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netfilter: conntrack: do not enable connection tracking unless needed 

Discussion during NFWS 2017 in Faro has shown that the current
conntrack behaviour is unreasonable.

Even if conntrack module is loaded on behalf of a single net namespace,
its turned on for all namespaces, which is expensive.  Commit
481fa37347 ("netfilter: conntrack: add nf_conntrack_default_on sysctl")
attempted to provide an alternative to the 'default on' behaviour by
adding a sysctl to change it.

However, as Eric points out, the sysctl only becomes available
once the module is loaded, and then its too late.

So we either have to move the sysctl to the core, or, alternatively,
change conntrack to become active only once the rule set requires this.

This does the latter, conntrack is only enabled when a rule needs it.

Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2017-07-28 11:22:04 +02:00 committed by Pablo Neira Ayuso
parent 9b7e26aee7
commit 4d3a57f23d
6 changed files with 4 additions and 94 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
Documentation/networking/nf_conntrack-sysctl.txt
View File

@ -96,17 +96,6 @@ nf_conntrack_max - INTEGER
Size of connection tracking table. Default value is
nf_conntrack_buckets value * 4.
nf_conntrack_default_on - BOOLEAN
0 - don't register conntrack in new net namespaces
1 - register conntrack in new net namespaces (default)
This controls wheter newly created network namespaces have connection
tracking enabled by default. It will be enabled automatically
regardless of this setting if the new net namespace requires
connection tracking, e.g. when NAT rules are created.
This setting is only visible in initial user namespace, it has no
effect on existing namespaces.
nf_conntrack_tcp_be_liberal - BOOLEAN
0 - disabled (default)
not 0 - enabled

15
include/net/netfilter/nf_conntrack_l3proto.h
View File

@ -73,21 +73,6 @@ struct nf_conntrack_l3proto {
extern struct nf_conntrack_l3proto __rcu *nf_ct_l3protos[NFPROTO_NUMPROTO];
#ifdef CONFIG_SYSCTL
/* Protocol pernet registration. */
int nf_ct_l3proto_pernet_register(struct net *net,
struct nf_conntrack_l3proto *proto);
#else
static inline int nf_ct_l3proto_pernet_register(struct net *n,
struct nf_conntrack_l3proto *p)
{
return 0;
}
#endif
void nf_ct_l3proto_pernet_unregister(struct net *net,
struct nf_conntrack_l3proto *proto);
/* Protocol global registration. */
int nf_ct_l3proto_register(struct nf_conntrack_l3proto *proto);
void nf_ct_l3proto_unregister(struct nf_conntrack_l3proto *proto);

16
net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
View File

@ -398,24 +398,12 @@ static struct nf_conntrack_l4proto *builtin_l4proto4[] = {
static int ipv4_net_init(struct net *net)
{
int ret = 0;
ret = nf_ct_l4proto_pernet_register(net, builtin_l4proto4,
ARRAY_SIZE(builtin_l4proto4));
if (ret < 0)
return ret;
ret = nf_ct_l3proto_pernet_register(net, &nf_conntrack_l3proto_ipv4);
if (ret < 0) {
pr_err("nf_conntrack_ipv4: pernet registration failed\n");
nf_ct_l4proto_pernet_unregister(net, builtin_l4proto4,
ARRAY_SIZE(builtin_l4proto4));
}
return ret;
return nf_ct_l4proto_pernet_register(net, builtin_l4proto4,
ARRAY_SIZE(builtin_l4proto4));
}
static void ipv4_net_exit(struct net *net)
{
nf_ct_l3proto_pernet_unregister(net, &nf_conntrack_l3proto_ipv4);
nf_ct_l4proto_pernet_unregister(net, builtin_l4proto4,
ARRAY_SIZE(builtin_l4proto4));
}

17
net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
View File

@ -398,25 +398,12 @@ static struct nf_conntrack_l4proto *builtin_l4proto6[] = {
static int ipv6_net_init(struct net *net)
{
int ret = 0;
ret = nf_ct_l4proto_pernet_register(net, builtin_l4proto6,
ARRAY_SIZE(builtin_l4proto6));
if (ret < 0)
return ret;
ret = nf_ct_l3proto_pernet_register(net, &nf_conntrack_l3proto_ipv6);
if (ret < 0) {
pr_err("nf_conntrack_ipv6: pernet registration failed.\n");
nf_ct_l4proto_pernet_unregister(net, builtin_l4proto6,
ARRAY_SIZE(builtin_l4proto6));
}
return ret;
return nf_ct_l4proto_pernet_register(net, builtin_l4proto6,
ARRAY_SIZE(builtin_l4proto6));
}
static void ipv6_net_exit(struct net *net)
{
nf_ct_l3proto_pernet_unregister(net, &nf_conntrack_l3proto_ipv6);
nf_ct_l4proto_pernet_unregister(net, builtin_l4proto6,
ARRAY_SIZE(builtin_l4proto6));
}

29
net/netfilter/nf_conntrack_proto.c
View File

@ -238,20 +238,6 @@ out_unlock:
}
EXPORT_SYMBOL_GPL(nf_ct_l3proto_register);
#ifdef CONFIG_SYSCTL
extern unsigned int nf_conntrack_default_on;
int nf_ct_l3proto_pernet_register(struct net *net,
struct nf_conntrack_l3proto *proto)
{
if (nf_conntrack_default_on == 0)
return 0;
return proto->net_ns_get ? proto->net_ns_get(net) : 0;
}
EXPORT_SYMBOL_GPL(nf_ct_l3proto_pernet_register);
#endif
void nf_ct_l3proto_unregister(struct nf_conntrack_l3proto *proto)
{
BUG_ON(proto->l3proto >= NFPROTO_NUMPROTO);
@ -270,21 +256,6 @@ void nf_ct_l3proto_unregister(struct nf_conntrack_l3proto *proto)
}
EXPORT_SYMBOL_GPL(nf_ct_l3proto_unregister);
void nf_ct_l3proto_pernet_unregister(struct net *net,
struct nf_conntrack_l3proto *proto)
{
/*
* nf_conntrack_default_on *might* have registered hooks.
* ->net_ns_put must cope with more puts() than get(), i.e.
* if nf_conntrack_default_on was 0 at time of
* nf_ct_l3proto_pernet_register invocation this net_ns_put()
* should be a noop.
*/
if (proto->net_ns_put)
proto->net_ns_put(net);
}
EXPORT_SYMBOL_GPL(nf_ct_l3proto_pernet_unregister);
static struct nf_proto_net *nf_ct_l4proto_net(struct net *net,
struct nf_conntrack_l4proto *l4proto)
{

10
net/netfilter/nf_conntrack_standalone.c
View File

@ -452,9 +452,6 @@ static int log_invalid_proto_max __read_mostly = 255;
/* size the user *wants to set */
static unsigned int nf_conntrack_htable_size_user __read_mostly;
extern unsigned int nf_conntrack_default_on;
unsigned int nf_conntrack_default_on __read_mostly = 1;
static int
nf_conntrack_hash_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
@ -520,13 +517,6 @@ static struct ctl_table nf_ct_sysctl_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "nf_conntrack_default_on",
.data = &nf_conntrack_default_on,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{ }
};