LXR linux/net/netfilter/nf_conntrack

   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
  18int 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        struct nf_conntrack_expect *exp;
  24        struct iphdr *iph = ip_hdr(skb);
  25        struct rtable *rt = skb_rtable(skb);
  26        struct in_device *in_dev;
  27        struct nf_conn_help *help = nfct_help(ct);
  28        __be32 mask = 0;
  29
  30        /* we're only interested in locally generated packets */
  31        if (skb->sk == NULL || !net_eq(nf_ct_net(ct), sock_net(skb->sk)))
  32                goto out;
  33        if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
  34                goto out;
  35        if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
  36                goto out;
  37
  38        in_dev = __in_dev_get_rcu(rt->dst.dev);
  39        if (in_dev != NULL) {
  40                const struct in_ifaddr *ifa;
  41
  42                in_dev_for_each_ifa_rcu(ifa, in_dev) {
  43                        if (ifa->ifa_flags & IFA_F_SECONDARY)
  44                                continue;
  45
  46                        if (ifa->ifa_broadcast == iph->daddr) {
  47                                mask = ifa->ifa_mask;
  48                                break;
  49                        }
  50                }
  51        }
  52
  53        if (mask == 0)
  54                goto out;
  55
  56        exp = nf_ct_expect_alloc(ct);
  57        if (exp == NULL)
  58                goto out;
  59
  60        exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  61        exp->tuple.src.u.udp.port = help->helper->tuple.src.u.udp.port;
  62
  63        exp->mask.src.u3.ip       = mask;
  64        exp->mask.src.u.udp.port  = htons(0xFFFF);
  65
  66        exp->expectfn             = NULL;
  67        exp->flags                = NF_CT_EXPECT_PERMANENT;
  68        exp->class                = NF_CT_EXPECT_CLASS_DEFAULT;
  69        exp->helper               = NULL;
  70
  71        nf_ct_expect_related(exp, 0);
  72        nf_ct_expect_put(exp);
  73
  74        nf_ct_refresh(ct, skb, timeout * HZ);
  75out:
  76        return NF_ACCEPT;
  77}
  78EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);
  79
  80MODULE_LICENSE("GPL");
  81