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Commit 79a13159 authored by Peter Nørlund's avatar Peter Nørlund Committed by David S. Miller
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ipv4: ICMP packet inspection for multipath 



ICMP packets are inspected to let them route together with the flow they
belong to, minimizing the chance that a problematic path will affect flows
on other paths, and so that anycast environments can work with ECMP.

Signed-off-by: default avatarPeter Nørlund <pch@ordbogen.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0e884c78

include/net/route.h

+10 −1
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <net/inetpeer.h>

#include <net/flow.h>

#include <net/inet_sock.h>

#include <net/ip_fib.h>

#include <net/l3mdev.h>

#include <linux/in_route.h>

#include <linux/rtnetlink.h>
@@ -113,7 +114,15 @@ struct in_device; 
int ip_rt_init(void);

void rt_cache_flush(struct net *net);

void rt_flush_dev(struct net_device *dev);

struct rtable *__ip_route_output_key(struct net *, struct flowi4 *flp);

struct rtable *__ip_route_output_key_hash(struct net *, struct flowi4 *flp,

					  int mp_hash);



static inline struct rtable *__ip_route_output_key(struct net *net,

						   struct flowi4 *flp)

{

	return __ip_route_output_key_hash(net, flp, -1);

}



struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,

				    const struct sock *sk);

struct dst_entry *ipv4_blackhole_route(struct net *net,

net/ipv4/icmp.c

+18 −1
Original line number Diff line number Diff line
@@ -440,6 +440,22 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 
	icmp_xmit_unlock(sk);

}



#ifdef CONFIG_IP_ROUTE_MULTIPATH



/* Source and destination is swapped. See ip_multipath_icmp_hash */

static int icmp_multipath_hash_skb(const struct sk_buff *skb)

{

	const struct iphdr *iph = ip_hdr(skb);



	return fib_multipath_hash(iph->daddr, iph->saddr);

}



#else



#define icmp_multipath_hash_skb(skb) (-1)



#endif



static struct rtable *icmp_route_lookup(struct net *net,

					struct flowi4 *fl4,

					struct sk_buff *skb_in,
@@ -464,7 +480,8 @@ static struct rtable *icmp_route_lookup(struct net *net, 
	fl4->flowi4_oif = l3mdev_master_ifindex(skb_in->dev);



	security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));

	rt = __ip_route_output_key(net, fl4);

	rt = __ip_route_output_key_hash(net, fl4,

					icmp_multipath_hash_skb(skb_in));

	if (IS_ERR(rt))

		return rt;

net/ipv4/route.c

+52 −7
Original line number Diff line number Diff line
@@ -1651,6 +1651,48 @@ static int __mkroute_input(struct sk_buff *skb, 
	return err;

}



#ifdef CONFIG_IP_ROUTE_MULTIPATH



/* To make ICMP packets follow the right flow, the multipath hash is

 * calculated from the inner IP addresses in reverse order.

 */

static int ip_multipath_icmp_hash(struct sk_buff *skb)

{

	const struct iphdr *outer_iph = ip_hdr(skb);

	struct icmphdr _icmph;

	const struct icmphdr *icmph;

	struct iphdr _inner_iph;

	const struct iphdr *inner_iph;



	if (unlikely((outer_iph->frag_off & htons(IP_OFFSET)) != 0))

		goto standard_hash;



	icmph = skb_header_pointer(skb, outer_iph->ihl * 4, sizeof(_icmph),

				   &_icmph);

	if (!icmph)

		goto standard_hash;



	if (icmph->type != ICMP_DEST_UNREACH &&

	    icmph->type != ICMP_REDIRECT &&

	    icmph->type != ICMP_TIME_EXCEEDED &&

	    icmph->type != ICMP_PARAMETERPROB) {

		goto standard_hash;

	}



	inner_iph = skb_header_pointer(skb,

				       outer_iph->ihl * 4 + sizeof(_icmph),

				       sizeof(_inner_iph), &_inner_iph);

	if (!inner_iph)

		goto standard_hash;



	return fib_multipath_hash(inner_iph->daddr, inner_iph->saddr);



standard_hash:

	return fib_multipath_hash(outer_iph->saddr, outer_iph->daddr);

}



#endif /* CONFIG_IP_ROUTE_MULTIPATH */



static int ip_mkroute_input(struct sk_buff *skb,

			    struct fib_result *res,

			    const struct flowi4 *fl4,
@@ -1661,6 +1703,9 @@ static int ip_mkroute_input(struct sk_buff *skb, 
	if (res->fi && res->fi->fib_nhs > 1) {

		int h;



		if (unlikely(ip_hdr(skb)->protocol == IPPROTO_ICMP))

			h = ip_multipath_icmp_hash(skb);

		else

			h = fib_multipath_hash(saddr, daddr);

		fib_select_multipath(res, h);

	}
@@ -2030,7 +2075,8 @@ static struct rtable *__mkroute_output(const struct fib_result *res, 
 * Major route resolver routine.

 */



struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)

struct rtable *__ip_route_output_key_hash(struct net *net, struct flowi4 *fl4,

					  int mp_hash)

{

	struct net_device *dev_out = NULL;

	__u8 tos = RT_FL_TOS(fl4);
@@ -2194,10 +2240,9 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4) 


#ifdef CONFIG_IP_ROUTE_MULTIPATH

	if (res.fi->fib_nhs > 1 && fl4->flowi4_oif == 0) {

		int h;



		h = fib_multipath_hash(fl4->saddr, fl4->daddr);

		fib_select_multipath(&res, h);

		if (mp_hash < 0)

			mp_hash = fib_multipath_hash(fl4->saddr, fl4->daddr);

		fib_select_multipath(&res, mp_hash);

	}

	else

#endif
@@ -2220,7 +2265,7 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4) 
	rcu_read_unlock();

	return rth;

}

EXPORT_SYMBOL_GPL(__ip_route_output_key);

EXPORT_SYMBOL_GPL(__ip_route_output_key_hash);



static struct dst_entry *ipv4_blackhole_dst_check(struct dst_entry *dst, u32 cookie)

{