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
@@ -17,6 +17,7 @@
 #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>
@@ -382,10 +383,66 @@ static int ct_open(struct inode *inode,
 			sizeof(struct ct_iter_state));
 }
 
+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 ssize_t ct_file_write(struct file *file, const char __user *buf,
+			     size_t count, loff_t *ppos)
+{
+	struct seq_file *seq = file->private_data;
+	struct net *net = seq_file_net(seq);
+	struct kill_request kr = { };
+	char req[INET6_ADDRSTRLEN] = { };
+
+	if (count == 0)
+		return 0;
+
+	if (count >= INET6_ADDRSTRLEN)
+		count = INET6_ADDRSTRLEN - 1;
+
+	if (copy_from_user(req, buf, count))
+		return -EFAULT;
+
+	if (strnchr(req, count, ':')) {
+		kr.family = AF_INET6;
+		if (!in6_pton(req, count, (void *)&kr.addr, '\n', NULL))
+			return -EINVAL;
+	} else if (strnchr(req, count, '.')) {
+		kr.family = AF_INET;
+		if (!in4_pton(req, count, (void *)&kr.addr, '\n', NULL))
+			return -EINVAL;
+	}
+
+	nf_ct_iterate_cleanup_net(net, kill_matching, &kr, 0, 0);
+
+	return count;
+}
+
 static const struct file_operations ct_file_ops = {
 	.owner   = THIS_MODULE,
 	.open    = ct_open,
 	.read    = seq_read,
+	.write	 = ct_file_write,
 	.llseek  = seq_lseek,
 	.release = seq_release_net,
 };
@@ -489,7 +546,7 @@ static int nf_conntrack_standalone_init_
 	kuid_t root_uid;
 	kgid_t root_gid;
 
-	pde = proc_create("nf_conntrack", 0440, net->proc_net, &ct_file_ops);
+	pde = proc_create("nf_conntrack", 0660, net->proc_net, &ct_file_ops);
 	if (!pde)
 		goto out_nf_conntrack;