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/sched.h>
  11 #include <linux/timer.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/in.h>
  14 #include <linux/ip.h>
  15 #include <linux/udp.h>
  16 #include <linux/seq_file.h>
  17 #include <net/checksum.h>
  18 #include <linux/netfilter_ipv4.h>
  19 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
  20
  21 unsigned int ip_ct_udp_timeout __read_mostly = 30*HZ;
  22 unsigned int ip_ct_udp_timeout_stream __read_mostly = 180*HZ;
  23
  24 static int udp_pkt_to_tuple(const struct sk_buff *skb,
  25                              unsigned int dataoff,
  26                              struct ip_conntrack_tuple *tuple)
  27 {
  28         struct udphdr _hdr, *hp;
  29
  30         /* Actually only need first 8 bytes. */
  31         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  32         if (hp == NULL)
  33                 return 0;
  34
  35         tuple->src.u.udp.port = hp->source;
  36         tuple->dst.u.udp.port = hp->dest;
  37
  38         return 1;
  39 }
  40
  41 static int udp_invert_tuple(struct ip_conntrack_tuple *tuple,
  42                             const struct ip_conntrack_tuple *orig)
  43 {
  44         tuple->src.u.udp.port = orig->dst.u.udp.port;
  45         tuple->dst.u.udp.port = orig->src.u.udp.port;
  46         return 1;
  47 }
  48
  49 /* Print out the per-protocol part of the tuple. */
  50 static int udp_print_tuple(struct seq_file *s,
  51                            const struct ip_conntrack_tuple *tuple)
  52 {
  53         return seq_printf(s, "sport=%hu dport=%hu ",
  54                           ntohs(tuple->src.u.udp.port),
  55                           ntohs(tuple->dst.u.udp.port));
  56 }
  57
  58 /* Print out the private part of the conntrack. */
  59 static int udp_print_conntrack(struct seq_file *s,
  60                                const struct ip_conntrack *conntrack)
  61 {
  62         return 0;
  63 }
  64
  65 /* Returns verdict for packet, and may modify conntracktype */
  66 static int udp_packet(struct ip_conntrack *conntrack,
  67                       const struct sk_buff *skb,
  68                       enum ip_conntrack_info ctinfo)
  69 {
  70         /* If we've seen traffic both ways, this is some kind of UDP
  71            stream.  Extend timeout. */
  72         if (test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
  73                 ip_ct_refresh_acct(conntrack, ctinfo, skb,
  74                                    ip_ct_udp_timeout_stream);
  75                 /* Also, more likely to be important, and not a probe */
  76                 if (!test_and_set_bit(IPS_ASSURED_BIT, &conntrack->status))
  77                         ip_conntrack_event_cache(IPCT_STATUS, skb);
  78         } else
  79                 ip_ct_refresh_acct(conntrack, ctinfo, skb, ip_ct_udp_timeout);
  80
  81         return NF_ACCEPT;
  82 }
  83
  84 /* Called when a new connection for this protocol found. */
  85 static int udp_new(struct ip_conntrack *conntrack, const struct sk_buff *skb)
  86 {
  87         return 1;
  88 }
  89
  90 static int udp_error(struct sk_buff *skb, enum ip_conntrack_info *ctinfo,
  91                      unsigned int hooknum)
  92 {
  93         struct iphdr *iph = skb->nh.iph;
  94         unsigned int udplen = skb->len - iph->ihl * 4;
  95         struct udphdr _hdr, *hdr;
  96
  97         /* Header is too small? */
  98         hdr = skb_header_pointer(skb, iph->ihl*4, sizeof(_hdr), &_hdr);
  99         if (hdr == NULL) {
 100                 if (LOG_INVALID(IPPROTO_UDP))
 101                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 102                                   "ip_ct_udp: short packet ");
 103                 return -NF_ACCEPT;
 104         }
 105
 106         /* Truncated/malformed packets */
 107         if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
 108                 if (LOG_INVALID(IPPROTO_UDP))
 109                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 110                                   "ip_ct_udp: truncated/malformed packet ");
 111                 return -NF_ACCEPT;
 112         }
 113
 114         /* Packet with no checksum */
 115         if (!hdr->check)
 116                 return NF_ACCEPT;
 117
 118         /* Checksum invalid? Ignore.
 119          * We skip checking packets on the outgoing path
 120          * because the checksum is assumed to be correct.
 121          * FIXME: Source route IP option packets --RR */
 122         if (ip_conntrack_checksum && hooknum == NF_IP_PRE_ROUTING &&
 123             nf_ip_checksum(skb, hooknum, iph->ihl * 4, IPPROTO_UDP)) {
 124                 if (LOG_INVALID(IPPROTO_UDP))
 125                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 126                                   "ip_ct_udp: bad UDP checksum ");
 127                 return -NF_ACCEPT;
 128         }
 129
 130         return NF_ACCEPT;
 131 }
 132
 133 struct ip_conntrack_protocol ip_conntrack_protocol_udp =
 134 {
 135         .proto                  = IPPROTO_UDP,
 136         .name                   = "udp",
 137         .pkt_to_tuple           = udp_pkt_to_tuple,
 138         .invert_tuple           = udp_invert_tuple,
 139         .print_tuple            = udp_print_tuple,
 140         .print_conntrack        = udp_print_conntrack,
 141         .packet                 = udp_packet,
 142         .new                    = udp_new,
 143         .error                  = udp_error,
 144 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 145     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 146         .tuple_to_nfattr        = ip_ct_port_tuple_to_nfattr,
 147         .nfattr_to_tuple        = ip_ct_port_nfattr_to_tuple,
 148 #endif
 149 };