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 <p...@ordbogen.com>
---
include/net/route.h | 11 +++++++++-
net/ipv4/icmp.c | 19 ++++++++++++++++-
net/ipv4/route.c | 57 +++++++++++++++++++++++++++++++++++++++++++++------
3 files changed, 79 insertions(+), 8 deletions(-)
diff --git a/include/net/route.h b/include/net/route.h
index 10a7d21..0f7abdc 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -28,6 +28,7 @@
#include <net/inetpeer.h>
#include <net/flow.h>
#include <net/inet_sock.h>
+#include <net/ip_fib.h>
#include <linux/in_route.h>
#include <linux/rtnetlink.h>
#include <linux/rcupdate.h>
@@ -112,7 +113,15 @@ 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,
struct sock *sk);
struct dst_entry *ipv4_blackhole_route(struct net *net,
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 79fe05b..f81daca 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -440,6 +440,22 @@ out_unlock:
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 = vrf_master_ifindex(skb_in->dev) ? :
skb_in->dev->ifindex;
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;
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 3dc83b6..29048e1 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1652,6 +1652,48 @@ out:
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,
@@ -1662,7 +1704,10 @@ 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
@@ -2032,7 +2077,8 @@ add:
* 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);
@@ -2195,10 +2241,9 @@ 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
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
