diff options
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/route.c | 36 |
1 files changed, 33 insertions, 3 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 278784e..d361dc0 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1344,8 +1344,35 @@ void rt_bind_peer(struct rtable *rt, __be32 daddr, int create) rt->rt_peer_genid = rt_peer_genid(); } -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 = random32(); + + 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) { @@ -1358,7 +1385,10 @@ 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); } |