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Linux/net/ipv4/netfilter/nf_tproxy_ipv4.c

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  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         const struct in_ifaddr *ifa;
 53         struct in_device *indev;
 54         __be32 laddr;
 55 
 56         if (user_laddr)
 57                 return user_laddr;
 58 
 59         laddr = 0;
 60         indev = __in_dev_get_rcu(skb->dev);
 61 
 62         in_dev_for_each_ifa_rcu(ifa, indev) {
 63                 if (ifa->ifa_flags & IFA_F_SECONDARY)
 64                         continue;
 65 
 66                 laddr = ifa->ifa_local;
 67                 break;
 68         }
 69 
 70         return laddr ? laddr : daddr;
 71 }
 72 EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
 73 
 74 struct sock *
 75 nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb,
 76                       const u8 protocol,
 77                       const __be32 saddr, const __be32 daddr,
 78                       const __be16 sport, const __be16 dport,
 79                       const struct net_device *in,
 80                       const enum nf_tproxy_lookup_t lookup_type)
 81 {
 82         struct sock *sk;
 83 
 84         switch (protocol) {
 85         case IPPROTO_TCP: {
 86                 struct tcphdr _hdr, *hp;
 87 
 88                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
 89                                         sizeof(struct tcphdr), &_hdr);
 90                 if (hp == NULL)
 91                         return NULL;
 92 
 93                 switch (lookup_type) {
 94                 case NF_TPROXY_LOOKUP_LISTENER:
 95                         sk = inet_lookup_listener(net, &tcp_hashinfo, skb,
 96                                                     ip_hdrlen(skb) +
 97                                                       __tcp_hdrlen(hp),
 98                                                     saddr, sport,
 99                                                     daddr, dport,
100                                                     in->ifindex, 0);
101 
102                         if (sk && !refcount_inc_not_zero(&sk->sk_refcnt))
103                                 sk = NULL;
104                         /* NOTE: we return listeners even if bound to
105                          * 0.0.0.0, those are filtered out in
106                          * xt_socket, since xt_TPROXY needs 0 bound
107                          * listeners too
108                          */
109                         break;
110                 case NF_TPROXY_LOOKUP_ESTABLISHED:
111                         sk = inet_lookup_established(net, &tcp_hashinfo,
112                                                     saddr, sport, daddr, dport,
113                                                     in->ifindex);
114                         break;
115                 default:
116                         BUG();
117                 }
118                 break;
119                 }
120         case IPPROTO_UDP:
121                 sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
122                                      in->ifindex);
123                 if (sk) {
124                         int connected = (sk->sk_state == TCP_ESTABLISHED);
125                         int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
126 
127                         /* NOTE: we return listeners even if bound to
128                          * 0.0.0.0, those are filtered out in
129                          * xt_socket, since xt_TPROXY needs 0 bound
130                          * listeners too
131                          */
132                         if ((lookup_type == NF_TPROXY_LOOKUP_ESTABLISHED &&
133                               (!connected || wildcard)) ||
134                             (lookup_type == NF_TPROXY_LOOKUP_LISTENER && connected)) {
135                                 sock_put(sk);
136                                 sk = NULL;
137                         }
138                 }
139                 break;
140         default:
141                 WARN_ON(1);
142                 sk = NULL;
143         }
144 
145         pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
146                  protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
147 
148         return sk;
149 }
150 EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
151 
152 MODULE_LICENSE("GPL");
153 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
154 MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");
155 

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