path: root/include/net/inetpeer.h
diff options
authorEric Dumazet <edumazet@google.com>2014-06-02 05:26:03 -0700
committerDavid S. Miller <davem@davemloft.net>2014-06-02 11:00:41 -0700
commit73f156a6e8c1074ac6327e0abd1169e95eb66463 (patch)
tree2c8b222f21784e738c397ba95dee70a8f256ea64 /include/net/inetpeer.h
parente067ee336a9d3f038ffa9699c59f2abec3376bf7 (diff)
inetpeer: get rid of ip_id_count
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>
Diffstat (limited to 'include/net/inetpeer.h')
1 files changed, 3 insertions, 20 deletions
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 6efe73c79c52..823ec7bb9c67 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -41,14 +41,13 @@ struct inet_peer {
struct rcu_head gc_rcu;
- * Once inet_peer is queued for deletion (refcnt == -1), following fields
- * are not available: rid, ip_id_count
+ * Once inet_peer is queued for deletion (refcnt == -1), following field
+ * is not available: rid
* 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 */
struct rcu_head rcu;
struct inet_peer *gc_next;
@@ -165,7 +164,7 @@ bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout);
void inetpeer_invalidate_tree(struct inet_peer_base *);
- * 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)
@@ -173,20 +172,4 @@ 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)
- int old, new;
- more++;
- inet_peer_refcheck(p);
- do {
- old = atomic_read(&p->ip_id_count);
- new = old + more;
- if (!new)
- new = 1;
- } while (atomic_cmpxchg(&p->ip_id_count, old, new) != old);
- return new;
#endif /* _NET_INETPEER_H */

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