dbd2be0646
The dynset expression matches if we can fit a new entry into the set.
If there is no room for it, then it breaks the rule evaluation.
This patch introduces the inversion flag so you can add rules to
explicitly drop packets that don't fit into the set. For example:
# nft filter input flow table xyz size 4 { ip saddr timeout 120s counter } overflow drop
This is useful to provide a replacement for connlimit.
For the rule above, every new entry uses the IPv4 address as key in the
set, this entry gets a timeout of 120 seconds that gets refresh on every
packet seen. If we get new flow and our set already contains 4 entries
already, then this packet is dropped.
You can already express this in positive logic, assuming default policy
to drop:
# nft filter input flow table xyz size 4 { ip saddr timeout 10s counter } accept
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
289 lines
7.5 KiB
C
289 lines
7.5 KiB
C
/*
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* Copyright (c) 2015 Patrick McHardy <kaber@trash.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/netlink.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter/nf_tables.h>
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#include <net/netfilter/nf_tables.h>
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#include <net/netfilter/nf_tables_core.h>
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struct nft_dynset {
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struct nft_set *set;
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struct nft_set_ext_tmpl tmpl;
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enum nft_dynset_ops op:8;
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enum nft_registers sreg_key:8;
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enum nft_registers sreg_data:8;
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bool invert;
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u64 timeout;
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struct nft_expr *expr;
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struct nft_set_binding binding;
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};
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static void *nft_dynset_new(struct nft_set *set, const struct nft_expr *expr,
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struct nft_regs *regs)
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{
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const struct nft_dynset *priv = nft_expr_priv(expr);
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struct nft_set_ext *ext;
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u64 timeout;
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void *elem;
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if (set->size && !atomic_add_unless(&set->nelems, 1, set->size))
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return NULL;
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timeout = priv->timeout ? : set->timeout;
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elem = nft_set_elem_init(set, &priv->tmpl,
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®s->data[priv->sreg_key],
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®s->data[priv->sreg_data],
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timeout, GFP_ATOMIC);
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if (elem == NULL) {
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if (set->size)
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atomic_dec(&set->nelems);
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return NULL;
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}
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ext = nft_set_elem_ext(set, elem);
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if (priv->expr != NULL &&
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nft_expr_clone(nft_set_ext_expr(ext), priv->expr) < 0)
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return NULL;
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return elem;
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}
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static void nft_dynset_eval(const struct nft_expr *expr,
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struct nft_regs *regs,
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const struct nft_pktinfo *pkt)
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{
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const struct nft_dynset *priv = nft_expr_priv(expr);
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struct nft_set *set = priv->set;
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const struct nft_set_ext *ext;
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const struct nft_expr *sexpr;
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u64 timeout;
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if (set->ops->update(set, ®s->data[priv->sreg_key], nft_dynset_new,
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expr, regs, &ext)) {
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sexpr = NULL;
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if (nft_set_ext_exists(ext, NFT_SET_EXT_EXPR))
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sexpr = nft_set_ext_expr(ext);
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if (priv->op == NFT_DYNSET_OP_UPDATE &&
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nft_set_ext_exists(ext, NFT_SET_EXT_EXPIRATION)) {
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timeout = priv->timeout ? : set->timeout;
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*nft_set_ext_expiration(ext) = jiffies + timeout;
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} else if (sexpr == NULL)
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goto out;
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if (sexpr != NULL)
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sexpr->ops->eval(sexpr, regs, pkt);
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if (priv->invert)
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regs->verdict.code = NFT_BREAK;
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return;
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}
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out:
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if (!priv->invert)
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regs->verdict.code = NFT_BREAK;
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}
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static const struct nla_policy nft_dynset_policy[NFTA_DYNSET_MAX + 1] = {
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[NFTA_DYNSET_SET_NAME] = { .type = NLA_STRING },
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[NFTA_DYNSET_SET_ID] = { .type = NLA_U32 },
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[NFTA_DYNSET_OP] = { .type = NLA_U32 },
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[NFTA_DYNSET_SREG_KEY] = { .type = NLA_U32 },
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[NFTA_DYNSET_SREG_DATA] = { .type = NLA_U32 },
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[NFTA_DYNSET_TIMEOUT] = { .type = NLA_U64 },
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[NFTA_DYNSET_EXPR] = { .type = NLA_NESTED },
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[NFTA_DYNSET_FLAGS] = { .type = NLA_U32 },
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};
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static int nft_dynset_init(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nlattr * const tb[])
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{
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struct nft_dynset *priv = nft_expr_priv(expr);
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u8 genmask = nft_genmask_next(ctx->net);
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struct nft_set *set;
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u64 timeout;
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int err;
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if (tb[NFTA_DYNSET_SET_NAME] == NULL ||
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tb[NFTA_DYNSET_OP] == NULL ||
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tb[NFTA_DYNSET_SREG_KEY] == NULL)
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return -EINVAL;
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if (tb[NFTA_DYNSET_FLAGS]) {
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u32 flags = ntohl(nla_get_be32(tb[NFTA_DYNSET_FLAGS]));
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if (flags & ~NFT_DYNSET_F_INV)
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return -EINVAL;
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if (flags & NFT_DYNSET_F_INV)
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priv->invert = true;
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}
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set = nf_tables_set_lookup(ctx->table, tb[NFTA_DYNSET_SET_NAME],
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genmask);
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if (IS_ERR(set)) {
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if (tb[NFTA_DYNSET_SET_ID])
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set = nf_tables_set_lookup_byid(ctx->net,
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tb[NFTA_DYNSET_SET_ID],
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genmask);
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if (IS_ERR(set))
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return PTR_ERR(set);
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}
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if (set->flags & NFT_SET_CONSTANT)
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return -EBUSY;
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priv->op = ntohl(nla_get_be32(tb[NFTA_DYNSET_OP]));
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switch (priv->op) {
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case NFT_DYNSET_OP_ADD:
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break;
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case NFT_DYNSET_OP_UPDATE:
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if (!(set->flags & NFT_SET_TIMEOUT))
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return -EOPNOTSUPP;
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break;
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default:
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return -EOPNOTSUPP;
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}
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timeout = 0;
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if (tb[NFTA_DYNSET_TIMEOUT] != NULL) {
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if (!(set->flags & NFT_SET_TIMEOUT))
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return -EINVAL;
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timeout = be64_to_cpu(nla_get_be64(tb[NFTA_DYNSET_TIMEOUT]));
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}
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priv->sreg_key = nft_parse_register(tb[NFTA_DYNSET_SREG_KEY]);
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err = nft_validate_register_load(priv->sreg_key, set->klen);;
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if (err < 0)
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return err;
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if (tb[NFTA_DYNSET_SREG_DATA] != NULL) {
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if (!(set->flags & NFT_SET_MAP))
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return -EINVAL;
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if (set->dtype == NFT_DATA_VERDICT)
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return -EOPNOTSUPP;
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priv->sreg_data = nft_parse_register(tb[NFTA_DYNSET_SREG_DATA]);
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err = nft_validate_register_load(priv->sreg_data, set->dlen);
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if (err < 0)
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return err;
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} else if (set->flags & NFT_SET_MAP)
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return -EINVAL;
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if (tb[NFTA_DYNSET_EXPR] != NULL) {
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if (!(set->flags & NFT_SET_EVAL))
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return -EINVAL;
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if (!(set->flags & NFT_SET_ANONYMOUS))
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return -EOPNOTSUPP;
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priv->expr = nft_expr_init(ctx, tb[NFTA_DYNSET_EXPR]);
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if (IS_ERR(priv->expr))
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return PTR_ERR(priv->expr);
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err = -EOPNOTSUPP;
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if (!(priv->expr->ops->type->flags & NFT_EXPR_STATEFUL))
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goto err1;
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} else if (set->flags & NFT_SET_EVAL)
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return -EINVAL;
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nft_set_ext_prepare(&priv->tmpl);
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nft_set_ext_add_length(&priv->tmpl, NFT_SET_EXT_KEY, set->klen);
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if (set->flags & NFT_SET_MAP)
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nft_set_ext_add_length(&priv->tmpl, NFT_SET_EXT_DATA, set->dlen);
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if (priv->expr != NULL)
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nft_set_ext_add_length(&priv->tmpl, NFT_SET_EXT_EXPR,
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priv->expr->ops->size);
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if (set->flags & NFT_SET_TIMEOUT) {
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if (timeout || set->timeout)
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nft_set_ext_add(&priv->tmpl, NFT_SET_EXT_EXPIRATION);
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}
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priv->timeout = timeout;
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err = nf_tables_bind_set(ctx, set, &priv->binding);
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if (err < 0)
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goto err1;
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priv->set = set;
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return 0;
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err1:
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if (priv->expr != NULL)
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nft_expr_destroy(ctx, priv->expr);
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return err;
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}
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static void nft_dynset_destroy(const struct nft_ctx *ctx,
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const struct nft_expr *expr)
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{
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struct nft_dynset *priv = nft_expr_priv(expr);
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nf_tables_unbind_set(ctx, priv->set, &priv->binding);
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if (priv->expr != NULL)
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nft_expr_destroy(ctx, priv->expr);
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}
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static int nft_dynset_dump(struct sk_buff *skb, const struct nft_expr *expr)
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{
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const struct nft_dynset *priv = nft_expr_priv(expr);
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u32 flags = priv->invert ? NFT_DYNSET_F_INV : 0;
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if (nft_dump_register(skb, NFTA_DYNSET_SREG_KEY, priv->sreg_key))
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goto nla_put_failure;
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if (priv->set->flags & NFT_SET_MAP &&
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nft_dump_register(skb, NFTA_DYNSET_SREG_DATA, priv->sreg_data))
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goto nla_put_failure;
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if (nla_put_be32(skb, NFTA_DYNSET_OP, htonl(priv->op)))
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goto nla_put_failure;
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if (nla_put_string(skb, NFTA_DYNSET_SET_NAME, priv->set->name))
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goto nla_put_failure;
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if (nla_put_be64(skb, NFTA_DYNSET_TIMEOUT, cpu_to_be64(priv->timeout),
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NFTA_DYNSET_PAD))
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goto nla_put_failure;
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if (priv->expr && nft_expr_dump(skb, NFTA_DYNSET_EXPR, priv->expr))
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goto nla_put_failure;
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if (nla_put_be32(skb, NFTA_DYNSET_FLAGS, htonl(flags)))
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goto nla_put_failure;
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return 0;
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nla_put_failure:
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return -1;
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}
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static struct nft_expr_type nft_dynset_type;
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static const struct nft_expr_ops nft_dynset_ops = {
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.type = &nft_dynset_type,
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.size = NFT_EXPR_SIZE(sizeof(struct nft_dynset)),
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.eval = nft_dynset_eval,
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.init = nft_dynset_init,
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.destroy = nft_dynset_destroy,
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.dump = nft_dynset_dump,
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};
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static struct nft_expr_type nft_dynset_type __read_mostly = {
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.name = "dynset",
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.ops = &nft_dynset_ops,
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.policy = nft_dynset_policy,
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.maxattr = NFTA_DYNSET_MAX,
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.owner = THIS_MODULE,
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};
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int __init nft_dynset_module_init(void)
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{
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return nft_register_expr(&nft_dynset_type);
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}
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void nft_dynset_module_exit(void)
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{
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nft_unregister_expr(&nft_dynset_type);
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}
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