net/ipv4/netfilter/nf_socket_ipv4.c

   1 /*
   2  * Copyright (C) 2007-2008 BalaBit IT Ltd.
   3  * Author: Krisztian Kovacs
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  */
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13 #include <net/tcp.h>
  14 #include <net/udp.h>
  15 #include <net/icmp.h>
  16 #include <net/sock.h>
  17 #include <net/inet_sock.h>
  18 #include <net/netfilter/nf_socket.h>
  19 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  20 #include <net/netfilter/nf_conntrack.h>
  21 #endif
  22
  23 static int
  24 extract_icmp4_fields(const struct sk_buff *skb, u8 *protocol,
  25                      __be32 *raddr, __be32 *laddr,
  26                      __be16 *rport, __be16 *lport)
  27 {
  28         unsigned int outside_hdrlen = ip_hdrlen(skb);
  29         struct iphdr *inside_iph, _inside_iph;
  30         struct icmphdr *icmph, _icmph;
  31         __be16 *ports, _ports[2];
  32
  33         icmph = skb_header_pointer(skb, outside_hdrlen,
  34                                    sizeof(_icmph), &_icmph);
  35         if (icmph == NULL)
  36                 return 1;
  37
  38         switch (icmph->type) {
  39         case ICMP_DEST_UNREACH:
  40         case ICMP_SOURCE_QUENCH:
  41         case ICMP_REDIRECT:
  42         case ICMP_TIME_EXCEEDED:
  43         case ICMP_PARAMETERPROB:
  44                 break;
  45         default:
  46                 return 1;
  47         }
  48
  49         inside_iph = skb_header_pointer(skb, outside_hdrlen +
  50                                         sizeof(struct icmphdr),
  51                                         sizeof(_inside_iph), &_inside_iph);
  52         if (inside_iph == NULL)
  53                 return 1;
  54
  55         if (inside_iph->protocol != IPPROTO_TCP &&
  56             inside_iph->protocol != IPPROTO_UDP)
  57                 return 1;
  58
  59         ports = skb_header_pointer(skb, outside_hdrlen +
  60                                    sizeof(struct icmphdr) +
  61                                    (inside_iph->ihl << 2),
  62                                    sizeof(_ports), &_ports);
  63         if (ports == NULL)
  64                 return 1;
  65
  66         /* the inside IP packet is the one quoted from our side, thus
  67          * its saddr is the local address */
  68         *protocol = inside_iph->protocol;
  69         *laddr = inside_iph->saddr;
  70         *lport = ports[0];
  71         *raddr = inside_iph->daddr;
  72         *rport = ports[1];
  73
  74         return 0;
  75 }
  76
  77 static struct sock *
  78 nf_socket_get_sock_v4(struct net *net, struct sk_buff *skb, const int doff,
  79                       const u8 protocol,
  80                       const __be32 saddr, const __be32 daddr,
  81                       const __be16 sport, const __be16 dport,
  82                       const struct net_device *in)
  83 {
  84         switch (protocol) {
  85         case IPPROTO_TCP:
  86                 return inet_lookup(net, &tcp_hashinfo, skb, doff,
  87                                    saddr, sport, daddr, dport,
  88                                    in->ifindex);
  89         case IPPROTO_UDP:
  90                 return udp4_lib_lookup(net, saddr, sport, daddr, dport,
  91                                        in->ifindex);
  92         }
  93         return NULL;
  94 }
  95
  96 struct sock *nf_sk_lookup_slow_v4(struct net *net, const struct sk_buff *skb,
  97                                   const struct net_device *indev)
  98 {
  99         __be32 uninitialized_var(daddr), uninitialized_var(saddr);
 100         __be16 uninitialized_var(dport), uninitialized_var(sport);
 101         const struct iphdr *iph = ip_hdr(skb);
 102         struct sk_buff *data_skb = NULL;
 103         u8 uninitialized_var(protocol);
 104 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 105         enum ip_conntrack_info ctinfo;
 106         struct nf_conn const *ct;
 107 #endif
 108         int doff = 0;
 109
 110         if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
 111                 struct tcphdr _hdr;
 112                 struct udphdr *hp;
 113
 114                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
 115                                         iph->protocol == IPPROTO_UDP ?
 116                                         sizeof(*hp) : sizeof(_hdr), &_hdr);
 117                 if (hp == NULL)
 118                         return NULL;
 119
 120                 protocol = iph->protocol;
 121                 saddr = iph->saddr;
 122                 sport = hp->source;
 123                 daddr = iph->daddr;
 124                 dport = hp->dest;
 125                 data_skb = (struct sk_buff *)skb;
 126                 doff = iph->protocol == IPPROTO_TCP ?
 127                         ip_hdrlen(skb) + __tcp_hdrlen((struct tcphdr *)hp) :
 128                         ip_hdrlen(skb) + sizeof(*hp);
 129
 130         } else if (iph->protocol == IPPROTO_ICMP) {
 131                 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
 132                                          &sport, &dport))
 133                         return NULL;
 134         } else {
 135                 return NULL;
 136         }
 137
 138 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 139         /* Do the lookup with the original socket address in
 140          * case this is a reply packet of an established
 141          * SNAT-ted connection.
 142          */
 143         ct = nf_ct_get(skb, &ctinfo);
 144         if (ct &&
 145             ((iph->protocol != IPPROTO_ICMP &&
 146               ctinfo == IP_CT_ESTABLISHED_REPLY) ||
 147              (iph->protocol == IPPROTO_ICMP &&
 148               ctinfo == IP_CT_RELATED_REPLY)) &&
 149             (ct->status & IPS_SRC_NAT_DONE)) {
 150
 151                 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
 152                 dport = (iph->protocol == IPPROTO_TCP) ?
 153                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
 154                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
 155         }
 156 #endif
 157
 158         return nf_socket_get_sock_v4(net, data_skb, doff, protocol, saddr,
 159                                      daddr, sport, dport, indev);
 160 }
 161 EXPORT_SYMBOL_GPL(nf_sk_lookup_slow_v4);
 162
 163 MODULE_LICENSE("GPL");
 164 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 165 MODULE_DESCRIPTION("Netfilter IPv4 socket lookup infrastructure");