/*-
* Copyright (c) 2014-2020 Mindaugas Rasiukevicius <rmind at noxt eu>
* Copyright (c) 2010-2014 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This material is based upon work partially supported by The
* NetBSD Foundation under a contract with Mindaugas Rasiukevicius.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* NPF connection tracking for stateful filtering and translation.
*
* Overview
*
* Packets can be incoming or outgoing with respect to an interface.
* Connection direction is identified by the direction of its first
* packet. The meaning of incoming/outgoing packet in the context of
* connection direction can be confusing. Therefore, we will use the
* terms "forwards stream" and "backwards stream", where packets in
* the forwards stream mean the packets travelling in the direction
* as the connection direction.
*
* All connections have two keys and thus two entries:
*
* - npf_conn_getforwkey(con) -- for the forwards stream;
* - npf_conn_getbackkey(con, alen) -- for the backwards stream.
*
* Note: the keys are stored in npf_conn_t::c_keys[], which is used
* to allocate variable-length npf_conn_t structures based on whether
* the IPv4 or IPv6 addresses are used.
*
* The key is an n-tuple used to identify the connection flow: see the
* npf_connkey.c source file for the description of the key layouts.
* The key may be formed using translated values in a case of NAT.
*
* Connections can serve two purposes: for the implicit passing and/or
* to accommodate the dynamic NAT. Connections for the former purpose
* are created by the rules with "stateful" attribute and are used for
* stateful filtering. Such connections indicate that the packet of
* the backwards stream should be passed without inspection of the
* ruleset. The other purpose is to associate a dynamic NAT mechanism
* with a connection. Such connections are created by the NAT policies
* and they have a relationship with NAT translation structure via
* npf_conn_t::c_nat. A single connection can serve both purposes,
* which is a common case.
*
* Connection life-cycle
*
* Connections are established when a packet matches said rule or
* NAT policy. Both keys of the established connection are inserted
* into the connection database. A garbage collection thread
* periodically scans all connections and depending on connection
* properties (e.g. last activity time, protocol) removes connection
* entries and expires the actual connections.
*
* Each connection has a reference count. The reference is acquired
* on lookup and should be released by the caller. It guarantees that
* the connection will not be destroyed, although it may be expired.
*
* Synchronization
*
* Connection database is accessed in a lock-free manner by the main
* routines: npf_conn_inspect() and npf_conn_establish(). Since they
* are always called from a software interrupt, the database is
* protected using EBR. The main place which can destroy a connection
* is npf_conn_worker(). The database itself can be replaced and
* destroyed in npf_conn_reload().
*
* ALG support
*
* Application-level gateways (ALGs) can override generic connection
* inspection (npf_alg_conn() call in npf_conn_inspect() function) by
* performing their own lookup using different key. Recursive call
* to npf_conn_inspect() is not allowed. The ALGs ought to use the
* npf_conn_lookup() function for this purpose.
*
* Lock order
*
* npf_t::config_lock ->
* conn_lock ->
* npf_conn_t::c_lock
*/
/*
* npf_conn_load: perform the load by flushing the current connection
* database and replacing it with the new one or just destroying.
*
* => The caller must disable the connection tracking and ensure that
* there are no connection database lookups or references in-flight.
*/
void
npf_conn_load(npf_t *npf, npf_conndb_t *ndb, bool track)
{
npf_conndb_t *odb = NULL;
KASSERT(npf_config_locked_p(npf));
/*
* The connection database is in the quiescent state.
* Prevent G/C thread from running and install a new database.
*/
mutex_enter(&npf->conn_lock);
if (ndb) {
KASSERT(atomic_load_relaxed(&npf->conn_tracking)
== CONN_TRACKING_OFF);
odb = atomic_load_relaxed(&npf->conn_db);
atomic_store_release(&npf->conn_db, ndb);
}
if (track) {
/* After this point lookups start flying in. */
membar_producer();
atomic_store_relaxed(&npf->conn_tracking, CONN_TRACKING_ON);
}
mutex_exit(&npf->conn_lock);
if (odb) {
/*
* Flush all, no sync since the caller did it for us.
* Also, release the pool cache memory.
*/
npf_conndb_gc(npf, odb, true, false);
npf_conndb_destroy(odb);
pool_cache_invalidate(npf->conn_cache[0]);
pool_cache_invalidate(npf->conn_cache[1]);
}
}
/*
* Check if connection tracking is on. Also, if layer 3 and 4 are
* not cached - protocol is not supported or packet is invalid.
*/
if (atomic_load_relaxed(&npf->conn_tracking) != CONN_TRACKING_ON) {
return false;
}
if (!npf_iscached(npc, NPC_IP46) || !npf_iscached(npc, NPC_LAYER4)) {
return false;
}
return true;
}
/*
* npf_conn_check: check that:
*
* - the connection is active;
*
* - the packet is travelling in the right direction with the respect
* to the connection direction (if interface-id is not zero);
*
* - the packet is travelling on the same interface as the
* connection interface (if interface-id is not zero).
*/
static bool
npf_conn_check(const npf_conn_t *con, const nbuf_t *nbuf,
const unsigned di, const npf_flow_t flow)
{
const uint32_t flags = atomic_load_relaxed(&con->c_flags);
const unsigned ifid = atomic_load_relaxed(&con->c_ifid);
bool active;
active = (flags & (CONN_ACTIVE | CONN_EXPIRE)) == CONN_ACTIVE;
if (__predict_false(!active)) {
return false;
}
if (ifid && nbuf) {
const bool match = (flags & PFIL_ALL) == di;
npf_flow_t pflow = match ? NPF_FLOW_FORW : NPF_FLOW_BACK;
if (__predict_false(flow != pflow)) {
return false;
}
if (__predict_false(ifid != nbuf->nb_ifid)) {
return false;
}
}
return true;
}
/*
* npf_conn_lookup: lookup if there is an established connection.
*
* => If found, we will hold a reference for the caller.
*/
npf_conn_t *
npf_conn_lookup(const npf_cache_t *npc, const unsigned di, npf_flow_t *flow)
{
npf_t *npf = npc->npc_ctx;
const nbuf_t *nbuf = npc->npc_nbuf;
npf_conn_t *con;
npf_connkey_t key;
/* Construct a key and lookup for a connection in the store. */
if (!npf_conn_conkey(npc, &key, di, NPF_FLOW_FORW)) {
return NULL;
}
con = npf_conndb_lookup(npf, &key, flow);
if (con == NULL) {
return NULL;
}
KASSERT(npc->npc_proto == atomic_load_relaxed(&con->c_proto));
/* Extra checks for the connection and packet. */
if (!npf_conn_check(con, nbuf, di, *flow)) {
atomic_dec_uint(&con->c_refcnt);
return NULL;
}
/* Update the last activity time. */
conn_update_atime(con);
return con;
}
/*
* npf_conn_inspect: lookup a connection and inspecting the protocol data.
*
* => If found, we will hold a reference for the caller.
*/
npf_conn_t *
npf_conn_inspect(npf_cache_t *npc, const unsigned di, int *error)
{
nbuf_t *nbuf = npc->npc_nbuf;
npf_flow_t flow;
npf_conn_t *con;
bool ok;
KASSERT(!nbuf_flag_p(nbuf, NBUF_DATAREF_RESET));
if (!npf_conn_trackable_p(npc)) {
return NULL;
}
/* Query ALG which may lookup connection for us. */
if ((con = npf_alg_conn(npc, di)) != NULL) {
/* Note: reference is held. */
return con;
}
if (nbuf_head_mbuf(nbuf) == NULL) {
*error = ENOMEM;
return NULL;
}
KASSERT(!nbuf_flag_p(nbuf, NBUF_DATAREF_RESET));
/* The main lookup of the connection (acquires a reference). */
if ((con = npf_conn_lookup(npc, di, &flow)) == NULL) {
return NULL;
}
/* Inspect the protocol data and handle state changes. */
mutex_enter(&con->c_lock);
ok = npf_state_inspect(npc, &con->c_state, flow);
mutex_exit(&con->c_lock);
/* If invalid state: let the rules deal with it. */
if (__predict_false(!ok)) {
npf_conn_release(con);
npf_stats_inc(npc->npc_ctx, NPF_STAT_INVALID_STATE);
return NULL;
}
#if 0
/*
* TODO -- determine when this might be wanted/used.
*
* Note: skipping the connection lookup and ruleset inspection
* on other interfaces will also bypass dynamic NAT.
*/
if (atomic_load_relaxed(&con->c_flags) & CONN_GPASS) {
/*
* Note: if tagging fails, then give this packet a chance
* to go through a regular ruleset.
*/
(void)nbuf_add_tag(nbuf, NPF_NTAG_PASS);
}
#endif
return con;
}
/*
* npf_conn_establish: create a new connection, insert into the global list.
*
* => Connection is created with the reference held for the caller.
* => Connection will be activated on the first reference release.
*/
npf_conn_t *
npf_conn_establish(npf_cache_t *npc, const unsigned di, bool global)
{
npf_t *npf = npc->npc_ctx;
const unsigned alen = npc->npc_alen;
const unsigned idx = NPF_CONNCACHE(alen);
const nbuf_t *nbuf = npc->npc_nbuf;
npf_connkey_t *fw, *bk;
npf_conndb_t *conn_db;
npf_conn_t *con;
int error = 0;
KASSERT(!nbuf_flag_p(nbuf, NBUF_DATAREF_RESET));
if (!npf_conn_trackable_p(npc)) {
return NULL;
}
/* Allocate and initialize the new connection. */
con = pool_cache_get(npf->conn_cache[idx], PR_NOWAIT);
if (__predict_false(!con)) {
npf_worker_signal(npf);
return NULL;
}
NPF_PRINTF(("NPF: create conn %p\n", con));
npf_stats_inc(npf, NPF_STAT_CONN_CREATE);
/* Initialize the protocol state. */
if (!npf_state_init(npc, &con->c_state)) {
npf_conn_destroy(npf, con);
return NULL;
}
KASSERT(npf_iscached(npc, NPC_IP46));
fw = npf_conn_getforwkey(con);
bk = npf_conn_getbackkey(con, alen);
/*
* Construct "forwards" and "backwards" keys. Also, set the
* interface ID for this connection (unless it is global).
*/
if (!npf_conn_conkey(npc, fw, di, NPF_FLOW_FORW) ||
!npf_conn_conkey(npc, bk, di ^ PFIL_ALL, NPF_FLOW_BACK)) {
npf_conn_destroy(npf, con);
return NULL;
}
con->c_ifid = global ? nbuf->nb_ifid : 0;
/*
* Set last activity time for a new connection and acquire
* a reference for the caller before we make it visible.
*/
conn_update_atime(con);
atomic_store_relaxed(&con->c_refcnt, 1);
/*
* Insert both keys (entries representing directions) of the
* connection. At this point it becomes visible, but we activate
* the connection later.
*/
mutex_enter(&con->c_lock);
conn_db = atomic_load_consume(&npf->conn_db);
if (!npf_conndb_insert(conn_db, fw, con, NPF_FLOW_FORW)) {
error = EISCONN;
goto err;
}
if (!npf_conndb_insert(conn_db, bk, con, NPF_FLOW_BACK)) {
npf_conn_t *ret __diagused;
ret = npf_conndb_remove(conn_db, fw);
KASSERT(ret == con);
error = EISCONN;
goto err;
}
err:
/*
* If we have hit the duplicate: mark the connection as expired
* and let the G/C thread to take care of it. We cannot do it
* here since there might be references acquired already.
*/
if (error) {
atomic_or_uint(&con->c_flags, CONN_REMOVED | CONN_EXPIRE);
atomic_dec_uint(&con->c_refcnt);
npf_stats_inc(npf, NPF_STAT_RACE_CONN);
} else {
NPF_PRINTF(("NPF: establish conn %p\n", con));
}
/* Finally, insert into the connection list. */
npf_conndb_enqueue(conn_db, con);
mutex_exit(&con->c_lock);
/* Acquire the lock and check for the races. */
mutex_enter(&con->c_lock);
flags = atomic_load_relaxed(&con->c_flags);
if (__predict_false(flags & CONN_EXPIRE)) {
/* The connection got expired. */
mutex_exit(&con->c_lock);
return EINVAL;
}
KASSERT((flags & CONN_REMOVED) == 0);
if (__predict_false(con->c_nat != NULL)) {
/* Race with a duplicate packet. */
mutex_exit(&con->c_lock);
npf_stats_inc(npc->npc_ctx, NPF_STAT_RACE_NAT);
return EISCONN;
}
/* Remove the "backwards" key. */
conn_db = atomic_load_consume(&npf->conn_db);
bk = npf_conn_getbackkey(con, con->c_alen);
ret = npf_conndb_remove(conn_db, bk);
KASSERT(ret == con);
/* Set the source/destination IDs to the translation values. */
npf_conn_adjkey(bk, taddr, tport, nat_type_which[ntype]);
/* Finally, re-insert the "backwards" key. */
if (!npf_conndb_insert(conn_db, bk, con, NPF_FLOW_BACK)) {
/*
* Race: we have hit the duplicate, remove the "forwards"
* key and expire our connection; it is no longer valid.
*/
npf_connkey_t *fw = npf_conn_getforwkey(con);
ret = npf_conndb_remove(conn_db, fw);
KASSERT(ret == con);
/* Associate the NAT entry and release the lock. */
con->c_nat = nt;
mutex_exit(&con->c_lock);
return 0;
}
/*
* npf_conn_expire: explicitly mark connection as expired.
*
* => Must be called with: a) reference held b) the relevant lock held.
* The relevant lock should prevent from connection destruction, e.g.
* npf_t::conn_lock or npf_natpolicy_t::n_lock.
*/
void
npf_conn_expire(npf_conn_t *con)
{
atomic_or_uint(&con->c_flags, CONN_EXPIRE);
}
/*
* npf_conn_setpass: mark connection as a "pass" one and associate the
* rule procedure with it.
*/
void
npf_conn_setpass(npf_conn_t *con, const npf_match_info_t *mi, npf_rproc_t *rp)
{
KASSERT((atomic_load_relaxed(&con->c_flags) & CONN_ACTIVE) == 0);
KASSERT(atomic_load_relaxed(&con->c_refcnt) > 0);
KASSERT(con->c_rproc == NULL);
/*
* No need for atomic since the connection is not yet active.
* If rproc is set, the caller transfers its reference to us,
* which will be released on npf_conn_destroy().
*/
atomic_or_uint(&con->c_flags, CONN_PASS);
con->c_rproc = rp;
if (rp) {
con->c_rid = mi->mi_rid;
con->c_retfl = mi->mi_retfl;
}
}
/*
* npf_conn_release: release a reference, which might allow G/C thread
* to destroy this connection.
*/
void
npf_conn_release(npf_conn_t *con)
{
const unsigned flags = atomic_load_relaxed(&con->c_flags);
if ((flags & (CONN_ACTIVE | CONN_EXPIRE)) == 0) {
/* Activate: after this, connection is globally visible. */
atomic_or_uint(&con->c_flags, CONN_ACTIVE);
}
KASSERT(atomic_load_relaxed(&con->c_refcnt) > 0);
atomic_dec_uint(&con->c_refcnt);
}
/*
* npf_conn_getnat: return the associated NAT entry, if any.
*/
npf_nat_t *
npf_conn_getnat(const npf_conn_t *con)
{
return con->c_nat;
}
/*
* npf_conn_expired: criterion to check if connection is expired.
*/
bool
npf_conn_expired(npf_t *npf, const npf_conn_t *con, uint64_t tsnow)
{
const unsigned flags = atomic_load_relaxed(&con->c_flags);
const int etime = npf_state_etime(npf, &con->c_state, con->c_proto);
int elapsed;
if (__predict_false(flags & CONN_EXPIRE)) {
/* Explicitly marked to be expired. */
return true;
}
/*
* Note: another thread may update 'atime' and it might
* become greater than 'now'.
*/
elapsed = (int64_t)tsnow - atomic_load_relaxed(&con->c_atime);
return elapsed > etime;
}
/*
* npf_conn_remove: unlink the connection and mark as expired.
*/
void
npf_conn_remove(npf_conndb_t *cd, npf_conn_t *con)
{
/* Remove both entries of the connection. */
mutex_enter(&con->c_lock);
if ((atomic_load_relaxed(&con->c_flags) & CONN_REMOVED) == 0) {
npf_connkey_t *fw, *bk;
npf_conn_t *ret __diagused;
fw = npf_conn_getforwkey(con);
ret = npf_conndb_remove(cd, fw);
KASSERT(ret == con);
bk = npf_conn_getbackkey(con, NPF_CONNKEY_ALEN(fw));
ret = npf_conndb_remove(cd, bk);
KASSERT(ret == con);
}
/* Flag the removal and expiration. */
atomic_or_uint(&con->c_flags, CONN_REMOVED | CONN_EXPIRE);
mutex_exit(&con->c_lock);
}
/*
* npf_conn_worker: G/C to run from a worker thread or via npfk_gc().
*/
void
npf_conn_worker(npf_t *npf)
{
npf_conndb_t *conn_db = atomic_load_consume(&npf->conn_db);
npf_conndb_gc(npf, conn_db, false, true);
}
/*
* npf_conndb_export: construct a list of connections prepared for saving.
* Note: this is expected to be an expensive operation.
*/
int
npf_conndb_export(npf_t *npf, nvlist_t *nvl)
{
npf_conn_t *head, *con;
npf_conndb_t *conn_db;
/*
* Note: acquire conn_lock to prevent from the database
* destruction and G/C thread.
*/
mutex_enter(&npf->conn_lock);
if (atomic_load_relaxed(&npf->conn_tracking) != CONN_TRACKING_ON) {
mutex_exit(&npf->conn_lock);
return 0;
}
conn_db = atomic_load_relaxed(&npf->conn_db);
head = npf_conndb_getlist(conn_db);
con = head;
while (con) {
nvlist_t *con_nvl;
/* Let the address length be based on on first key. */
nvlist_add_number(nvl, "alen", alen);
if (con->c_nat) {
npf_nat_export(npf, con->c_nat, nvl);
}
return 0;
}
/*
* npf_conn_import: fully reconstruct a single connection from a
* nvlist and insert into the given database.
*/
int
npf_conn_import(npf_t *npf, npf_conndb_t *cd, const nvlist_t *cdict,
npf_ruleset_t *natlist)
{
npf_conn_t *con;
npf_connkey_t *fw, *bk;
const nvlist_t *nat, *conkey;
unsigned flags, alen, idx;
const char *ifname;
const void *state;
size_t len;
/*
* To determine the length of the connection, which depends
* on the address length in the connection keys.
*/
alen = dnvlist_get_number(cdict, "alen", 0);
idx = NPF_CONNCACHE(alen);
/* Allocate a connection and initialize it (clear first). */
con = pool_cache_get(npf->conn_cache[idx], PR_WAITOK);
memset(con, 0, sizeof(npf_conn_t));
mutex_init(&con->c_lock, MUTEX_DEFAULT, IPL_SOFTNET);
npf_stats_inc(npf, NPF_STAT_CONN_CREATE);
/*
* npf_conn_find: lookup a connection in the list of connections
*/
int
npf_conn_find(npf_t *npf, const nvlist_t *req, nvlist_t *resp)
{
const nvlist_t *key_nv;
npf_conn_t *con;
npf_connkey_t key;
npf_flow_t flow;
int error;
