linux/net/netfilter/nfnetlink.c

378 lines
8.8 KiB
C

/* Netfilter messages via netlink socket. Allows for user space
* protocol helpers and general trouble making from userspace.
*
* (C) 2001 by Jay Schulist <jschlst@samba.org>,
* (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
* (C) 2005 by Pablo Neira Ayuso <pablo@eurodev.net>
*
* Initial netfilter messages via netlink development funded and
* generally made possible by Network Robots, Inc. (www.networkrobots.com)
*
* Further development of this code funded by Astaro AG (http://www.astaro.com)
*
* This software may be used and distributed according to the terms
* of the GNU General Public License, incorporated herein by reference.
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/fcntl.h>
#include <linux/skbuff.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <net/sock.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/netfilter.h>
#include <linux/netlink.h>
#include <linux/netfilter/nfnetlink.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
static char __initdata nfversion[] = "0.30";
#if 0
#define DEBUGP(format, args...) \
printk(KERN_DEBUG "%s(%d):%s(): " format, __FILE__, \
__LINE__, __FUNCTION__, ## args)
#else
#define DEBUGP(format, args...)
#endif
static struct sock *nfnl = NULL;
static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
DECLARE_MUTEX(nfnl_sem);
void nfnl_lock(void)
{
nfnl_shlock();
}
void nfnl_unlock(void)
{
nfnl_shunlock();
}
int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
{
DEBUGP("registering subsystem ID %u\n", n->subsys_id);
nfnl_lock();
if (subsys_table[n->subsys_id]) {
nfnl_unlock();
return -EBUSY;
}
subsys_table[n->subsys_id] = n;
nfnl_unlock();
return 0;
}
int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
{
DEBUGP("unregistering subsystem ID %u\n", n->subsys_id);
nfnl_lock();
subsys_table[n->subsys_id] = NULL;
nfnl_unlock();
return 0;
}
static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
{
u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
if (subsys_id >= NFNL_SUBSYS_COUNT
|| subsys_table[subsys_id] == NULL)
return NULL;
return subsys_table[subsys_id];
}
static inline struct nfnl_callback *
nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
{
u_int8_t cb_id = NFNL_MSG_TYPE(type);
if (cb_id >= ss->cb_count) {
DEBUGP("msgtype %u >= %u, returning\n", type, ss->cb_count);
return NULL;
}
return &ss->cb[cb_id];
}
void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
const void *data)
{
struct nfattr *nfa;
int size = NFA_LENGTH(attrlen);
nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
nfa->nfa_type = attrtype;
nfa->nfa_len = size;
memcpy(NFA_DATA(nfa), data, attrlen);
memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
}
void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
{
memset(tb, 0, sizeof(struct nfattr *) * maxattr);
while (NFA_OK(nfa, len)) {
unsigned flavor = NFA_TYPE(nfa);
if (flavor && flavor <= maxattr)
tb[flavor-1] = nfa;
nfa = NFA_NEXT(nfa, len);
}
}
/**
* nfnetlink_check_attributes - check and parse nfnetlink attributes
*
* subsys: nfnl subsystem for which this message is to be parsed
* nlmsghdr: netlink message to be checked/parsed
* cda: array of pointers, needs to be at least subsys->attr_count big
*
*/
static int
nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
struct nlmsghdr *nlh, struct nfattr *cda[])
{
int min_len;
u_int16_t attr_count;
u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
if (unlikely(cb_id >= subsys->cb_count)) {
DEBUGP("msgtype %u >= %u, returning\n",
cb_id, subsys->cb_count);
return -EINVAL;
}
min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
if (unlikely(nlh->nlmsg_len < min_len))
return -EINVAL;
attr_count = subsys->cb[cb_id].attr_count;
memset(cda, 0, sizeof(struct nfattr *) * attr_count);
/* check attribute lengths. */
if (likely(nlh->nlmsg_len > min_len)) {
struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
while (NFA_OK(attr, attrlen)) {
unsigned flavor = NFA_TYPE(attr);
if (flavor) {
if (flavor > attr_count)
return -EINVAL;
cda[flavor - 1] = attr;
}
attr = NFA_NEXT(attr, attrlen);
}
}
/* implicit: if nlmsg_len == min_len, we return 0, and an empty
* (zeroed) cda[] array. The message is valid, but empty. */
return 0;
}
int nfnetlink_has_listeners(unsigned int group)
{
return netlink_has_listeners(nfnl, group);
}
EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
{
gfp_t allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
int err = 0;
NETLINK_CB(skb).dst_group = group;
if (echo)
atomic_inc(&skb->users);
netlink_broadcast(nfnl, skb, pid, group, allocation);
if (echo)
err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
return err;
}
int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
{
return netlink_unicast(nfnl, skb, pid, flags);
}
/* Process one complete nfnetlink message. */
static int nfnetlink_rcv_msg(struct sk_buff *skb,
struct nlmsghdr *nlh, int *errp)
{
struct nfnl_callback *nc;
struct nfnetlink_subsystem *ss;
int type, err = 0;
DEBUGP("entered; subsys=%u, msgtype=%u\n",
NFNL_SUBSYS_ID(nlh->nlmsg_type),
NFNL_MSG_TYPE(nlh->nlmsg_type));
if (security_netlink_recv(skb, CAP_NET_ADMIN)) {
DEBUGP("missing CAP_NET_ADMIN\n");
*errp = -EPERM;
return -1;
}
/* Only requests are handled by kernel now. */
if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
DEBUGP("received non-request message\n");
return 0;
}
/* All the messages must at least contain nfgenmsg */
if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg))) {
DEBUGP("received message was too short\n");
return 0;
}
type = nlh->nlmsg_type;
ss = nfnetlink_get_subsys(type);
if (!ss) {
#ifdef CONFIG_KMOD
/* don't call nfnl_shunlock, since it would reenter
* with further packet processing */
up(&nfnl_sem);
request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
nfnl_shlock();
ss = nfnetlink_get_subsys(type);
if (!ss)
#endif
goto err_inval;
}
nc = nfnetlink_find_client(type, ss);
if (!nc) {
DEBUGP("unable to find client for type %d\n", type);
goto err_inval;
}
{
u_int16_t attr_count =
ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
struct nfattr *cda[attr_count];
memset(cda, 0, sizeof(struct nfattr *) * attr_count);
err = nfnetlink_check_attributes(ss, nlh, cda);
if (err < 0)
goto err_inval;
DEBUGP("calling handler\n");
err = nc->call(nfnl, skb, nlh, cda, errp);
*errp = err;
return err;
}
err_inval:
DEBUGP("returning -EINVAL\n");
*errp = -EINVAL;
return -1;
}
/* Process one packet of messages. */
static inline int nfnetlink_rcv_skb(struct sk_buff *skb)
{
int err;
struct nlmsghdr *nlh;
while (skb->len >= NLMSG_SPACE(0)) {
u32 rlen;
nlh = (struct nlmsghdr *)skb->data;
if (nlh->nlmsg_len < sizeof(struct nlmsghdr)
|| skb->len < nlh->nlmsg_len)
return 0;
rlen = NLMSG_ALIGN(nlh->nlmsg_len);
if (rlen > skb->len)
rlen = skb->len;
if (nfnetlink_rcv_msg(skb, nlh, &err)) {
if (!err)
return -1;
netlink_ack(skb, nlh, err);
} else
if (nlh->nlmsg_flags & NLM_F_ACK)
netlink_ack(skb, nlh, 0);
skb_pull(skb, rlen);
}
return 0;
}
static void nfnetlink_rcv(struct sock *sk, int len)
{
do {
struct sk_buff *skb;
if (nfnl_shlock_nowait())
return;
while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
if (nfnetlink_rcv_skb(skb)) {
if (skb->len)
skb_queue_head(&sk->sk_receive_queue,
skb);
else
kfree_skb(skb);
break;
}
kfree_skb(skb);
}
/* don't call nfnl_shunlock, since it would reenter
* with further packet processing */
up(&nfnl_sem);
} while(nfnl && nfnl->sk_receive_queue.qlen);
}
static void __exit nfnetlink_exit(void)
{
printk("Removing netfilter NETLINK layer.\n");
sock_release(nfnl->sk_socket);
return;
}
static int __init nfnetlink_init(void)
{
printk("Netfilter messages via NETLINK v%s.\n", nfversion);
nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
nfnetlink_rcv, THIS_MODULE);
if (!nfnl) {
printk(KERN_ERR "cannot initialize nfnetlink!\n");
return -1;
}
return 0;
}
module_init(nfnetlink_init);
module_exit(nfnetlink_exit);
EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
EXPORT_SYMBOL_GPL(nfnetlink_send);
EXPORT_SYMBOL_GPL(nfnetlink_unicast);
EXPORT_SYMBOL_GPL(nfattr_parse);
EXPORT_SYMBOL_GPL(__nfa_fill);