1 files changed, 33 insertions, 3 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index bbd08354e593..9089c4f2965c 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -466,8 +466,35 @@ static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst,
 	return neigh_create(&arp_tbl, pkey, dev);
 }
 
-atomic_t *ip_idents __read_mostly;
-EXPORT_SYMBOL(ip_idents);
+#define IP_IDENTS_SZ 2048u
+struct ip_ident_bucket {
+	atomic_t	id;
+	u32		stamp32;
+};
+
+static struct ip_ident_bucket *ip_idents __read_mostly;
+
+/* In order to protect privacy, we add a perturbation to identifiers
+ * if one generator is seldom used. This makes hard for an attacker
+ * to infer how many packets were sent between two points in time.
+ */
+u32 ip_idents_reserve(u32 hash, int segs)
+{
+	struct ip_ident_bucket *bucket = ip_idents + hash % IP_IDENTS_SZ;
+	u32 old = ACCESS_ONCE(bucket->stamp32);
+	u32 now = (u32)jiffies;
+	u32 delta = 0;
+
+	if (old != now && cmpxchg(&bucket->stamp32, old, now) == old) {
+		u64 x = prandom_u32();
+
+		x *= (now - old);
+		delta = (u32)(x >> 32);
+	}
+
+	return atomic_add_return(segs + delta, &bucket->id) - segs;
+}
+EXPORT_SYMBOL(ip_idents_reserve);
 
 void __ip_select_ident(struct iphdr *iph, int segs)
 {
@@ -480,7 +507,10 @@ void __ip_select_ident(struct iphdr *iph, int segs)
 		get_random_bytes(&ip_idents_hashrnd, sizeof(ip_idents_hashrnd));
 	}
 
-	hash = jhash_1word((__force u32)iph->daddr, ip_idents_hashrnd);
+	hash = jhash_3words((__force u32)iph->daddr,
+			    (__force u32)iph->saddr,
+			    iph->protocol,
+			    ip_idents_hashrnd);
 	id = ip_idents_reserve(hash, segs);
 	iph->id = htons(id);
 }