net/ipv4/netfilter/nf_tproxy_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
  11 #include <net/netfilter/nf_tproxy.h>
  12 #include <linux/module.h>
  13 #include <linux/skbuff.h>
  14 #include <net/sock.h>
  15 #include <net/inet_sock.h>
  16 #include <linux/ip.h>
  17 #include <net/checksum.h>
  18 #include <net/udp.h>
  19 #include <net/tcp.h>
  20 #include <linux/inetdevice.h>
  21
  22 struct sock *
  23 nf_tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb,
  24                          __be32 laddr, __be16 lport, struct sock *sk)
  25 {
  26         const struct iphdr *iph = ip_hdr(skb);
  27         struct tcphdr _hdr, *hp;
  28
  29         hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
  30         if (hp == NULL) {
  31                 inet_twsk_put(inet_twsk(sk));
  32                 return NULL;
  33         }
  34
  35         if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
  36                 /* SYN to a TIME_WAIT socket, we'd rather redirect it
  37                  * to a listener socket if there's one */
  38                 struct sock *sk2;
  39
  40                 sk2 = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
  41                                             iph->saddr, laddr ? laddr : iph->daddr,
  42                                             hp->source, lport ? lport : hp->dest,
  43                                             skb->dev, NF_TPROXY_LOOKUP_LISTENER);
  44                 if (sk2) {
  45                         inet_twsk_deschedule_put(inet_twsk(sk));
  46                         sk = sk2;
  47                 }
  48         }
  49
  50         return sk;
  51 }
  52 EXPORT_SYMBOL_GPL(nf_tproxy_handle_time_wait4);
  53
  54 __be32 nf_tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
  55 {
  56         struct in_device *indev;
  57         __be32 laddr;
  58
  59         if (user_laddr)
  60                 return user_laddr;
  61
  62         laddr = 0;
  63         indev = __in_dev_get_rcu(skb->dev);
  64         for_primary_ifa(indev) {
  65                 laddr = ifa->ifa_local;
  66                 break;
  67         } endfor_ifa(indev);
  68
  69         return laddr ? laddr : daddr;
  70 }
  71 EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
  72
  73 struct sock *
  74 nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb,
  75                       const u8 protocol,
  76                       const __be32 saddr, const __be32 daddr,
  77                       const __be16 sport, const __be16 dport,
  78                       const struct net_device *in,
  79                       const enum nf_tproxy_lookup_t lookup_type)
  80 {
  81         struct sock *sk;
  82
  83         switch (protocol) {
  84         case IPPROTO_TCP: {
  85                 struct tcphdr _hdr, *hp;
  86
  87                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
  88                                         sizeof(struct tcphdr), &_hdr);
  89                 if (hp == NULL)
  90                         return NULL;
  91
  92                 switch (lookup_type) {
  93                 case NF_TPROXY_LOOKUP_LISTENER:
  94                         sk = inet_lookup_listener(net, &tcp_hashinfo, skb,
  95                                                     ip_hdrlen(skb) +
  96                                                       __tcp_hdrlen(hp),
  97                                                     saddr, sport,
  98                                                     daddr, dport,
  99                                                     in->ifindex, 0);
 100
 101                         if (sk && !refcount_inc_not_zero(&sk->sk_refcnt))
 102                                 sk = NULL;
 103                         /* NOTE: we return listeners even if bound to
 104                          * 0.0.0.0, those are filtered out in
 105                          * xt_socket, since xt_TPROXY needs 0 bound
 106                          * listeners too
 107                          */
 108                         break;
 109                 case NF_TPROXY_LOOKUP_ESTABLISHED:
 110                         sk = inet_lookup_established(net, &tcp_hashinfo,
 111                                                     saddr, sport, daddr, dport,
 112                                                     in->ifindex);
 113                         break;
 114                 default:
 115                         BUG();
 116                 }
 117                 break;
 118                 }
 119         case IPPROTO_UDP:
 120                 sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
 121                                      in->ifindex);
 122                 if (sk) {
 123                         int connected = (sk->sk_state == TCP_ESTABLISHED);
 124                         int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
 125
 126                         /* NOTE: we return listeners even if bound to
 127                          * 0.0.0.0, those are filtered out in
 128                          * xt_socket, since xt_TPROXY needs 0 bound
 129                          * listeners too
 130                          */
 131                         if ((lookup_type == NF_TPROXY_LOOKUP_ESTABLISHED &&
 132                               (!connected || wildcard)) ||
 133                             (lookup_type == NF_TPROXY_LOOKUP_LISTENER && connected)) {
 134                                 sock_put(sk);
 135                                 sk = NULL;
 136                         }
 137                 }
 138                 break;
 139         default:
 140                 WARN_ON(1);
 141                 sk = NULL;
 142         }
 143
 144         pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
 145                  protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
 146
 147         return sk;
 148 }
 149 EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
 150
 151 MODULE_LICENSE("GPL");
 152 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
 153 MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");