[PATCH 3.4 01/23] inetpeer: get rid of ip_id_count

From: Greg Kroah-Hartman
Date: Fri Aug 08 2014 - 18:17:05 EST

3.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ Upstream commit 73f156a6e8c1074ac6327e0abd1169e95eb66463 ]

Ideally, we would need to generate IP ID using a per destination IP
generator.

linux kernels used inet_peer cache for this purpose, but this had a huge
cost on servers disabling MTU discovery.

1) each inet_peer struct consumes 192 bytes

2) inetpeer cache uses a binary tree of inet_peer structs,
with a nominal size of ~66000 elements under load.

3) lookups in this tree are hitting a lot of cache lines, as tree depth
is about 20.

4) If server deals with many tcp flows, we have a high probability of
not finding the inet_peer, allocating a fresh one, inserting it in
the tree with same initial ip_id_count, (cf secure_ip_id())

5) We garbage collect inet_peer aggressively.

IP ID generation do not have to be 'perfect'

Goal is trying to avoid duplicates in a short period of time,
so that reassembly units have a chance to complete reassembly of
fragments belonging to one message before receiving other fragments
with a recycled ID.

We simply use an array of generators, and a Jenkin hash using the dst IP
as a key.

ipv6_select_ident() is put back into net/ipv6/ip6_output.c where it
belongs (it is only used from this file)

secure_ip_id() and secure_ipv6_id() no longer are needed.

Rename ip_select_ident_more() to ip_select_ident_segs() to avoid
unnecessary decrement/increment of the number of segments.

Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/ppp/pptp.c | 2 -
include/net/inetpeer.h | 14 +---------
include/net/ip.h | 40 ++++++++++++++++------------
include/net/ipip.h | 2 -
include/net/ipv6.h | 9 +++++-
include/net/secure_seq.h | 2 -
net/core/secure_seq.c | 23 ----------------
net/ipv4/igmp.c | 4 +-
net/ipv4/inetpeer.c | 18 ------------
net/ipv4/ip_output.c | 7 ++---
net/ipv4/ipmr.c | 2 -
net/ipv4/raw.c | 2 -
net/ipv4/route.c | 56 +++++++++++++---------------------------
net/ipv4/xfrm4_mode_tunnel.c | 2 -
net/ipv6/ip6_output.c | 23 ++++++----------
net/netfilter/ipvs/ip_vs_xmit.c | 2 -
16 files changed, 71 insertions(+), 137 deletions(-)

--- a/drivers/net/ppp/pptp.c
+++ b/drivers/net/ppp/pptp.c
@@ -281,7 +281,7 @@ static int pptp_xmit(struct ppp_channel
nf_reset(skb);

skb->ip_summed = CHECKSUM_NONE;
- ip_select_ident(skb, &rt->dst, NULL);
+ ip_select_ident(skb, NULL);
ip_send_check(iph);

ip_local_out(skb);
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -46,13 +46,12 @@ struct inet_peer {
};
/*
* Once inet_peer is queued for deletion (refcnt == -1), following fields
- * are not available: rid, ip_id_count, tcp_ts, tcp_ts_stamp
+ * are not available: rid, tcp_ts, tcp_ts_stamp
* We can share memory with rcu_head to help keep inet_peer small.
*/
union {
struct {
atomic_t rid; /* Frag reception counter */
- atomic_t ip_id_count; /* IP ID for the next packet */
__u32 tcp_ts;
__u32 tcp_ts_stamp;
};
@@ -102,7 +101,7 @@ extern bool inet_peer_xrlim_allow(struct
extern void inetpeer_invalidate_tree(int family);

/*
- * temporary check to make sure we dont access rid, ip_id_count, tcp_ts,
+ * temporary check to make sure we dont access rid, tcp_ts,
* tcp_ts_stamp if no refcount is taken on inet_peer
*/
static inline void inet_peer_refcheck(const struct inet_peer *p)
@@ -110,13 +109,4 @@ static inline void inet_peer_refcheck(co
WARN_ON_ONCE(atomic_read(&p->refcnt) <= 0);
}

-
-/* can be called with or without local BH being disabled */
-static inline int inet_getid(struct inet_peer *p, int more)
-{
- more++;
- inet_peer_refcheck(p);
- return atomic_add_return(more, &p->ip_id_count) - more;
-}
-
#endif /* _NET_INETPEER_H */
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -264,9 +264,19 @@ int ip_dont_fragment(struct sock *sk, st
!(dst_metric_locked(dst, RTAX_MTU)));
}

-extern void __ip_select_ident(struct iphdr *iph, struct dst_entry *dst, int more);
+#define IP_IDENTS_SZ 2048u
+extern atomic_t *ip_idents;

-static inline void ip_select_ident(struct sk_buff *skb, struct dst_entry *dst, struct sock *sk)
+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;
+}
+
+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)
{
struct iphdr *iph = ip_hdr(skb);

@@ -276,24 +286,20 @@ static inline void ip_select_ident(struc
* does not change, they drop every other packet in
* a TCP stream using header compression.
*/
- iph->id = (sk && inet_sk(sk)->inet_daddr) ?
- htons(inet_sk(sk)->inet_id++) : 0;
- } else
- __ip_select_ident(iph, dst, 0);
-}
-
-static inline void ip_select_ident_more(struct sk_buff *skb, struct dst_entry *dst, struct sock *sk, int more)
-{
- struct iphdr *iph = ip_hdr(skb);
-
- if ((iph->frag_off & htons(IP_DF)) && !skb->local_df) {
if (sk && inet_sk(sk)->inet_daddr) {
iph->id = htons(inet_sk(sk)->inet_id);
- inet_sk(sk)->inet_id += 1 + more;
- } else
+ inet_sk(sk)->inet_id += segs;
+ } else {
iph->id = 0;
- } else
- __ip_select_ident(iph, dst, more);
+ }
+ } else {
+ __ip_select_ident(iph, segs);
+ }
+}
+
+static inline void ip_select_ident(struct sk_buff *skb, struct sock *sk)
+{
+ ip_select_ident_segs(skb, sk, 1);
}

/*
--- a/include/net/ipip.h
+++ b/include/net/ipip.h
@@ -50,7 +50,7 @@ struct ip_tunnel_prl_entry {
int pkt_len = skb->len - skb_transport_offset(skb); \
\
skb->ip_summed = CHECKSUM_NONE; \
- ip_select_ident(skb, &rt->dst, NULL); \
+ ip_select_ident(skb, NULL); \
\
err = ip_local_out(skb); \
if (likely(net_xmit_eval(err) == 0)) { \
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -392,14 +392,19 @@ void ip6_frag_init(struct inet_frag_queu
int ip6_frag_match(struct inet_frag_queue *q, void *a);

/* more secured version of ipv6_addr_hash() */
-static inline u32 ipv6_addr_jhash(const struct in6_addr *a)
+static inline u32 __ipv6_addr_jhash(const struct in6_addr *a, const u32 initval)
{
u32 v = (__force u32)a->s6_addr32[0] ^ (__force u32)a->s6_addr32[1];

return jhash_3words(v,
(__force u32)a->s6_addr32[2],
(__force u32)a->s6_addr32[3],
- ipv6_hash_secret);
+ initval);
+}
+
+static inline u32 ipv6_addr_jhash(const struct in6_addr *a)
+{
+ return __ipv6_addr_jhash(a, ipv6_hash_secret);
}

static inline int ipv6_addr_any(const struct in6_addr *a)
--- a/include/net/secure_seq.h
+++ b/include/net/secure_seq.h
@@ -3,8 +3,6 @@

#include <linux/types.h>

-extern __u32 secure_ip_id(__be32 daddr);
-extern __u32 secure_ipv6_id(const __be32 daddr[4]);
extern u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);
extern u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
__be16 dport);
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -79,29 +79,6 @@ u32 secure_ipv6_port_ephemeral(const __b
#endif

#ifdef CONFIG_INET
-__u32 secure_ip_id(__be32 daddr)
-{
- u32 hash[MD5_DIGEST_WORDS];
-
- hash[0] = (__force __u32) daddr;
- hash[1] = net_secret[13];
- hash[2] = net_secret[14];
- hash[3] = net_secret[15];
-
- md5_transform(hash, net_secret);
-
- return hash[0];
-}
-
-__u32 secure_ipv6_id(const __be32 daddr[4])
-{
- __u32 hash[4];
-
- memcpy(hash, daddr, 16);
- md5_transform(hash, net_secret);
-
- return hash[0];
-}

__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -343,7 +343,7 @@ static struct sk_buff *igmpv3_newpack(st
pip->saddr = fl4.saddr;
pip->protocol = IPPROTO_IGMP;
pip->tot_len = 0; /* filled in later */
- ip_select_ident(skb, &rt->dst, NULL);
+ ip_select_ident(skb, NULL);
((u8*)&pip[1])[0] = IPOPT_RA;
((u8*)&pip[1])[1] = 4;
((u8*)&pip[1])[2] = 0;
@@ -687,7 +687,7 @@ static int igmp_send_report(struct in_de
iph->daddr = dst;
iph->saddr = fl4.saddr;
iph->protocol = IPPROTO_IGMP;
- ip_select_ident(skb, &rt->dst, NULL);
+ ip_select_ident(skb, NULL);
((u8*)&iph[1])[0] = IPOPT_RA;
((u8*)&iph[1])[1] = 4;
((u8*)&iph[1])[2] = 0;
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -26,20 +26,7 @@
* Theory of operations.
* We keep one entry for each peer IP address. The nodes contains long-living
* information about the peer which doesn't depend on routes.
- * At this moment this information consists only of ID field for the next
- * outgoing IP packet. This field is incremented with each packet as encoded
- * in inet_getid() function (include/net/inetpeer.h).
- * At the moment of writing this notes identifier of IP packets is generated
- * to be unpredictable using this code only for packets subjected
- * (actually or potentially) to defragmentation. I.e. DF packets less than
- * PMTU in size when local fragmentation is disabled use a constant ID and do
- * not use this code (see ip_select_ident() in include/net/ip.h).
*
- * Route cache entries hold references to our nodes.
- * New cache entries get references via lookup by destination IP address in
- * the avl tree. The reference is grabbed only when it's needed i.e. only
- * when we try to output IP packet which needs an unpredictable ID (see
- * __ip_select_ident() in net/ipv4/route.c).
* Nodes are removed only when reference counter goes to 0.
* When it's happened the node may be removed when a sufficient amount of
* time has been passed since its last use. The less-recently-used entry can
@@ -62,7 +49,6 @@
* refcnt: atomically against modifications on other CPU;
* usually under some other lock to prevent node disappearing
* daddr: unchangeable
- * ip_id_count: atomic value (no lock needed)
*/

static struct kmem_cache *peer_cachep __read_mostly;
@@ -488,10 +474,6 @@ relookup:
p->daddr = *daddr;
atomic_set(&p->refcnt, 1);
atomic_set(&p->rid, 0);
- atomic_set(&p->ip_id_count,
- (daddr->family == AF_INET) ?
- secure_ip_id(daddr->addr.a4) :
- secure_ipv6_id(daddr->addr.a6));
p->tcp_ts_stamp = 0;
p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
p->rate_tokens = 0;
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -161,7 +161,7 @@ int ip_build_and_send_pkt(struct sk_buff
iph->daddr = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
iph->saddr = saddr;
iph->protocol = sk->sk_protocol;
- ip_select_ident(skb, &rt->dst, sk);
+ ip_select_ident(skb, sk);

if (opt && opt->opt.optlen) {
iph->ihl += opt->opt.optlen>>2;
@@ -403,8 +403,7 @@ packet_routed:
ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
}

- ip_select_ident_more(skb, &rt->dst, sk,
- (skb_shinfo(skb)->gso_segs ?: 1) - 1);
+ ip_select_ident_segs(skb, sk, skb_shinfo(skb)->gso_segs ?: 1);

skb->priority = sk->sk_priority;
skb->mark = sk->sk_mark;
@@ -1347,7 +1346,7 @@ struct sk_buff *__ip_make_skb(struct soc
iph->ihl = 5;
iph->tos = inet->tos;
iph->frag_off = df;
- ip_select_ident(skb, &rt->dst, sk);
+ ip_select_ident(skb, sk);
iph->ttl = ttl;
iph->protocol = sk->sk_protocol;
ip_copy_addrs(iph, fl4);
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1576,7 +1576,7 @@ static void ip_encap(struct sk_buff *skb
iph->protocol = IPPROTO_IPIP;
iph->ihl = 5;
iph->tot_len = htons(skb->len);
- ip_select_ident(skb, skb_dst(skb), NULL);
+ ip_select_ident(skb, NULL);
ip_send_check(iph);

memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -384,7 +384,7 @@ static int raw_send_hdrinc(struct sock *
iph->check = 0;
iph->tot_len = htons(length);
if (!iph->id)
- ip_select_ident(skb, &rt->dst, NULL);
+ ip_select_ident(skb, NULL);

iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
}
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1341,46 +1341,23 @@ void rt_bind_peer(struct rtable *rt, __b
rt->rt_peer_genid = rt_peer_genid();
}

-/*
- * Peer allocation may fail only in serious out-of-memory conditions. However
- * we still can generate some output.
- * Random ID selection looks a bit dangerous because we have no chances to
- * select ID being unique in a reasonable period of time.
- * But broken packet identifier may be better than no packet at all.
- */
-static void ip_select_fb_ident(struct iphdr *iph)
-{
- static DEFINE_SPINLOCK(ip_fb_id_lock);
- static u32 ip_fallback_id;
- u32 salt;
+atomic_t *ip_idents __read_mostly;
+EXPORT_SYMBOL(ip_idents);

- spin_lock_bh(&ip_fb_id_lock);
- salt = secure_ip_id((__force __be32)ip_fallback_id ^ iph->daddr);
- iph->id = htons(salt & 0xFFFF);
- ip_fallback_id = salt;
- spin_unlock_bh(&ip_fb_id_lock);
-}
-
-void __ip_select_ident(struct iphdr *iph, struct dst_entry *dst, int more)
+void __ip_select_ident(struct iphdr *iph, int segs)
{
- struct rtable *rt = (struct rtable *) dst;
+ static u32 ip_idents_hashrnd __read_mostly;
+ static bool hashrnd_initialized = false;
+ u32 hash, id;

- if (rt && !(rt->dst.flags & DST_NOPEER)) {
- if (rt->peer == NULL)
- rt_bind_peer(rt, rt->rt_dst, 1);
-
- /* If peer is attached to destination, it is never detached,
- so that we need not to grab a lock to dereference it.
- */
- if (rt->peer) {
- iph->id = htons(inet_getid(rt->peer, more));
- return;
- }
- } else if (!rt)
- printk(KERN_DEBUG "rt_bind_peer(0) @%p\n",
- __builtin_return_address(0));
+ if (unlikely(!hashrnd_initialized)) {
+ hashrnd_initialized = true;
+ get_random_bytes(&ip_idents_hashrnd, sizeof(ip_idents_hashrnd));
+ }

- ip_select_fb_ident(iph);
+ hash = jhash_1word((__force u32)iph->daddr, ip_idents_hashrnd);
+ id = ip_idents_reserve(hash, segs);
+ iph->id = htons(id);
}
EXPORT_SYMBOL(__ip_select_ident);

@@ -3009,7 +2986,6 @@ static int rt_fill_info(struct net *net,
error = rt->dst.error;
if (peer) {
inet_peer_refcheck(rt->peer);
- id = atomic_read(&peer->ip_id_count) & 0xffff;
if (peer->tcp_ts_stamp) {
ts = peer->tcp_ts;
tsage = get_seconds() - peer->tcp_ts_stamp;
@@ -3441,6 +3417,12 @@ int __init ip_rt_init(void)
{
int rc = 0;

+ ip_idents = kmalloc(IP_IDENTS_SZ * sizeof(*ip_idents), GFP_KERNEL);
+ if (!ip_idents)
+ panic("IP: failed to allocate ip_idents\n");
+
+ get_random_bytes(ip_idents, IP_IDENTS_SZ * sizeof(*ip_idents));
+
#ifdef CONFIG_IP_ROUTE_CLASSID
ip_rt_acct = __alloc_percpu(256 * sizeof(struct ip_rt_acct), __alignof__(struct ip_rt_acct));
if (!ip_rt_acct)
--- a/net/ipv4/xfrm4_mode_tunnel.c
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -54,12 +54,12 @@ static int xfrm4_mode_tunnel_output(stru

top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
- ip_select_ident(skb, dst->child, NULL);

top_iph->ttl = ip4_dst_hoplimit(dst->child);

top_iph->saddr = x->props.saddr.a4;
top_iph->daddr = x->id.daddr.a4;
+ ip_select_ident(skb, NULL);

return 0;
}
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -599,22 +599,17 @@ int ip6_find_1stfragopt(struct sk_buff *

void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
{
- static atomic_t ipv6_fragmentation_id;
- int ident;
+ static u32 ip6_idents_hashrnd __read_mostly;
+ static bool hashrnd_initialized = false;
+ u32 hash, id;

- if (rt && !(rt->dst.flags & DST_NOPEER)) {
- struct inet_peer *peer;
-
- if (!rt->rt6i_peer)
- rt6_bind_peer(rt, 1);
- peer = rt->rt6i_peer;
- if (peer) {
- fhdr->identification = htonl(inet_getid(peer, 0));
- return;
- }
+ if (unlikely(!hashrnd_initialized)) {
+ hashrnd_initialized = true;
+ get_random_bytes(&ip6_idents_hashrnd, sizeof(ip6_idents_hashrnd));
}
- ident = atomic_inc_return(&ipv6_fragmentation_id);
- fhdr->identification = htonl(ident);
+ hash = __ipv6_addr_jhash(&rt->rt6i_dst.addr, ip6_idents_hashrnd);
+ id = ip_idents_reserve(hash, 1);
+ fhdr->identification = htonl(id);
}

int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
--- a/net/netfilter/ipvs/ip_vs_xmit.c
+++ b/net/netfilter/ipvs/ip_vs_xmit.c
@@ -853,7 +853,7 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, s
iph->daddr = cp->daddr.ip;
iph->saddr = saddr;
iph->ttl = old_iph->ttl;
- ip_select_ident(skb, &rt->dst, NULL);
+ ip_select_ident(skb, NULL);

/* Another hack: avoid icmp_send in ip_fragment */
skb->local_df = 1;


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/