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netfilter: ctnetlink: add support for user-space expectation helpers

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This patch adds the basic infrastructure to support user-space
expectation helpers via ctnetlink and the netfilter queuing
infrastructure NFQUEUE. Basically, this patch:

* adds NF_CT_EXPECT_USERSPACE flag to identify user-space
  created expectations. I have also added a sanity check in
  __nf_ct_expect_check() to avoid that kernel-space helpers
  may create an expectation if the master conntrack has no
  helper assigned.
* adds some branches to check if the master conntrack helper
  exists, otherwise we skip the code that refers to kernel-space
  helper such as the local expectation list and the expectation
  policy.
* allows to set the timeout for user-space expectations with
  no helper assigned.
* a list of expectations created from user-space that depends
  on ctnetlink (if this module is removed, they are deleted).
* includes USERSPACE in the /proc output for expectations
  that have been created by a user-space helper.

This patch also modifies ctnetlink to skip including the helper
name in the Netlink messages if no kernel-space helper is set
(since no user-space expectation has not kernel-space kernel
assigned).

You can access an example user-space FTP conntrack helper at:
http://people.netfilter.org/pablo/userspace-conntrack-helpers/nf-ftp-helper-userspace-POC.tar.bz

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Pablo Neira Ayuso 2010-09-28 21:06:34 +02:00 committed by Patrick McHardy
parent 8b008faf92
commit bc01befdcf
4 changed files with 79 additions and 31 deletions
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1
include/linux/netfilter/nf_conntrack_common.h
View File

@ -103,6 +103,7 @@ enum ip_conntrack_expect_events {
/* expectation flags */
#define NF_CT_EXPECT_PERMANENT 0x1
#define NF_CT_EXPECT_INACTIVE 0x2
#define NF_CT_EXPECT_USERSPACE 0x4
#ifdef __KERNEL__
struct ip_conntrack_stat {

1
include/net/netfilter/nf_conntrack_expect.h
View File

@ -85,6 +85,7 @@ nf_ct_find_expectation(struct net *net, u16 zone,
void nf_ct_unlink_expect(struct nf_conntrack_expect *exp);
void nf_ct_remove_expectations(struct nf_conn *ct);
void nf_ct_unexpect_related(struct nf_conntrack_expect *exp);
void nf_ct_remove_userspace_expectations(void);
/* Allocate space for an expectation: this is mandatory before calling
nf_ct_expect_related. You will have to call put afterwards. */

62
net/netfilter/nf_conntrack_expect.c
View File

@ -38,20 +38,23 @@ static int nf_ct_expect_hash_rnd_initted __read_mostly;
static struct kmem_cache *nf_ct_expect_cachep __read_mostly;
static HLIST_HEAD(nf_ct_userspace_expect_list);
/* nf_conntrack_expect helper functions */
void nf_ct_unlink_expect(struct nf_conntrack_expect *exp)
{
struct nf_conn_help *master_help = nfct_help(exp->master);
struct net *net = nf_ct_exp_net(exp);
NF_CT_ASSERT(master_help);
NF_CT_ASSERT(!timer_pending(&exp->timeout));
hlist_del_rcu(&exp->hnode);
net->ct.expect_count--;
hlist_del(&exp->lnode);
master_help->expecting[exp->class]--;
if (!(exp->flags & NF_CT_EXPECT_USERSPACE))
master_help->expecting[exp->class]--;
nf_ct_expect_put(exp);
NF_CT_STAT_INC(net, expect_delete);
@ -320,16 +323,21 @@ static void nf_ct_expect_insert(struct nf_conntrack_expect *exp)
atomic_inc(&exp->use);
hlist_add_head(&exp->lnode, &master_help->expectations);
master_help->expecting[exp->class]++;
if (master_help) {
hlist_add_head(&exp->lnode, &master_help->expectations);
master_help->expecting[exp->class]++;
} else if (exp->flags & NF_CT_EXPECT_USERSPACE)
hlist_add_head(&exp->lnode, &nf_ct_userspace_expect_list);
hlist_add_head_rcu(&exp->hnode, &net->ct.expect_hash[h]);
net->ct.expect_count++;
setup_timer(&exp->timeout, nf_ct_expectation_timed_out,
(unsigned long)exp);
p = &master_help->helper->expect_policy[exp->class];
exp->timeout.expires = jiffies + p->timeout * HZ;
if (master_help) {
p = &master_help->helper->expect_policy[exp->class];
exp->timeout.expires = jiffies + p->timeout * HZ;
}
add_timer(&exp->timeout);
atomic_inc(&exp->use);
@ -380,7 +388,9 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect)
unsigned int h;
int ret = 1;
if (!master_help->helper) {
/* Don't allow expectations created from kernel-space with no helper */
if (!(expect->flags & NF_CT_EXPECT_USERSPACE) &&
(!master_help || (master_help && !master_help->helper))) {
ret = -ESHUTDOWN;
goto out;
}
@ -398,13 +408,16 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect)
}
}
/* Will be over limit? */
p = &master_help->helper->expect_policy[expect->class];
if (p->max_expected &&
master_help->expecting[expect->class] >= p->max_expected) {
evict_oldest_expect(master, expect);
if (master_help->expecting[expect->class] >= p->max_expected) {
ret = -EMFILE;
goto out;
if (master_help) {
p = &master_help->helper->expect_policy[expect->class];
if (p->max_expected &&
master_help->expecting[expect->class] >= p->max_expected) {
evict_oldest_expect(master, expect);
if (master_help->expecting[expect->class]
>= p->max_expected) {
ret = -EMFILE;
goto out;
}
}
}
@ -439,6 +452,21 @@ out:
}
EXPORT_SYMBOL_GPL(nf_ct_expect_related_report);
void nf_ct_remove_userspace_expectations(void)
{
struct nf_conntrack_expect *exp;
struct hlist_node *n, *next;
hlist_for_each_entry_safe(exp, n, next,
&nf_ct_userspace_expect_list, lnode) {
if (del_timer(&exp->timeout)) {
nf_ct_unlink_expect(exp);
nf_ct_expect_put(exp);
}
}
}
EXPORT_SYMBOL_GPL(nf_ct_remove_userspace_expectations);
#ifdef CONFIG_PROC_FS
struct ct_expect_iter_state {
struct seq_net_private p;
@ -529,8 +557,12 @@ static int exp_seq_show(struct seq_file *s, void *v)
seq_printf(s, "PERMANENT");
delim = ",";
}
if (expect->flags & NF_CT_EXPECT_INACTIVE)
if (expect->flags & NF_CT_EXPECT_INACTIVE) {
seq_printf(s, "%sINACTIVE", delim);
delim = ",";
}
if (expect->flags & NF_CT_EXPECT_USERSPACE)
seq_printf(s, "%sUSERSPACE", delim);
helper = rcu_dereference(nfct_help(expect->master)->helper);
if (helper) {

46
net/netfilter/nf_conntrack_netlink.c
View File

@ -1560,8 +1560,8 @@ ctnetlink_exp_dump_expect(struct sk_buff *skb,
const struct nf_conntrack_expect *exp)
{
struct nf_conn *master = exp->master;
struct nf_conntrack_helper *helper;
long timeout = (exp->timeout.expires - jiffies) / HZ;
struct nf_conn_help *help;
if (timeout < 0)
timeout = 0;
@ -1578,9 +1578,14 @@ ctnetlink_exp_dump_expect(struct sk_buff *skb,
NLA_PUT_BE32(skb, CTA_EXPECT_TIMEOUT, htonl(timeout));
NLA_PUT_BE32(skb, CTA_EXPECT_ID, htonl((unsigned long)exp));
NLA_PUT_BE32(skb, CTA_EXPECT_FLAGS, htonl(exp->flags));
helper = rcu_dereference(nfct_help(master)->helper);
if (helper)
NLA_PUT_STRING(skb, CTA_EXPECT_HELP_NAME, helper->name);
help = nfct_help(master);
if (help) {
struct nf_conntrack_helper *helper;
helper = rcu_dereference(help->helper);
if (helper)
NLA_PUT_STRING(skb, CTA_EXPECT_HELP_NAME, helper->name);
}
return 0;
@ -1921,24 +1926,32 @@ ctnetlink_create_expect(struct net *net, u16 zone,
if (!h)
return -ENOENT;
ct = nf_ct_tuplehash_to_ctrack(h);
help = nfct_help(ct);
if (!help || !help->helper) {
/* such conntrack hasn't got any helper, abort */
err = -EOPNOTSUPP;
goto out;
}
exp = nf_ct_expect_alloc(ct);
if (!exp) {
err = -ENOMEM;
goto out;
}
help = nfct_help(ct);
if (!help) {
if (!cda[CTA_EXPECT_TIMEOUT]) {
err = -EINVAL;
goto out;
}
exp->timeout.expires =
jiffies + ntohl(nla_get_be32(cda[CTA_EXPECT_TIMEOUT])) * HZ;
if (cda[CTA_EXPECT_FLAGS])
exp->flags = ntohl(nla_get_be32(cda[CTA_EXPECT_FLAGS]));
else
exp->flags = 0;
exp->flags = NF_CT_EXPECT_USERSPACE;
if (cda[CTA_EXPECT_FLAGS]) {
exp->flags |=
ntohl(nla_get_be32(cda[CTA_EXPECT_FLAGS]));
}
} else {
if (cda[CTA_EXPECT_FLAGS]) {
exp->flags = ntohl(nla_get_be32(cda[CTA_EXPECT_FLAGS]));
exp->flags &= ~NF_CT_EXPECT_USERSPACE;
} else
exp->flags = 0;
}
exp->class = 0;
exp->expectfn = NULL;
@ -2109,6 +2122,7 @@ static void __exit ctnetlink_exit(void)
{
pr_info("ctnetlink: unregistering from nfnetlink.\n");
nf_ct_remove_userspace_expectations();
#ifdef CONFIG_NF_CONNTRACK_EVENTS
nf_ct_expect_unregister_notifier(&ctnl_notifier_exp);
nf_conntrack_unregister_notifier(&ctnl_notifier);