1 /* (C) 1999-2001 Paul `Rusty' Russell 2 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 */ 8 9 #include <linux/types.h> 10 #include <linux/ip.h> 11 #include <linux/netfilter.h> 12 #include <linux/module.h> 13 #include <linux/skbuff.h> 14 #include <net/netns/generic.h> 15 #include <net/route.h> 16 #include <net/ip.h> 17 18 #include <linux/netfilter_bridge.h> 19 #include <linux/netfilter_ipv4.h> 20 #include <net/netfilter/ipv4/nf_defrag_ipv4.h> 21 #if IS_ENABLED(CONFIG_NF_CONNTRACK) 22 #include <net/netfilter/nf_conntrack.h> 23 #endif 24 #include <net/netfilter/nf_conntrack_zones.h> 25 26 static DEFINE_MUTEX(defrag4_mutex); 27 28 static int nf_ct_ipv4_gather_frags(struct net *net, struct sk_buff *skb, 29 u_int32_t user) 30 { 31 int err; 32 33 local_bh_disable(); 34 err = ip_defrag(net, skb, user); 35 local_bh_enable(); 36 37 if (!err) 38 skb->ignore_df = 1; 39 40 return err; 41 } 42 43 static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum, 44 struct sk_buff *skb) 45 { 46 u16 zone_id = NF_CT_DEFAULT_ZONE_ID; 47 #if IS_ENABLED(CONFIG_NF_CONNTRACK) 48 if (skb_nfct(skb)) { 49 enum ip_conntrack_info ctinfo; 50 const struct nf_conn *ct = nf_ct_get(skb, &ctinfo); 51 52 zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo)); 53 } 54 #endif 55 if (nf_bridge_in_prerouting(skb)) 56 return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id; 57 58 if (hooknum == NF_INET_PRE_ROUTING) 59 return IP_DEFRAG_CONNTRACK_IN + zone_id; 60 else 61 return IP_DEFRAG_CONNTRACK_OUT + zone_id; 62 } 63 64 static unsigned int ipv4_conntrack_defrag(void *priv, 65 struct sk_buff *skb, 66 const struct nf_hook_state *state) 67 { 68 struct sock *sk = skb->sk; 69 70 if (sk && sk_fullsock(sk) && (sk->sk_family == PF_INET) && 71 inet_sk(sk)->nodefrag) 72 return NF_ACCEPT; 73 74 #if IS_ENABLED(CONFIG_NF_CONNTRACK) 75 #if !IS_ENABLED(CONFIG_NF_NAT) 76 /* Previously seen (loopback)? Ignore. Do this before 77 fragment check. */ 78 if (skb_nfct(skb) && !nf_ct_is_template((struct nf_conn *)skb_nfct(skb))) 79 return NF_ACCEPT; 80 #endif 81 #endif 82 /* Gather fragments. */ 83 if (ip_is_fragment(ip_hdr(skb))) { 84 enum ip_defrag_users user = 85 nf_ct_defrag_user(state->hook, skb); 86 87 if (nf_ct_ipv4_gather_frags(state->net, skb, user)) 88 return NF_STOLEN; 89 } 90 return NF_ACCEPT; 91 } 92 93 static const struct nf_hook_ops ipv4_defrag_ops[] = { 94 { 95 .hook = ipv4_conntrack_defrag, 96 .pf = NFPROTO_IPV4, 97 .hooknum = NF_INET_PRE_ROUTING, 98 .priority = NF_IP_PRI_CONNTRACK_DEFRAG, 99 }, 100 { 101 .hook = ipv4_conntrack_defrag, 102 .pf = NFPROTO_IPV4, 103 .hooknum = NF_INET_LOCAL_OUT, 104 .priority = NF_IP_PRI_CONNTRACK_DEFRAG, 105 }, 106 }; 107 108 static void __net_exit defrag4_net_exit(struct net *net) 109 { 110 if (net->nf.defrag_ipv4) { 111 nf_unregister_net_hooks(net, ipv4_defrag_ops, 112 ARRAY_SIZE(ipv4_defrag_ops)); 113 net->nf.defrag_ipv4 = false; 114 } 115 } 116 117 static struct pernet_operations defrag4_net_ops = { 118 .exit = defrag4_net_exit, 119 }; 120 121 static int __init nf_defrag_init(void) 122 { 123 return register_pernet_subsys(&defrag4_net_ops); 124 } 125 126 static void __exit nf_defrag_fini(void) 127 { 128 unregister_pernet_subsys(&defrag4_net_ops); 129 } 130 131 int nf_defrag_ipv4_enable(struct net *net) 132 { 133 int err = 0; 134 135 might_sleep(); 136 137 if (net->nf.defrag_ipv4) 138 return 0; 139 140 mutex_lock(&defrag4_mutex); 141 if (net->nf.defrag_ipv4) 142 goto out_unlock; 143 144 err = nf_register_net_hooks(net, ipv4_defrag_ops, 145 ARRAY_SIZE(ipv4_defrag_ops)); 146 if (err == 0) 147 net->nf.defrag_ipv4 = true; 148 149 out_unlock: 150 mutex_unlock(&defrag4_mutex); 151 return err; 152 } 153 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable); 154 155 module_init(nf_defrag_init); 156 module_exit(nf_defrag_fini); 157 158 MODULE_LICENSE("GPL"); 159