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IPv6: add the option to use anycast addresses as source addresses in echo reply

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This change allows to follow a recommandation of RFC4942.

- Add "anycast_src_echo_reply" sysctl to control the use of anycast addresses
  as source addresses for ICMPv6 echo reply. This sysctl is false by default
  to preserve existing behavior.
- Add inline check ipv6_anycast_destination().
- Use them in icmpv6_echo_reply().

Reference:
RFC4942 - IPv6 Transition/Coexistence Security Considerations
   (http://tools.ietf.org/html/rfc4942#section-2.1.6)

2.1.6. Anycast Traffic Identification and Security

   [...]
   To avoid exposing knowledge about the internal structure of the
   network, it is recommended that anycast servers now take advantage of
   the ability to return responses with the anycast address as the
   source address if possible.

Signed-off-by: Francois-Xavier Le Bail <fx.lebail@yahoo.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
FX Le Bail 2014-01-07 14:57:27 +01:00 committed by David S. Miller
parent 9ba75fb0c4
commit 509aba3b0d
5 changed files with 26 additions and 1 deletions
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7
Documentation/networking/ip-sysctl.txt
View File

@ -1094,6 +1094,13 @@ bindv6only - BOOLEAN
Default: FALSE (as specified in RFC3493)
anycast_src_echo_reply - BOOLEAN
Controls the use of anycast addresses as source addresses for ICMPv6
echo reply
TRUE: enabled
FALSE: disabled
Default: FALSE
IPv6 Fragmentation:
ip6frag_high_thresh - INTEGER

7
include/net/ip6_route.h
View File

@ -152,6 +152,13 @@ static inline bool ipv6_unicast_destination(const struct sk_buff *skb)
return rt->rt6i_flags & RTF_LOCAL;
}
static inline bool ipv6_anycast_destination(const struct sk_buff *skb)
{
struct rt6_info *rt = (struct rt6_info *) skb_dst(skb);
return rt->rt6i_flags & RTF_ANYCAST;
}
int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
static inline int ip6_skb_dst_mtu(struct sk_buff *skb)

1
include/net/netns/ipv6.h
View File

@ -73,6 +73,7 @@ struct netns_ipv6 {
#endif
atomic_t dev_addr_genid;
atomic_t rt_genid;
int anycast_src_echo_reply;
};
#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)

4
net/ipv6/icmp.c
View File

@ -556,7 +556,9 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
saddr = &ipv6_hdr(skb)->daddr;
if (!ipv6_unicast_destination(skb))
if (!ipv6_unicast_destination(skb) &&
!(net->ipv6.anycast_src_echo_reply &&
ipv6_anycast_destination(skb)))
saddr = NULL;
memcpy(&tmp_hdr, icmph, sizeof(tmp_hdr));

8
net/ipv6/sysctl_net_ipv6.c
View File

@ -24,6 +24,13 @@ static struct ctl_table ipv6_table_template[] = {
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "anycast_src_echo_reply",
.data = &init_net.ipv6.anycast_src_echo_reply,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{ }
};
@ -51,6 +58,7 @@ static int __net_init ipv6_sysctl_net_init(struct net *net)
if (!ipv6_table)
goto out;
ipv6_table[0].data = &net->ipv6.sysctl.bindv6only;
ipv6_table[1].data = &net->ipv6.anycast_src_echo_reply;
ipv6_route_table = ipv6_route_sysctl_init(net);
if (!ipv6_route_table)