net/netfilter/nf_conntrack_proto_udp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   4  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
   5  */
   6
   7 #include <linux/types.h>
   8 #include <linux/timer.h>
   9 #include <linux/module.h>
  10 #include <linux/udp.h>
  11 #include <linux/seq_file.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/ipv6.h>
  14 #include <net/ip6_checksum.h>
  15 #include <net/checksum.h>
  16
  17 #include <linux/netfilter.h>
  18 #include <linux/netfilter_ipv4.h>
  19 #include <linux/netfilter_ipv6.h>
  20 #include <net/netfilter/nf_conntrack_l4proto.h>
  21 #include <net/netfilter/nf_conntrack_ecache.h>
  22 #include <net/netfilter/nf_conntrack_timeout.h>
  23 #include <net/netfilter/nf_log.h>
  24 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  25 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
  26
  27 static const unsigned int udp_timeouts[UDP_CT_MAX] = {
  28         [UDP_CT_UNREPLIED]      = 30*HZ,
  29         [UDP_CT_REPLIED]        = 120*HZ,
  30 };
  31
  32 static unsigned int *udp_get_timeouts(struct net *net)
  33 {
  34         return nf_udp_pernet(net)->timeouts;
  35 }
  36
  37 static void udp_error_log(const struct sk_buff *skb,
  38                           const struct nf_hook_state *state,
  39                           const char *msg)
  40 {
  41         nf_l4proto_log_invalid(skb, state->net, state->pf,
  42                                IPPROTO_UDP, "%s", msg);
  43 }
  44
  45 static bool udp_error(struct sk_buff *skb,
  46                       unsigned int dataoff,
  47                       const struct nf_hook_state *state)
  48 {
  49         unsigned int udplen = skb->len - dataoff;
  50         const struct udphdr *hdr;
  51         struct udphdr _hdr;
  52
  53         /* Header is too small? */
  54         hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  55         if (!hdr) {
  56                 udp_error_log(skb, state, "short packet");
  57                 return true;
  58         }
  59
  60         /* Truncated/malformed packets */
  61         if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
  62                 udp_error_log(skb, state, "truncated/malformed packet");
  63                 return true;
  64         }
  65
  66         /* Packet with no checksum */
  67         if (!hdr->check)
  68                 return false;
  69
  70         /* Checksum invalid? Ignore.
  71          * We skip checking packets on the outgoing path
  72          * because the checksum is assumed to be correct.
  73          * FIXME: Source route IP option packets --RR */
  74         if (state->hook == NF_INET_PRE_ROUTING &&
  75             state->net->ct.sysctl_checksum &&
  76             nf_checksum(skb, state->hook, dataoff, IPPROTO_UDP, state->pf)) {
  77                 udp_error_log(skb, state, "bad checksum");
  78                 return true;
  79         }
  80
  81         return false;
  82 }
  83
  84 /* Returns verdict for packet, and may modify conntracktype */
  85 int nf_conntrack_udp_packet(struct nf_conn *ct,
  86                             struct sk_buff *skb,
  87                             unsigned int dataoff,
  88                             enum ip_conntrack_info ctinfo,
  89                             const struct nf_hook_state *state)
  90 {
  91         unsigned int *timeouts;
  92
  93         if (udp_error(skb, dataoff, state))
  94                 return -NF_ACCEPT;
  95
  96         timeouts = nf_ct_timeout_lookup(ct);
  97         if (!timeouts)
  98                 timeouts = udp_get_timeouts(nf_ct_net(ct));
  99
 100         if (!nf_ct_is_confirmed(ct))
 101                 ct->proto.udp.stream_ts = 2 * HZ + jiffies;
 102
 103         /* If we've seen traffic both ways, this is some kind of UDP
 104          * stream. Set Assured.
 105          */
 106         if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
 107                 unsigned long extra = timeouts[UDP_CT_UNREPLIED];
 108
 109                 /* Still active after two seconds? Extend timeout. */
 110                 if (time_after(jiffies, ct->proto.udp.stream_ts))
 111                         extra = timeouts[UDP_CT_REPLIED];
 112
 113                 nf_ct_refresh_acct(ct, ctinfo, skb, extra);
 114
 115                 /* never set ASSURED for IPS_NAT_CLASH, they time out soon */
 116                 if (unlikely((ct->status & IPS_NAT_CLASH)))
 117                         return NF_ACCEPT;
 118
 119                 /* Also, more likely to be important, and not a probe */
 120                 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 121                         nf_conntrack_event_cache(IPCT_ASSURED, ct);
 122         } else {
 123                 nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
 124         }
 125         return NF_ACCEPT;
 126 }
 127
 128 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
 129 static void udplite_error_log(const struct sk_buff *skb,
 130                               const struct nf_hook_state *state,
 131                               const char *msg)
 132 {
 133         nf_l4proto_log_invalid(skb, state->net, state->pf,
 134                                IPPROTO_UDPLITE, "%s", msg);
 135 }
 136
 137 static bool udplite_error(struct sk_buff *skb,
 138                           unsigned int dataoff,
 139                           const struct nf_hook_state *state)
 140 {
 141         unsigned int udplen = skb->len - dataoff;
 142         const struct udphdr *hdr;
 143         struct udphdr _hdr;
 144         unsigned int cscov;
 145
 146         /* Header is too small? */
 147         hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
 148         if (!hdr) {
 149                 udplite_error_log(skb, state, "short packet");
 150                 return true;
 151         }
 152
 153         cscov = ntohs(hdr->len);
 154         if (cscov == 0) {
 155                 cscov = udplen;
 156         } else if (cscov < sizeof(*hdr) || cscov > udplen) {
 157                 udplite_error_log(skb, state, "invalid checksum coverage");
 158                 return true;
 159         }
 160
 161         /* UDPLITE mandates checksums */
 162         if (!hdr->check) {
 163                 udplite_error_log(skb, state, "checksum missing");
 164                 return true;
 165         }
 166
 167         /* Checksum invalid? Ignore. */
 168         if (state->hook == NF_INET_PRE_ROUTING &&
 169             state->net->ct.sysctl_checksum &&
 170             nf_checksum_partial(skb, state->hook, dataoff, cscov, IPPROTO_UDP,
 171                                 state->pf)) {
 172                 udplite_error_log(skb, state, "bad checksum");
 173                 return true;
 174         }
 175
 176         return false;
 177 }
 178
 179 /* Returns verdict for packet, and may modify conntracktype */
 180 int nf_conntrack_udplite_packet(struct nf_conn *ct,
 181                                 struct sk_buff *skb,
 182                                 unsigned int dataoff,
 183                                 enum ip_conntrack_info ctinfo,
 184                                 const struct nf_hook_state *state)
 185 {
 186         unsigned int *timeouts;
 187
 188         if (udplite_error(skb, dataoff, state))
 189                 return -NF_ACCEPT;
 190
 191         timeouts = nf_ct_timeout_lookup(ct);
 192         if (!timeouts)
 193                 timeouts = udp_get_timeouts(nf_ct_net(ct));
 194
 195         /* If we've seen traffic both ways, this is some kind of UDP
 196            stream.  Extend timeout. */
 197         if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
 198                 nf_ct_refresh_acct(ct, ctinfo, skb,
 199                                    timeouts[UDP_CT_REPLIED]);
 200
 201                 if (unlikely((ct->status & IPS_NAT_CLASH)))
 202                         return NF_ACCEPT;
 203
 204                 /* Also, more likely to be important, and not a probe */
 205                 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 206                         nf_conntrack_event_cache(IPCT_ASSURED, ct);
 207         } else {
 208                 nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
 209         }
 210         return NF_ACCEPT;
 211 }
 212 #endif
 213
 214 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 215
 216 #include <linux/netfilter/nfnetlink.h>
 217 #include <linux/netfilter/nfnetlink_cttimeout.h>
 218
 219 static int udp_timeout_nlattr_to_obj(struct nlattr *tb[],
 220                                      struct net *net, void *data)
 221 {
 222         unsigned int *timeouts = data;
 223         struct nf_udp_net *un = nf_udp_pernet(net);
 224
 225         if (!timeouts)
 226                 timeouts = un->timeouts;
 227
 228         /* set default timeouts for UDP. */
 229         timeouts[UDP_CT_UNREPLIED] = un->timeouts[UDP_CT_UNREPLIED];
 230         timeouts[UDP_CT_REPLIED] = un->timeouts[UDP_CT_REPLIED];
 231
 232         if (tb[CTA_TIMEOUT_UDP_UNREPLIED]) {
 233                 timeouts[UDP_CT_UNREPLIED] =
 234                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_UNREPLIED])) * HZ;
 235         }
 236         if (tb[CTA_TIMEOUT_UDP_REPLIED]) {
 237                 timeouts[UDP_CT_REPLIED] =
 238                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_REPLIED])) * HZ;
 239         }
 240         return 0;
 241 }
 242
 243 static int
 244 udp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 245 {
 246         const unsigned int *timeouts = data;
 247
 248         if (nla_put_be32(skb, CTA_TIMEOUT_UDP_UNREPLIED,
 249                          htonl(timeouts[UDP_CT_UNREPLIED] / HZ)) ||
 250             nla_put_be32(skb, CTA_TIMEOUT_UDP_REPLIED,
 251                          htonl(timeouts[UDP_CT_REPLIED] / HZ)))
 252                 goto nla_put_failure;
 253         return 0;
 254
 255 nla_put_failure:
 256         return -ENOSPC;
 257 }
 258
 259 static const struct nla_policy
 260 udp_timeout_nla_policy[CTA_TIMEOUT_UDP_MAX+1] = {
 261        [CTA_TIMEOUT_UDP_UNREPLIED]      = { .type = NLA_U32 },
 262        [CTA_TIMEOUT_UDP_REPLIED]        = { .type = NLA_U32 },
 263 };
 264 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 265
 266 void nf_conntrack_udp_init_net(struct net *net)
 267 {
 268         struct nf_udp_net *un = nf_udp_pernet(net);
 269         int i;
 270
 271         for (i = 0; i < UDP_CT_MAX; i++)
 272                 un->timeouts[i] = udp_timeouts[i];
 273 }
 274
 275 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udp =
 276 {
 277         .l4proto                = IPPROTO_UDP,
 278         .allow_clash            = true,
 279 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 280         .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
 281         .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
 282         .nlattr_tuple_size      = nf_ct_port_nlattr_tuple_size,
 283         .nla_policy             = nf_ct_port_nla_policy,
 284 #endif
 285 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 286         .ctnl_timeout           = {
 287                 .nlattr_to_obj  = udp_timeout_nlattr_to_obj,
 288                 .obj_to_nlattr  = udp_timeout_obj_to_nlattr,
 289                 .nlattr_max     = CTA_TIMEOUT_UDP_MAX,
 290                 .obj_size       = sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
 291                 .nla_policy     = udp_timeout_nla_policy,
 292         },
 293 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 294 };
 295
 296 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
 297 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udplite =
 298 {
 299         .l4proto                = IPPROTO_UDPLITE,
 300         .allow_clash            = true,
 301 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 302         .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
 303         .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
 304         .nlattr_tuple_size      = nf_ct_port_nlattr_tuple_size,
 305         .nla_policy             = nf_ct_port_nla_policy,
 306 #endif
 307 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 308         .ctnl_timeout           = {
 309                 .nlattr_to_obj  = udp_timeout_nlattr_to_obj,
 310                 .obj_to_nlattr  = udp_timeout_obj_to_nlattr,
 311                 .nlattr_max     = CTA_TIMEOUT_UDP_MAX,
 312                 .obj_size       = sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
 313                 .nla_policy     = udp_timeout_nla_policy,
 314         },
 315 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 316 };
 317 #endif