@@ -277,8 +277,9 @@ Netfilter
=========
The bridge netfilter module is a legacy feature that allows to filter bridged
-packets with iptables and ip6tables. Its use is discouraged. Users should
-consider using nftables for packet filtering.
+packets with iptables and ip6tables. This feature is scheduled for removal and
+not available in user namespaces. Consider using nftables for packet filtering
+instead.
The older ebtables tool is more feature-limited compared to nftables, but
just like nftables it doesn't need this module either to function.
@@ -54,6 +54,7 @@ static unsigned int brnf_net_id __read_mostly;
struct brnf_net {
bool enabled;
+ bool in_userns;
#ifdef CONFIG_SYSCTL
struct ctl_table_header *ctl_hdr;
@@ -1100,7 +1101,7 @@ static int brnf_device_event(struct notifier_block *unused, unsigned long event,
net = dev_net(dev);
brnet = net_generic(net, brnf_net_id);
- if (brnet->enabled)
+ if (brnet->enabled || brnet->in_userns)
return NOTIFY_OK;
ret = nf_register_net_hooks(net, br_nf_ops, ARRAY_SIZE(br_nf_ops));
@@ -1229,9 +1230,11 @@ static inline void br_netfilter_sysctl_default(struct brnf_net *brnf)
brnf->filter_pppoe_tagged = 0;
brnf->pass_vlan_indev = 0;
}
+#endif
static int br_netfilter_sysctl_init_net(struct net *net)
{
+#ifdef CONFIG_SYSCTL
struct ctl_table *table = brnf_table;
struct brnf_net *brnet;
@@ -1259,25 +1262,39 @@ static int br_netfilter_sysctl_init_net(struct net *net)
return -ENOMEM;
}
-
+#endif
return 0;
}
static void br_netfilter_sysctl_exit_net(struct net *net,
struct brnf_net *brnet)
{
- const struct ctl_table *table = brnet->ctl_hdr->ctl_table_arg;
+#ifdef CONFIG_SYSCTL
+ struct ctl_table_header *header = brnet->ctl_hdr;
+ const struct ctl_table *table;
- unregister_net_sysctl_table(brnet->ctl_hdr);
+ if (!header)
+ return;
+
+ table = header->ctl_table_arg;
+ unregister_net_sysctl_table(header);
if (!net_eq(net, &init_net))
kfree(table);
+#endif
}
static int __net_init brnf_init_net(struct net *net)
{
+ if (net->user_ns != &init_user_ns) {
+ struct brnf_net *brnet = net_generic(net, brnf_net_id);
+
+ brnet->in_userns = true;
+ pr_warn_once("br_netfilter no longer supported in user namespaces\n");
+ return 0;
+ }
+
return br_netfilter_sysctl_init_net(net);
}
-#endif
static void __net_exit brnf_exit_net(struct net *net)
{
@@ -1289,15 +1306,11 @@ static void __net_exit brnf_exit_net(struct net *net)
brnet->enabled = false;
}
-#ifdef CONFIG_SYSCTL
br_netfilter_sysctl_exit_net(net, brnet);
-#endif
}
static struct pernet_operations brnf_net_ops __read_mostly = {
-#ifdef CONFIG_SYSCTL
.init = brnf_init_net,
-#endif
.exit = brnf_exit_net,
.id = &brnf_net_id,
.size = sizeof(struct brnf_net),
@@ -1318,7 +1331,7 @@ static int __init br_netfilter_init(void)
}
RCU_INIT_POINTER(nf_br_ops, &br_ops);
- printk(KERN_NOTICE "Bridge firewalling registered\n");
+ pr_warn("br_netfilter is slated for removal in 2027.\n");
return 0;
}
br_netfilter has way too many bugs, schedule for removal and disable the feature in user namespaces. In particular, we get more and more gadgets to have bridge ports escape rcu_read_lock() protection, then underlying device gets reconfigured (macvlan or something else), then reinject into network stack causes crash because net_device is assumed to still have bridge rx data associated with it. br_netfilter is an ancient kludge that emulates ip stack from within the bridge and then calls into ipv4/ipv6 netfilter hooks to have bridged frames processed via iptables/ip6tables by setting the 'call-iptables' sysctls to 1. It is NOT related to ebtables or nftables 'bridge' family at all. Note that in addition to call-iptables, sysctls, the bridge also exposes call-iptables per bridge device via netlink and sysfs ('BROPT_NF_CALL_IPTABLES') toggles. Those are still available, the brnet structure is scoped to br_netfilter; exposing it bridge-wide is a big no-no. This relies on brnf_device_event() no longer registering the base br_netfilter hooks, so while BROPT_NF_CALL_IPTABLES can be set, it has no effect because the hooks that evaluate this feature bit are never registered. brnf_init_net can no longer depend on CONFIG_SYSCTL, else such builds never disable support in user namespaces. Cc: Nikolay Aleksandrov <razor@blackwall.org> Signed-off-by: Florian Westphal <fw@strlen.de> --- v3: also update Documentation, correct changelog: toggle is per bridge device, not per bridge port (Nik) Documentation/networking/bridge.rst | 5 +++-- net/bridge/br_netfilter_hooks.c | 33 ++++++++++++++++++++--------- 2 files changed, 26 insertions(+), 12 deletions(-)