netfilter: add nftables

This patch adds nftables which is the intended successor of iptables.
This packet filtering framework reuses the existing netfilter hooks,
the connection tracking system, the NAT subsystem, the transparent
proxying engine, the logging infrastructure and the userspace packet
queueing facilities.

In a nutshell, nftables provides a pseudo-state machine with 4 general
purpose registers of 128 bits and 1 specific purpose register to store
verdicts. This pseudo-machine comes with an extensible instruction set,
a.k.a. "expressions" in the nftables jargon. The expressions included
in this patch provide the basic functionality, they are:

* bitwise: to perform bitwise operations.
* byteorder: to change from host/network endianess.
* cmp: to compare data with the content of the registers.
* counter: to enable counters on rules.
* ct: to store conntrack keys into register.
* exthdr: to match IPv6 extension headers.
* immediate: to load data into registers.
* limit: to limit matching based on packet rate.
* log: to log packets.
* meta: to match metainformation that usually comes with the skbuff.
* nat: to perform Network Address Translation.
* payload: to fetch data from the packet payload and store it into
  registers.
* reject (IPv4 only): to explicitly close connection, eg. TCP RST.

Using this instruction-set, the userspace utility 'nft' can transform
the rules expressed in human-readable text representation (using a
new syntax, inspired by tcpdump) to nftables bytecode.

nftables also inherits the table, chain and rule objects from
iptables, but in a more configurable way, and it also includes the
original datatype-agnostic set infrastructure with mapping support.
This set infrastructure is enhanced in the follow up patch (netfilter:
nf_tables: add netlink set API).

This patch includes the following components:

* the netlink API: net/netfilter/nf_tables_api.c and
  include/uapi/netfilter/nf_tables.h
* the packet filter core: net/netfilter/nf_tables_core.c
* the expressions (described above): net/netfilter/nft_*.c
* the filter tables: arp, IPv4, IPv6 and bridge:
  net/ipv4/netfilter/nf_tables_ipv4.c
  net/ipv6/netfilter/nf_tables_ipv6.c
  net/ipv4/netfilter/nf_tables_arp.c
  net/bridge/netfilter/nf_tables_bridge.c
* the NAT table (IPv4 only):
  net/ipv4/netfilter/nf_table_nat_ipv4.c
* the route table (similar to mangle):
  net/ipv4/netfilter/nf_table_route_ipv4.c
  net/ipv6/netfilter/nf_table_route_ipv6.c
* internal definitions under:
  include/net/netfilter/nf_tables.h
  include/net/netfilter/nf_tables_core.h
* It also includes an skeleton expression:
  net/netfilter/nft_expr_template.c
  and the preliminary implementation of the meta target
  net/netfilter/nft_meta_target.c

It also includes a change in struct nf_hook_ops to add a new
pointer to store private data to the hook, that is used to store
the rule list per chain.

This patch is based on the patch from Patrick McHardy, plus merged
accumulated cleanups, fixes and small enhancements to the nftables
code that has been done since 2009, which are:

From Patrick McHardy:
* nf_tables: adjust netlink handler function signatures
* nf_tables: only retry table lookup after successful table module load
* nf_tables: fix event notification echo and avoid unnecessary messages
* nft_ct: add l3proto support
* nf_tables: pass expression context to nft_validate_data_load()
* nf_tables: remove redundant definition
* nft_ct: fix maxattr initialization
* nf_tables: fix invalid event type in nf_tables_getrule()
* nf_tables: simplify nft_data_init() usage
* nf_tables: build in more core modules
* nf_tables: fix double lookup expression unregistation
* nf_tables: move expression initialization to nf_tables_core.c
* nf_tables: build in payload module
* nf_tables: use NFPROTO constants
* nf_tables: rename pid variables to portid
* nf_tables: save 48 bits per rule
* nf_tables: introduce chain rename
* nf_tables: check for duplicate names on chain rename
* nf_tables: remove ability to specify handles for new rules
* nf_tables: return error for rule change request
* nf_tables: return error for NLM_F_REPLACE without rule handle
* nf_tables: include NLM_F_APPEND/NLM_F_REPLACE flags in rule notification
* nf_tables: fix NLM_F_MULTI usage in netlink notifications
* nf_tables: include NLM_F_APPEND in rule dumps

From Pablo Neira Ayuso:
* nf_tables: fix stack overflow in nf_tables_newrule
* nf_tables: nft_ct: fix compilation warning
* nf_tables: nft_ct: fix crash with invalid packets
* nft_log: group and qthreshold are 2^16
* nf_tables: nft_meta: fix socket uid,gid handling
* nft_counter: allow to restore counters
* nf_tables: fix module autoload
* nf_tables: allow to remove all rules placed in one chain
* nf_tables: use 64-bits rule handle instead of 16-bits
* nf_tables: fix chain after rule deletion
* nf_tables: improve deletion performance
* nf_tables: add missing code in route chain type
* nf_tables: rise maximum number of expressions from 12 to 128
* nf_tables: don't delete table if in use
* nf_tables: fix basechain release

From Tomasz Bursztyka:
* nf_tables: Add support for changing users chain's name
* nf_tables: Change chain's name to be fixed sized
* nf_tables: Add support for replacing a rule by another one
* nf_tables: Update uapi nftables netlink header documentation

From Florian Westphal:
* nft_log: group is u16, snaplen u32

From Phil Oester:
* nf_tables: operational limit match

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

1 files changed, 252 insertions, 0 deletions

diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
new file mode 100644
index 000000000000..a1756d678226
--- /dev/null
+++ b/net/netfilter/nft_ct.c
@@ -0,0 +1,252 @@
+/*
+ * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
+ *
+ * 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.
+ *
+ * Development of this code funded by Astaro AG (http://www.astaro.com/)
+ */
+
+#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.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_tuple.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+
+struct nft_ct {
+	enum nft_ct_keys	key:8;
+	enum ip_conntrack_dir	dir:8;
+	enum nft_registers	dreg:8;
+	uint8_t			family;
+};
+
+static void nft_ct_eval(const struct nft_expr *expr,
+			struct nft_data data[NFT_REG_MAX + 1],
+			const struct nft_pktinfo *pkt)
+{
+	const struct nft_ct *priv = nft_expr_priv(expr);
+	struct nft_data *dest = &data[priv->dreg];
+	enum ip_conntrack_info ctinfo;
+	const struct nf_conn *ct;
+	const struct nf_conn_help *help;
+	const struct nf_conntrack_tuple *tuple;
+	const struct nf_conntrack_helper *helper;
+	long diff;
+	unsigned int state;
+
+	ct = nf_ct_get(pkt->skb, &ctinfo);
+
+	switch (priv->key) {
+	case NFT_CT_STATE:
+		if (ct == NULL)
+			state = NF_CT_STATE_INVALID_BIT;
+		else if (nf_ct_is_untracked(ct))
+			state = NF_CT_STATE_UNTRACKED_BIT;
+		else
+			state = NF_CT_STATE_BIT(ctinfo);
+		dest->data[0] = state;
+		return;
+	}
+
+	if (ct == NULL)
+		goto err;
+
+	switch (priv->key) {
+	case NFT_CT_DIRECTION:
+		dest->data[0] = CTINFO2DIR(ctinfo);
+		return;
+	case NFT_CT_STATUS:
+		dest->data[0] = ct->status;
+		return;
+#ifdef CONFIG_NF_CONNTRACK_MARK
+	case NFT_CT_MARK:
+		dest->data[0] = ct->mark;
+		return;
+#endif
+#ifdef CONFIG_NF_CONNTRACK_SECMARK
+	case NFT_CT_SECMARK:
+		dest->data[0] = ct->secmark;
+		return;
+#endif
+	case NFT_CT_EXPIRATION:
+		diff = (long)jiffies - (long)ct->timeout.expires;
+		if (diff < 0)
+			diff = 0;
+		dest->data[0] = jiffies_to_msecs(diff);
+		return;
+	case NFT_CT_HELPER:
+		if (ct->master == NULL)
+			goto err;
+		help = nfct_help(ct->master);
+		if (help == NULL)
+			goto err;
+		helper = rcu_dereference(help->helper);
+		if (helper == NULL)
+			goto err;
+		if (strlen(helper->name) >= sizeof(dest->data))
+			goto err;
+		strncpy((char *)dest->data, helper->name, sizeof(dest->data));
+		return;
+	}
+
+	tuple = &ct->tuplehash[priv->dir].tuple;
+	switch (priv->key) {
+	case NFT_CT_L3PROTOCOL:
+		dest->data[0] = nf_ct_l3num(ct);
+		return;
+	case NFT_CT_SRC:
+		memcpy(dest->data, tuple->src.u3.all,
+		       nf_ct_l3num(ct) == NFPROTO_IPV4 ? 4 : 16);
+		return;
+	case NFT_CT_DST:
+		memcpy(dest->data, tuple->dst.u3.all,
+		       nf_ct_l3num(ct) == NFPROTO_IPV4 ? 4 : 16);
+		return;
+	case NFT_CT_PROTOCOL:
+		dest->data[0] = nf_ct_protonum(ct);
+		return;
+	case NFT_CT_PROTO_SRC:
+		dest->data[0] = (__force __u16)tuple->src.u.all;
+		return;
+	case NFT_CT_PROTO_DST:
+		dest->data[0] = (__force __u16)tuple->dst.u.all;
+		return;
+	}
+	return;
+err:
+	data[NFT_REG_VERDICT].verdict = NFT_BREAK;
+}
+
+static const struct nla_policy nft_ct_policy[NFTA_CT_MAX + 1] = {
+	[NFTA_CT_DREG]		= { .type = NLA_U32 },
+	[NFTA_CT_KEY]		= { .type = NLA_U32 },
+	[NFTA_CT_DIRECTION]	= { .type = NLA_U8 },
+};
+
+static int nft_ct_init(const struct nft_ctx *ctx,
+		       const struct nft_expr *expr,
+		       const struct nlattr * const tb[])
+{
+	struct nft_ct *priv = nft_expr_priv(expr);
+	int err;
+
+	if (tb[NFTA_CT_DREG] == NULL ||
+	    tb[NFTA_CT_KEY] == NULL)
+		return -EINVAL;
+
+	priv->key = ntohl(nla_get_be32(tb[NFTA_CT_KEY]));
+	if (tb[NFTA_CT_DIRECTION] != NULL) {
+		priv->dir = nla_get_u8(tb[NFTA_CT_DIRECTION]);
+		switch (priv->dir) {
+		case IP_CT_DIR_ORIGINAL:
+		case IP_CT_DIR_REPLY:
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	switch (priv->key) {
+	case NFT_CT_STATE:
+	case NFT_CT_DIRECTION:
+	case NFT_CT_STATUS:
+#ifdef CONFIG_NF_CONNTRACK_MARK
+	case NFT_CT_MARK:
+#endif
+#ifdef CONFIG_NF_CONNTRACK_SECMARK
+	case NFT_CT_SECMARK:
+#endif
+	case NFT_CT_EXPIRATION:
+	case NFT_CT_HELPER:
+		if (tb[NFTA_CT_DIRECTION] != NULL)
+			return -EINVAL;
+		break;
+	case NFT_CT_PROTOCOL:
+	case NFT_CT_SRC:
+	case NFT_CT_DST:
+	case NFT_CT_PROTO_SRC:
+	case NFT_CT_PROTO_DST:
+		if (tb[NFTA_CT_DIRECTION] == NULL)
+			return -EINVAL;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	err = nf_ct_l3proto_try_module_get(ctx->afi->family);
+	if (err < 0)
+		return err;
+	priv->family = ctx->afi->family;
+
+	priv->dreg = ntohl(nla_get_be32(tb[NFTA_CT_DREG]));
+	err = nft_validate_output_register(priv->dreg);
+	if (err < 0)
+		goto err1;
+
+	err = nft_validate_data_load(ctx, priv->dreg, NULL, NFT_DATA_VALUE);
+	if (err < 0)
+		goto err1;
+	return 0;
+
+err1:
+	nf_ct_l3proto_module_put(ctx->afi->family);
+	return err;
+}
+
+static void nft_ct_destroy(const struct nft_expr *expr)
+{
+	struct nft_ct *priv = nft_expr_priv(expr);
+
+	nf_ct_l3proto_module_put(priv->family);
+}
+
+static int nft_ct_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	const struct nft_ct *priv = nft_expr_priv(expr);
+
+	if (nla_put_be32(skb, NFTA_CT_DREG, htonl(priv->dreg)))
+		goto nla_put_failure;
+	if (nla_put_be32(skb, NFTA_CT_KEY, htonl(priv->key)))
+		goto nla_put_failure;
+	if (nla_put_u8(skb, NFTA_CT_DIRECTION, priv->dir))
+		goto nla_put_failure;
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+static struct nft_expr_ops nft_ct_ops __read_mostly = {
+	.name		= "ct",
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_ct)),
+	.owner		= THIS_MODULE,
+	.eval		= nft_ct_eval,
+	.init		= nft_ct_init,
+	.destroy	= nft_ct_destroy,
+	.dump		= nft_ct_dump,
+	.policy		= nft_ct_policy,
+	.maxattr	= NFTA_CT_MAX,
+};
+
+static int __init nft_ct_module_init(void)
+{
+	return nft_register_expr(&nft_ct_ops);
+}
+
+static void __exit nft_ct_module_exit(void)
+{
+	nft_unregister_expr(&nft_ct_ops);
+}
+
+module_init(nft_ct_module_init);
+module_exit(nft_ct_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
+MODULE_ALIAS_NFT_EXPR("ct");