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linux/net/ipv4/netfilter.c
Julian Anastasov ed6e4ef836 netfilter: Fix ip_route_me_harder triggering ip_rt_bug 
Avoid creating input routes with ip_route_me_harder.
It does not work for locally generated packets. Instead,
restrict sockets to provide valid saddr for output route (or
unicast saddr for transparent proxy). For other traffic
allow saddr to be unicast or local but if callers forget
to check saddr type use 0 for the output route.

	The resulting handling should be:

- REJECT TCP:
	- in INPUT we can provide addr_type = RTN_LOCAL but
	better allow rejecting traffic delivered with
	local route (no IP address => use RTN_UNSPEC to
	allow also RTN_UNICAST).
	- FORWARD: RTN_UNSPEC => allow RTN_LOCAL/RTN_UNICAST
	saddr, add fix to ignore RTN_BROADCAST and RTN_MULTICAST
	- OUTPUT: RTN_UNSPEC

- NAT, mangle, ip_queue, nf_ip_reroute: RTN_UNSPEC in LOCAL_OUT

- IPVS:
	- use RTN_LOCAL in LOCAL_OUT and FORWARD after SNAT
	to restrict saddr to be local

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-06-29 05:47:32 -07:00

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/* IPv4 specific functions of netfilter core */
#include <linux/kernel.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/ip.h>
#include <linux/skbuff.h>
#include <linux/gfp.h>
#include <net/route.h>
#include <net/xfrm.h>
#include <net/ip.h>
#include <net/netfilter/nf_queue.h>
/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
{
struct net *net = dev_net(skb_dst(skb)->dev);
const struct iphdr *iph = ip_hdr(skb);
struct rtable *rt;
struct flowi4 fl4 = {};
__be32 saddr = iph->saddr;
__u8 flags = 0;
unsigned int hh_len;
if (!skb->sk && addr_type != RTN_LOCAL) {
if (addr_type == RTN_UNSPEC)
addr_type = inet_addr_type(net, saddr);
if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
flags |= FLOWI_FLAG_ANYSRC;
else
saddr = 0;
}
/* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
* packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
*/
fl4.daddr = iph->daddr;
fl4.saddr = saddr;
fl4.flowi4_tos = RT_TOS(iph->tos);
fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
fl4.flowi4_mark = skb->mark;
fl4.flowi4_flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : flags;
rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt))
return -1;
/* Drop old route. */
skb_dst_drop(skb);
skb_dst_set(skb, &rt->dst);
if (skb_dst(skb)->error)
return -1;
#ifdef CONFIG_XFRM
if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
struct dst_entry *dst = skb_dst(skb);
skb_dst_set(skb, NULL);
dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);
if (IS_ERR(dst))
return -1;
skb_dst_set(skb, dst);
}
#endif
/* Change in oif may mean change in hh_len. */
hh_len = skb_dst(skb)->dev->hard_header_len;
if (skb_headroom(skb) < hh_len &&
pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
return -1;
return 0;
}
EXPORT_SYMBOL(ip_route_me_harder);
#ifdef CONFIG_XFRM
int ip_xfrm_me_harder(struct sk_buff *skb)
{
struct flowi fl;
unsigned int hh_len;
struct dst_entry *dst;
if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
return 0;
if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
return -1;
dst = skb_dst(skb);
if (dst->xfrm)
dst = ((struct xfrm_dst *)dst)->route;
dst_hold(dst);
dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0);
if (IS_ERR(dst))
return -1;
skb_dst_drop(skb);
skb_dst_set(skb, dst);
/* Change in oif may mean change in hh_len. */
hh_len = skb_dst(skb)->dev->hard_header_len;
if (skb_headroom(skb) < hh_len &&
pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
return -1;
return 0;
}
EXPORT_SYMBOL(ip_xfrm_me_harder);
#endif
void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
EXPORT_SYMBOL(ip_nat_decode_session);
/*
* Extra routing may needed on local out, as the QUEUE target never
* returns control to the table.
*/
struct ip_rt_info {
__be32 daddr;
__be32 saddr;
u_int8_t tos;
u_int32_t mark;
};
static void nf_ip_saveroute(const struct sk_buff *skb,
struct nf_queue_entry *entry)
{
struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
if (entry->hook == NF_INET_LOCAL_OUT) {
const struct iphdr *iph = ip_hdr(skb);
rt_info->tos = iph->tos;
rt_info->daddr = iph->daddr;
rt_info->saddr = iph->saddr;
rt_info->mark = skb->mark;
}
}
static int nf_ip_reroute(struct sk_buff *skb,
const struct nf_queue_entry *entry)
{
const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
if (entry->hook == NF_INET_LOCAL_OUT) {
const struct iphdr *iph = ip_hdr(skb);
if (!(iph->tos == rt_info->tos &&
skb->mark == rt_info->mark &&
iph->daddr == rt_info->daddr &&
iph->saddr == rt_info->saddr))
return ip_route_me_harder(skb, RTN_UNSPEC);
}
return 0;
}
__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
unsigned int dataoff, u_int8_t protocol)
{
const struct iphdr *iph = ip_hdr(skb);
__sum16 csum = 0;
switch (skb->ip_summed) {
case CHECKSUM_COMPLETE:
if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
break;
if ((protocol == 0 && !csum_fold(skb->csum)) ||
!csum_tcpudp_magic(iph->saddr, iph->daddr,
skb->len - dataoff, protocol,
skb->csum)) {
skb->ip_summed = CHECKSUM_UNNECESSARY;
break;
}
/* fall through */
case CHECKSUM_NONE:
if (protocol == 0)
skb->csum = 0;
else
skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
skb->len - dataoff,
protocol, 0);
csum = __skb_checksum_complete(skb);
}
return csum;
}
EXPORT_SYMBOL(nf_ip_checksum);
static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
unsigned int dataoff, unsigned int len,
u_int8_t protocol)
{
const struct iphdr *iph = ip_hdr(skb);
__sum16 csum = 0;
switch (skb->ip_summed) {
case CHECKSUM_COMPLETE:
if (len == skb->len - dataoff)
return nf_ip_checksum(skb, hook, dataoff, protocol);
/* fall through */
case CHECKSUM_NONE:
skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
skb->len - dataoff, 0);
skb->ip_summed = CHECKSUM_NONE;
return __skb_checksum_complete_head(skb, dataoff + len);
}
return csum;
}
static int nf_ip_route(struct net *net, struct dst_entry **dst,
struct flowi *fl, bool strict __always_unused)
{
struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
if (IS_ERR(rt))
return PTR_ERR(rt);
*dst = &rt->dst;
return 0;
}
static const struct nf_afinfo nf_ip_afinfo = {
.family = AF_INET,
.checksum = nf_ip_checksum,
.checksum_partial = nf_ip_checksum_partial,
.route = nf_ip_route,
.saveroute = nf_ip_saveroute,
.reroute = nf_ip_reroute,
.route_key_size = sizeof(struct ip_rt_info),
};
static int ipv4_netfilter_init(void)
{
return nf_register_afinfo(&nf_ip_afinfo);
}
static void ipv4_netfilter_fini(void)
{
nf_unregister_afinfo(&nf_ip_afinfo);
}
module_init(ipv4_netfilter_init);
module_exit(ipv4_netfilter_fini);
#ifdef CONFIG_SYSCTL
struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = {
{ .procname = "net", },
{ .procname = "ipv4", },
{ .procname = "netfilter", },
{ }
};
EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);
#endif /* CONFIG_SYSCTL */
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