LXR linux/net/ipv4/netfilter/nf_tproxy

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (C) 2007-2008 BalaBit IT Ltd.
   4 * Author: Krisztian Kovacs
   5 */
   6
   7#include <net/netfilter/nf_tproxy.h>
   8#include <linux/module.h>
   9#include <linux/skbuff.h>
  10#include <net/sock.h>
  11#include <net/inet_sock.h>
  12#include <linux/ip.h>
  13#include <net/checksum.h>
  14#include <net/udp.h>
  15#include <net/tcp.h>
  16#include <linux/inetdevice.h>
  17
  18struct sock *
  19nf_tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb,
  20                         __be32 laddr, __be16 lport, struct sock *sk)
  21{
  22        const struct iphdr *iph = ip_hdr(skb);
  23        struct tcphdr _hdr, *hp;
  24
  25        hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
  26        if (hp == NULL) {
  27                inet_twsk_put(inet_twsk(sk));
  28                return NULL;
  29        }
  30
  31        if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
  32                /* SYN to a TIME_WAIT socket, we'd rather redirect it
  33                 * to a listener socket if there's one */
  34                struct sock *sk2;
  35
  36                sk2 = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
  37                                            iph->saddr, laddr ? laddr : iph->daddr,
  38                                            hp->source, lport ? lport : hp->dest,
  39                                            skb->dev, NF_TPROXY_LOOKUP_LISTENER);
  40                if (sk2) {
  41                        inet_twsk_deschedule_put(inet_twsk(sk));
  42                        sk = sk2;
  43                }
  44        }
  45
  46        return sk;
  47}
  48EXPORT_SYMBOL_GPL(nf_tproxy_handle_time_wait4);
  49
  50__be32 nf_tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
  51{
  52        struct in_device *indev;
  53        __be32 laddr;
  54
  55        if (user_laddr)
  56                return user_laddr;
  57
  58        laddr = 0;
  59        indev = __in_dev_get_rcu(skb->dev);
  60        for_primary_ifa(indev) {
  61                laddr = ifa->ifa_local;
  62                break;
  63        } endfor_ifa(indev);
  64
  65        return laddr ? laddr : daddr;
  66}
  67EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
  68
  69struct sock *
  70nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb,
  71                      const u8 protocol,
  72                      const __be32 saddr, const __be32 daddr,
  73                      const __be16 sport, const __be16 dport,
  74                      const struct net_device *in,
  75                      const enum nf_tproxy_lookup_t lookup_type)
  76{
  77        struct sock *sk;
  78
  79        switch (protocol) {
  80        case IPPROTO_TCP: {
  81                struct tcphdr _hdr, *hp;
  82
  83                hp = skb_header_pointer(skb, ip_hdrlen(skb),
  84                                        sizeof(struct tcphdr), &_hdr);
  85                if (hp == NULL)
  86                        return NULL;
  87
  88                switch (lookup_type) {
  89                case NF_TPROXY_LOOKUP_LISTENER:
  90                        sk = inet_lookup_listener(net, &tcp_hashinfo, skb,
  91                                                    ip_hdrlen(skb) +
  92                                                      __tcp_hdrlen(hp),
  93                                                    saddr, sport,
  94                                                    daddr, dport,
  95                                                    in->ifindex, 0);
  96
  97                        if (sk && !refcount_inc_not_zero(&sk->sk_refcnt))
  98                                sk = NULL;
  99                        /* NOTE: we return listeners even if bound to
 100                         * 0.0.0.0, those are filtered out in
 101                         * xt_socket, since xt_TPROXY needs 0 bound
 102                         * listeners too
 103                         */
 104                        break;
 105                case NF_TPROXY_LOOKUP_ESTABLISHED:
 106                        sk = inet_lookup_established(net, &tcp_hashinfo,
 107                                                    saddr, sport, daddr, dport,
 108                                                    in->ifindex);
 109                        break;
 110                default:
 111                        BUG();
 112                }
 113                break;
 114                }
 115        case IPPROTO_UDP:
 116                sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
 117                                     in->ifindex);
 118                if (sk) {
 119                        int connected = (sk->sk_state == TCP_ESTABLISHED);
 120                        int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
 121
 122                        /* NOTE: we return listeners even if bound to
 123                         * 0.0.0.0, those are filtered out in
 124                         * xt_socket, since xt_TPROXY needs 0 bound
 125                         * listeners too
 126                         */
 127                        if ((lookup_type == NF_TPROXY_LOOKUP_ESTABLISHED &&
 128                              (!connected || wildcard)) ||
 129                            (lookup_type == NF_TPROXY_LOOKUP_LISTENER && connected)) {
 130                                sock_put(sk);
 131                                sk = NULL;
 132                        }
 133                }
 134                break;
 135        default:
 136                WARN_ON(1);
 137                sk = NULL;
 138        }
 139
 140        pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
 141                 protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
 142
 143        return sk;
 144}
 145EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
 146
 147MODULE_LICENSE("GPL");
 148MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
 149MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");
 150