ipt_ULOG.c
/*
* netfilter module for userspace packet logging daemons
*
* (C) 2000-2004 by Harald Welte <laforge@netfilter.org>
* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
*
* 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.
*
* This module accepts two parameters:
*
* nlbufsiz:
* The parameter specifies how big the buffer for each netlink multicast
* group is. e.g. If you say nlbufsiz=8192, up to eight kb of packets will
* get accumulated in the kernel until they are sent to userspace. It is
* NOT possible to allocate more than 128kB, and it is strongly discouraged,
* because atomically allocating 128kB inside the network rx softirq is not
* reliable. Please also keep in mind that this buffer size is allocated for
* each nlgroup you are using, so the total kernel memory usage increases
* by that factor.
*
* Actually you should use nlbufsiz a bit smaller than PAGE_SIZE, since
* nlbufsiz is used with alloc_skb, which adds another
* sizeof(struct skb_shared_info). Use NLMSG_GOODSIZE instead.
*
* flushtimeout:
* Specify, after how many hundredths of a second the queue should be
* flushed even if it is not full yet.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/socket.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/netlink.h>
#include <linux/netdevice.h>
#include <linux/mm.h>
#include <linux/moduleparam.h>
#include <linux/netfilter.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ipt_ULOG.h>
#include <net/netfilter/nf_log.h>
#include <net/sock.h>
#include <linux/bitops.h>
#include <asm/unaligned.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
MODULE_DESCRIPTION("Xtables: packet logging to netlink using ULOG");
MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NFLOG);
#define ULOG_NL_EVENT 111 /* Harald's favorite number */
#define ULOG_MAXNLGROUPS 32 /* numer of nlgroups */
static unsigned int nlbufsiz = NLMSG_GOODSIZE;
module_param(nlbufsiz, uint, 0400);
MODULE_PARM_DESC(nlbufsiz, "netlink buffer size");
static unsigned int flushtimeout = 10;
module_param(flushtimeout, uint, 0600);
MODULE_PARM_DESC(flushtimeout, "buffer flush timeout (hundredths of a second)");
static bool nflog = true;
module_param(nflog, bool, 0400);
MODULE_PARM_DESC(nflog, "register as internal netfilter logging module");
/* global data structures */
typedef struct {
unsigned int qlen; /* number of nlmsgs' in the skb */
struct nlmsghdr *lastnlh; /* netlink header of last msg in skb */
struct sk_buff *skb; /* the pre-allocated skb */
struct timer_list timer; /* the timer function */
} ulog_buff_t;
static ulog_buff_t ulog_buffers[ULOG_MAXNLGROUPS]; /* array of buffers */
static struct sock *nflognl; /* our socket */
static DEFINE_SPINLOCK(ulog_lock); /* spinlock */
/* send one ulog_buff_t to userspace */
static void ulog_send(unsigned int nlgroupnum)
{
ulog_buff_t *ub = &ulog_buffers[nlgroupnum];
if (timer_pending(&ub->timer)) {
pr_debug("ulog_send: timer was pending, deleting\n");
del_timer(&ub->timer);
}
if (!ub->skb) {
pr_debug("ulog_send: nothing to send\n");
return;
}
/* last nlmsg needs NLMSG_DONE */
if (ub->qlen > 1)
ub->lastnlh->nlmsg_type = NLMSG_DONE;
NETLINK_CB(ub->skb).dst_group = nlgroupnum + 1;
pr_debug("throwing %d packets to netlink group %u\n",
ub->qlen, nlgroupnum + 1);
netlink_broadcast(nflognl, ub->skb, 0, nlgroupnum + 1, GFP_ATOMIC);
ub->qlen = 0;
ub->skb = NULL;
ub->lastnlh = NULL;
}
/* timer function to flush queue in flushtimeout time */
static void ulog_timer(unsigned long data)
{
pr_debug("timer function called, calling ulog_send\n");
/* lock to protect against somebody modifying our structure
* from ipt_ulog_target at the same time */
spin_lock_bh(&ulog_lock);
ulog_send(data);
spin_unlock_bh(&ulog_lock);
}
static struct sk_buff *ulog_alloc_skb(unsigned int size)
{
struct sk_buff *skb;
unsigned int n;
/* alloc skb which should be big enough for a whole
* multipart message. WARNING: has to be <= 131000
* due to slab allocator restrictions */
n = max(size, nlbufsiz);
skb = alloc_skb(n, GFP_ATOMIC | __GFP_NOWARN);
if (!skb) {
if (n > size) {
/* try to allocate only as much as we need for
* current packet */
skb = alloc_skb(size, GFP_ATOMIC);
if (!skb)
pr_debug("cannot even allocate %ub\n", size);
}
}
return skb;
}
static void ipt_ulog_packet(unsigned int hooknum,
const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const struct ipt_ulog_info *loginfo,
const char *prefix)
{
ulog_buff_t *ub;
ulog_packet_msg_t *pm;
size_t size, copy_len;
struct nlmsghdr *nlh;
struct timeval tv;
/* ffs == find first bit set, necessary because userspace
* is already shifting groupnumber, but we need unshifted.
* ffs() returns [1..32], we need [0..31] */
unsigned int groupnum = ffs(loginfo->nl_group) - 1;
/* calculate the size of the skb needed */
if (loginfo->copy_range == 0 || loginfo->copy_range > skb->len)
copy_len = skb->len;
else
copy_len = loginfo->copy_range;
size = NLMSG_SPACE(sizeof(*pm) + copy_len);
ub = &ulog_buffers[groupnum];
spin_lock_bh(&ulog_lock);
if (!ub->skb) {
if (!(ub->skb = ulog_alloc_skb(size)))
goto alloc_failure;
} else if (ub->qlen >= loginfo->qthreshold ||
size > skb_tailroom(ub->skb)) {
/* either the queue len is too high or we don't have
* enough room in nlskb left. send it to userspace. */
ulog_send(groupnum);
if (!(ub->skb = ulog_alloc_skb(size)))
goto alloc_failure;
}
pr_debug("qlen %d, qthreshold %Zu\n", ub->qlen, loginfo->qthreshold);
nlh = nlmsg_put(ub->skb, 0, ub->qlen, ULOG_NL_EVENT,
sizeof(*pm)+copy_len, 0);
if (!nlh) {
pr_debug("error during nlmsg_put\n");
goto out_unlock;
}
ub->qlen++;
pm = nlmsg_data(nlh);
/* We might not have a timestamp, get one */
if (skb->tstamp.tv64 == 0)
__net_timestamp((struct sk_buff *)skb);
/* copy hook, prefix, timestamp, payload, etc. */
pm->data_len = copy_len;
tv = ktime_to_timeval(skb->tstamp);
put_unaligned(tv.tv_sec, &pm->timestamp_sec);
put_unaligned(tv.tv_usec, &pm->timestamp_usec);
put_unaligned(skb->mark, &pm->mark);
pm->hook = hooknum;
if (prefix != NULL)
strncpy(pm->prefix, prefix, sizeof(pm->prefix));
else if (loginfo->prefix[0] != '\0')
strncpy(pm->prefix, loginfo->prefix, sizeof(pm->prefix));
else
*(pm->prefix) = '\0';
if (in && in->hard_header_len > 0 &&
skb->mac_header != skb->network_header &&
in->hard_header_len <= ULOG_MAC_LEN) {
memcpy(pm->mac, skb_mac_header(skb), in->hard_header_len);
pm->mac_len = in->hard_header_len;
} else
pm->mac_len = 0;
if (in)
strncpy(pm->indev_name, in->name, sizeof(pm->indev_name));
else
pm->indev_name[0] = '\0';
if (out)
strncpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
else
pm->outdev_name[0] = '\0';
/* copy_len <= skb->len, so can't fail. */
if (skb_copy_bits(skb, 0, pm->payload, copy_len) < 0)
BUG();
/* check if we are building multi-part messages */
if (ub->qlen > 1)
ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;
ub->lastnlh = nlh;
/* if timer isn't already running, start it */
if (!timer_pending(&ub->timer)) {
ub->timer.expires = jiffies + flushtimeout * HZ / 100;
add_timer(&ub->timer);
}
/* if threshold is reached, send message to userspace */
if (ub->qlen >= loginfo->qthreshold) {
if (loginfo->qthreshold > 1)
nlh->nlmsg_type = NLMSG_DONE;
ulog_send(groupnum);
}
out_unlock:
spin_unlock_bh(&ulog_lock);
return;
alloc_failure:
pr_debug("Error building netlink message\n");
spin_unlock_bh(&ulog_lock);
}
static unsigned int
ulog_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
ipt_ulog_packet(par->hooknum, skb, par->in, par->out,
par->targinfo, NULL);
return XT_CONTINUE;
}
static void ipt_logfn(u_int8_t pf,
unsigned int hooknum,
const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const struct nf_loginfo *li,
const char *prefix)
{
struct ipt_ulog_info loginfo;
if (!li || li->type != NF_LOG_TYPE_ULOG) {
loginfo.nl_group = ULOG_DEFAULT_NLGROUP;
loginfo.copy_range = 0;
loginfo.qthreshold = ULOG_DEFAULT_QTHRESHOLD;
loginfo.prefix[0] = '\0';
} else {
loginfo.nl_group = li->u.ulog.group;
loginfo.copy_range = li->u.ulog.copy_len;
loginfo.qthreshold = li->u.ulog.qthreshold;
strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
}
ipt_ulog_packet(hooknum, skb, in, out, &loginfo, prefix);
}
static int ulog_tg_check(const struct xt_tgchk_param *par)
{
const struct ipt_ulog_info *loginfo = par->targinfo;
if (loginfo->prefix[sizeof(loginfo->prefix) - 1] != '\0') {
pr_debug("prefix not null-terminated\n");
return -EINVAL;
}
if (loginfo->qthreshold > ULOG_MAX_QLEN) {
pr_debug("queue threshold %Zu > MAX_QLEN\n",
loginfo->qthreshold);
return -EINVAL;
}
return 0;
}
#ifdef CONFIG_COMPAT
struct compat_ipt_ulog_info {
compat_uint_t nl_group;
compat_size_t copy_range;
compat_size_t qthreshold;
char prefix[ULOG_PREFIX_LEN];
};
static void ulog_tg_compat_from_user(void *dst, const void *src)
{
const struct compat_ipt_ulog_info *cl = src;
struct ipt_ulog_info l = {
.nl_group = cl->nl_group,
.copy_range = cl->copy_range,
.qthreshold = cl->qthreshold,
};
memcpy(l.prefix, cl->prefix, sizeof(l.prefix));
memcpy(dst, &l, sizeof(l));
}
static int ulog_tg_compat_to_user(void __user *dst, const void *src)
{
const struct ipt_ulog_info *l = src;
struct compat_ipt_ulog_info cl = {
.nl_group = l->nl_group,
.copy_range = l->copy_range,
.qthreshold = l->qthreshold,
};
memcpy(cl.prefix, l->prefix, sizeof(cl.prefix));
return copy_to_user(dst, &cl, sizeof(cl)) ? -EFAULT : 0;
}
#endif /* CONFIG_COMPAT */
static struct xt_target ulog_tg_reg __read_mostly = {
.name = "ULOG",
.family = NFPROTO_IPV4,
.target = ulog_tg,
.targetsize = sizeof(struct ipt_ulog_info),
.checkentry = ulog_tg_check,
#ifdef CONFIG_COMPAT
.compatsize = sizeof(struct compat_ipt_ulog_info),
.compat_from_user = ulog_tg_compat_from_user,
.compat_to_user = ulog_tg_compat_to_user,
#endif
.me = THIS_MODULE,
};
static struct nf_logger ipt_ulog_logger __read_mostly = {
.name = "ipt_ULOG",
.logfn = ipt_logfn,
.me = THIS_MODULE,
};
static int __init ulog_tg_init(void)
{
int ret, i;
struct netlink_kernel_cfg cfg = {
.groups = ULOG_MAXNLGROUPS,
};
pr_debug("init module\n");
if (nlbufsiz > 128*1024) {
pr_warning("Netlink buffer has to be <= 128kB\n");
return -EINVAL;
}
/* initialize ulog_buffers */
for (i = 0; i < ULOG_MAXNLGROUPS; i++)
setup_timer(&ulog_buffers[i].timer, ulog_timer, i);
nflognl = netlink_kernel_create(&init_net, NETLINK_NFLOG, &cfg);
if (!nflognl)
return -ENOMEM;
ret = xt_register_target(&ulog_tg_reg);
if (ret < 0) {
netlink_kernel_release(nflognl);
return ret;
}
if (nflog)
nf_log_register(NFPROTO_IPV4, &ipt_ulog_logger);
return 0;
}
static void __exit ulog_tg_exit(void)
{
ulog_buff_t *ub;
int i;
pr_debug("cleanup_module\n");
if (nflog)
nf_log_unregister(&ipt_ulog_logger);
xt_unregister_target(&ulog_tg_reg);
netlink_kernel_release(nflognl);
/* remove pending timers and free allocated skb's */
for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
ub = &ulog_buffers[i];
if (timer_pending(&ub->timer)) {
pr_debug("timer was pending, deleting\n");
del_timer(&ub->timer);
}
if (ub->skb) {
kfree_skb(ub->skb);
ub->skb = NULL;
}
}
}
module_init(ulog_tg_init);
module_exit(ulog_tg_exit);