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Linux/net/ipv4/netfilter/nf_socket_ipv4.c

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  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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 11 #include <linux/module.h>
 12 #include <linux/skbuff.h>
 13 #include <net/tcp.h>
 14 #include <net/udp.h>
 15 #include <net/icmp.h>
 16 #include <net/sock.h>
 17 #include <net/inet_sock.h>
 18 #include <net/netfilter/nf_socket.h>
 19 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 20 #include <net/netfilter/nf_conntrack.h>
 21 #endif
 22 
 23 static int
 24 extract_icmp4_fields(const struct sk_buff *skb, u8 *protocol,
 25                      __be32 *raddr, __be32 *laddr,
 26                      __be16 *rport, __be16 *lport)
 27 {
 28         unsigned int outside_hdrlen = ip_hdrlen(skb);
 29         struct iphdr *inside_iph, _inside_iph;
 30         struct icmphdr *icmph, _icmph;
 31         __be16 *ports, _ports[2];
 32 
 33         icmph = skb_header_pointer(skb, outside_hdrlen,
 34                                    sizeof(_icmph), &_icmph);
 35         if (icmph == NULL)
 36                 return 1;
 37 
 38         switch (icmph->type) {
 39         case ICMP_DEST_UNREACH:
 40         case ICMP_SOURCE_QUENCH:
 41         case ICMP_REDIRECT:
 42         case ICMP_TIME_EXCEEDED:
 43         case ICMP_PARAMETERPROB:
 44                 break;
 45         default:
 46                 return 1;
 47         }
 48 
 49         inside_iph = skb_header_pointer(skb, outside_hdrlen +
 50                                         sizeof(struct icmphdr),
 51                                         sizeof(_inside_iph), &_inside_iph);
 52         if (inside_iph == NULL)
 53                 return 1;
 54 
 55         if (inside_iph->protocol != IPPROTO_TCP &&
 56             inside_iph->protocol != IPPROTO_UDP)
 57                 return 1;
 58 
 59         ports = skb_header_pointer(skb, outside_hdrlen +
 60                                    sizeof(struct icmphdr) +
 61                                    (inside_iph->ihl << 2),
 62                                    sizeof(_ports), &_ports);
 63         if (ports == NULL)
 64                 return 1;
 65 
 66         /* the inside IP packet is the one quoted from our side, thus
 67          * its saddr is the local address */
 68         *protocol = inside_iph->protocol;
 69         *laddr = inside_iph->saddr;
 70         *lport = ports[0];
 71         *raddr = inside_iph->daddr;
 72         *rport = ports[1];
 73 
 74         return 0;
 75 }
 76 
 77 static struct sock *
 78 nf_socket_get_sock_v4(struct net *net, struct sk_buff *skb, const int doff,
 79                       const u8 protocol,
 80                       const __be32 saddr, const __be32 daddr,
 81                       const __be16 sport, const __be16 dport,
 82                       const struct net_device *in)
 83 {
 84         switch (protocol) {
 85         case IPPROTO_TCP:
 86                 return inet_lookup(net, &tcp_hashinfo, skb, doff,
 87                                    saddr, sport, daddr, dport,
 88                                    in->ifindex);
 89         case IPPROTO_UDP:
 90                 return udp4_lib_lookup(net, saddr, sport, daddr, dport,
 91                                        in->ifindex);
 92         }
 93         return NULL;
 94 }
 95 
 96 struct sock *nf_sk_lookup_slow_v4(struct net *net, const struct sk_buff *skb,
 97                                   const struct net_device *indev)
 98 {
 99         __be32 uninitialized_var(daddr), uninitialized_var(saddr);
100         __be16 uninitialized_var(dport), uninitialized_var(sport);
101         const struct iphdr *iph = ip_hdr(skb);
102         struct sk_buff *data_skb = NULL;
103         u8 uninitialized_var(protocol);
104 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
105         enum ip_conntrack_info ctinfo;
106         struct nf_conn const *ct;
107 #endif
108         int doff = 0;
109 
110         if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
111                 struct tcphdr _hdr;
112                 struct udphdr *hp;
113 
114                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
115                                         iph->protocol == IPPROTO_UDP ?
116                                         sizeof(*hp) : sizeof(_hdr), &_hdr);
117                 if (hp == NULL)
118                         return NULL;
119 
120                 protocol = iph->protocol;
121                 saddr = iph->saddr;
122                 sport = hp->source;
123                 daddr = iph->daddr;
124                 dport = hp->dest;
125                 data_skb = (struct sk_buff *)skb;
126                 doff = iph->protocol == IPPROTO_TCP ?
127                         ip_hdrlen(skb) + __tcp_hdrlen((struct tcphdr *)hp) :
128                         ip_hdrlen(skb) + sizeof(*hp);
129 
130         } else if (iph->protocol == IPPROTO_ICMP) {
131                 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
132                                          &sport, &dport))
133                         return NULL;
134         } else {
135                 return NULL;
136         }
137 
138 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
139         /* Do the lookup with the original socket address in
140          * case this is a reply packet of an established
141          * SNAT-ted connection.
142          */
143         ct = nf_ct_get(skb, &ctinfo);
144         if (ct &&
145             ((iph->protocol != IPPROTO_ICMP &&
146               ctinfo == IP_CT_ESTABLISHED_REPLY) ||
147              (iph->protocol == IPPROTO_ICMP &&
148               ctinfo == IP_CT_RELATED_REPLY)) &&
149             (ct->status & IPS_SRC_NAT_DONE)) {
150 
151                 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
152                 dport = (iph->protocol == IPPROTO_TCP) ?
153                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
154                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
155         }
156 #endif
157 
158         return nf_socket_get_sock_v4(net, data_skb, doff, protocol, saddr,
159                                      daddr, sport, dport, indev);
160 }
161 EXPORT_SYMBOL_GPL(nf_sk_lookup_slow_v4);
162 
163 MODULE_LICENSE("GPL");
164 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
165 MODULE_DESCRIPTION("Netfilter IPv4 socket lookup infrastructure");
166 

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