netfilter: ctnetlink: make event listener tracking global

pernet tracking doesn't work correctly because other netns might have
set NETLINK_LISTEN_ALL_NSID on its event socket.

In this case its expected that events originating in other net
namespaces are also received.

Making pernet-tracking work while also honoring NETLINK_LISTEN_ALL_NSID
requires much more intrusive changes both in netlink and nfnetlink,
f.e. adding a 'setsockopt' callback that lets nfnetlink know that the
event socket entered (or left) ALL_NSID mode.

Move to global tracking instead: if there is an event socket anywhere
on the system, all net namespaces which have conntrack enabled and
use autobind mode will allocate the ecache extension.

netlink_has_listeners() returns false only if the given group has no
subscribers in any net namespace, the 'net' argument passed to
nfnetlink_has_listeners is only used to derive the protocol (nfnetlink),
it has no other effect.

For proper NETLINK_LISTEN_ALL_NSID-aware pernet tracking of event
listeners a new netlink_has_net_listeners() is also needed.

Fixes: 90d1daa45849 ("netfilter: conntrack: add nf_conntrack_events autodetect mode")
Reported-by: Bryce Kahle <bryce.kahle@datadoghq.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index d8817d3..bef8db9 100644 (file)
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -488,4 +488,9 @@ extern const struct nfnl_ct_hook __rcu *nfnl_ct_hook;
  */
 DECLARE_PER_CPU(bool, nf_skb_duplicated);
 
+/**
+ * Contains bitmask of ctnetlink event subscribers, if any.
+ * Can't be pernet due to NETLINK_LISTEN_ALL_NSID setsockopt flag.
+ */
+extern u8 nf_ctnetlink_has_listener;
 #endif /*__LINUX_NETFILTER_H*/

diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index e1290c1..1f463b3 100644 (file)
--- a/include/net/netns/conntrack.h
+++ b/include/net/netns/conntrack.h
@@ -95,7 +95,6 @@ struct nf_ip_net {
 
 struct netns_ct {
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
-       u8 ctnetlink_has_listener;
        bool ecache_dwork_pending;
 #endif
        u8                      sysctl_log_invalid; /* Log invalid packets */

diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 5a6705a..6e80f0f 100644 (file)
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -669,6 +669,9 @@ const struct nf_ct_hook __rcu *nf_ct_hook __read_mostly;
 EXPORT_SYMBOL_GPL(nf_ct_hook);
 
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
+u8 nf_ctnetlink_has_listener;
+EXPORT_SYMBOL_GPL(nf_ctnetlink_has_listener);
+
 const struct nf_nat_hook __rcu *nf_nat_hook __read_mostly;
 EXPORT_SYMBOL_GPL(nf_nat_hook);
 

diff --git a/net/netfilter/nf_conntrack_ecache.c b/net/netfilter/nf_conntrack_ecache.c
index 8698b34..69948e1 100644 (file)
--- a/net/netfilter/nf_conntrack_ecache.c
+++ b/net/netfilter/nf_conntrack_ecache.c
@@ -309,7 +309,7 @@ bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, gfp_t gfp
                        break;
                return true;
        case 2: /* autodetect: no event listener, don't allocate extension. */
-               if (!READ_ONCE(net->ct.ctnetlink_has_listener))
+               if (!READ_ONCE(nf_ctnetlink_has_listener))
                        return true;
                fallthrough;
        case 1:

diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 6d18fb3..81c7737 100644 (file)
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -29,6 +29,7 @@
 
 #include <net/netlink.h>
 #include <net/netns/generic.h>
+#include <linux/netfilter.h>
 #include <linux/netfilter/nfnetlink.h>
 
 MODULE_LICENSE("GPL");
@@ -685,12 +686,12 @@ static void nfnetlink_bind_event(struct net *net, unsigned int group)
        group_bit = (1 << group);
 
        spin_lock(&nfnl_grp_active_lock);
-       v = READ_ONCE(net->ct.ctnetlink_has_listener);
+       v = READ_ONCE(nf_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);
+               WRITE_ONCE(nf_ctnetlink_has_listener, v);
        }
 
        spin_unlock(&nfnl_grp_active_lock);
@@ -744,12 +745,12 @@ static void nfnetlink_unbind(struct net *net, int group)
 
        spin_lock(&nfnl_grp_active_lock);
        if (!nfnetlink_has_listeners(net, group)) {
-               u8 v = READ_ONCE(net->ct.ctnetlink_has_listener);
+               u8 v = READ_ONCE(nf_ctnetlink_has_listener);
 
                v &= ~group_bit;
 
                /* read concurrently without nfnl_grp_active_lock held. */
-               WRITE_ONCE(net->ct.ctnetlink_has_listener, v);
+               WRITE_ONCE(nf_ctnetlink_has_listener, v);
        }
        spin_unlock(&nfnl_grp_active_lock);
 #endif