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: Peter Nørlund <pch@ordbogen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Peter Nørlund 2015-09-30 10:12:22 +02:00 committed by David S. Miller
parent 0e884c78ee
commit 79a131592d
3 changed files with 80 additions and 9 deletions

View file

@ -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,

View file

@ -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;

View file

@ -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,
@ -1661,7 +1703,10 @@ static int ip_mkroute_input(struct sk_buff *skb,
if (res->fi && res->fi->fib_nhs > 1) {
int h;
h = fib_multipath_hash(saddr, daddr);
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);
}
#endif
@ -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)
{