[PATCH bpf-next v5 4/8] net: netfilter: Add kfuncs to set and change CT timeout

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

Introduce bpf_ct_set_timeout and bpf_ct_change_timeout kfunc helpers in
order to change nf_conn timeout. This is same as ctnetlink_change_timeout,
hence code is shared between both by extracting it out to
__nf_ct_change_timeout. It is also updated to return an error when it
sees IPS_FIXED_TIMEOUT_BIT bit in ct->status, as that check was missing.

It is required to introduce two kfuncs taking nf_conn___init and nf_conn
instead of sharing one because __ref suffix on the parameter name causes
strict type checking. This would disallow passing nf_conn___init to
kfunc taking nf_conn, and vice versa. We cannot remove the __ref suffix
as we only want to accept refcounted pointers and not e.g. ct->master.

Apart from this, bpf_ct_set_timeout is only called for newly allocated
CT so it doesn't need to inspect the status field just yet. Sharing the
helpers even if it was possible would make timeout setting helper
sensitive to order of setting status and timeout after allocation.

Hence, bpf_ct_set_* kfuncs are meant to be used on allocated CT, and
bpf_ct_change_* kfuncs are meant to be used on inserted or looked up
CT entry.

Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/net/netfilter/nf_conntrack_core.h |  2 ++
 net/netfilter/nf_conntrack_bpf.c          | 34 +++++++++++++++++++++++
 net/netfilter/nf_conntrack_core.c         | 22 +++++++++++++++
 net/netfilter/nf_conntrack_netlink.c      |  9 +-----
 4 files changed, 59 insertions(+), 8 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h
index 83a60c684e6c..3b0f7d0eebae 100644
--- a/include/net/netfilter/nf_conntrack_core.h
+++ b/include/net/netfilter/nf_conntrack_core.h
@@ -97,6 +97,8 @@ static inline void __nf_ct_set_timeout(struct nf_conn *ct, u64 timeout)
 	WRITE_ONCE(ct->timeout, nfct_time_stamp + (u32)timeout);
 }
 
+int __nf_ct_change_timeout(struct nf_conn *ct, u64 cta_timeout);
+
 #endif
 
 #endif /* _NF_CONNTRACK_CORE_H */
diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
index 1d3c1d1e2d8b..db04874da950 100644
--- a/net/netfilter/nf_conntrack_bpf.c
+++ b/net/netfilter/nf_conntrack_bpf.c
@@ -364,6 +364,36 @@ void bpf_ct_release(struct nf_conn *nfct)
 	nf_ct_put(nfct);
 }
 
+/* bpf_ct_set_timeout - Set timeout of allocated nf_conn
+ *
+ * Sets the default timeout of newly allocated nf_conn before insertion.
+ * This helper must be invoked for refcounted pointer to nf_conn___init.
+ *
+ * Parameters:
+ * @nfct__ref    - Pointer to referenced nf_conn object, obtained using
+ *                 bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
+ * @timeout      - Timeout in msecs.
+ */
+void bpf_ct_set_timeout(struct nf_conn___init *nfct__ref, u32 timeout)
+{
+	__nf_ct_set_timeout((struct nf_conn *)nfct__ref, msecs_to_jiffies(timeout));
+}
+
+/* bpf_ct_change_timeout - Change timeout of inserted nf_conn
+ *
+ * Change timeout associated of the inserted or looked up nf_conn.
+ * This helper must be invoked for refcounted pointer to nf_conn.
+ *
+ * Parameters:
+ * @nfct__ref    - Pointer to referenced nf_conn object, obtained using
+ *		   bpf_ct_insert_entry, bpf_xdp_ct_lookup, or bpf_skb_ct_lookup.
+ * @timeout      - New timeout in msecs.
+ */
+int bpf_ct_change_timeout(struct nf_conn *nfct__ref, u32 timeout)
+{
+	return __nf_ct_change_timeout(nfct__ref, msecs_to_jiffies(timeout));
+}
+
 __diag_pop()
 
 BTF_SET_START(nf_ct_xdp_check_kfunc_ids)
@@ -371,6 +401,8 @@ BTF_ID(func, bpf_xdp_ct_alloc)
 BTF_ID(func, bpf_xdp_ct_lookup)
 BTF_ID(func, bpf_ct_insert_entry)
 BTF_ID(func, bpf_ct_release)
+BTF_ID(func, bpf_ct_set_timeout);
+BTF_ID(func, bpf_ct_change_timeout);
 BTF_SET_END(nf_ct_xdp_check_kfunc_ids)
 
 BTF_SET_START(nf_ct_tc_check_kfunc_ids)
@@ -378,6 +410,8 @@ BTF_ID(func, bpf_skb_ct_alloc)
 BTF_ID(func, bpf_skb_ct_lookup)
 BTF_ID(func, bpf_ct_insert_entry)
 BTF_ID(func, bpf_ct_release)
+BTF_ID(func, bpf_ct_set_timeout);
+BTF_ID(func, bpf_ct_change_timeout);
 BTF_SET_END(nf_ct_tc_check_kfunc_ids)
 
 BTF_SET_START(nf_ct_acquire_kfunc_ids)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 082a2fd8d85b..572f59a5e936 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2786,3 +2786,25 @@ int nf_conntrack_init_net(struct net *net)
 	free_percpu(net->ct.stat);
 	return ret;
 }
+
+#if (IS_BUILTIN(CONFIG_NF_CONNTRACK) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) || \
+    (IS_MODULE(CONFIG_NF_CONNTRACK) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES) || \
+    IS_ENABLED(CONFIG_NF_CT_NETLINK))
+
+/* ctnetlink code shared by both ctnetlink and nf_conntrack_bpf */
+
+int __nf_ct_change_timeout(struct nf_conn *ct, u64 timeout)
+{
+	if (test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status))
+		return -EPERM;
+
+	__nf_ct_set_timeout(ct, timeout);
+
+	if (test_bit(IPS_DYING_BIT, &ct->status))
+		return -ETIME;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__nf_ct_change_timeout);
+
+#endif
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 0729b2f0d44f..b1de07c73845 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -2023,14 +2023,7 @@ static int ctnetlink_change_helper(struct nf_conn *ct,
 static int ctnetlink_change_timeout(struct nf_conn *ct,
 				    const struct nlattr * const cda[])
 {
-	u64 timeout = (u64)ntohl(nla_get_be32(cda[CTA_TIMEOUT])) * HZ;
-
-	__nf_ct_set_timeout(ct, timeout);
-
-	if (test_bit(IPS_DYING_BIT, &ct->status))
-		return -ETIME;
-
-	return 0;
+	return __nf_ct_change_timeout(ct, (u64)ntohl(nla_get_be32(cda[CTA_TIMEOUT])) * HZ);
 }
 
 #if defined(CONFIG_NF_CONNTRACK_MARK)
-- 
2.36.1