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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 /net/ipv6/ip6_output.c
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 'net/ipv6/ip6_output.c')
-rw-r--r--net/ipv6/ip6_output.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 85aaeca1f7f3..cb9df0eb4023 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -537,6 +537,18 @@ static void ip6_copy_metadata(struct sk_buff *to, struct sk_buff *from)
skb_copy_secmark(to, from);
}
+static void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
+{
+ static u32 ip6_idents_hashrnd __read_mostly;
+ u32 hash, id;
+
+ net_get_random_once(&ip6_idents_hashrnd, sizeof(ip6_idents_hashrnd));
+
+ 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 *))
{
struct sk_buff *frag;