net/netfilter/nf_conntrack_broadcast.c

   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");