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authorDavid S. Miller <davem@davemloft.net>2014-07-30 13:25:49 -0700
committerDavid S. Miller <davem@davemloft.net>2014-07-30 13:25:49 -0700
commitf139c74a8df071217dcd63f3ef06ae7be7071c4d (patch)
tree5711f695577a18a06dbcd0101956e97b388ffa1a /net/ipv4
parentbd695a5f0ccf7b38982c426d86055ff3591c9b5b (diff)
parent26bcd8b72563b4c54892c4c2a409f6656fb8ae8b (diff)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/route.c32
1 files changed, 29 insertions, 3 deletions
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);
}