// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   *      broadcast connection tracking helper
   *
   *      (c) 2005 Patrick McHardy <kaber@trash.net>

   */
  
  #include <linux/module.h>
  #include <linux/ip.h>
  #include <net/route.h>
  #include <linux/inetdevice.h>
  #include <linux/skbuff.h>
  
  #include <net/netfilter/nf_conntrack.h>
  #include <net/netfilter/nf_conntrack_helper.h>
  #include <net/netfilter/nf_conntrack_expect.h>
  
  int nf_conntrack_broadcast_help(struct sk_buff *skb,

  				struct nf_conn *ct,
  				enum ip_conntrack_info ctinfo,
  				unsigned int timeout)
  {
  	struct nf_conntrack_expect *exp;
  	struct iphdr *iph = ip_hdr(skb);
  	struct rtable *rt = skb_rtable(skb);
  	struct in_device *in_dev;
  	struct nf_conn_help *help = nfct_help(ct);
  	__be32 mask = 0;
  
  	/* we're only interested in locally generated packets */

  	if (skb->sk == NULL || !net_eq(nf_ct_net(ct), sock_net(skb->sk)))

  		goto out;
  	if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
  		goto out;
  	if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
  		goto out;

  	in_dev = __in_dev_get_rcu(rt->dst.dev);
  	if (in_dev != NULL) {

  		const struct in_ifaddr *ifa;
  
  		in_dev_for_each_ifa_rcu(ifa, in_dev) {
  			if (ifa->ifa_flags & IFA_F_SECONDARY)
  				continue;

  			if (ifa->ifa_broadcast == iph->daddr) {
  				mask = ifa->ifa_mask;
  				break;
  			}

  		}

  	}

  
  	if (mask == 0)
  		goto out;
  
  	exp = nf_ct_expect_alloc(ct);
  	if (exp == NULL)
  		goto out;
  
  	exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  	exp->tuple.src.u.udp.port = help->helper->tuple.src.u.udp.port;
  
  	exp->mask.src.u3.ip       = mask;
  	exp->mask.src.u.udp.port  = htons(0xFFFF);
  
  	exp->expectfn             = NULL;
  	exp->flags                = NF_CT_EXPECT_PERMANENT;
  	exp->class		  = NF_CT_EXPECT_CLASS_DEFAULT;
  	exp->helper               = NULL;

  	nf_ct_expect_related(exp, 0);

  	nf_ct_expect_put(exp);
  
  	nf_ct_refresh(ct, skb, timeout * HZ);
  out:
  	return NF_ACCEPT;
  }
  EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);
  
  MODULE_LICENSE("GPL");