// 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)
{
        const struct nf_conntrack_helper *helper;
        struct net *net = read_pnet(&ct->ct_net);
        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;

        helper = rcu_dereference(help->helper);
        if (helper)
                exp->tuple.src.u.udp.port = 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;
        rcu_assign_pointer(exp->helper, helper);
        write_pnet(&exp->net, net);
#ifdef CONFIG_NF_CONNTRACK_ZONES
        exp->zone = ct->zone;
#endif
        nf_ct_expect_related(exp, 0);
        nf_ct_expect_put(exp);

        nf_ct_refresh(ct, timeout * HZ);
out:
        return NF_ACCEPT;
}
EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Broadcast connection tracking helper");