LXR linux/net/ipv4/netfilter/nf_tproxy

   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
  22struct sock *
  23nf_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}
  52EXPORT_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}
  71EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
  72
  73struct sock *
  74nf_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}
 149EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
 150
 151MODULE_LICENSE("GPL");
 152MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
 153MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");
 154