![Pablo Neira Ayuso](/assets/img/avatar_default.png)
This partially reworks bc01befdcf
which added userspace expectation support.
This patch removes the nf_ct_userspace_expect_list since now we
force to use the new iptables CT target feature to add the helper
extension for conntracks that have attached expectations from
userspace.
A new version of the proof-of-concept code to implement userspace
helpers from userspace is available at:
http://people.netfilter.org/pablo/userspace-conntrack-helpers/nf-ftp-helper-POC.tar.bz2
This patch also modifies the CT target to allow to set the
conntrack's userspace helper status flags. This flag is used
to tell the conntrack system to explicitly allocate the helper
extension.
This helper extension is useful to link the userspace expectations
with the master conntrack that is being tracked from one userspace
helper.
This feature fixes a problem in the current approach of the
userspace helper support. Basically, if the master conntrack that
has got a userspace expectation vanishes, the expectations point to
one invalid memory address. Thus, triggering an oops in the
expectation deletion event path.
I decided not to add a new revision of the CT target because
I only needed to add a new flag for it. I'll document in this
issue in the iptables manpage. I have also changed the return
value from EINVAL to EOPNOTSUPP if one flag not supported is
specified. Thus, in the future adding new features that only
require a new flag can be added without a new revision.
There is no official code using this in userspace (apart from
the proof-of-concept) that uses this infrastructure but there
will be some by beginning 2012.
Reported-by: Sam Roberts <vieuxtech@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
179 lines
4.1 KiB
C
179 lines
4.1 KiB
C
/*
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* Copyright (c) 2010 Patrick McHardy <kaber@trash.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/gfp.h>
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#include <linux/skbuff.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_CT.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_ecache.h>
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#include <net/netfilter/nf_conntrack_zones.h>
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static unsigned int xt_ct_target(struct sk_buff *skb,
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const struct xt_action_param *par)
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{
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const struct xt_ct_target_info *info = par->targinfo;
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struct nf_conn *ct = info->ct;
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/* Previously seen (loopback)? Ignore. */
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if (skb->nfct != NULL)
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return XT_CONTINUE;
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atomic_inc(&ct->ct_general.use);
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skb->nfct = &ct->ct_general;
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skb->nfctinfo = IP_CT_NEW;
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return XT_CONTINUE;
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}
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static u8 xt_ct_find_proto(const struct xt_tgchk_param *par)
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{
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if (par->family == NFPROTO_IPV4) {
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const struct ipt_entry *e = par->entryinfo;
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if (e->ip.invflags & IPT_INV_PROTO)
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return 0;
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return e->ip.proto;
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} else if (par->family == NFPROTO_IPV6) {
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const struct ip6t_entry *e = par->entryinfo;
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if (e->ipv6.invflags & IP6T_INV_PROTO)
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return 0;
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return e->ipv6.proto;
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} else
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return 0;
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}
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static int xt_ct_tg_check(const struct xt_tgchk_param *par)
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{
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struct xt_ct_target_info *info = par->targinfo;
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struct nf_conntrack_tuple t;
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struct nf_conn_help *help;
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struct nf_conn *ct;
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int ret = 0;
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u8 proto;
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if (info->flags & ~(XT_CT_NOTRACK | XT_CT_USERSPACE_HELPER))
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return -EOPNOTSUPP;
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if (info->flags & XT_CT_NOTRACK) {
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ct = nf_ct_untracked_get();
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atomic_inc(&ct->ct_general.use);
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goto out;
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}
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#ifndef CONFIG_NF_CONNTRACK_ZONES
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if (info->zone)
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goto err1;
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#endif
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ret = nf_ct_l3proto_try_module_get(par->family);
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if (ret < 0)
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goto err1;
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memset(&t, 0, sizeof(t));
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ct = nf_conntrack_alloc(par->net, info->zone, &t, &t, GFP_KERNEL);
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ret = PTR_ERR(ct);
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if (IS_ERR(ct))
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goto err2;
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ret = 0;
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if ((info->ct_events || info->exp_events) &&
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!nf_ct_ecache_ext_add(ct, info->ct_events, info->exp_events,
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GFP_KERNEL))
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goto err3;
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if (info->flags & XT_CT_USERSPACE_HELPER) {
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__set_bit(IPS_USERSPACE_HELPER_BIT, &ct->status);
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} else if (info->helper[0]) {
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ret = -ENOENT;
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proto = xt_ct_find_proto(par);
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if (!proto) {
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pr_info("You must specify a L4 protocol, "
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"and not use inversions on it.\n");
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goto err3;
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}
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ret = -ENOMEM;
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help = nf_ct_helper_ext_add(ct, GFP_KERNEL);
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if (help == NULL)
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goto err3;
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ret = -ENOENT;
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help->helper = nf_conntrack_helper_try_module_get(info->helper,
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par->family,
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proto);
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if (help->helper == NULL) {
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pr_info("No such helper \"%s\"\n", info->helper);
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goto err3;
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}
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}
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__set_bit(IPS_TEMPLATE_BIT, &ct->status);
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__set_bit(IPS_CONFIRMED_BIT, &ct->status);
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out:
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info->ct = ct;
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return 0;
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err3:
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nf_conntrack_free(ct);
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err2:
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nf_ct_l3proto_module_put(par->family);
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err1:
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return ret;
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}
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static void xt_ct_tg_destroy(const struct xt_tgdtor_param *par)
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{
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struct xt_ct_target_info *info = par->targinfo;
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struct nf_conn *ct = info->ct;
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struct nf_conn_help *help;
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if (!nf_ct_is_untracked(ct)) {
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help = nfct_help(ct);
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if (help)
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module_put(help->helper->me);
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nf_ct_l3proto_module_put(par->family);
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}
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nf_ct_put(info->ct);
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}
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static struct xt_target xt_ct_tg __read_mostly = {
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.name = "CT",
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.family = NFPROTO_UNSPEC,
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.targetsize = sizeof(struct xt_ct_target_info),
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.checkentry = xt_ct_tg_check,
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.destroy = xt_ct_tg_destroy,
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.target = xt_ct_target,
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.table = "raw",
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.me = THIS_MODULE,
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};
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static int __init xt_ct_tg_init(void)
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{
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return xt_register_target(&xt_ct_tg);
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}
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static void __exit xt_ct_tg_exit(void)
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{
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xt_unregister_target(&xt_ct_tg);
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}
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module_init(xt_ct_tg_init);
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module_exit(xt_ct_tg_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("Xtables: connection tracking target");
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MODULE_ALIAS("ipt_CT");
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MODULE_ALIAS("ip6t_CT");
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