[PATCH bpf-next 3/7] netfilter: defrag: Add glue hooks for enabling/disabling defrag

Daniel Xu
2023-06-26T23:02:48Z

We want to be able to enable/disable IP packet defrag from core
bpf/netfilter code. In other words, execute code from core that could
possibly be built as a module.

To help avoid symbol resolution errors, use glue hooks that the modules
will register callbacks with during module init.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
include/linux/netfilter.h | 12 ++++++++++++
net/ipv4/netfilter/nf_defrag_ipv4.c | 8 ++++++++
net/ipv6/netfilter/nf_defrag_ipv6_hooks.c | 10 ++++++++++
net/netfilter/core.c | 6 ++++++
4 files changed, 36 insertions(+)

diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 0762444e3767..1d68499de03e 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -481,6 +481,18 @@ struct nfnl_ct_hook {
};
extern const struct nfnl_ct_hook __rcu *nfnl_ct_hook;

+struct nf_defrag_v4_hook {
+ int (*enable)(struct net *net);
+ void (*disable)(struct net *net);
+};
+extern const struct nf_defrag_v4_hook __rcu *nf_defrag_v4_hook;
+
+struct nf_defrag_v6_hook {
+ int (*enable)(struct net *net);
+ void (*disable)(struct net *net);
+};
+extern const struct nf_defrag_v6_hook __rcu *nf_defrag_v6_hook;
+
/**
* nf_skb_duplicated - TEE target has sent a packet
*
diff --git a/net/ipv4/netfilter/nf_defrag_ipv4.c b/net/ipv4/netfilter/nf_defrag_ipv4.c
index e61ea428ea18..436e629b0969 100644
--- a/net/ipv4/netfilter/nf_defrag_ipv4.c
+++ b/net/ipv4/netfilter/nf_defrag_ipv4.c
@@ -7,6 +7,7 @@
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <linux/module.h>
+#include <linux/rcupdate.h>
#include <linux/skbuff.h>
#include <net/netns/generic.h>
#include <net/route.h>
@@ -113,17 +114,24 @@ static void __net_exit defrag4_net_exit(struct net *net)
}
}

+static struct nf_defrag_v4_hook defrag_hook = {
+ .enable = nf_defrag_ipv4_enable,
+ .disable = nf_defrag_ipv4_disable,
+};
+
static struct pernet_operations defrag4_net_ops = {
.exit = defrag4_net_exit,
};

static int __init nf_defrag_init(void)
{
+ rcu_assign_pointer(nf_defrag_v4_hook, &defrag_hook);
return register_pernet_subsys(&defrag4_net_ops);
}

static void __exit nf_defrag_fini(void)
{
+ rcu_assign_pointer(nf_defrag_v4_hook, NULL);
unregister_pernet_subsys(&defrag4_net_ops);
}

diff --git a/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c b/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c
index cb4eb1d2c620..205fb692f524 100644
--- a/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c
+++ b/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c
@@ -10,6 +10,7 @@
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/icmp.h>
+#include <linux/rcupdate.h>
#include <linux/sysctl.h>
#include <net/ipv6_frag.h>

@@ -96,6 +97,11 @@ static void __net_exit defrag6_net_exit(struct net *net)
}
}

+static struct nf_defrag_v6_hook defrag_hook = {
+ .enable = nf_defrag_ipv6_enable,
+ .disable = nf_defrag_ipv6_disable,
+};
+
static struct pernet_operations defrag6_net_ops = {
.exit = defrag6_net_exit,
};
@@ -114,6 +120,9 @@ static int __init nf_defrag_init(void)
pr_err("nf_defrag_ipv6: can't register pernet ops\n");
goto cleanup_frag6;
}
+
+ rcu_assign_pointer(nf_defrag_v6_hook, &defrag_hook);
+
return ret;

cleanup_frag6:
@@ -124,6 +133,7 @@ static int __init nf_defrag_init(void)

static void __exit nf_defrag_fini(void)
{
+ rcu_assign_pointer(nf_defrag_v6_hook, NULL);
unregister_pernet_subsys(&defrag6_net_ops);
nf_ct_frag6_cleanup();
}
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 5f76ae86a656..34845155bb85 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -680,6 +680,12 @@ EXPORT_SYMBOL_GPL(nfnl_ct_hook);
const struct nf_ct_hook __rcu *nf_ct_hook __read_mostly;
EXPORT_SYMBOL_GPL(nf_ct_hook);

+const struct nf_defrag_v4_hook __rcu *nf_defrag_v4_hook __read_mostly;
+EXPORT_SYMBOL_GPL(nf_defrag_v4_hook);
+
+const struct nf_defrag_v6_hook __rcu *nf_defrag_v6_hook __read_mostly;
+EXPORT_SYMBOL_GPL(nf_defrag_v6_hook);
+
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
u8 nf_ctnetlink_has_listener;
EXPORT_SYMBOL_GPL(nf_ctnetlink_has_listener);
--
2.40.1