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freebsd-nq/sys/netpfil/ipfw/ip_fw_dynamic.c
Gleb Smirnoff eb1b1807af Mechanically substitute flags from historic mbuf allocator with 
malloc(9) flags within sys.

Exceptions:

- sys/contrib not touched
- sys/mbuf.h edited manually
2012-12-05 08:04:20 +00:00

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/*-
* Copyright (c) 2002 Luigi Rizzo, Universita` di Pisa
*
* 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 AUTHOR 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 AUTHOR 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#define DEB(x)
#define DDB(x) x
/*
* Dynamic rule support for ipfw
*/
#include "opt_ipfw.h"
#include "opt_inet.h"
#ifndef INET
#error IPFIREWALL requires INET.
#endif /* INET */
#include "opt_inet6.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <net/ethernet.h> /* for ETHERTYPE_IP */
#include <net/if.h>
#include <net/vnet.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h> /* ip_defttl */
#include <netinet/ip_fw.h>
#include <netinet/tcp_var.h>
#include <netinet/udp.h>
#include <netinet/ip6.h> /* IN6_ARE_ADDR_EQUAL */
#ifdef INET6
#include <netinet6/in6_var.h>
#include <netinet6/ip6_var.h>
#endif
#include <netpfil/ipfw/ip_fw_private.h>
#include <machine/in_cksum.h> /* XXX for in_cksum */
#ifdef MAC
#include <security/mac/mac_framework.h>
#endif
/*
* Description of dynamic rules.
*
* Dynamic rules are stored in lists accessed through a hash table
* (ipfw_dyn_v) whose size is curr_dyn_buckets. This value can
* be modified through the sysctl variable dyn_buckets which is
* updated when the table becomes empty.
*
* XXX currently there is only one list, ipfw_dyn.
*
* When a packet is received, its address fields are first masked
* with the mask defined for the rule, then hashed, then matched
* against the entries in the corresponding list.
* Dynamic rules can be used for different purposes:
* + stateful rules;
* + enforcing limits on the number of sessions;
* + in-kernel NAT (not implemented yet)
*
* The lifetime of dynamic rules is regulated by dyn_*_lifetime,
* measured in seconds and depending on the flags.
*
* The total number of dynamic rules is equal to UMA zone items count.
* The max number of dynamic rules is dyn_max. When we reach
* the maximum number of rules we do not create anymore. This is
* done to avoid consuming too much memory, but also too much
* time when searching on each packet (ideally, we should try instead
* to put a limit on the length of the list on each bucket...).
*
* Each dynamic rule holds a pointer to the parent ipfw rule so
* we know what action to perform. Dynamic rules are removed when
* the parent rule is deleted. XXX we should make them survive.
*
* There are some limitations with dynamic rules -- we do not
* obey the 'randomized match', and we do not do multiple
* passes through the firewall. XXX check the latter!!!
*/
struct ipfw_dyn_bucket {
struct mtx mtx; /* Bucket protecting lock */
ipfw_dyn_rule *head; /* Pointer to first rule */
};
/*
* Static variables followed by global ones
*/
static VNET_DEFINE(struct ipfw_dyn_bucket *, ipfw_dyn_v);
static VNET_DEFINE(u_int32_t, dyn_buckets_max);
static VNET_DEFINE(u_int32_t, curr_dyn_buckets);
static VNET_DEFINE(struct callout, ipfw_timeout);
#define V_ipfw_dyn_v VNET(ipfw_dyn_v)
#define V_dyn_buckets_max VNET(dyn_buckets_max)
#define V_curr_dyn_buckets VNET(curr_dyn_buckets)
#define V_ipfw_timeout VNET(ipfw_timeout)
static VNET_DEFINE(uma_zone_t, ipfw_dyn_rule_zone);
#define V_ipfw_dyn_rule_zone VNET(ipfw_dyn_rule_zone)
#define IPFW_BUCK_LOCK_INIT(b) \
mtx_init(&(b)->mtx, "IPFW dynamic bucket", NULL, MTX_DEF)
#define IPFW_BUCK_LOCK_DESTROY(b) \
mtx_destroy(&(b)->mtx)
#define IPFW_BUCK_LOCK(i) mtx_lock(&V_ipfw_dyn_v[(i)].mtx)
#define IPFW_BUCK_UNLOCK(i) mtx_unlock(&V_ipfw_dyn_v[(i)].mtx)
#define IPFW_BUCK_ASSERT(i) mtx_assert(&V_ipfw_dyn_v[(i)].mtx, MA_OWNED)
/*
* Timeouts for various events in handing dynamic rules.
*/
static VNET_DEFINE(u_int32_t, dyn_ack_lifetime);
static VNET_DEFINE(u_int32_t, dyn_syn_lifetime);
static VNET_DEFINE(u_int32_t, dyn_fin_lifetime);
static VNET_DEFINE(u_int32_t, dyn_rst_lifetime);
static VNET_DEFINE(u_int32_t, dyn_udp_lifetime);
static VNET_DEFINE(u_int32_t, dyn_short_lifetime);
#define V_dyn_ack_lifetime VNET(dyn_ack_lifetime)
#define V_dyn_syn_lifetime VNET(dyn_syn_lifetime)
#define V_dyn_fin_lifetime VNET(dyn_fin_lifetime)
#define V_dyn_rst_lifetime VNET(dyn_rst_lifetime)
#define V_dyn_udp_lifetime VNET(dyn_udp_lifetime)
#define V_dyn_short_lifetime VNET(dyn_short_lifetime)
/*
* Keepalives are sent if dyn_keepalive is set. They are sent every
* dyn_keepalive_period seconds, in the last dyn_keepalive_interval
* seconds of lifetime of a rule.
* dyn_rst_lifetime and dyn_fin_lifetime should be strictly lower
* than dyn_keepalive_period.
*/
static VNET_DEFINE(u_int32_t, dyn_keepalive_interval);
static VNET_DEFINE(u_int32_t, dyn_keepalive_period);
static VNET_DEFINE(u_int32_t, dyn_keepalive);
static VNET_DEFINE(time_t, dyn_keepalive_last);
#define V_dyn_keepalive_interval VNET(dyn_keepalive_interval)
#define V_dyn_keepalive_period VNET(dyn_keepalive_period)
#define V_dyn_keepalive VNET(dyn_keepalive)
#define V_dyn_keepalive_last VNET(dyn_keepalive_last)
static VNET_DEFINE(u_int32_t, dyn_max); /* max # of dynamic rules */
#define DYN_COUNT uma_zone_get_cur(V_ipfw_dyn_rule_zone)
#define V_dyn_max VNET(dyn_max)
static int last_log; /* Log ratelimiting */
static void ipfw_dyn_tick(void *vnetx);
static void check_dyn_rules(struct ip_fw_chain *, struct ip_fw *,
int, int, int);
#ifdef SYSCTL_NODE
static int sysctl_ipfw_dyn_count(SYSCTL_HANDLER_ARGS);
static int sysctl_ipfw_dyn_max(SYSCTL_HANDLER_ARGS);
SYSBEGIN(f2)
SYSCTL_DECL(_net_inet_ip_fw);
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, dyn_buckets,
CTLFLAG_RW, &VNET_NAME(dyn_buckets_max), 0,
"Max number of dyn. buckets");
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, curr_dyn_buckets,
CTLFLAG_RD, &VNET_NAME(curr_dyn_buckets), 0,
"Current Number of dyn. buckets");
SYSCTL_VNET_PROC(_net_inet_ip_fw, OID_AUTO, dyn_count,
CTLTYPE_UINT|CTLFLAG_RD, 0, 0, sysctl_ipfw_dyn_count, "IU",
"Number of dyn. rules");
SYSCTL_VNET_PROC(_net_inet_ip_fw, OID_AUTO, dyn_max,
CTLTYPE_UINT|CTLFLAG_RW, 0, 0, sysctl_ipfw_dyn_max, "IU",
"Max number of dyn. rules");
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, dyn_ack_lifetime,
CTLFLAG_RW, &VNET_NAME(dyn_ack_lifetime), 0,
"Lifetime of dyn. rules for acks");
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, dyn_syn_lifetime,
CTLFLAG_RW, &VNET_NAME(dyn_syn_lifetime), 0,
"Lifetime of dyn. rules for syn");
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, dyn_fin_lifetime,
CTLFLAG_RW, &VNET_NAME(dyn_fin_lifetime), 0,
"Lifetime of dyn. rules for fin");
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, dyn_rst_lifetime,
CTLFLAG_RW, &VNET_NAME(dyn_rst_lifetime), 0,
"Lifetime of dyn. rules for rst");
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, dyn_udp_lifetime,
CTLFLAG_RW, &VNET_NAME(dyn_udp_lifetime), 0,
"Lifetime of dyn. rules for UDP");
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, dyn_short_lifetime,
CTLFLAG_RW, &VNET_NAME(dyn_short_lifetime), 0,
"Lifetime of dyn. rules for other situations");
SYSCTL_VNET_UINT(_net_inet_ip_fw, OID_AUTO, dyn_keepalive,
CTLFLAG_RW, &VNET_NAME(dyn_keepalive), 0,
"Enable keepalives for dyn. rules");
SYSEND
#endif /* SYSCTL_NODE */
static __inline int
hash_packet6(struct ipfw_flow_id *id)
{
u_int32_t i;
i = (id->dst_ip6.__u6_addr.__u6_addr32[2]) ^
(id->dst_ip6.__u6_addr.__u6_addr32[3]) ^
(id->src_ip6.__u6_addr.__u6_addr32[2]) ^
(id->src_ip6.__u6_addr.__u6_addr32[3]) ^
(id->dst_port) ^ (id->src_port);
return i;
}
/*
* IMPORTANT: the hash function for dynamic rules must be commutative
* in source and destination (ip,port), because rules are bidirectional
* and we want to find both in the same bucket.
*/
static __inline int
hash_packet(struct ipfw_flow_id *id, int buckets)
{
u_int32_t i;
#ifdef INET6
if (IS_IP6_FLOW_ID(id))
i = hash_packet6(id);
else
#endif /* INET6 */
i = (id->dst_ip) ^ (id->src_ip) ^ (id->dst_port) ^ (id->src_port);
i &= (buckets - 1);
return i;
}
/**
* Print customizable flow id description via log(9) facility.
*/
static void
print_dyn_rule_flags(struct ipfw_flow_id *id, int dyn_type, int log_flags,
char *prefix, char *postfix)
{
struct in_addr da;
#ifdef INET6
char src[INET6_ADDRSTRLEN], dst[INET6_ADDRSTRLEN];
#else
char src[INET_ADDRSTRLEN], dst[INET_ADDRSTRLEN];
#endif
#ifdef INET6
if (IS_IP6_FLOW_ID(id)) {
ip6_sprintf(src, &id->src_ip6);
ip6_sprintf(dst, &id->dst_ip6);
} else
#endif
{
da.s_addr = htonl(id->src_ip);
inet_ntop(AF_INET, &da, src, sizeof(src));
da.s_addr = htonl(id->dst_ip);
inet_ntop(AF_INET, &da, dst, sizeof(dst));
}
log(log_flags, "ipfw: %s type %d %s %d -> %s %d, %d %s\n",
prefix, dyn_type, src, id->src_port, dst,
id->dst_port, DYN_COUNT, postfix);
}
#define print_dyn_rule(id, dtype, prefix, postfix) \
print_dyn_rule_flags(id, dtype, LOG_DEBUG, prefix, postfix)
#define TIME_LEQ(a,b) ((int)((a)-(b)) <= 0)
/*
* Lookup a dynamic rule, locked version.
*/
static ipfw_dyn_rule *
lookup_dyn_rule_locked(struct ipfw_flow_id *pkt, int i, int *match_direction,
struct tcphdr *tcp)
{
/*
* Stateful ipfw extensions.
* Lookup into dynamic session queue.
*/
#define MATCH_REVERSE 0
#define MATCH_FORWARD 1
#define MATCH_NONE 2
#define MATCH_UNKNOWN 3
int dir = MATCH_NONE;
ipfw_dyn_rule *prev, *q = NULL;
IPFW_BUCK_ASSERT(i);
for (prev = NULL, q = V_ipfw_dyn_v[i].head; q; prev = q, q = q->next) {
if (q->dyn_type == O_LIMIT_PARENT && q->count)
continue;
if (pkt->proto != q->id.proto || q->dyn_type == O_LIMIT_PARENT)
continue;
if (IS_IP6_FLOW_ID(pkt)) {
if (IN6_ARE_ADDR_EQUAL(&pkt->src_ip6, &q->id.src_ip6) &&
IN6_ARE_ADDR_EQUAL(&pkt->dst_ip6, &q->id.dst_ip6) &&
pkt->src_port == q->id.src_port &&
pkt->dst_port == q->id.dst_port) {
dir = MATCH_FORWARD;
break;
}
if (IN6_ARE_ADDR_EQUAL(&pkt->src_ip6, &q->id.dst_ip6) &&
IN6_ARE_ADDR_EQUAL(&pkt->dst_ip6, &q->id.src_ip6) &&
pkt->src_port == q->id.dst_port &&
pkt->dst_port == q->id.src_port) {
dir = MATCH_REVERSE;
break;
}
} else {
if (pkt->src_ip == q->id.src_ip &&
pkt->dst_ip == q->id.dst_ip &&
pkt->src_port == q->id.src_port &&
pkt->dst_port == q->id.dst_port) {
dir = MATCH_FORWARD;
break;
}
if (pkt->src_ip == q->id.dst_ip &&
pkt->dst_ip == q->id.src_ip &&
pkt->src_port == q->id.dst_port &&
pkt->dst_port == q->id.src_port) {
dir = MATCH_REVERSE;
break;
}
}
}
if (q == NULL)
goto done; /* q = NULL, not found */
if (prev != NULL) { /* found and not in front */
prev->next = q->next;
q->next = V_ipfw_dyn_v[i].head;
V_ipfw_dyn_v[i].head = q;
}
if (pkt->proto == IPPROTO_TCP) { /* update state according to flags */
uint32_t ack;
u_char flags = pkt->_flags & (TH_FIN | TH_SYN | TH_RST);
#define BOTH_SYN (TH_SYN | (TH_SYN << 8))
#define BOTH_FIN (TH_FIN | (TH_FIN << 8))
#define TCP_FLAGS (TH_FLAGS | (TH_FLAGS << 8))
#define ACK_FWD 0x10000 /* fwd ack seen */
#define ACK_REV 0x20000 /* rev ack seen */
q->state |= (dir == MATCH_FORWARD) ? flags : (flags << 8);
switch (q->state & TCP_FLAGS) {
case TH_SYN: /* opening */
q->expire = time_uptime + V_dyn_syn_lifetime;
break;
case BOTH_SYN: /* move to established */
case BOTH_SYN | TH_FIN: /* one side tries to close */
case BOTH_SYN | (TH_FIN << 8):
#define _SEQ_GE(a,b) ((int)(a) - (int)(b) >= 0)
if (tcp == NULL)
break;
ack = ntohl(tcp->th_ack);
if (dir == MATCH_FORWARD) {
if (q->ack_fwd == 0 ||
_SEQ_GE(ack, q->ack_fwd)) {
q->ack_fwd = ack;
q->state |= ACK_FWD;
}
} else {
if (q->ack_rev == 0 ||
_SEQ_GE(ack, q->ack_rev)) {
q->ack_rev = ack;
q->state |= ACK_REV;
}
}
if ((q->state & (ACK_FWD | ACK_REV)) ==
(ACK_FWD | ACK_REV)) {
q->expire = time_uptime + V_dyn_ack_lifetime;
q->state &= ~(ACK_FWD | ACK_REV);
}
break;
case BOTH_SYN | BOTH_FIN: /* both sides closed */
if (V_dyn_fin_lifetime >= V_dyn_keepalive_period)
V_dyn_fin_lifetime = V_dyn_keepalive_period - 1;
q->expire = time_uptime + V_dyn_fin_lifetime;
break;
default:
#if 0
/*
* reset or some invalid combination, but can also
* occur if we use keep-state the wrong way.
*/
if ( (q->state & ((TH_RST << 8)|TH_RST)) == 0)
printf("invalid state: 0x%x\n", q->state);
#endif
if (V_dyn_rst_lifetime >= V_dyn_keepalive_period)
V_dyn_rst_lifetime = V_dyn_keepalive_period - 1;
q->expire = time_uptime + V_dyn_rst_lifetime;
break;
}
} else if (pkt->proto == IPPROTO_UDP) {
q->expire = time_uptime + V_dyn_udp_lifetime;
} else {
/* other protocols */
q->expire = time_uptime + V_dyn_short_lifetime;
}
done:
if (match_direction != NULL)
*match_direction = dir;
return (q);
}
ipfw_dyn_rule *
ipfw_lookup_dyn_rule(struct ipfw_flow_id *pkt, int *match_direction,
struct tcphdr *tcp)
{
ipfw_dyn_rule *q;
int i;
i = hash_packet(pkt, V_curr_dyn_buckets);
IPFW_BUCK_LOCK(i);
q = lookup_dyn_rule_locked(pkt, i, match_direction, tcp);
if (q == NULL)
IPFW_BUCK_UNLOCK(i);
/* NB: return table locked when q is not NULL */
return q;
}
/*
* Unlock bucket mtx
* @p - pointer to dynamic rule
*/
void
ipfw_dyn_unlock(ipfw_dyn_rule *q)
{
IPFW_BUCK_UNLOCK(q->bucket);
}
static int
resize_dynamic_table(struct ip_fw_chain *chain, int nbuckets)
{
int i, k, nbuckets_old;
ipfw_dyn_rule *q;
struct ipfw_dyn_bucket *dyn_v, *dyn_v_old;
/* Check if given number is power of 2 and less than 64k */
if ((nbuckets > 65536) || (!powerof2(nbuckets)))
return 1;
CTR3(KTR_NET, "%s: resize dynamic hash: %d -> %d", __func__,
V_curr_dyn_buckets, nbuckets);
/* Allocate and initialize new hash */
dyn_v = malloc(nbuckets * sizeof(ipfw_dyn_rule), M_IPFW,
M_WAITOK | M_ZERO);
for (i = 0 ; i < nbuckets; i++)
IPFW_BUCK_LOCK_INIT(&dyn_v[i]);
/*
* Call upper half lock, as get_map() do to ease
* read-only access to dynamic rules hash from sysctl
*/
IPFW_UH_WLOCK(chain);
/*
* Acquire chain write lock to permit hash access
* for main traffic path without additional locks
*/
IPFW_WLOCK(chain);
/* Save old values */
nbuckets_old = V_curr_dyn_buckets;
dyn_v_old = V_ipfw_dyn_v;
/* Skip relinking if array is not set up */
if (V_ipfw_dyn_v == NULL)
V_curr_dyn_buckets = 0;
/* Re-link all dynamic states */
for (i = 0 ; i < V_curr_dyn_buckets ; i++) {
while (V_ipfw_dyn_v[i].head != NULL) {
/* Remove from current chain */
q = V_ipfw_dyn_v[i].head;
V_ipfw_dyn_v[i].head = q->next;
/* Get new hash value */
k = hash_packet(&q->id, nbuckets);
q->bucket = k;
/* Add to the new head */
q->next = dyn_v[k].head;
dyn_v[k].head = q;
}
}
/* Update current pointers/buckets values */
V_curr_dyn_buckets = nbuckets;
V_ipfw_dyn_v = dyn_v;
IPFW_WUNLOCK(chain);
IPFW_UH_WUNLOCK(chain);
/* Start periodic callout on initial creation */
if (dyn_v_old == NULL) {
callout_reset_on(&V_ipfw_timeout, hz, ipfw_dyn_tick, curvnet, 0);
return (0);
}
/* Destroy all mutexes */
for (i = 0 ; i < nbuckets_old ; i++)
IPFW_BUCK_LOCK_DESTROY(&dyn_v_old[i]);
/* Free old hash */
free(dyn_v_old, M_IPFW);
return 0;
}
/**
* Install state of type 'type' for a dynamic session.
* The hash table contains two type of rules:
* - regular rules (O_KEEP_STATE)
* - rules for sessions with limited number of sess per user
* (O_LIMIT). When they are created, the parent is
* increased by 1, and decreased on delete. In this case,
* the third parameter is the parent rule and not the chain.
* - "parent" rules for the above (O_LIMIT_PARENT).
*/
static ipfw_dyn_rule *
add_dyn_rule(struct ipfw_flow_id *id, int i, u_int8_t dyn_type, struct ip_fw *rule)
{
ipfw_dyn_rule *r;
IPFW_BUCK_ASSERT(i);
r = uma_zalloc(V_ipfw_dyn_rule_zone, M_NOWAIT | M_ZERO);
if (r == NULL) {
if (last_log != time_uptime) {
last_log = time_uptime;
log(LOG_DEBUG, "ipfw: %s: Cannot allocate rule\n",
__func__);
}
return NULL;
}
/*
* refcount on parent is already incremented, so
* it is safe to use parent unlocked.
*/
if (dyn_type == O_LIMIT) {
ipfw_dyn_rule *parent = (ipfw_dyn_rule *)rule;
if ( parent->dyn_type != O_LIMIT_PARENT)
panic("invalid parent");
r->parent = parent;
rule = parent->rule;
}
r->id = *id;
r->expire = time_uptime + V_dyn_syn_lifetime;
r->rule = rule;
r->dyn_type = dyn_type;
IPFW_ZERO_DYN_COUNTER(r);
r->count = 0;
r->bucket = i;
r->next = V_ipfw_dyn_v[i].head;
V_ipfw_dyn_v[i].head = r;
DEB(print_dyn_rule(id, dyn_type, "add dyn entry", "total");)
return r;
}
/**
* lookup dynamic parent rule using pkt and rule as search keys.
* If the lookup fails, then install one.
*/
static ipfw_dyn_rule *
lookup_dyn_parent(struct ipfw_flow_id *pkt, int *pindex, struct ip_fw *rule)
{
ipfw_dyn_rule *q;
int i, is_v6;
is_v6 = IS_IP6_FLOW_ID(pkt);
i = hash_packet( pkt, V_curr_dyn_buckets );
*pindex = i;
IPFW_BUCK_LOCK(i);
for (q = V_ipfw_dyn_v[i].head ; q != NULL ; q=q->next)
if (q->dyn_type == O_LIMIT_PARENT &&
rule== q->rule &&
pkt->proto == q->id.proto &&
pkt->src_port == q->id.src_port &&
pkt->dst_port == q->id.dst_port &&
(
(is_v6 &&
IN6_ARE_ADDR_EQUAL(&(pkt->src_ip6),
&(q->id.src_ip6)) &&
IN6_ARE_ADDR_EQUAL(&(pkt->dst_ip6),
&(q->id.dst_ip6))) ||
(!is_v6 &&
pkt->src_ip == q->id.src_ip &&
pkt->dst_ip == q->id.dst_ip)
)
) {
q->expire = time_uptime + V_dyn_short_lifetime;
DEB(print_dyn_rule(pkt, q->dyn_type,
"lookup_dyn_parent found", "");)
return q;
}
/* Add virtual limiting rule */
return add_dyn_rule(pkt, i, O_LIMIT_PARENT, rule);
}
/**
* Install dynamic state for rule type cmd->o.opcode
*
* Returns 1 (failure) if state is not installed because of errors or because
* session limitations are enforced.
*/
int
ipfw_install_state(struct ip_fw *rule, ipfw_insn_limit *cmd,
struct ip_fw_args *args, uint32_t tablearg)
{
ipfw_dyn_rule *q;
int i;
DEB(print_dyn_rule(&args->f_id, cmd->o.opcode, "install_state", "");)
i = hash_packet(&args->f_id, V_curr_dyn_buckets);
IPFW_BUCK_LOCK(i);
q = lookup_dyn_rule_locked(&args->f_id, i, NULL, NULL);
if (q != NULL) { /* should never occur */
DEB(
if (last_log != time_uptime) {
last_log = time_uptime;
printf("ipfw: %s: entry already present, done\n",
__func__);
})
IPFW_BUCK_UNLOCK(i);
return (0);
}
/*
* State limiting is done via uma(9) zone limiting.
* Save pointer to newly-installed rule and reject
* packet if add_dyn_rule() returned NULL.
* Note q is currently set to NULL.
*/
switch (cmd->o.opcode) {
case O_KEEP_STATE: /* bidir rule */
q = add_dyn_rule(&args->f_id, i, O_KEEP_STATE, rule);
break;
case O_LIMIT: { /* limit number of sessions */
struct ipfw_flow_id id;
ipfw_dyn_rule *parent;
uint32_t conn_limit;
uint16_t limit_mask = cmd->limit_mask;
int pindex;
conn_limit = (cmd->conn_limit == IP_FW_TABLEARG) ?
tablearg : cmd->conn_limit;
DEB(
if (cmd->conn_limit == IP_FW_TABLEARG)
printf("ipfw: %s: O_LIMIT rule, conn_limit: %u "
"(tablearg)\n", __func__, conn_limit);
else
printf("ipfw: %s: O_LIMIT rule, conn_limit: %u\n",
__func__, conn_limit);
)
id.dst_ip = id.src_ip = id.dst_port = id.src_port = 0;
id.proto = args->f_id.proto;
id.addr_type = args->f_id.addr_type;
id.fib = M_GETFIB(args->m);
if (IS_IP6_FLOW_ID (&(args->f_id))) {
if (limit_mask & DYN_SRC_ADDR)
id.src_ip6 = args->f_id.src_ip6;
if (limit_mask & DYN_DST_ADDR)
id.dst_ip6 = args->f_id.dst_ip6;
} else {
if (limit_mask & DYN_SRC_ADDR)
id.src_ip = args->f_id.src_ip;
if (limit_mask & DYN_DST_ADDR)
id.dst_ip = args->f_id.dst_ip;
}
if (limit_mask & DYN_SRC_PORT)
id.src_port = args->f_id.src_port;
if (limit_mask & DYN_DST_PORT)
id.dst_port = args->f_id.dst_port;
/*
* We have to release lock for previous bucket to
* avoid possible deadlock
*/
IPFW_BUCK_UNLOCK(i);
if ((parent = lookup_dyn_parent(&id, &pindex, rule)) == NULL) {
printf("ipfw: %s: add parent failed\n", __func__);
IPFW_BUCK_UNLOCK(pindex);
return (1);
}
if (parent->count >= conn_limit) {
if (V_fw_verbose && last_log != time_uptime) {
last_log = time_uptime;
char sbuf[24];
last_log = time_uptime;
snprintf(sbuf, sizeof(sbuf),
"%d drop session",
parent->rule->rulenum);
print_dyn_rule_flags(&args->f_id,
cmd->o.opcode,
LOG_SECURITY | LOG_DEBUG,
sbuf, "too many entries");
}
IPFW_BUCK_UNLOCK(pindex);
return (1);
}
/* Increment counter on parent */
parent->count++;
IPFW_BUCK_UNLOCK(pindex);
IPFW_BUCK_LOCK(i);
q = add_dyn_rule(&args->f_id, i, O_LIMIT, (struct ip_fw *)parent);
if (q == NULL) {
/* Decrement index and notify caller */
IPFW_BUCK_UNLOCK(i);
IPFW_BUCK_LOCK(pindex);
parent->count--;
IPFW_BUCK_UNLOCK(pindex);
return (1);
}
break;
}
default:
printf("ipfw: %s: unknown dynamic rule type %u\n",
__func__, cmd->o.opcode);
}
if (q == NULL) {
IPFW_BUCK_UNLOCK(i);
return (1); /* Notify caller about failure */
}
/* XXX just set lifetime */
lookup_dyn_rule_locked(&args->f_id, i, NULL, NULL);
IPFW_BUCK_UNLOCK(i);
return (0);
}
/*
* Generate a TCP packet, containing either a RST or a keepalive.
* When flags & TH_RST, we are sending a RST packet, because of a
* "reset" action matched the packet.
* Otherwise we are sending a keepalive, and flags & TH_
* The 'replyto' mbuf is the mbuf being replied to, if any, and is required
* so that MAC can label the reply appropriately.
*/
struct mbuf *
ipfw_send_pkt(struct mbuf *replyto, struct ipfw_flow_id *id, u_int32_t seq,
u_int32_t ack, int flags)
{
struct mbuf *m = NULL; /* stupid compiler */
int len, dir;
struct ip *h = NULL; /* stupid compiler */
#ifdef INET6
struct ip6_hdr *h6 = NULL;
#endif
struct tcphdr *th = NULL;
MGETHDR(m, M_NOWAIT, MT_DATA);
if (m == NULL)
return (NULL);
M_SETFIB(m, id->fib);
#ifdef MAC
if (replyto != NULL)
mac_netinet_firewall_reply(replyto, m);
else
mac_netinet_firewall_send(m);
#else
(void)replyto; /* don't warn about unused arg */
#endif
switch (id->addr_type) {
case 4:
len = sizeof(struct ip) + sizeof(struct tcphdr);
break;
#ifdef INET6
case 6:
len = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
break;
#endif
default:
/* XXX: log me?!? */
FREE_PKT(m);
return (NULL);
}
dir = ((flags & (TH_SYN | TH_RST)) == TH_SYN);
m->m_data += max_linkhdr;
m->m_flags |= M_SKIP_FIREWALL;
m->m_pkthdr.len = m->m_len = len;
m->m_pkthdr.rcvif = NULL;
bzero(m->m_data, len);
switch (id->addr_type) {
case 4:
h = mtod(m, struct ip *);
/* prepare for checksum */
h->ip_p = IPPROTO_TCP;
h->ip_len = htons(sizeof(struct tcphdr));
if (dir) {
h->ip_src.s_addr = htonl(id->src_ip);
h->ip_dst.s_addr = htonl(id->dst_ip);
} else {
h->ip_src.s_addr = htonl(id->dst_ip);
h->ip_dst.s_addr = htonl(id->src_ip);
}
th = (struct tcphdr *)(h + 1);
break;
#ifdef INET6
case 6:
h6 = mtod(m, struct ip6_hdr *);
/* prepare for checksum */
h6->ip6_nxt = IPPROTO_TCP;
h6->ip6_plen = htons(sizeof(struct tcphdr));
if (dir) {
h6->ip6_src = id->src_ip6;
h6->ip6_dst = id->dst_ip6;
} else {
h6->ip6_src = id->dst_ip6;
h6->ip6_dst = id->src_ip6;
}
th = (struct tcphdr *)(h6 + 1);
break;
#endif
}
if (dir) {
th->th_sport = htons(id->src_port);
th->th_dport = htons(id->dst_port);
} else {
th->th_sport = htons(id->dst_port);
th->th_dport = htons(id->src_port);
}
th->th_off = sizeof(struct tcphdr) >> 2;
if (flags & TH_RST) {
if (flags & TH_ACK) {
th->th_seq = htonl(ack);
th->th_flags = TH_RST;
} else {
if (flags & TH_SYN)
seq++;
th->th_ack = htonl(seq);
th->th_flags = TH_RST | TH_ACK;
}
} else {
/*
* Keepalive - use caller provided sequence numbers
*/
th->th_seq = htonl(seq);
th->th_ack = htonl(ack);
th->th_flags = TH_ACK;
}
switch (id->addr_type) {
case 4:
th->th_sum = in_cksum(m, len);
/* finish the ip header */
h->ip_v = 4;
h->ip_hl = sizeof(*h) >> 2;
h->ip_tos = IPTOS_LOWDELAY;
h->ip_off = htons(0);
h->ip_len = htons(len);
h->ip_ttl = V_ip_defttl;
h->ip_sum = 0;
break;
#ifdef INET6
case 6:
th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(*h6),
sizeof(struct tcphdr));
/* finish the ip6 header */
h6->ip6_vfc |= IPV6_VERSION;
h6->ip6_hlim = IPV6_DEFHLIM;
break;
#endif
}
return (m);
}
/*
* Queue keepalive packets for given dynamic rule
*/
static struct mbuf **
ipfw_dyn_send_ka(struct mbuf **mtailp, ipfw_dyn_rule *q)
{
struct mbuf *m_rev, *m_fwd;
m_rev = (q->state & ACK_REV) ? NULL :
ipfw_send_pkt(NULL, &(q->id), q->ack_rev - 1, q->ack_fwd, TH_SYN);
m_fwd = (q->state & ACK_FWD) ? NULL :
ipfw_send_pkt(NULL, &(q->id), q->ack_fwd - 1, q->ack_rev, 0);
if (m_rev != NULL) {
*mtailp = m_rev;
mtailp = &(*mtailp)->m_nextpkt;
}
if (m_fwd != NULL) {
*mtailp = m_fwd;
mtailp = &(*mtailp)->m_nextpkt;
}
return (mtailp);
}
/*
* This procedure is used to perform various maintance
* on dynamic hash list. Currently it is called every second.
*/
static void
ipfw_dyn_tick(void * vnetx)
{
struct ip_fw_chain *chain;
int check_ka = 0;
#ifdef VIMAGE
struct vnet *vp = vnetx;
#endif
CURVNET_SET(vp);
chain = &V_layer3_chain;
/* Run keepalive checks every keepalive_interval iff ka is enabled */
if ((V_dyn_keepalive_last + V_dyn_keepalive_interval >= time_uptime) &&
(V_dyn_keepalive != 0)) {
V_dyn_keepalive_last = time_uptime;
check_ka = 1;
}
check_dyn_rules(chain, NULL, RESVD_SET, check_ka, 1);
callout_reset_on(&V_ipfw_timeout, hz, ipfw_dyn_tick, vnetx, 0);
CURVNET_RESTORE();
}
/*
* Walk thru all dynamic states doing generic maintance:
* 1) free expired states
* 2) free all states based on deleted rule / set
* 3) send keepalives for states if needed
*
* @chain - pointer to current ipfw rules chain
* @rule - delete all states originated by given rule if != NULL
* @set - delete all states originated by any rule in set @set if != RESVD_SET
* @check_ka - perform checking/sending keepalives
* @timer - indicate call from timer routine.
*
* Timer routine must call this function unlocked to permit
* sending keepalives/resizing table.
*
* Others has to call function with IPFW_UH_WLOCK held.
* Additionally, function assume that dynamic rule/set is
* ALREADY deleted so no new states can be generated by
* 'deleted' rules.
*
* Write lock is needed to ensure that unused parent rules
* are not freed by other instance (see stage 2, 3)
*/
static void
check_dyn_rules(struct ip_fw_chain *chain, struct ip_fw *rule,
int set, int check_ka, int timer)
{
struct mbuf *m0, *m, *mnext, **mtailp;
struct ip *h;
int i, dyn_count, new_buckets = 0, max_buckets;
int expired = 0, expired_limits = 0, parents = 0, total = 0;
ipfw_dyn_rule *q, *q_prev, *q_next;
ipfw_dyn_rule *exp_head, **exptailp;
ipfw_dyn_rule *exp_lhead, **expltailp;
KASSERT(V_ipfw_dyn_v != NULL, ("%s: dynamic table not allocated",
__func__));
/* Avoid possible LOR */
KASSERT(!check_ka || timer, ("%s: keepalive check with lock held",
__func__));
/*
* Do not perform any checks if we currently have no dynamic states
*/
if (DYN_COUNT == 0)
return;
/* Expired states */
exp_head = NULL;
exptailp = &exp_head;
/* Expired limit states */
exp_lhead = NULL;
expltailp = &exp_lhead;
/*
* We make a chain of packets to go out here -- not deferring
* until after we drop the IPFW dynamic rule lock would result
* in a lock order reversal with the normal packet input -> ipfw
* call stack.
*/
m0 = NULL;
mtailp = &m0;
/* Protect from hash resizing */
if (timer != 0)
IPFW_UH_WLOCK(chain);
else
IPFW_UH_WLOCK_ASSERT(chain);
#define NEXT_RULE() { q_prev = q; q = q->next ; continue; }
/* Stage 1: perform requested deletion */
for (i = 0 ; i < V_curr_dyn_buckets ; i++) {
IPFW_BUCK_LOCK(i);
for (q = V_ipfw_dyn_v[i].head, q_prev = q; q ; ) {
/* account every rule */
total++;
/* Skip parent rules at all */
if (q->dyn_type == O_LIMIT_PARENT) {
parents++;
NEXT_RULE();
}
/*
* Remove rules which are:
* 1) expired
* 2) created by given rule
* 3) created by any rule in given set
*/
if ((TIME_LEQ(q->expire, time_uptime)) ||
((rule != NULL) && (q->rule == rule)) ||
((set != RESVD_SET) && (q->rule->set == set))) {
/* Unlink q from current list */
q_next = q->next;
if (q == V_ipfw_dyn_v[i].head)
V_ipfw_dyn_v[i].head = q_next;
else
q_prev->next = q_next;
q->next = NULL;
/* queue q to expire list */
if (q->dyn_type != O_LIMIT) {
*exptailp = q;
exptailp = &(*exptailp)->next;
DEB(print_dyn_rule(&q->id, q->dyn_type,
"unlink entry", "left");
)
} else {
/* Separate list for limit rules */
*expltailp = q;
expltailp = &(*expltailp)->next;
expired_limits++;
DEB(print_dyn_rule(&q->id, q->dyn_type,
"unlink limit entry", "left");
)
}
q = q_next;
expired++;
continue;
}
/*
* Check if we need to send keepalive:
* we need to ensure if is time to do KA,
* this is established TCP session, and
* expire time is within keepalive interval
*/
if ((check_ka != 0) && (q->id.proto == IPPROTO_TCP) &&
((q->state & BOTH_SYN) == BOTH_SYN) &&
(TIME_LEQ(q->expire, time_uptime +
V_dyn_keepalive_interval)))
mtailp = ipfw_dyn_send_ka(mtailp, q);
NEXT_RULE();
}
IPFW_BUCK_UNLOCK(i);
}
/* Stage 2: decrement counters from O_LIMIT parents */
if (expired_limits != 0) {
/*
* XXX: Note that deleting set with more than one
* heavily-used LIMIT rules can result in overwhelming
* locking due to lack of per-hash value sorting
*
* We should probably think about:
* 1) pre-allocating hash of size, say,
* MAX(16, V_curr_dyn_buckets / 1024)
* 2) checking if expired_limits is large enough
* 3) If yes, init hash (or its part), re-link
* current list and start decrementing procedure in
* each bucket separately
*/
/*
* Small optimization: do not unlock bucket until
* we see the next item resides in different bucket
*/
if (exp_lhead != NULL) {
i = exp_lhead->parent->bucket;
IPFW_BUCK_LOCK(i);
}
for (q = exp_lhead; q != NULL; q = q->next) {
if (i != q->parent->bucket) {
IPFW_BUCK_UNLOCK(i);
i = q->parent->bucket;
IPFW_BUCK_LOCK(i);
}
/* Decrease parent refcount */
q->parent->count--;
}
if (exp_lhead != NULL)
IPFW_BUCK_UNLOCK(i);
}
/*
* We protectet ourselves from unused parent deletion
* (from the timer function) by holding UH write lock.
*/
/* Stage 3: remove unused parent rules */
if ((parents != 0) && (expired != 0)) {
for (i = 0 ; i < V_curr_dyn_buckets ; i++) {
IPFW_BUCK_LOCK(i);
for (q = V_ipfw_dyn_v[i].head, q_prev = q ; q ; ) {
if (q->dyn_type != O_LIMIT_PARENT)
NEXT_RULE();
if (q->count != 0)
NEXT_RULE();
/* Parent rule without consumers */
/* Unlink q from current list */
q_next = q->next;
if (q == V_ipfw_dyn_v[i].head)
V_ipfw_dyn_v[i].head = q_next;
else
q_prev->next = q_next;
q->next = NULL;
/* Add to expired list */
*exptailp = q;
exptailp = &(*exptailp)->next;
DEB(print_dyn_rule(&q->id, q->dyn_type,
"unlink parent entry", "left");
)
expired++;
q = q_next;
}
IPFW_BUCK_UNLOCK(i);
}
}
#undef NEXT_RULE
if (timer != 0) {
/*
* Check if we need to resize hash:
* if current number of states exceeds number of buckes in hash,
* grow hash size to the minimum power of 2 which is bigger than
* current states count. Limit hash size by 64k.
*/
max_buckets = (V_dyn_buckets_max > 65536) ?
65536 : V_dyn_buckets_max;
dyn_count = DYN_COUNT;
if ((dyn_count > V_curr_dyn_buckets * 2) &&
(dyn_count < max_buckets)) {
new_buckets = V_curr_dyn_buckets;
while (new_buckets < dyn_count) {
new_buckets *= 2;
if (new_buckets >= max_buckets)
break;
}
}
IPFW_UH_WUNLOCK(chain);
}
/* Finally delete old states ad limits if any */
for (q = exp_head; q != NULL; q = q_next) {
q_next = q->next;
uma_zfree(V_ipfw_dyn_rule_zone, q);
}
for (q = exp_lhead; q != NULL; q = q_next) {
q_next = q->next;
uma_zfree(V_ipfw_dyn_rule_zone, q);
}
/*
* The rest code MUST be called from timer routine only
* without holding any locks
*/
if (timer == 0)
return;
/* Send keepalive packets if any */
for (m = m0; m != NULL; m = mnext) {
mnext = m->m_nextpkt;
m->m_nextpkt = NULL;
h = mtod(m, struct ip *);
if (h->ip_v == 4)
ip_output(m, NULL, NULL, 0, NULL, NULL);
#ifdef INET6
else
ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
#endif
}
/* Run table resize without holding any locks */
if (new_buckets != 0)
resize_dynamic_table(chain, new_buckets);
}
/*
* Deletes all dynamic rules originated by given rule or all rules in
* given set. Specify RESVD_SET to indicate set should not be used.
* @chain - pointer to current ipfw rules chain
* @rule - delete all states originated by given rule if != NULL
* @set - delete all states originated by any rule in set @set if != RESVD_SET
*
* Function has to be called with IPFW_UH_WLOCK held.
* Additionally, function assume that dynamic rule/set is
* ALREADY deleted so no new states can be generated by
* 'deleted' rules.
*/
void
ipfw_expire_dyn_rules(struct ip_fw_chain *chain, struct ip_fw *rule, int set)
{
check_dyn_rules(chain, rule, set, 0, 0);
}
void
ipfw_dyn_init(struct ip_fw_chain *chain)
{
V_ipfw_dyn_v = NULL;
V_dyn_buckets_max = 256; /* must be power of 2 */
V_curr_dyn_buckets = 256; /* must be power of 2 */
V_dyn_ack_lifetime = 300;
V_dyn_syn_lifetime = 20;
V_dyn_fin_lifetime = 1;
V_dyn_rst_lifetime = 1;
V_dyn_udp_lifetime = 10;
V_dyn_short_lifetime = 5;
V_dyn_keepalive_interval = 20;
V_dyn_keepalive_period = 5;
V_dyn_keepalive = 1; /* do send keepalives */
V_dyn_keepalive = time_uptime;
V_dyn_max = 4096; /* max # of dynamic rules */
V_ipfw_dyn_rule_zone = uma_zcreate("IPFW dynamic rule",
sizeof(ipfw_dyn_rule), NULL, NULL, NULL, NULL,
UMA_ALIGN_PTR, 0);
/* Enforce limit on dynamic rules */
uma_zone_set_max(V_ipfw_dyn_rule_zone, V_dyn_max);
callout_init(&V_ipfw_timeout, CALLOUT_MPSAFE);
/*
* This can potentially be done on first dynamic rule
* being added to chain.
*/
resize_dynamic_table(chain, V_curr_dyn_buckets);
}
void
ipfw_dyn_uninit(int pass)
{
int i;
if (pass == 0) {
callout_drain(&V_ipfw_timeout);
return;
}
if (V_ipfw_dyn_v != NULL) {
/*
* Skip deleting all dynamic states -
* uma_zdestroy() does this more efficiently;
*/
/* Destroy all mutexes */
for (i = 0 ; i < V_curr_dyn_buckets ; i++)
IPFW_BUCK_LOCK_DESTROY(&V_ipfw_dyn_v[i]);
free(V_ipfw_dyn_v, M_IPFW);
V_ipfw_dyn_v = NULL;
}
uma_zdestroy(V_ipfw_dyn_rule_zone);
}
#ifdef SYSCTL_NODE
/*
* Get/set maximum number of dynamic states in given VNET instance.
*/
static int
sysctl_ipfw_dyn_max(SYSCTL_HANDLER_ARGS)
{
int error;
unsigned int nstates;
nstates = V_dyn_max;
error = sysctl_handle_int(oidp, &nstates, 0, req);
/* Read operation or some error */
if ((error != 0) || (req->newptr == NULL))
return (error);
V_dyn_max = nstates;
uma_zone_set_max(V_ipfw_dyn_rule_zone, V_dyn_max);
return (0);
}
/*
* Get current number of dynamic states in given VNET instance.
*/
static int
sysctl_ipfw_dyn_count(SYSCTL_HANDLER_ARGS)
{
int error;
unsigned int nstates;
nstates = DYN_COUNT;
error = sysctl_handle_int(oidp, &nstates, 0, req);
return (error);
}
#endif
/*
* Returns number of dynamic rules.
*/
int
ipfw_dyn_len(void)
{
return (V_ipfw_dyn_v == NULL) ? 0 :
(DYN_COUNT * sizeof(ipfw_dyn_rule));
}
/*
* Fill given buffer with dynamic states.
* IPFW_UH_RLOCK has to be held while calling.
*/
void
ipfw_get_dynamic(struct ip_fw_chain *chain, char **pbp, const char *ep)
{
ipfw_dyn_rule *p, *last = NULL;
char *bp;
int i;
if (V_ipfw_dyn_v == NULL)
return;
bp = *pbp;
IPFW_UH_RLOCK_ASSERT(chain);
for (i = 0 ; i < V_curr_dyn_buckets; i++) {
IPFW_BUCK_LOCK(i);
for (p = V_ipfw_dyn_v[i].head ; p != NULL; p = p->next) {
if (bp + sizeof *p <= ep) {
ipfw_dyn_rule *dst =
(ipfw_dyn_rule *)bp;
bcopy(p, dst, sizeof *p);
bcopy(&(p->rule->rulenum), &(dst->rule),
sizeof(p->rule->rulenum));
/*
* store set number into high word of
* dst->rule pointer.
*/
bcopy(&(p->rule->set),
(char *)&dst->rule +
sizeof(p->rule->rulenum),
sizeof(p->rule->set));
/*
* store a non-null value in "next".
* The userland code will interpret a
* NULL here as a marker
* for the last dynamic rule.
*/
bcopy(&dst, &dst->next, sizeof(dst));
last = dst;
dst->expire =
TIME_LEQ(dst->expire, time_uptime) ?
0 : dst->expire - time_uptime ;
bp += sizeof(ipfw_dyn_rule);
}
}
IPFW_BUCK_UNLOCK(i);
}
if (last != NULL) /* mark last dynamic rule */
bzero(&last->next, sizeof(last));
*pbp = bp;
}
/* end of file */
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