diff options
Diffstat (limited to 'net/ipv4/route.c')
| -rw-r--r-- | net/ipv4/route.c | 32 |
1 files changed, 29 insertions, 3 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 3162ea923de..190199851c9 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); } |