From: Felix Fietkau <nbd@nbd.name>
Subject: netfilter: add support for flushing conntrack via /proc

lede-commit 8193bbe59a74d34d6a26d4a8cb857b1952905314
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/netfilter/nf_conntrack_standalone.c | 59 ++++++++++++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -9,6 +9,7 @@
 #include <linux/percpu.h>
 #include <linux/netdevice.h>
 #include <linux/security.h>
+#include <linux/inet.h>
 #include <net/net_namespace.h>
 #ifdef CONFIG_SYSCTL
 #include <linux/sysctl.h>
@@ -462,6 +463,56 @@ static int ct_cpu_seq_show(struct seq_fi
 	return 0;
 }
 
+struct kill_request {
+	u16 family;
+	union nf_inet_addr addr;
+};
+
+static int kill_matching(struct nf_conn *i, void *data)
+{
+	struct kill_request *kr = data;
+	struct nf_conntrack_tuple *t1 = &i->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
+	struct nf_conntrack_tuple *t2 = &i->tuplehash[IP_CT_DIR_REPLY].tuple;
+
+	if (!kr->family)
+		return 1;
+
+	if (t1->src.l3num != kr->family)
+		return 0;
+
+	return (nf_inet_addr_cmp(&kr->addr, &t1->src.u3) ||
+	        nf_inet_addr_cmp(&kr->addr, &t1->dst.u3) ||
+	        nf_inet_addr_cmp(&kr->addr, &t2->src.u3) ||
+	        nf_inet_addr_cmp(&kr->addr, &t2->dst.u3));
+}
+
+static int ct_file_write(struct file *file, char *buf, size_t count)
+{
+	struct seq_file *seq = file->private_data;
+	struct net *net = seq_file_net(seq);
+	struct kill_request kr = { };
+
+	if (count == 0)
+		return 0;
+
+	if (count >= INET6_ADDRSTRLEN)
+		count = INET6_ADDRSTRLEN - 1;
+
+	if (strnchr(buf, count, ':')) {
+		kr.family = AF_INET6;
+		if (!in6_pton(buf, count, (void *)&kr.addr, '\n', NULL))
+			return -EINVAL;
+	} else if (strnchr(buf, count, '.')) {
+		kr.family = AF_INET;
+		if (!in4_pton(buf, count, (void *)&kr.addr, '\n', NULL))
+			return -EINVAL;
+	}
+
+	nf_ct_iterate_cleanup_net(net, kill_matching, &kr, 0, 0);
+
+	return 0;
+}
+
 static const struct seq_operations ct_cpu_seq_ops = {
 	.start	= ct_cpu_seq_start,
 	.next	= ct_cpu_seq_next,
@@ -475,8 +526,9 @@ static int nf_conntrack_standalone_init_
 	kuid_t root_uid;
 	kgid_t root_gid;
 
-	pde = proc_create_net("nf_conntrack", 0440, net->proc_net, &ct_seq_ops,
-			sizeof(struct ct_iter_state));
+	pde = proc_create_net_data_write("nf_conntrack", 0440, net->proc_net,
+					 &ct_seq_ops, &ct_file_write,
+					 sizeof(struct ct_iter_state), NULL);
 	if (!pde)
 		goto out_nf_conntrack;