[PATCH 1/1] netfilter: load nf_log_syslog on enabling nf_conntrack_log_invalid

[Lance Yang <ioworker0@gmail.com>]

From: Lance Yang <lance.yang@linux.dev>

When nf_log_syslog is not loaded, nf_conntrack_log_invalid fails to log
invalid packets, leaving users unaware of actual invalid traffic. Improve
this by loading nf_log_syslog, similar to how 'iptables -I FORWARD 1 -m
conntrack --ctstate INVALID -j LOG' triggers it.

Signed-off-by: Zi Li <zili@linux.dev>
Signed-off-by: Lance Yang <lance.yang@linux.dev>
---
 net/netfilter/nf_conntrack_standalone.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 2f666751c7e7..b4acff01088f 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -543,6 +543,24 @@ nf_conntrack_hash_sysctl(const struct ctl_table *table, int write,
 	return ret;
 }
 
+static int
+nf_conntrack_log_invalid_sysctl(const struct ctl_table *table, int write,
+				void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_dou8vec_minmax(table, write, buffer, lenp, ppos);
+	if (ret < 0 || !write)
+		return ret;
+
+	if (*(u8 *)table->data == 0)
+		return ret;
+
+	request_module("%s", "nf_log_syslog");
+
+	return ret;
+}
+
 static struct ctl_table_header *nf_ct_netfilter_header;
 
 enum nf_ct_sysctl_index {
@@ -649,7 +667,7 @@ static struct ctl_table nf_ct_sysctl_table[] = {
 		.data		= &init_net.ct.sysctl_log_invalid,
 		.maxlen		= sizeof(u8),
 		.mode		= 0644,
-		.proc_handler	= proc_dou8vec_minmax,
+		.proc_handler	= nf_conntrack_log_invalid_sysctl,
 	},
 	[NF_SYSCTL_CT_EXPECT_MAX] = {
 		.procname	= "nf_conntrack_expect_max",
-- 
2.49.0