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netfilter: move nat hlist_head to nf_conn 

The nat extension structure is 32bytes in size on x86_64:

struct nf_conn_nat {
        struct hlist_node          bysource;             /*     0    16 */
        struct nf_conn *           ct;                   /*    16     8 */
        union nf_conntrack_nat_help help;                /*    24     4 */
        int                        masq_index;           /*    28     4 */
        /* size: 32, cachelines: 1, members: 4 */
        /* last cacheline: 32 bytes */
};

The hlist is needed to quickly check for possible tuple collisions
when installing a new nat binding. Storing this in the extension
area has two drawbacks:

1. We need ct backpointer to get the conntrack struct from the extension.
2. When reallocation of extension area occurs we need to fixup the bysource
   hash head via hlist_replace_rcu.

We can avoid both by placing the hlist_head in nf_conn and place nf_conn in
the bysource hash rather than the extenstion.

We can also remove the ->move support; no other extension needs it.

Moving the entire nat extension into nf_conn would be possible as well but
then we have to add yet another callback for deletion from the bysource
hash table rather than just using nat extension ->destroy hook for this.

nf_conn size doesn't increase due to aligment, followup patch replaces
hlist_node with single pointer.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2016-07-05 12:07:23 +02:00 committed by Pablo Neira Ayuso
parent 242922a027
commit 7c96643519
5 changed files with 12 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/net/netfilter/nf_conntrack.h
View File

@ -117,6 +117,9 @@ struct nf_conn {
/* Extensions */
struct nf_ct_ext *ext;
#if IS_ENABLED(CONFIG_NF_NAT)
struct hlist_node nat_bysource;
#endif
/* Storage reserved for other modules, must be the last member */
union nf_conntrack_proto proto;
};

3
include/net/netfilter/nf_conntrack_extend.h
View File

@ -99,9 +99,6 @@ void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id,
struct nf_ct_ext_type {
/* Destroys relationships (can be NULL). */
void (*destroy)(struct nf_conn *ct);
/* Called when realloacted (can be NULL).
Contents has already been moved. */
void (*move)(void *new, void *old);
enum nf_ct_ext_id id;

2
include/net/netfilter/nf_nat.h
View File

@ -29,8 +29,6 @@ struct nf_conn;
/* The structure embedded in the conntrack structure. */
struct nf_conn_nat {
struct hlist_node bysource;
struct nf_conn *ct;
union nf_conntrack_nat_help help;
#if IS_ENABLED(CONFIG_NF_NAT_MASQUERADE_IPV4) || \
IS_ENABLED(CONFIG_NF_NAT_MASQUERADE_IPV6)

15
net/netfilter/nf_conntrack_extend.c
View File

@ -73,7 +73,7 @@ void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id,
size_t var_alloc_len, gfp_t gfp)
{
struct nf_ct_ext *old, *new;
int i, newlen, newoff;
int newlen, newoff;
struct nf_ct_ext_type *t;
/* Conntrack must not be confirmed to avoid races on reallocation. */
@ -99,19 +99,8 @@ void *__nf_ct_ext_add_length(struct nf_conn *ct, enum nf_ct_ext_id id,
return NULL;
if (new != old) {
for (i = 0; i < NF_CT_EXT_NUM; i++) {
if (!__nf_ct_ext_exist(old, i))
continue;
rcu_read_lock();
t = rcu_dereference(nf_ct_ext_types[i]);
if (t && t->move)
t->move((void *)new + new->offset[i],
(void *)old + old->offset[i]);
rcu_read_unlock();
}
kfree_rcu(old, rcu);
ct->ext = new;
rcu_assign_pointer(ct->ext, new);
}
new->offset[id] = newoff;

33
net/netfilter/nf_nat_core.c
View File

@ -198,11 +198,9 @@ find_appropriate_src(struct net *net,
const struct nf_nat_range *range)
{
unsigned int h = hash_by_src(net, tuple);
const struct nf_conn_nat *nat;
const struct nf_conn *ct;
hlist_for_each_entry_rcu(nat, &nf_nat_bysource[h], bysource) {
ct = nat->ct;
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)) {
@ -435,8 +433,7 @@ nf_nat_setup_info(struct nf_conn *ct,
spin_lock_bh(&nf_nat_lock);
/* nf_conntrack_alter_reply might re-allocate extension aera */
nat = nfct_nat(ct);
nat->ct = ct;
hlist_add_head_rcu(&nat->bysource,
hlist_add_head_rcu(&ct->nat_bysource,
&nf_nat_bysource[srchash]);
spin_unlock_bh(&nf_nat_lock);
}
@ -543,7 +540,7 @@ static int nf_nat_proto_clean(struct nf_conn *ct, void *data)
if (nf_nat_proto_remove(ct, data))
return 1;
if (!nat || !nat->ct)
if (!nat)
return 0;
/* This netns is being destroyed, and conntrack has nat null binding.
@ -556,9 +553,8 @@ static int nf_nat_proto_clean(struct nf_conn *ct, void *data)
return 1;
spin_lock_bh(&nf_nat_lock);
hlist_del_rcu(&nat->bysource);
hlist_del_rcu(&ct->nat_bysource);
ct->status &= ~IPS_NAT_DONE_MASK;
nat->ct = NULL;
spin_unlock_bh(&nf_nat_lock);
add_timer(&ct->timeout);
@ -688,27 +684,13 @@ static void nf_nat_cleanup_conntrack(struct nf_conn *ct)
{
struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);
if (nat == NULL || nat->ct == NULL)
if (!nat)
return;
NF_CT_ASSERT(nat->ct->status & IPS_SRC_NAT_DONE);
NF_CT_ASSERT(ct->status & IPS_SRC_NAT_DONE);
spin_lock_bh(&nf_nat_lock);
hlist_del_rcu(&nat->bysource);
spin_unlock_bh(&nf_nat_lock);
}
static void nf_nat_move_storage(void *new, void *old)
{
struct nf_conn_nat *new_nat = new;
struct nf_conn_nat *old_nat = old;
struct nf_conn *ct = old_nat->ct;
if (!ct || !(ct->status & IPS_SRC_NAT_DONE))
return;
spin_lock_bh(&nf_nat_lock);
hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource);
hlist_del_rcu(&ct->nat_bysource);
spin_unlock_bh(&nf_nat_lock);
}
@ -716,7 +698,6 @@ static struct nf_ct_ext_type nat_extend __read_mostly = {
.len = sizeof(struct nf_conn_nat),
.align = __alignof__(struct nf_conn_nat),
.destroy = nf_nat_cleanup_conntrack,
.move = nf_nat_move_storage,
.id = NF_CT_EXT_NAT,
.flags = NF_CT_EXT_F_PREALLOC,
};