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>
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 39d1230..4233e6f 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -71,7 +71,7 @@
}
/* can be called with or without local BH being disabled */
-struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create);
+struct inet_peer *inet_getpeer(const struct inetpeer_addr *daddr, int create);
static inline struct inet_peer *inet_getpeer_v4(__be32 v4daddr, int create)
{
@@ -106,11 +106,18 @@
/* can be called with or without local BH being disabled */
-static inline __u16 inet_getid(struct inet_peer *p, int more)
+static inline int inet_getid(struct inet_peer *p, int more)
{
+ int old, new;
more++;
inet_peer_refcheck(p);
- return atomic_add_return(more, &p->ip_id_count) - more;
+ do {
+ old = atomic_read(&p->ip_id_count);
+ new = old + more;
+ if (!new)
+ new = 1;
+ } while (atomic_cmpxchg(&p->ip_id_count, old, new) != old);
+ return new;
}
#endif /* _NET_INETPEER_H */
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index c033ed0..3b5ac1f 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -463,17 +463,7 @@
return __ipv6_addr_diff(a1, a2, sizeof(struct in6_addr));
}
-static __inline__ void ipv6_select_ident(struct frag_hdr *fhdr)
-{
- static u32 ipv6_fragmentation_id = 1;
- static DEFINE_SPINLOCK(ip6_id_lock);
-
- spin_lock_bh(&ip6_id_lock);
- fhdr->identification = htonl(ipv6_fragmentation_id);
- if (++ipv6_fragmentation_id == 0)
- ipv6_fragmentation_id = 1;
- spin_unlock_bh(&ip6_id_lock);
-}
+extern void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt);
/*
* Prototypes exported by ipv6