netfilter: nf_tables: support optional userdata for set elements

Add an userdata set extension and allow the user to attach arbitrary
data to set elements. This is intended to hold TLV encoded data like
comments or DNS annotations that have no meaning to the kernel.

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

1 files changed, 34 insertions, 0 deletions

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 598e53eb64b3..0b96fa0d64b2 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2872,6 +2872,10 @@ const struct nft_set_ext_type nft_set_ext_types[] = {
                 .len    = sizeof(unsigned long),
                 .align  = __alignof__(unsigned long),
         },
+        [NFT_SET_EXT_USERDATA]          = {
+                .len    = sizeof(struct nft_userdata),
+                .align  = __alignof__(struct nft_userdata),
+        },
 };
 EXPORT_SYMBOL_GPL(nft_set_ext_types);
 
@@ -2884,6 +2888,8 @@ static const struct nla_policy nft_set_elem_policy[NFTA_SET_ELEM_MAX + 1] = {
         [NFTA_SET_ELEM_DATA]            = { .type = NLA_NESTED },
         [NFTA_SET_ELEM_FLAGS]           = { .type = NLA_U32 },
         [NFTA_SET_ELEM_TIMEOUT]         = { .type = NLA_U64 },
+        [NFTA_SET_ELEM_USERDATA]        = { .type = NLA_BINARY,
+                                            .len = NFT_USERDATA_MAXLEN },
 };
 
 static const struct nla_policy nft_set_elem_list_policy[NFTA_SET_ELEM_LIST_MAX + 1] = {
@@ -2964,6 +2970,15 @@ static int nf_tables_fill_setelem(struct sk_buff *skb,
                         goto nla_put_failure;
         }
 
+        if (nft_set_ext_exists(ext, NFT_SET_EXT_USERDATA)) {
+                struct nft_userdata *udata;
+
+                udata = nft_set_ext_userdata(ext);
+                if (nla_put(skb, NFTA_SET_ELEM_USERDATA,
+                            udata->len + 1, udata->data))
+                        goto nla_put_failure;
+        }
+
         nla_nest_end(skb, nest);
         return 0;
 
@@ -3232,11 +3247,13 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
         struct nft_set_ext *ext;
         struct nft_set_elem elem;
         struct nft_set_binding *binding;
+        struct nft_userdata *udata;
         struct nft_data data;
         enum nft_registers dreg;
         struct nft_trans *trans;
         u64 timeout;
         u32 flags;
+        u8 ulen;
         int err;
 
         err = nla_parse_nested(nla, NFTA_SET_ELEM_MAX, attr,
@@ -3325,6 +3342,18 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
                 nft_set_ext_add(&tmpl, NFT_SET_EXT_DATA);
         }
 
+        /* The full maximum length of userdata can exceed the maximum
+         * offset value (U8_MAX) for following extensions, therefor it
+         * must be the last extension added.
+         */
+        ulen = 0;
+        if (nla[NFTA_SET_ELEM_USERDATA] != NULL) {
+                ulen = nla_len(nla[NFTA_SET_ELEM_USERDATA]);
+                if (ulen > 0)
+                        nft_set_ext_add_length(&tmpl, NFT_SET_EXT_USERDATA,
+                                               ulen);
+        }
+
         err = -ENOMEM;
         elem.priv = nft_set_elem_init(set, &tmpl, &elem.key, &data,
                                       timeout, GFP_KERNEL);
@@ -3334,6 +3363,11 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
         ext = nft_set_elem_ext(set, elem.priv);
         if (flags)
                 *nft_set_ext_flags(ext) = flags;
+        if (ulen > 0) {
+                udata = nft_set_ext_userdata(ext);
+                udata->len = ulen - 1;
+                nla_memcpy(&udata->data, nla[NFTA_SET_ELEM_USERDATA], ulen);
+        }
 
         trans = nft_trans_elem_alloc(ctx, NFT_MSG_NEWSETELEM, set);
         if (trans == NULL)