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-rw-r--r--include/net/ip.h11
-rw-r--r--net/ipv4/route.c32
-rw-r--r--net/ipv6/ip6_output.c2
3 files changed, 32 insertions, 13 deletions
diff --git a/include/net/ip.h b/include/net/ip.h
index 0e795df05ec9..7596eb22e1ce 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -309,16 +309,7 @@ static inline unsigned int ip_skb_dst_mtu(const struct sk_buff *skb)
}
}
-#define IP_IDENTS_SZ 2048u
-extern atomic_t *ip_idents;
-
-static inline u32 ip_idents_reserve(u32 hash, int segs)
-{
- atomic_t *id_ptr = ip_idents + hash % IP_IDENTS_SZ;
-
- return atomic_add_return(segs, id_ptr) - segs;
-}
-
+u32 ip_idents_reserve(u32 hash, int segs);
void __ip_select_ident(struct iphdr *iph, int segs);
static inline void ip_select_ident_segs(struct sk_buff *skb, struct sock *sk, int segs)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 3162ea923ded..190199851c9a 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -457,8 +457,31 @@ 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)
+ delta = prandom_u32_max(now - old);
+
+ return atomic_add_return(segs + delta, &bucket->id) - segs;
+}
+EXPORT_SYMBOL(ip_idents_reserve);
void __ip_select_ident(struct iphdr *iph, int segs)
{
@@ -467,7 +490,10 @@ void __ip_select_ident(struct iphdr *iph, int segs)
net_get_random_once(&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);
}
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index cb9df0eb4023..45702b8cd141 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -545,6 +545,8 @@ static void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
net_get_random_once(&ip6_idents_hashrnd, sizeof(ip6_idents_hashrnd));
hash = __ipv6_addr_jhash(&rt->rt6i_dst.addr, ip6_idents_hashrnd);
+ hash = __ipv6_addr_jhash(&rt->rt6i_src.addr, hash);
+
id = ip_idents_reserve(hash, 1);
fhdr->identification = htonl(id);
}