inetpeer: get rid of ip_id_count

[ 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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ppp/pptp.c b/drivers/net/ppp/pptp.c
index 8327cc5..9f047a0 100644 (file)
--- a/drivers/net/ppp/pptp.c
+++ b/drivers/net/ppp/pptp.c
@@ -281,7 +281,7 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
        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);

diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 2d64364..168d30d 100644 (file)
--- 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 inet_peer *peer, int timeout);
 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(const struct inet_peer *p)
        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 */

diff --git a/include/net/ip.h b/include/net/ip.h
index 6d6b12f..f70e64b 100644 (file)
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -264,9 +264,19 @@ int ip_dont_fragment(struct sock *sk, struct dst_entry *dst)
                 !(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(struct sk_buff *skb, struct dst_entry *dst, s
                 * 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);
 }
 
 /*

diff --git a/include/net/ipip.h b/include/net/ipip.h
index 4dccfe3..e8ee3bb 100644 (file)
--- 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)) {                          \

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index fa7af91..117eaa5 100644 (file)
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -392,14 +392,19 @@ void ip6_frag_init(struct inet_frag_queue *q, void *a);
 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)

diff --git a/include/net/secure_seq.h b/include/net/secure_seq.h
index c2e542b..b1c3d1c 100644 (file)
--- 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);

diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index 99b2596..6ecbd58 100644 (file)
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -79,29 +79,6 @@ u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
 #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)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 3f0bb3b..7824677 100644 (file)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -343,7 +343,7 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
        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_device *in_dev, struct ip_mc_list *pmc,
        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;

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index d63a926..db1b6a7 100644 (file)
--- 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;

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index d6407b5..7827436 100644 (file)
--- 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 *skb, struct sock *sk,
        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 sock *sk,
        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);

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 94cd1ef..5ccef6e 100644 (file)
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1576,7 +1576,7 @@ static void ip_encap(struct sk_buff *skb, __be32 saddr, __be32 daddr)
        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));

diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 48c6ebc..c1b3970 100644 (file)
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -384,7 +384,7 @@ static int raw_send_hdrinc(struct sock *sk, struct flowi4 *fl4,
                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);
        }

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 90bc88b..2836f56 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1341,46 +1341,23 @@ void rt_bind_peer(struct rtable *rt, __be32 daddr, int create)
                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)

diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
index 938553e..5531eb2 100644 (file)
--- a/net/ipv4/xfrm4_mode_tunnel.c
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -54,12 +54,12 @@ static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
 
        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;
 }

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 6225b7c..7a28466 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -599,22 +599,17 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
 
 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 *))

diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
index ec78ab6..559d307 100644 (file)
--- 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, struct ip_vs_conn *cp,
        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;