net/ipv4/netfilter/ip_conntrack_proto_udp.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/types.h>
  10 #include <linux/timer.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/in.h>
  13 #include <linux/ip.h>
  14 #include <linux/udp.h>
  15 #include <linux/seq_file.h>
  16 #include <net/checksum.h>
  17 #include <linux/netfilter_ipv4.h>
  18 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
  19
  20 unsigned int ip_ct_udp_timeout __read_mostly = 30*HZ;
  21 unsigned int ip_ct_udp_timeout_stream __read_mostly = 180*HZ;
  22
  23 static int udp_pkt_to_tuple(const struct sk_buff *skb,
  24                              unsigned int dataoff,
  25                              struct ip_conntrack_tuple *tuple)
  26 {
  27         struct udphdr _hdr, *hp;
  28
  29         /* Actually only need first 8 bytes. */
  30         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  31         if (hp == NULL)
  32                 return 0;
  33
  34         tuple->src.u.udp.port = hp->source;
  35         tuple->dst.u.udp.port = hp->dest;
  36
  37         return 1;
  38 }
  39
  40 static int udp_invert_tuple(struct ip_conntrack_tuple *tuple,
  41                             const struct ip_conntrack_tuple *orig)
  42 {
  43         tuple->src.u.udp.port = orig->dst.u.udp.port;
  44         tuple->dst.u.udp.port = orig->src.u.udp.port;
  45         return 1;
  46 }
  47
  48 /* Print out the per-protocol part of the tuple. */
  49 static int udp_print_tuple(struct seq_file *s,
  50                            const struct ip_conntrack_tuple *tuple)
  51 {
  52         return seq_printf(s, "sport=%hu dport=%hu ",
  53                           ntohs(tuple->src.u.udp.port),
  54                           ntohs(tuple->dst.u.udp.port));
  55 }
  56
  57 /* Print out the private part of the conntrack. */
  58 static int udp_print_conntrack(struct seq_file *s,
  59                                const struct ip_conntrack *conntrack)
  60 {
  61         return 0;
  62 }
  63
  64 /* Returns verdict for packet, and may modify conntracktype */
  65 static int udp_packet(struct ip_conntrack *conntrack,
  66                       const struct sk_buff *skb,
  67                       enum ip_conntrack_info ctinfo)
  68 {
  69         /* If we've seen traffic both ways, this is some kind of UDP
  70            stream.  Extend timeout. */
  71         if (test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
  72                 ip_ct_refresh_acct(conntrack, ctinfo, skb,
  73                                    ip_ct_udp_timeout_stream);
  74                 /* Also, more likely to be important, and not a probe */
  75                 if (!test_and_set_bit(IPS_ASSURED_BIT, &conntrack->status))
  76                         ip_conntrack_event_cache(IPCT_STATUS, skb);
  77         } else
  78                 ip_ct_refresh_acct(conntrack, ctinfo, skb, ip_ct_udp_timeout);
  79
  80         return NF_ACCEPT;
  81 }
  82
  83 /* Called when a new connection for this protocol found. */
  84 static int udp_new(struct ip_conntrack *conntrack, const struct sk_buff *skb)
  85 {
  86         return 1;
  87 }
  88
  89 static int udp_error(struct sk_buff *skb, enum ip_conntrack_info *ctinfo,
  90                      unsigned int hooknum)
  91 {
  92         struct iphdr *iph = skb->nh.iph;
  93         unsigned int udplen = skb->len - iph->ihl * 4;
  94         struct udphdr _hdr, *hdr;
  95
  96         /* Header is too small? */
  97         hdr = skb_header_pointer(skb, iph->ihl*4, sizeof(_hdr), &_hdr);
  98         if (hdr == NULL) {
  99                 if (LOG_INVALID(IPPROTO_UDP))
 100                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 101                                   "ip_ct_udp: short packet ");
 102                 return -NF_ACCEPT;
 103         }
 104
 105         /* Truncated/malformed packets */
 106         if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
 107                 if (LOG_INVALID(IPPROTO_UDP))
 108                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 109                                   "ip_ct_udp: truncated/malformed packet ");
 110                 return -NF_ACCEPT;
 111         }
 112
 113         /* Packet with no checksum */
 114         if (!hdr->check)
 115                 return NF_ACCEPT;
 116
 117         /* Checksum invalid? Ignore.
 118          * We skip checking packets on the outgoing path
 119          * because the checksum is assumed to be correct.
 120          * FIXME: Source route IP option packets --RR */
 121         if (ip_conntrack_checksum && hooknum == NF_IP_PRE_ROUTING &&
 122             nf_ip_checksum(skb, hooknum, iph->ihl * 4, IPPROTO_UDP)) {
 123                 if (LOG_INVALID(IPPROTO_UDP))
 124                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 125                                   "ip_ct_udp: bad UDP checksum ");
 126                 return -NF_ACCEPT;
 127         }
 128
 129         return NF_ACCEPT;
 130 }
 131
 132 struct ip_conntrack_protocol ip_conntrack_protocol_udp =
 133 {
 134         .proto                  = IPPROTO_UDP,
 135         .name                   = "udp",
 136         .pkt_to_tuple           = udp_pkt_to_tuple,
 137         .invert_tuple           = udp_invert_tuple,
 138         .print_tuple            = udp_print_tuple,
 139         .print_conntrack        = udp_print_conntrack,
 140         .packet                 = udp_packet,
 141         .new                    = udp_new,
 142         .error                  = udp_error,
 143 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 144     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 145         .tuple_to_nfattr        = ip_ct_port_tuple_to_nfattr,
 146         .nfattr_to_tuple        = ip_ct_port_nfattr_to_tuple,
 147 #endif
 148 };