* [PATCH nf] netfilter: nfnetlink: re-enable conntrack expectation events
@ 2022-08-05 14:47 Florian Westphal
2022-08-09 17:36 ` Pablo Neira Ayuso
0 siblings, 1 reply; 2+ messages in thread
From: Florian Westphal @ 2022-08-05 14:47 UTC (permalink / raw)
To: netfilter-devel; +Cc: Florian Westphal, Yi Chen
To avoid allocation of the conntrack extension area when possible,
the default behaviour was changed to only allocate the event extension
if a userspace program is subscribed to a notification group.
Problem is that while 'conntrack -E' does enable the event allocation
behind the scenes, 'conntrack -E expect' does not: no expectation events
are delivered unless user sets
"net.netfilter.nf_conntrack_events" back to 1 (always on).
Fix the autodetection to also consider EXP type group.
We need to track the 6 event groups (3+3, new/update/destroy for events and
for expectations each) independently, else we'd disable events again
if an expectation group becomes empty while there is still an active
event group.
Fixes: 2794cdb0b97b ("netfilter: nfnetlink: allow to detect if ctnetlink listeners exist")
Reported-by: Yi Chen <yiche@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
include/net/netns/conntrack.h | 2 +-
net/netfilter/nfnetlink.c | 83 ++++++++++++++++++++++++++++++-----
2 files changed, 72 insertions(+), 13 deletions(-)
diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index 0677cd3de034..c396a3862e80 100644
--- a/include/net/netns/conntrack.h
+++ b/include/net/netns/conntrack.h
@@ -95,7 +95,7 @@ struct nf_ip_net {
struct netns_ct {
#ifdef CONFIG_NF_CONNTRACK_EVENTS
- bool ctnetlink_has_listener;
+ u8 ctnetlink_has_listener;
bool ecache_dwork_pending;
#endif
u8 sysctl_log_invalid; /* Log invalid packets */
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index c24b1240908f..6c268f1c201a 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -44,6 +44,10 @@ MODULE_DESCRIPTION("Netfilter messages via netlink socket");
static unsigned int nfnetlink_pernet_id __read_mostly;
+#ifdef CONFIG_NF_CONNTRACK_EVENTS
+static DEFINE_SPINLOCK(nfnl_grp_active_lock);
+#endif
+
struct nfnl_net {
struct sock *nfnl;
};
@@ -654,6 +658,44 @@ static void nfnetlink_rcv(struct sk_buff *skb)
netlink_rcv_skb(skb, nfnetlink_rcv_msg);
}
+static void nfnetlink_bind_event(struct net *net, unsigned int group)
+{
+#ifdef CONFIG_NF_CONNTRACK_EVENTS
+ int type, group_bit;
+ u8 v;
+
+ /* ctnetlink_has_listener is u8, all NFNLGRP_CONNTRACK_* groups
+ * coming from userspace are < 8.
+ */
+ if (group >= 8)
+ return;
+
+ type = nfnl_group2type[group];
+
+ switch (type) {
+ case NFNL_SUBSYS_CTNETLINK:
+ break;
+ case NFNL_SUBSYS_CTNETLINK_EXP:
+ break;
+ default:
+ return;
+ }
+
+ group_bit = (1 << group);
+
+ spin_lock(&nfnl_grp_active_lock);
+ v = READ_ONCE(net->ct.ctnetlink_has_listener);
+ if ((v & group_bit) == 0) {
+ v |= group_bit;
+
+ /* read concurrently without nfnl_grp_active_lock held. */
+ WRITE_ONCE(net->ct.ctnetlink_has_listener, v);
+ }
+
+ spin_unlock(&nfnl_grp_active_lock);
+#endif
+}
+
static int nfnetlink_bind(struct net *net, int group)
{
const struct nfnetlink_subsystem *ss;
@@ -670,28 +712,45 @@ static int nfnetlink_bind(struct net *net, int group)
if (!ss)
request_module_nowait("nfnetlink-subsys-%d", type);
-#ifdef CONFIG_NF_CONNTRACK_EVENTS
- if (type == NFNL_SUBSYS_CTNETLINK) {
- nfnl_lock(NFNL_SUBSYS_CTNETLINK);
- WRITE_ONCE(net->ct.ctnetlink_has_listener, true);
- nfnl_unlock(NFNL_SUBSYS_CTNETLINK);
- }
-#endif
+ nfnetlink_bind_event(net, group);
return 0;
}
static void nfnetlink_unbind(struct net *net, int group)
{
#ifdef CONFIG_NF_CONNTRACK_EVENTS
+ int type, group_bit;
+
if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
return;
- if (nfnl_group2type[group] == NFNL_SUBSYS_CTNETLINK) {
- nfnl_lock(NFNL_SUBSYS_CTNETLINK);
- if (!nfnetlink_has_listeners(net, group))
- WRITE_ONCE(net->ct.ctnetlink_has_listener, false);
- nfnl_unlock(NFNL_SUBSYS_CTNETLINK);
+ type = nfnl_group2type[group];
+
+ switch (type) {
+ case NFNL_SUBSYS_CTNETLINK:
+ break;
+ case NFNL_SUBSYS_CTNETLINK_EXP:
+ break;
+ default:
+ return;
+ }
+
+ /* ctnetlink_has_listener is u8 */
+ if (group >= 8)
+ return;
+
+ group_bit = (1 << group);
+
+ spin_lock(&nfnl_grp_active_lock);
+ if (!nfnetlink_has_listeners(net, group)) {
+ u8 v = READ_ONCE(net->ct.ctnetlink_has_listener);
+
+ v &= ~group_bit;
+
+ /* read concurrently without nfnl_grp_active_lock held. */
+ WRITE_ONCE(net->ct.ctnetlink_has_listener, v);
}
+ spin_unlock(&nfnl_grp_active_lock);
#endif
}
--
2.35.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH nf] netfilter: nfnetlink: re-enable conntrack expectation events
2022-08-05 14:47 [PATCH nf] netfilter: nfnetlink: re-enable conntrack expectation events Florian Westphal
@ 2022-08-09 17:36 ` Pablo Neira Ayuso
0 siblings, 0 replies; 2+ messages in thread
From: Pablo Neira Ayuso @ 2022-08-09 17:36 UTC (permalink / raw)
To: Florian Westphal; +Cc: netfilter-devel, Yi Chen
Hi Florian,
a few questions, comments.
On Fri, Aug 05, 2022 at 04:47:45PM +0200, Florian Westphal wrote:
> To avoid allocation of the conntrack extension area when possible,
> the default behaviour was changed to only allocate the event extension
> if a userspace program is subscribed to a notification group.
>
> Problem is that while 'conntrack -E' does enable the event allocation
> behind the scenes, 'conntrack -E expect' does not: no expectation events
> are delivered unless user sets
> "net.netfilter.nf_conntrack_events" back to 1 (always on).
>
> Fix the autodetection to also consider EXP type group.
>
> We need to track the 6 event groups (3+3, new/update/destroy for events and
> for expectations each) independently, else we'd disable events again
> if an expectation group becomes empty while there is still an active
> event group.
>
> Fixes: 2794cdb0b97b ("netfilter: nfnetlink: allow to detect if ctnetlink listeners exist")
> Reported-by: Yi Chen <yiche@redhat.com>
> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
> include/net/netns/conntrack.h | 2 +-
> net/netfilter/nfnetlink.c | 83 ++++++++++++++++++++++++++++++-----
> 2 files changed, 72 insertions(+), 13 deletions(-)
>
> diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
> index 0677cd3de034..c396a3862e80 100644
> --- a/include/net/netns/conntrack.h
> +++ b/include/net/netns/conntrack.h
> @@ -95,7 +95,7 @@ struct nf_ip_net {
>
> struct netns_ct {
> #ifdef CONFIG_NF_CONNTRACK_EVENTS
> - bool ctnetlink_has_listener;
> + u8 ctnetlink_has_listener;
so now ctnetlink_has_listener is a bitmask, right?
> bool ecache_dwork_pending;
> #endif
> u8 sysctl_log_invalid; /* Log invalid packets */
> diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
> index c24b1240908f..6c268f1c201a 100644
> --- a/net/netfilter/nfnetlink.c
> +++ b/net/netfilter/nfnetlink.c
> @@ -44,6 +44,10 @@ MODULE_DESCRIPTION("Netfilter messages via netlink socket");
>
> static unsigned int nfnetlink_pernet_id __read_mostly;
>
> +#ifdef CONFIG_NF_CONNTRACK_EVENTS
> +static DEFINE_SPINLOCK(nfnl_grp_active_lock);
> +#endif
> +
> struct nfnl_net {
> struct sock *nfnl;
> };
> @@ -654,6 +658,44 @@ static void nfnetlink_rcv(struct sk_buff *skb)
> netlink_rcv_skb(skb, nfnetlink_rcv_msg);
> }
>
> +static void nfnetlink_bind_event(struct net *net, unsigned int group)
> +{
> +#ifdef CONFIG_NF_CONNTRACK_EVENTS
> + int type, group_bit;
> + u8 v;
> +
> + /* ctnetlink_has_listener is u8, all NFNLGRP_CONNTRACK_* groups
> + * coming from userspace are < 8.
Nit. is ctnetlink_has_listener relevant in the comment? It reads a bit
confusing.
> + */
> + if (group >= 8)
Nit.
enum nfnetlink_groups has __NFNLGRP_MAX, which is 9.
This skips NFNLGRP_NFTRACE which is the last one in the array, not a
big deal since the switch (type) results in return; but better fix
this for the future?
> + return;
> +
> + type = nfnl_group2type[group];
> +
> + switch (type) {
> + case NFNL_SUBSYS_CTNETLINK:
> + break;
> + case NFNL_SUBSYS_CTNETLINK_EXP:
> + break;
> + default:
> + return;
> + }
> +
> + group_bit = (1 << group);
> +
> + spin_lock(&nfnl_grp_active_lock);
suggestion: maybe mutex instead?
> + v = READ_ONCE(net->ct.ctnetlink_has_listener);
> + if ((v & group_bit) == 0) {
> + v |= group_bit;
> +
> + /* read concurrently without nfnl_grp_active_lock held. */
> + WRITE_ONCE(net->ct.ctnetlink_has_listener, v);
> + }
> +
> + spin_unlock(&nfnl_grp_active_lock);
> +#endif
> +}
> +
> static int nfnetlink_bind(struct net *net, int group)
> {
> const struct nfnetlink_subsystem *ss;
> @@ -670,28 +712,45 @@ static int nfnetlink_bind(struct net *net, int group)
> if (!ss)
> request_module_nowait("nfnetlink-subsys-%d", type);
>
> -#ifdef CONFIG_NF_CONNTRACK_EVENTS
> - if (type == NFNL_SUBSYS_CTNETLINK) {
> - nfnl_lock(NFNL_SUBSYS_CTNETLINK);
> - WRITE_ONCE(net->ct.ctnetlink_has_listener, true);
> - nfnl_unlock(NFNL_SUBSYS_CTNETLINK);
> - }
> -#endif
> + nfnetlink_bind_event(net, group);
> return 0;
> }
>
> static void nfnetlink_unbind(struct net *net, int group)
> {
> #ifdef CONFIG_NF_CONNTRACK_EVENTS
> + int type, group_bit;
> +
> if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
> return;
>
> - if (nfnl_group2type[group] == NFNL_SUBSYS_CTNETLINK) {
> - nfnl_lock(NFNL_SUBSYS_CTNETLINK);
> - if (!nfnetlink_has_listeners(net, group))
> - WRITE_ONCE(net->ct.ctnetlink_has_listener, false);
> - nfnl_unlock(NFNL_SUBSYS_CTNETLINK);
> + type = nfnl_group2type[group];
> +
> + switch (type) {
> + case NFNL_SUBSYS_CTNETLINK:
> + break;
> + case NFNL_SUBSYS_CTNETLINK_EXP:
> + break;
> + default:
> + return;
> + }
> +
> + /* ctnetlink_has_listener is u8 */
> + if (group >= 8)
Same here?
> + return;
> +
> + group_bit = (1 << group);
> +
> + spin_lock(&nfnl_grp_active_lock);
> + if (!nfnetlink_has_listeners(net, group)) {
> + u8 v = READ_ONCE(net->ct.ctnetlink_has_listener);
> +
> + v &= ~group_bit;
> +
> + /* read concurrently without nfnl_grp_active_lock held. */
> + WRITE_ONCE(net->ct.ctnetlink_has_listener, v);
> }
> + spin_unlock(&nfnl_grp_active_lock);
> #endif
> }
>
> --
> 2.35.1
>
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