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SubjectRe: [PATCH 4.9 85/87] netfilter: nat: Revert "netfilter: nat: convert nat bysrc hash to rhashtable"
Hi Greg,

Please, hold on a bit with this revert patch entitled:

nat: Revert "netfilter: nat: convert nat bysrc hash to rhashtable")


for 4.9-stable.

Until we clarify what is going on.

Guillame (he's on Cc) is reporting some problems after this.

Thanks!

On Mon, Nov 13, 2017 at 01:56:42PM +0100, Greg Kroah-Hartman wrote:
> 4.9-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Florian Westphal <fw@strlen.de>
>
> commit e1bf1687740ce1a3598a1c5e452b852ff2190682 upstream.
>
> This reverts commit 870190a9ec9075205c0fa795a09fa931694a3ff1.
>
> It was not a good idea. The custom hash table was a much better
> fit for this purpose.
>
> A fast lookup is not essential, in fact for most cases there is no lookup
> at all because original tuple is not taken and can be used as-is.
> What needs to be fast is insertion and deletion.
>
> rhlist removal however requires a rhlist walk.
> We can have thousands of entries in such a list if source port/addresses
> are reused for multiple flows, if this happens removal requests are so
> expensive that deletions of a few thousand flows can take several
> seconds(!).
>
> The advantages that we got from rhashtable are:
> 1) table auto-sizing
> 2) multiple locks
>
> 1) would be nice to have, but it is not essential as we have at
> most one lookup per new flow, so even a million flows in the bysource
> table are not a problem compared to current deletion cost.
> 2) is easy to add to custom hash table.
>
> I tried to add hlist_node to rhlist to speed up rhltable_remove but this
> isn't doable without changing semantics. rhltable_remove_fast will
> check that the to-be-deleted object is part of the table and that
> requires a list walk that we want to avoid.
>
> Furthermore, using hlist_node increases size of struct rhlist_head, which
> in turn increases nf_conn size.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=196821
> Reported-by: Ivan Babrou <ibobrik@gmail.com>
> Signed-off-by: Florian Westphal <fw@strlen.de>
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
>
> ---
> include/net/netfilter/nf_conntrack.h | 3
> include/net/netfilter/nf_nat.h | 1
> net/netfilter/nf_nat_core.c | 131 ++++++++++++++---------------------
> 3 files changed, 56 insertions(+), 79 deletions(-)
>
> --- a/include/net/netfilter/nf_conntrack.h
> +++ b/include/net/netfilter/nf_conntrack.h
> @@ -17,7 +17,6 @@
> #include <linux/bitops.h>
> #include <linux/compiler.h>
> #include <linux/atomic.h>
> -#include <linux/rhashtable.h>
>
> #include <linux/netfilter/nf_conntrack_tcp.h>
> #include <linux/netfilter/nf_conntrack_dccp.h>
> @@ -101,7 +100,7 @@ struct nf_conn {
> possible_net_t ct_net;
>
> #if IS_ENABLED(CONFIG_NF_NAT)
> - struct rhlist_head nat_bysource;
> + struct hlist_node nat_bysource;
> #endif
> /* all members below initialized via memset */
> u8 __nfct_init_offset[0];
> --- a/include/net/netfilter/nf_nat.h
> +++ b/include/net/netfilter/nf_nat.h
> @@ -1,6 +1,5 @@
> #ifndef _NF_NAT_H
> #define _NF_NAT_H
> -#include <linux/rhashtable.h>
> #include <linux/netfilter_ipv4.h>
> #include <linux/netfilter/nf_nat.h>
> #include <net/netfilter/nf_conntrack_tuple.h>
> --- a/net/netfilter/nf_nat_core.c
> +++ b/net/netfilter/nf_nat_core.c
> @@ -30,19 +30,17 @@
> #include <net/netfilter/nf_conntrack_zones.h>
> #include <linux/netfilter/nf_nat.h>
>
> +static DEFINE_SPINLOCK(nf_nat_lock);
> +
> static DEFINE_MUTEX(nf_nat_proto_mutex);
> static const struct nf_nat_l3proto __rcu *nf_nat_l3protos[NFPROTO_NUMPROTO]
> __read_mostly;
> static const struct nf_nat_l4proto __rcu **nf_nat_l4protos[NFPROTO_NUMPROTO]
> __read_mostly;
>
> -struct nf_nat_conn_key {
> - const struct net *net;
> - const struct nf_conntrack_tuple *tuple;
> - const struct nf_conntrack_zone *zone;
> -};
> -
> -static struct rhltable nf_nat_bysource_table;
> +static struct hlist_head *nf_nat_bysource __read_mostly;
> +static unsigned int nf_nat_htable_size __read_mostly;
> +static unsigned int nf_nat_hash_rnd __read_mostly;
>
> inline const struct nf_nat_l3proto *
> __nf_nat_l3proto_find(u8 family)
> @@ -121,17 +119,19 @@ int nf_xfrm_me_harder(struct net *net, s
> EXPORT_SYMBOL(nf_xfrm_me_harder);
> #endif /* CONFIG_XFRM */
>
> -static u32 nf_nat_bysource_hash(const void *data, u32 len, u32 seed)
> +/* We keep an extra hash for each conntrack, for fast searching. */
> +static inline unsigned int
> +hash_by_src(const struct net *n, const struct nf_conntrack_tuple *tuple)
> {
> - const struct nf_conntrack_tuple *t;
> - const struct nf_conn *ct = data;
> + unsigned int hash;
> +
> + get_random_once(&nf_nat_hash_rnd, sizeof(nf_nat_hash_rnd));
>
> - t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
> /* Original src, to ensure we map it consistently if poss. */
> + hash = jhash2((u32 *)&tuple->src, sizeof(tuple->src) / sizeof(u32),
> + tuple->dst.protonum ^ nf_nat_hash_rnd ^ net_hash_mix(n));
>
> - seed ^= net_hash_mix(nf_ct_net(ct));
> - return jhash2((const u32 *)&t->src, sizeof(t->src) / sizeof(u32),
> - t->dst.protonum ^ seed);
> + return reciprocal_scale(hash, nf_nat_htable_size);
> }
>
> /* Is this tuple already taken? (not by us) */
> @@ -187,28 +187,6 @@ same_src(const struct nf_conn *ct,
> t->src.u.all == tuple->src.u.all);
> }
>
> -static int nf_nat_bysource_cmp(struct rhashtable_compare_arg *arg,
> - const void *obj)
> -{
> - const struct nf_nat_conn_key *key = arg->key;
> - const struct nf_conn *ct = obj;
> -
> - if (!same_src(ct, key->tuple) ||
> - !net_eq(nf_ct_net(ct), key->net) ||
> - !nf_ct_zone_equal(ct, key->zone, IP_CT_DIR_ORIGINAL))
> - return 1;
> -
> - return 0;
> -}
> -
> -static struct rhashtable_params nf_nat_bysource_params = {
> - .head_offset = offsetof(struct nf_conn, nat_bysource),
> - .obj_hashfn = nf_nat_bysource_hash,
> - .obj_cmpfn = nf_nat_bysource_cmp,
> - .nelem_hint = 256,
> - .min_size = 1024,
> -};
> -
> /* Only called for SRC manip */
> static int
> find_appropriate_src(struct net *net,
> @@ -219,26 +197,22 @@ find_appropriate_src(struct net *net,
> struct nf_conntrack_tuple *result,
> const struct nf_nat_range *range)
> {
> + unsigned int h = hash_by_src(net, tuple);
> const struct nf_conn *ct;
> - struct nf_nat_conn_key key = {
> - .net = net,
> - .tuple = tuple,
> - .zone = zone
> - };
> - struct rhlist_head *hl, *h;
> -
> - hl = rhltable_lookup(&nf_nat_bysource_table, &key,
> - nf_nat_bysource_params);
>
> - rhl_for_each_entry_rcu(ct, h, hl, nat_bysource) {
> - nf_ct_invert_tuplepr(result,
> - &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
> - result->dst = tuple->dst;
> + hlist_for_each_entry_rcu(ct, &nf_nat_bysource[h], nat_bysource) {
> + if (same_src(ct, tuple) &&
> + net_eq(net, nf_ct_net(ct)) &&
> + nf_ct_zone_equal(ct, zone, IP_CT_DIR_ORIGINAL)) {
> + /* Copy source part from reply tuple. */
> + nf_ct_invert_tuplepr(result,
> + &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
> + result->dst = tuple->dst;
>
> - if (in_range(l3proto, l4proto, result, range))
> - return 1;
> + if (in_range(l3proto, l4proto, result, range))
> + return 1;
> + }
> }
> -
> return 0;
> }
>
> @@ -411,6 +385,7 @@ nf_nat_setup_info(struct nf_conn *ct,
> const struct nf_nat_range *range,
> enum nf_nat_manip_type maniptype)
> {
> + struct net *net = nf_ct_net(ct);
> struct nf_conntrack_tuple curr_tuple, new_tuple;
> struct nf_conn_nat *nat;
>
> @@ -452,19 +427,16 @@ nf_nat_setup_info(struct nf_conn *ct,
> }
>
> if (maniptype == NF_NAT_MANIP_SRC) {
> - struct nf_nat_conn_key key = {
> - .net = nf_ct_net(ct),
> - .tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
> - .zone = nf_ct_zone(ct),
> - };
> - int err;
> -
> - err = rhltable_insert_key(&nf_nat_bysource_table,
> - &key,
> - &ct->nat_bysource,
> - nf_nat_bysource_params);
> - if (err)
> - return NF_DROP;
> + unsigned int srchash;
> +
> + srchash = hash_by_src(net,
> + &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
> + spin_lock_bh(&nf_nat_lock);
> + /* nf_conntrack_alter_reply might re-allocate extension aera */
> + nat = nfct_nat(ct);
> + hlist_add_head_rcu(&ct->nat_bysource,
> + &nf_nat_bysource[srchash]);
> + spin_unlock_bh(&nf_nat_lock);
> }
>
> /* It's done. */
> @@ -578,9 +550,10 @@ static int nf_nat_proto_clean(struct nf_
> * Else, when the conntrack is destoyed, nf_nat_cleanup_conntrack()
> * will delete entry from already-freed table.
> */
> + spin_lock_bh(&nf_nat_lock);
> + hlist_del_rcu(&ct->nat_bysource);
> ct->status &= ~IPS_NAT_DONE_MASK;
> - rhltable_remove(&nf_nat_bysource_table, &ct->nat_bysource,
> - nf_nat_bysource_params);
> + spin_unlock_bh(&nf_nat_lock);
>
> /* don't delete conntrack. Although that would make things a lot
> * simpler, we'd end up flushing all conntracks on nat rmmod.
> @@ -710,8 +683,11 @@ static void nf_nat_cleanup_conntrack(str
> if (!nat)
> return;
>
> - rhltable_remove(&nf_nat_bysource_table, &ct->nat_bysource,
> - nf_nat_bysource_params);
> + NF_CT_ASSERT(ct->status & IPS_SRC_NAT_DONE);
> +
> + spin_lock_bh(&nf_nat_lock);
> + hlist_del_rcu(&ct->nat_bysource);
> + spin_unlock_bh(&nf_nat_lock);
> }
>
> static struct nf_ct_ext_type nat_extend __read_mostly = {
> @@ -846,13 +822,16 @@ static int __init nf_nat_init(void)
> {
> int ret;
>
> - ret = rhltable_init(&nf_nat_bysource_table, &nf_nat_bysource_params);
> - if (ret)
> - return ret;
> + /* Leave them the same for the moment. */
> + nf_nat_htable_size = nf_conntrack_htable_size;
> +
> + nf_nat_bysource = nf_ct_alloc_hashtable(&nf_nat_htable_size, 0);
> + if (!nf_nat_bysource)
> + return -ENOMEM;
>
> ret = nf_ct_extend_register(&nat_extend);
> if (ret < 0) {
> - rhltable_destroy(&nf_nat_bysource_table);
> + nf_ct_free_hashtable(nf_nat_bysource, nf_nat_htable_size);
> printk(KERN_ERR "nf_nat_core: Unable to register extension\n");
> return ret;
> }
> @@ -876,7 +855,7 @@ static int __init nf_nat_init(void)
> return 0;
>
> cleanup_extend:
> - rhltable_destroy(&nf_nat_bysource_table);
> + nf_ct_free_hashtable(nf_nat_bysource, nf_nat_htable_size);
> nf_ct_extend_unregister(&nat_extend);
> return ret;
> }
> @@ -896,8 +875,8 @@ static void __exit nf_nat_cleanup(void)
>
> for (i = 0; i < NFPROTO_NUMPROTO; i++)
> kfree(nf_nat_l4protos[i]);
> -
> - rhltable_destroy(&nf_nat_bysource_table);
> + synchronize_net();
> + nf_ct_free_hashtable(nf_nat_bysource, nf_nat_htable_size);
> }
>
> MODULE_LICENSE("GPL");
>
>

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