net/ipv4/netfilter/nf_tproxy_ipv4.c

   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
  18 struct sock *
  19 nf_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 }
  48 EXPORT_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 }
  67 EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
  68
  69 struct sock *
  70 nf_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 }
 145 EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
 146
 147 MODULE_LICENSE("GPL");
 148 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
 149 MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");