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>

4 files changed, 591 insertions, 1 deletions

diff --git a/include/uapi/linux/netfilter/Kbuild b/include/uapi/linux/netfilter/Kbuild
index 174915420d3f..6ce0b7f566a7 100644
--- a/include/uapi/linux/netfilter/Kbuild
+++ b/include/uapi/linux/netfilter/Kbuild
@@ -5,6 +5,7 @@ header-y += nf_conntrack_ftp.h
 header-y += nf_conntrack_sctp.h
 header-y += nf_conntrack_tcp.h
 header-y += nf_conntrack_tuple_common.h
+header-y += nf_tables.h
 header-y += nf_nat.h
 header-y += nfnetlink.h
 header-y += nfnetlink_acct.h
diff --git a/include/uapi/linux/netfilter/nf_conntrack_common.h b/include/uapi/linux/netfilter/nf_conntrack_common.h
index 8dd803818ebe..319f47128db8 100644
--- a/include/uapi/linux/netfilter/nf_conntrack_common.h
+++ b/include/uapi/linux/netfilter/nf_conntrack_common.h
@@ -25,6 +25,10 @@ enum ip_conntrack_info {
         IP_CT_NUMBER = IP_CT_IS_REPLY * 2 - 1
 };
 
+#define NF_CT_STATE_INVALID_BIT                 (1 << 0)
+#define NF_CT_STATE_BIT(ctinfo)                 (1 << ((ctinfo) % IP_CT_IS_REPLY + 1))
+#define NF_CT_STATE_UNTRACKED_BIT               (1 << (IP_CT_NUMBER + 1))
+
 /* Bitset representing status of connection. */
 enum ip_conntrack_status {
         /* It's an expected connection: bit 0 set.  This bit never changed */
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
new file mode 100644
index 000000000000..ec6d84a8ed1e
--- /dev/null
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -0,0 +1,582 @@
+#ifndef _LINUX_NF_TABLES_H
+#define _LINUX_NF_TABLES_H
+
+#define NFT_CHAIN_MAXNAMELEN 32
+
+enum nft_registers {
+        NFT_REG_VERDICT,
+        NFT_REG_1,
+        NFT_REG_2,
+        NFT_REG_3,
+        NFT_REG_4,
+        __NFT_REG_MAX
+};
+#define NFT_REG_MAX     (__NFT_REG_MAX - 1)
+
+/**
+ * enum nft_verdicts - nf_tables internal verdicts
+ *
+ * @NFT_CONTINUE: continue evaluation of the current rule
+ * @NFT_BREAK: terminate evaluation of the current rule
+ * @NFT_JUMP: push the current chain on the jump stack and jump to a chain
+ * @NFT_GOTO: jump to a chain without pushing the current chain on the jump stack
+ * @NFT_RETURN: return to the topmost chain on the jump stack
+ *
+ * The nf_tables verdicts share their numeric space with the netfilter verdicts.
+ */
+enum nft_verdicts {
+        NFT_CONTINUE    = -1,
+        NFT_BREAK       = -2,
+        NFT_JUMP        = -3,
+        NFT_GOTO        = -4,
+        NFT_RETURN      = -5,
+};
+
+/**
+ * enum nf_tables_msg_types - nf_tables netlink message types
+ *
+ * @NFT_MSG_NEWTABLE: create a new table (enum nft_table_attributes)
+ * @NFT_MSG_GETTABLE: get a table (enum nft_table_attributes)
+ * @NFT_MSG_DELTABLE: delete a table (enum nft_table_attributes)
+ * @NFT_MSG_NEWCHAIN: create a new chain (enum nft_chain_attributes)
+ * @NFT_MSG_GETCHAIN: get a chain (enum nft_chain_attributes)
+ * @NFT_MSG_DELCHAIN: delete a chain (enum nft_chain_attributes)
+ * @NFT_MSG_NEWRULE: create a new rule (enum nft_rule_attributes)
+ * @NFT_MSG_GETRULE: get a rule (enum nft_rule_attributes)
+ * @NFT_MSG_DELRULE: delete a rule (enum nft_rule_attributes)
+ */
+enum nf_tables_msg_types {
+        NFT_MSG_NEWTABLE,
+        NFT_MSG_GETTABLE,
+        NFT_MSG_DELTABLE,
+        NFT_MSG_NEWCHAIN,
+        NFT_MSG_GETCHAIN,
+        NFT_MSG_DELCHAIN,
+        NFT_MSG_NEWRULE,
+        NFT_MSG_GETRULE,
+        NFT_MSG_DELRULE,
+        NFT_MSG_MAX,
+};
+
+enum nft_list_attributes {
+        NFTA_LIST_UNPEC,
+        NFTA_LIST_ELEM,
+        __NFTA_LIST_MAX
+};
+#define NFTA_LIST_MAX           (__NFTA_LIST_MAX - 1)
+
+/**
+ * enum nft_hook_attributes - nf_tables netfilter hook netlink attributes
+ *
+ * @NFTA_HOOK_HOOKNUM: netfilter hook number (NLA_U32)
+ * @NFTA_HOOK_PRIORITY: netfilter hook priority (NLA_U32)
+ */
+enum nft_hook_attributes {
+        NFTA_HOOK_UNSPEC,
+        NFTA_HOOK_HOOKNUM,
+        NFTA_HOOK_PRIORITY,
+        __NFTA_HOOK_MAX
+};
+#define NFTA_HOOK_MAX           (__NFTA_HOOK_MAX - 1)
+
+/**
+ * enum nft_table_attributes - nf_tables table netlink attributes
+ *
+ * @NFTA_TABLE_NAME: name of the table (NLA_STRING)
+ */
+enum nft_table_attributes {
+        NFTA_TABLE_UNSPEC,
+        NFTA_TABLE_NAME,
+        __NFTA_TABLE_MAX
+};
+#define NFTA_TABLE_MAX          (__NFTA_TABLE_MAX - 1)
+
+/**
+ * enum nft_chain_attributes - nf_tables chain netlink attributes
+ *
+ * @NFTA_CHAIN_TABLE: name of the table containing the chain (NLA_STRING)
+ * @NFTA_CHAIN_HANDLE: numeric handle of the chain (NLA_U64)
+ * @NFTA_CHAIN_NAME: name of the chain (NLA_STRING)
+ * @NFTA_CHAIN_HOOK: hook specification for basechains (NLA_NESTED: nft_hook_attributes)
+ */
+enum nft_chain_attributes {
+        NFTA_CHAIN_UNSPEC,
+        NFTA_CHAIN_TABLE,
+        NFTA_CHAIN_HANDLE,
+        NFTA_CHAIN_NAME,
+        NFTA_CHAIN_HOOK,
+        __NFTA_CHAIN_MAX
+};
+#define NFTA_CHAIN_MAX          (__NFTA_CHAIN_MAX - 1)
+
+/**
+ * enum nft_rule_attributes - nf_tables rule netlink attributes
+ *
+ * @NFTA_RULE_TABLE: name of the table containing the rule (NLA_STRING)
+ * @NFTA_RULE_CHAIN: name of the chain containing the rule (NLA_STRING)
+ * @NFTA_RULE_HANDLE: numeric handle of the rule (NLA_U64)
+ * @NFTA_RULE_EXPRESSIONS: list of expressions (NLA_NESTED: nft_expr_attributes)
+ */
+enum nft_rule_attributes {
+        NFTA_RULE_UNSPEC,
+        NFTA_RULE_TABLE,
+        NFTA_RULE_CHAIN,
+        NFTA_RULE_HANDLE,
+        NFTA_RULE_EXPRESSIONS,
+        __NFTA_RULE_MAX
+};
+#define NFTA_RULE_MAX           (__NFTA_RULE_MAX - 1)
+
+enum nft_data_attributes {
+        NFTA_DATA_UNSPEC,
+        NFTA_DATA_VALUE,