTA_LOOKUP_SET] == NULL ||
@@ -91,6 +95,12 @@ static int nft_lookup_init(const struct nft_ctx *ctx,
        } else if (set->flags & NFT_SET_MAP)
                return -EINVAL;
 
+       if (tb[NFTA_LOOKUP_FLAGS]) {
+               flags = ntohl(nla_get_be32(tb[NFTA_LOOKUP_FLAGS]));
+               if (flags & NFT_LOOKUP_F_INV)
+                       priv->invert = true;
+       }
+
        priv->binding.flags = set->flags & NFT_SET_MAP;
 
        err = nf_tables_bind_set(ctx, set, &priv->binding);
@@ -112,6 +122,7 @@ static void nft_lookup_destroy(const struct nft_ctx *ctx,
 static int nft_lookup_dump(struct sk_buff *skb, const struct nft_expr *expr)
 {
        const struct nft_lookup *priv = nft_expr_priv(expr);
+       u32 flags = priv->invert ? NFT_LOOKUP_F_INV : 0;
 
        if (nla_put_string(skb, NFTA_LOOKUP_SET, priv->set->name))
                goto nla_put_failure;
@@ -120,6 +131,8 @@ static int nft_lookup_dump(struct sk_buff *skb, const 
struct nft_expr *expr)
        if (priv->set->flags & NFT_SET_MAP)
                if (nft_dump_register(skb, NFTA_LOOKUP_DREG, priv->dreg))
                        goto nla_put_failure;
+       if (nla_put_be32(skb, NFTA_LOOKUP_FLAGS, htonl(flags)))
+               goto nla_put_failure;
        return 0;
 
 nla_put_failure:

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