1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * broadcast connection tracking helper 4 * 5 * (c) 2005 Patrick McHardy <kaber@trash.net> 6 */ 7 8 #include <linux/module.h> 9 #include <linux/ip.h> 10 #include <net/route.h> 11 #include <linux/inetdevice.h> 12 #include <linux/skbuff.h> 13 14 #include <net/netfilter/nf_conntrack.h> 15 #include <net/netfilter/nf_conntrack_helper.h> 16 #include <net/netfilter/nf_conntrack_expect.h> 17 18 int nf_conntrack_broadcast_help(struct sk_buff *skb, 19 struct nf_conn *ct, 20 enum ip_conntrack_info ctinfo, 21 unsigned int timeout) 22 { 23 const struct nf_conntrack_helper *helper; 24 struct nf_conntrack_expect *exp; 25 struct iphdr *iph = ip_hdr(skb); 26 struct rtable *rt = skb_rtable(skb); 27 struct in_device *in_dev; 28 struct nf_conn_help *help = nfct_help(ct); 29 __be32 mask = 0; 30 31 /* we're only interested in locally generated packets */ 32 if (skb->sk == NULL || !net_eq(nf_ct_net(ct), sock_net(skb->sk))) 33 goto out; 34 if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST)) 35 goto out; 36 if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) 37 goto out; 38 39 in_dev = __in_dev_get_rcu(rt->dst.dev); 40 if (in_dev != NULL) { 41 const struct in_ifaddr *ifa; 42 43 in_dev_for_each_ifa_rcu(ifa, in_dev) { 44 if (ifa->ifa_flags & IFA_F_SECONDARY) 45 continue; 46 47 if (ifa->ifa_broadcast == iph->daddr) { 48 mask = ifa->ifa_mask; 49 break; 50 } 51 } 52 } 53 54 if (mask == 0) 55 goto out; 56 57 exp = nf_ct_expect_alloc(ct); 58 if (exp == NULL) 59 goto out; 60 61 exp->tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple; 62 63 helper = rcu_dereference(help->helper); 64 if (helper) 65 exp->tuple.src.u.udp.port = helper->tuple.src.u.udp.port; 66 67 exp->mask.src.u3.ip = mask; 68 exp->mask.src.u.udp.port = htons(0xFFFF); 69 70 exp->expectfn = NULL; 71 exp->flags = NF_CT_EXPECT_PERMANENT; 72 exp->class = NF_CT_EXPECT_CLASS_DEFAULT; 73 exp->helper = NULL; 74 75 nf_ct_expect_related(exp, 0); 76 nf_ct_expect_put(exp); 77 78 nf_ct_refresh(ct, skb, timeout * HZ); 79 out: 80 return NF_ACCEPT; 81 } 82 EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help); 83 84 MODULE_LICENSE("GPL"); 85