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, 222 insertions, 0 deletions

diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
new file mode 100644
index 000000000000..96735aa2f039
--- /dev/null
+++ b/net/netfilter/nft_meta.c
@@ -0,0 +1,222 @@
+/*
+ * 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/dst.h>
+#include <net/sock.h>
+#include <net/tcp_states.h> /* for TCP_TIME_WAIT */
+#include <net/netfilter/nf_tables.h>
+
+struct nft_meta {
+	enum nft_meta_keys	key:8;
+	enum nft_registers	dreg:8;
+};
+
+static void nft_meta_eval(const struct nft_expr *expr,
+			  struct nft_data data[NFT_REG_MAX + 1],
+			  const struct nft_pktinfo *pkt)
+{
+	const struct nft_meta *priv = nft_expr_priv(expr);
+	const struct sk_buff *skb = pkt->skb;
+	const struct net_device *in = pkt->in, *out = pkt->out;
+	struct nft_data *dest = &data[priv->dreg];
+
+	switch (priv->key) {
+	case NFT_META_LEN:
+		dest->data[0] = skb->len;
+		break;
+	case NFT_META_PROTOCOL:
+		*(__be16 *)dest->data = skb->protocol;
+		break;
+	case NFT_META_PRIORITY:
+		dest->data[0] = skb->priority;
+		break;
+	case NFT_META_MARK:
+		dest->data[0] = skb->mark;
+		break;
+	case NFT_META_IIF:
+		if (in == NULL)
+			goto err;
+		dest->data[0] = in->ifindex;
+		break;
+	case NFT_META_OIF:
+		if (out == NULL)
+			goto err;
+		dest->data[0] = out->ifindex;
+		break;
+	case NFT_META_IIFNAME:
+		if (in == NULL)
+			goto err;
+		strncpy((char *)dest->data, in->name, sizeof(dest->data));
+		break;
+	case NFT_META_OIFNAME:
+		if (out == NULL)
+			goto err;
+		strncpy((char *)dest->data, out->name, sizeof(dest->data));
+		break;
+	case NFT_META_IIFTYPE:
+		if (in == NULL)
+			goto err;
+		*(u16 *)dest->data = in->type;
+		break;
+	case NFT_META_OIFTYPE:
+		if (out == NULL)
+			goto err;
+		*(u16 *)dest->data = out->type;
+		break;
+	case NFT_META_SKUID:
+		if (skb->sk == NULL || skb->sk->sk_state == TCP_TIME_WAIT)
+			goto err;
+
+		read_lock_bh(&skb->sk->sk_callback_lock);
+		if (skb->sk->sk_socket == NULL ||
+		    skb->sk->sk_socket->file == NULL) {
+			read_unlock_bh(&skb->sk->sk_callback_lock);
+			goto err;
+		}
+
+		dest->data[0] =
+			from_kuid_munged(&init_user_ns,
+				skb->sk->sk_socket->file->f_cred->fsuid);
+		read_unlock_bh(&skb->sk->sk_callback_lock);
+		break;
+	case NFT_META_SKGID:
+		if (skb->sk == NULL || skb->sk->sk_state == TCP_TIME_WAIT)
+			goto err;
+
+		read_lock_bh(&skb->sk->sk_callback_lock);
+		if (skb->sk->sk_socket == NULL ||
+		    skb->sk->sk_socket->file == NULL) {
+			read_unlock_bh(&skb->sk->sk_callback_lock);
+			goto err;
+		}
+		dest->data[0] =
+			from_kgid_munged(&init_user_ns,
+				 skb->sk->sk_socket->file->f_cred->fsgid);
+		read_unlock_bh(&skb->sk->sk_callback_lock);
+		break;
+#ifdef CONFIG_NET_CLS_ROUTE
+	case NFT_META_RTCLASSID: {
+		const struct dst_entry *dst = skb_dst(skb);
+
+		if (dst == NULL)
+			goto err;
+		dest->data[0] = dst->tclassid;
+		break;
+	}
+#endif
+#ifdef CONFIG_NETWORK_SECMARK
+	case NFT_META_SECMARK:
+		dest->data[0] = skb->secmark;
+		break;
+#endif
+	default:
+		WARN_ON(1);
+		goto err;
+	}
+	return;
+
+err:
+	data[NFT_REG_VERDICT].verdict = NFT_BREAK;
+}
+
+static const struct nla_policy nft_meta_policy[NFTA_META_MAX + 1] = {
+	[NFTA_META_DREG]	= { .type = NLA_U32 },
+	[NFTA_META_KEY]		= { .type = NLA_U32 },
+};
+
+static int nft_meta_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
+			 const struct nlattr * const tb[])
+{
+	struct nft_meta *priv = nft_expr_priv(expr);
+	int err;
+
+	if (tb[NFTA_META_DREG] == NULL ||
+	    tb[NFTA_META_KEY] == NULL)
+		return -EINVAL;
+
+	priv->key = ntohl(nla_get_be32(tb[NFTA_META_KEY]));
+	switch (priv->key) {
+	case NFT_META_LEN:
+	case NFT_META_PROTOCOL:
+	case NFT_META_PRIORITY:
+	case NFT_META_MARK:
+	case NFT_META_IIF:
+	case NFT_META_OIF:
+	case NFT_META_IIFNAME:
+	case NFT_META_OIFNAME:
+	case NFT_META_IIFTYPE:
+	case NFT_META_OIFTYPE:
+	case NFT_META_SKUID:
+	case NFT_META_SKGID:
+#ifdef CONFIG_NET_CLS_ROUTE
+	case NFT_META_RTCLASSID:
+#endif
+#ifdef CONFIG_NETWORK_SECMARK
+	case NFT_META_SECMARK:
+#endif
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	priv->dreg = ntohl(nla_get_be32(tb[NFTA_META_DREG]));
+	err = nft_validate_output_register(priv->dreg);
+	if (err < 0)
+		return err;
+	return nft_validate_data_load(ctx, priv->dreg, NULL, NFT_DATA_VALUE);
+}
+
+static int nft_meta_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	const struct nft_meta *priv = nft_expr_priv(expr);
+
+	if (nla_put_be32(skb, NFTA_META_DREG, htonl(priv->dreg)))
+		goto nla_put_failure;
+	if (nla_put_be32(skb, NFTA_META_KEY, htonl(priv->key)))
+		goto nla_put_failure;
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+static struct nft_expr_ops nft_meta_ops __read_mostly = {
+	.name		= "meta",
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_meta)),
+	.owner		= THIS_MODULE,
+	.eval		= nft_meta_eval,
+	.init		= nft_meta_init,
+	.dump		= nft_meta_dump,
+	.policy		= nft_meta_policy,
+	.maxattr	= NFTA_META_MAX,
+};
+
+static int __init nft_meta_module_init(void)
+{
+	return nft_register_expr(&nft_meta_ops);
+}
+
+static void __exit nft_meta_module_exit(void)
+{
+	nft_unregister_expr(&nft_meta_ops);
+}
+
+module_init(nft_meta_module_init);
+module_exit(nft_meta_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
+MODULE_ALIAS_NFT_EXPR("meta");