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.h>
  19 #include <linux/netfilter_ipv4.h>
  20 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
  21
  22 unsigned long ip_ct_udp_timeout = 30*HZ;
  23 unsigned long ip_ct_udp_timeout_stream = 180*HZ;
  24
  25 static int udp_pkt_to_tuple(const struct sk_buff *skb,
  26                              unsigned int dataoff,
  27                              struct ip_conntrack_tuple *tuple)
  28 {
  29         struct udphdr _hdr, *hp;
  30
  31         /* Actually only need first 8 bytes. */
  32         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  33         if (hp == NULL)
  34                 return 0;
  35
  36         tuple->src.u.udp.port = hp->source;
  37         tuple->dst.u.udp.port = hp->dest;
  38
  39         return 1;
  40 }
  41
  42 static int udp_invert_tuple(struct ip_conntrack_tuple *tuple,
  43                             const struct ip_conntrack_tuple *orig)
  44 {
  45         tuple->src.u.udp.port = orig->dst.u.udp.port;
  46         tuple->dst.u.udp.port = orig->src.u.udp.port;
  47         return 1;
  48 }
  49
  50 /* Print out the per-protocol part of the tuple. */
  51 static int udp_print_tuple(struct seq_file *s,
  52                            const struct ip_conntrack_tuple *tuple)
  53 {
  54         return seq_printf(s, "sport=%hu dport=%hu ",
  55                           ntohs(tuple->src.u.udp.port),
  56                           ntohs(tuple->dst.u.udp.port));
  57 }
  58
  59 /* Print out the private part of the conntrack. */
  60 static int udp_print_conntrack(struct seq_file *s,
  61                                const struct ip_conntrack *conntrack)
  62 {
  63         return 0;
  64 }
  65
  66 /* Returns verdict for packet, and may modify conntracktype */
  67 static int udp_packet(struct ip_conntrack *conntrack,
  68                       const struct sk_buff *skb,
  69                       enum ip_conntrack_info ctinfo)
  70 {
  71         /* If we've seen traffic both ways, this is some kind of UDP
  72            stream.  Extend timeout. */
  73         if (test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
  74                 ip_ct_refresh_acct(conntrack, ctinfo, skb,
  75                                    ip_ct_udp_timeout_stream);
  76                 /* Also, more likely to be important, and not a probe */
  77                 if (!test_and_set_bit(IPS_ASSURED_BIT, &conntrack->status))
  78                         ip_conntrack_event_cache(IPCT_STATUS, skb);
  79         } else
  80                 ip_ct_refresh_acct(conntrack, ctinfo, skb, ip_ct_udp_timeout);
  81
  82         return NF_ACCEPT;
  83 }
  84
  85 /* Called when a new connection for this protocol found. */
  86 static int udp_new(struct ip_conntrack *conntrack, const struct sk_buff *skb)
  87 {
  88         return 1;
  89 }
  90
  91 static int udp_error(struct sk_buff *skb, enum ip_conntrack_info *ctinfo,
  92                      unsigned int hooknum)
  93 {
  94         struct iphdr *iph = skb->nh.iph;
  95         unsigned int udplen = skb->len - iph->ihl * 4;
  96         struct udphdr _hdr, *hdr;
  97
  98         /* Header is too small? */
  99         hdr = skb_header_pointer(skb, iph->ihl*4, sizeof(_hdr), &_hdr);
 100         if (hdr == NULL) {
 101                 if (LOG_INVALID(IPPROTO_UDP))
 102                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 103                                   "ip_ct_udp: short packet ");
 104                 return -NF_ACCEPT;
 105         }
 106
 107         /* Truncated/malformed packets */
 108         if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
 109                 if (LOG_INVALID(IPPROTO_UDP))
 110                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 111                                   "ip_ct_udp: truncated/malformed packet ");
 112                 return -NF_ACCEPT;
 113         }
 114
 115         /* Packet with no checksum */
 116         if (!hdr->check)
 117                 return NF_ACCEPT;
 118
 119         /* Checksum invalid? Ignore.
 120          * We skip checking packets on the outgoing path
 121          * because the semantic of CHECKSUM_HW is different there
 122          * and moreover root might send raw packets.
 123          * FIXME: Source route IP option packets --RR */
 124         if (hooknum == NF_IP_PRE_ROUTING
 125             && skb->ip_summed != CHECKSUM_UNNECESSARY
 126             && csum_tcpudp_magic(iph->saddr, iph->daddr, udplen, IPPROTO_UDP,
 127                                  skb->ip_summed == CHECKSUM_HW ? skb->csum
 128                                  : skb_checksum(skb, iph->ihl*4, udplen, 0))) {
 129                 if (LOG_INVALID(IPPROTO_UDP))
 130                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 131                                   "ip_ct_udp: bad UDP checksum ");
 132                 return -NF_ACCEPT;
 133         }
 134
 135         return NF_ACCEPT;
 136 }
 137
 138 struct ip_conntrack_protocol ip_conntrack_protocol_udp =
 139 {
 140         .proto                  = IPPROTO_UDP,
 141         .name                   = "udp",
 142         .pkt_to_tuple           = udp_pkt_to_tuple,
 143         .invert_tuple           = udp_invert_tuple,
 144         .print_tuple            = udp_print_tuple,
 145         .print_conntrack        = udp_print_conntrack,
 146         .packet                 = udp_packet,
 147         .new                    = udp_new,
 148         .error                  = udp_error,
 149 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 150     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 151         .tuple_to_nfattr        = ip_ct_port_tuple_to_nfattr,
 152         .nfattr_to_tuple        = ip_ct_port_nfattr_to_tuple,
 153 #endif
 154 };