ipv6: make fragment identifications less predictable

IPv6 fragment identification generation is way beyond what we use for
IPv4 : It uses a single generator. Its not scalable and allows DOS
attacks.

Now inetpeer is IPv6 aware, we can use it to provide a more secure and
scalable frag ident generator (per destination, instead of system wide)

This patch :
1) defines a new secure_ipv6_id() helper
2) extends inet_getid() to provide 32bit results
3) extends ipv6_select_ident() with a new dest parameter

Reported-by: Fernando Gont <fernando@gont.com.ar>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 90c5f0d1bcf..e38213817d0 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -391,7 +391,7 @@ static int inet_peer_gc(struct inet_peer_base *base,
         return cnt;
 }
 
-struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create)
+struct inet_peer *inet_getpeer(const struct inetpeer_addr *daddr, int create)
 {
         struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
         struct inet_peer_base *base = family_to_base(daddr->family);
@@ -436,7 +436,10 @@ relookup:
                 p->daddr = *daddr;
                 atomic_set(&p->refcnt, 1);
                 atomic_set(&p->rid, 0);
-                atomic_set(&p->ip_id_count, secure_ip_id(daddr->addr.a4));
+                atomic_set(&p->ip_id_count,
+                                (daddr->family == AF_INET) ?
+                                        secure_ip_id(daddr->addr.a4) :
+                                        secure_ipv6_id(daddr->addr.a6));
                 p->tcp_ts_stamp = 0;
                 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
                 p->rate_tokens = 0;