netfilter: nf_tables: add optional user data area to rules
This allows us to store user comment strings, but it could be also
used to store any kind of information that the user application needs
to link to the rule.
Scratch 8 bits for the new ulen field that indicates the length the
user data area. 4 bits from the handle (so it's 42 bits long, according
to Patrick, it would last 139 years with 1000 new rules per second)
and 4 bits from dlen (so the expression data area is 4K, which seems
sufficient by now even considering the compatibility layer).
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 0b56340..f25d011 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1295,6 +1295,8 @@
[NFTA_RULE_EXPRESSIONS] = { .type = NLA_NESTED },
[NFTA_RULE_COMPAT] = { .type = NLA_NESTED },
[NFTA_RULE_POSITION] = { .type = NLA_U64 },
+ [NFTA_RULE_USERDATA] = { .type = NLA_BINARY,
+ .len = NFT_USERDATA_MAXLEN },
};
static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
@@ -1347,6 +1349,10 @@
}
nla_nest_end(skb, list);
+ if (rule->ulen &&
+ nla_put(skb, NFTA_RULE_USERDATA, rule->ulen, nft_userdata(rule)))
+ goto nla_put_failure;
+
return nlmsg_end(skb, nlh);
nla_put_failure:
@@ -1583,7 +1589,7 @@
struct nft_expr *expr;
struct nft_ctx ctx;
struct nlattr *tmp;
- unsigned int size, i, n;
+ unsigned int size, i, n, ulen = 0;
int err, rem;
bool create;
u64 handle, pos_handle;
@@ -1649,8 +1655,11 @@
}
}
+ if (nla[NFTA_RULE_USERDATA])
+ ulen = nla_len(nla[NFTA_RULE_USERDATA]);
+
err = -ENOMEM;
- rule = kzalloc(sizeof(*rule) + size, GFP_KERNEL);
+ rule = kzalloc(sizeof(*rule) + size + ulen, GFP_KERNEL);
if (rule == NULL)
goto err1;
@@ -1658,6 +1667,10 @@
rule->handle = handle;
rule->dlen = size;
+ rule->ulen = ulen;
+
+ if (ulen)
+ nla_memcpy(nft_userdata(rule), nla[NFTA_RULE_USERDATA], ulen);
expr = nft_expr_first(rule);
for (i = 0; i < n; i++) {