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netfilter: factor out packet duplication for IPv4/IPv6

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Extracted from the xtables TEE target. This creates two new modules for IPv4
and IPv6 that are shared between the TEE target and the new nf_tables dup
expressions.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2015-05-31 17:54:44 +02:00
parent 24b7811fa5
commit bbde9fc182
10 changed files with 254 additions and 152 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/net/netfilter/ipv4/nf_dup_ipv4.h Normal file
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@ -0,0 +1,7 @@
#ifndef _NF_DUP_IPV4_H_
#define _NF_DUP_IPV4_H_
void nf_dup_ipv4(struct sk_buff *skb, unsigned int hooknum,
const struct in_addr *gw, int oif);
#endif /* _NF_DUP_IPV4_H_ */

7
include/net/netfilter/ipv6/nf_dup_ipv6.h Normal file
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@ -0,0 +1,7 @@
#ifndef _NF_DUP_IPV6_H_
#define _NF_DUP_IPV6_H_
void nf_dup_ipv6(struct sk_buff *skb, unsigned int hooknum,
const struct in6_addr *gw, int oif);
#endif /* _NF_DUP_IPV6_H_ */

6
net/ipv4/netfilter/Kconfig
View File

@ -67,6 +67,12 @@ config NF_TABLES_ARP
endif # NF_TABLES
config NF_DUP_IPV4
tristate "Netfilter IPv4 packet duplication to alternate destination"
help
This option enables the nf_dup_ipv4 core, which duplicates an IPv4
packet to be rerouted to another destination.
config NF_LOG_ARP
tristate "ARP packet logging"
default m if NETFILTER_ADVANCED=n

2
net/ipv4/netfilter/Makefile
View File

@ -70,3 +70,5 @@ obj-$(CONFIG_IP_NF_ARP_MANGLE) += arpt_mangle.o
# just filtering instance of ARP tables for now
obj-$(CONFIG_IP_NF_ARPFILTER) += arptable_filter.o
obj-$(CONFIG_NF_DUP_IPV4) += nf_dup_ipv4.o

120
net/ipv4/netfilter/nf_dup_ipv4.c Normal file
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@ -0,0 +1,120 @@
/*
* (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
* (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
*
* Extracted from xt_TEE.c
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 or later, as
* published by the Free Software Foundation.
*/
#include <linux/ip.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/route.h>
#include <linux/skbuff.h>
#include <net/checksum.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/netfilter/ipv4/nf_dup_ipv4.h>
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#include <net/netfilter/nf_conntrack.h>
#endif
static struct net *pick_net(struct sk_buff *skb)
{
#ifdef CONFIG_NET_NS
const struct dst_entry *dst;
if (skb->dev != NULL)
return dev_net(skb->dev);
dst = skb_dst(skb);
if (dst != NULL && dst->dev != NULL)
return dev_net(dst->dev);
#endif
return &init_net;
}
static bool nf_dup_ipv4_route(struct sk_buff *skb, const struct in_addr *gw,
int oif)
{
const struct iphdr *iph = ip_hdr(skb);
struct net *net = pick_net(skb);
struct rtable *rt;
struct flowi4 fl4;
memset(&fl4, 0, sizeof(fl4));
if (oif != -1)
fl4.flowi4_oif = oif;
fl4.daddr = gw->s_addr;
fl4.flowi4_tos = RT_TOS(iph->tos);
fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
fl4.flowi4_flags = FLOWI_FLAG_KNOWN_NH;
rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt))
return false;
skb_dst_drop(skb);
skb_dst_set(skb, &rt->dst);
skb->dev = rt->dst.dev;
skb->protocol = htons(ETH_P_IP);
return true;
}
void nf_dup_ipv4(struct sk_buff *skb, unsigned int hooknum,
const struct in_addr *gw, int oif)
{
struct iphdr *iph;
if (__this_cpu_read(nf_skb_duplicated))
return;
/*
* Copy the skb, and route the copy. Will later return %XT_CONTINUE for
* the original skb, which should continue on its way as if nothing has
* happened. The copy should be independently delivered to the gateway.
*/
skb = pskb_copy(skb, GFP_ATOMIC);
if (skb == NULL)
return;
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
/* Avoid counting cloned packets towards the original connection. */
nf_conntrack_put(skb->nfct);
skb->nfct = &nf_ct_untracked_get()->ct_general;
skb->nfctinfo = IP_CT_NEW;
nf_conntrack_get(skb->nfct);
#endif
/*
* If we are in PREROUTING/INPUT, the checksum must be recalculated
* since the length could have changed as a result of defragmentation.
*
* We also decrease the TTL to mitigate potential loops between two
* hosts.
*
* Set %IP_DF so that the original source is notified of a potentially
* decreased MTU on the clone route. IPv6 does this too.
*/
iph = ip_hdr(skb);
iph->frag_off |= htons(IP_DF);
if (hooknum == NF_INET_PRE_ROUTING ||
hooknum == NF_INET_LOCAL_IN)
--iph->ttl;
ip_send_check(iph);
if (nf_dup_ipv4_route(skb, gw, oif)) {
__this_cpu_write(nf_skb_duplicated, true);
ip_local_out(skb);
__this_cpu_write(nf_skb_duplicated, false);
} else {
kfree_skb(skb);
}
}
EXPORT_SYMBOL_GPL(nf_dup_ipv4);
MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("nf_dup_ipv4: Duplicate IPv4 packet");
MODULE_LICENSE("GPL");

6
net/ipv6/netfilter/Kconfig
View File

@ -50,6 +50,12 @@ config NFT_REJECT_IPV6
endif # NF_TABLES_IPV6
endif # NF_TABLES
config NF_DUP_IPV6
tristate "Netfilter IPv6 packet duplication to alternate destination"
help
This option enables the nf_dup_ipv6 core, which duplicates an IPv6
packet to be rerouted to another destination.
config NF_REJECT_IPV6
tristate "IPv6 packet rejection"
default m if NETFILTER_ADVANCED=n

2
net/ipv6/netfilter/Makefile
View File

@ -30,6 +30,8 @@ obj-$(CONFIG_NF_LOG_IPV6) += nf_log_ipv6.o
# reject
obj-$(CONFIG_NF_REJECT_IPV6) += nf_reject_ipv6.o
obj-$(CONFIG_NF_DUP_IPV6) += nf_dup_ipv6.o
# nf_tables
obj-$(CONFIG_NF_TABLES_IPV6) += nf_tables_ipv6.o
obj-$(CONFIG_NFT_CHAIN_ROUTE_IPV6) += nft_chain_route_ipv6.o

96
net/ipv6/netfilter/nf_dup_ipv6.c Normal file
View File

@ -0,0 +1,96 @@
/*
* (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
* (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
*
* Extracted from xt_TEE.c
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 or later, as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/skbuff.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/netfilter/ipv6/nf_dup_ipv6.h>
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#include <net/netfilter/nf_conntrack.h>
#endif
static struct net *pick_net(struct sk_buff *skb)
{
#ifdef CONFIG_NET_NS
const struct dst_entry *dst;
if (skb->dev != NULL)
return dev_net(skb->dev);
dst = skb_dst(skb);
if (dst != NULL && dst->dev != NULL)
return dev_net(dst->dev);
#endif
return &init_net;
}
static bool nf_dup_ipv6_route(struct sk_buff *skb, const struct in6_addr *gw,
int oif)
{
const struct ipv6hdr *iph = ipv6_hdr(skb);
struct net *net = pick_net(skb);
struct dst_entry *dst;
struct flowi6 fl6;
memset(&fl6, 0, sizeof(fl6));
if (oif != -1)
fl6.flowi6_oif = oif;
fl6.daddr = *gw;
fl6.flowlabel = ((iph->flow_lbl[0] & 0xF) << 16) |
(iph->flow_lbl[1] << 8) | iph->flow_lbl[2];
dst = ip6_route_output(net, NULL, &fl6);
if (dst->error) {
dst_release(dst);
return false;
}
skb_dst_drop(skb);
skb_dst_set(skb, dst);
skb->dev = dst->dev;
skb->protocol = htons(ETH_P_IPV6);
return true;
}
void nf_dup_ipv6(struct sk_buff *skb, unsigned int hooknum,
const struct in6_addr *gw, int oif)
{
if (__this_cpu_read(nf_skb_duplicated))
return;
skb = pskb_copy(skb, GFP_ATOMIC);
if (skb == NULL)
return;
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
nf_conntrack_put(skb->nfct);
skb->nfct = &nf_ct_untracked_get()->ct_general;
skb->nfctinfo = IP_CT_NEW;
nf_conntrack_get(skb->nfct);
#endif
if (hooknum == NF_INET_PRE_ROUTING ||
hooknum == NF_INET_LOCAL_IN) {
struct ipv6hdr *iph = ipv6_hdr(skb);
--iph->hop_limit;
}
if (nf_dup_ipv6_route(skb, gw, oif)) {
__this_cpu_write(nf_skb_duplicated, true);
ip6_local_out(skb);
__this_cpu_write(nf_skb_duplicated, false);
} else {
kfree_skb(skb);
}
}
EXPORT_SYMBOL_GPL(nf_dup_ipv6);
MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("nf_dup_ipv6: IPv6 packet duplication");
MODULE_LICENSE("GPL");

2
net/netfilter/Kconfig
View File

@ -867,6 +867,8 @@ config NETFILTER_XT_TARGET_TEE
depends on NETFILTER_ADVANCED
depends on IPV6 || IPV6=n
depends on !NF_CONNTRACK || NF_CONNTRACK
select NF_DUP_IPV4
select NF_DUP_IPV6 if IP6_NF_IPTABLES
---help---
This option adds a "TEE" target with which a packet can be cloned and
this clone be rerouted to another nexthop.

158
net/netfilter/xt_TEE.c
View File

@ -10,23 +10,14 @@
* modify it under the terms of the GNU General Public License
* version 2 or later, as published by the Free Software Foundation.
*/
#include <linux/ip.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/route.h>
#include <linux/skbuff.h>
#include <linux/notifier.h>
#include <net/checksum.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/route.h>
#include <linux/route.h>
#include <linux/netfilter/x_tables.h>
#include <net/route.h>
#include <net/netfilter/ipv4/nf_dup_ipv4.h>
#include <net/netfilter/ipv6/nf_dup_ipv6.h>
#include <linux/netfilter/xt_TEE.h>
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#include <net/netfilter/nf_conntrack.h>
#endif
struct xt_tee_priv {
struct notifier_block notifier;
@ -36,161 +27,24 @@ struct xt_tee_priv {
static const union nf_inet_addr tee_zero_address;
static struct net *pick_net(struct sk_buff *skb)
{
#ifdef CONFIG_NET_NS
const struct dst_entry *dst;
if (skb->dev != NULL)
return dev_net(skb->dev);
dst = skb_dst(skb);
if (dst != NULL && dst->dev != NULL)
return dev_net(dst->dev);
#endif
return &init_net;
}
static bool
tee_tg_route4(struct sk_buff *skb, const struct xt_tee_tginfo *info)
{
const struct iphdr *iph = ip_hdr(skb);
struct net *net = pick_net(skb);
struct rtable *rt;
struct flowi4 fl4;
memset(&fl4, 0, sizeof(fl4));
if (info->priv) {
if (info->priv->oif == -1)
return false;
fl4.flowi4_oif = info->priv->oif;
}
fl4.daddr = info->gw.ip;
fl4.flowi4_tos = RT_TOS(iph->tos);
fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
fl4.flowi4_flags = FLOWI_FLAG_KNOWN_NH;
rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt))
return false;
skb_dst_drop(skb);
skb_dst_set(skb, &rt->dst);
skb->dev = rt->dst.dev;
skb->protocol = htons(ETH_P_IP);
return true;
}
static unsigned int
tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct xt_tee_tginfo *info = par->targinfo;
struct iphdr *iph;
if (__this_cpu_read(nf_skb_duplicated))
return XT_CONTINUE;
/*
* Copy the skb, and route the copy. Will later return %XT_CONTINUE for
* the original skb, which should continue on its way as if nothing has
* happened. The copy should be independently delivered to the TEE
* --gateway.
*/
skb = pskb_copy(skb, GFP_ATOMIC);
if (skb == NULL)
return XT_CONTINUE;
nf_dup_ipv4(skb, par->hooknum, &info->gw.in, info->priv->oif);
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
/* Avoid counting cloned packets towards the original connection. */
nf_conntrack_put(skb->nfct);
skb->nfct = &nf_ct_untracked_get()->ct_general;
skb->nfctinfo = IP_CT_NEW;
nf_conntrack_get(skb->nfct);
#endif
/*
* If we are in PREROUTING/INPUT, the checksum must be recalculated
* since the length could have changed as a result of defragmentation.
*
* We also decrease the TTL to mitigate potential TEE loops
* between two hosts.
*
* Set %IP_DF so that the original source is notified of a potentially
* decreased MTU on the clone route. IPv6 does this too.
*/
iph = ip_hdr(skb);
iph->frag_off |= htons(IP_DF);
if (par->hooknum == NF_INET_PRE_ROUTING ||
par->hooknum == NF_INET_LOCAL_IN)
--iph->ttl;
ip_send_check(iph);
if (tee_tg_route4(skb, info)) {
__this_cpu_write(nf_skb_duplicated, true);
ip_local_out(skb);
__this_cpu_write(nf_skb_duplicated, false);
} else {
kfree_skb(skb);
}
return XT_CONTINUE;
}
#if IS_ENABLED(CONFIG_IPV6)
static bool
tee_tg_route6(struct sk_buff *skb, const struct xt_tee_tginfo *info)
{
const struct ipv6hdr *iph = ipv6_hdr(skb);
struct net *net = pick_net(skb);
struct dst_entry *dst;
struct flowi6 fl6;
memset(&fl6, 0, sizeof(fl6));
if (info->priv) {
if (info->priv->oif == -1)
return false;
fl6.flowi6_oif = info->priv->oif;
}
fl6.daddr = info->gw.in6;
fl6.flowlabel = ((iph->flow_lbl[0] & 0xF) << 16) |
(iph->flow_lbl[1] << 8) | iph->flow_lbl[2];
fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;
dst = ip6_route_output(net, NULL, &fl6);
if (dst->error) {
dst_release(dst);
return false;
}
skb_dst_drop(skb);
skb_dst_set(skb, dst);
skb->dev = dst->dev;
skb->protocol = htons(ETH_P_IPV6);
return true;
}
static unsigned int
tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct xt_tee_tginfo *info = par->targinfo;
if (__this_cpu_read(nf_skb_duplicated))
return XT_CONTINUE;
skb = pskb_copy(skb, GFP_ATOMIC);
if (skb == NULL)
return XT_CONTINUE;
nf_dup_ipv6(skb, par->hooknum, &info->gw.in6, info->priv->oif);
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
nf_conntrack_put(skb->nfct);
skb->nfct = &nf_ct_untracked_get()->ct_general;
skb->nfctinfo = IP_CT_NEW;
nf_conntrack_get(skb->nfct);
#endif
if (par->hooknum == NF_INET_PRE_ROUTING ||
par->hooknum == NF_INET_LOCAL_IN) {
struct ipv6hdr *iph = ipv6_hdr(skb);
--iph->hop_limit;
}
if (tee_tg_route6(skb, info)) {
__this_cpu_write(nf_skb_duplicated, true);
ip6_local_out(skb);
__this_cpu_write(nf_skb_duplicated, false);
} else {
kfree_skb(skb);
}
return XT_CONTINUE;
}
#endif