net/netfilter/nf_tables_trace.c

   1 /*
   2  * (C) 2015 Red Hat GmbH
   3  * Author: Florian Westphal <fw@strlen.de>
   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 #include <linux/module.h>
  11 #include <linux/static_key.h>
  12 #include <linux/hash.h>
  13 #include <linux/jhash.h>
  14 #include <linux/if_vlan.h>
  15 #include <linux/init.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/netlink.h>
  18 #include <linux/netfilter.h>
  19 #include <linux/netfilter/nfnetlink.h>
  20 #include <linux/netfilter/nf_tables.h>
  21 #include <net/netfilter/nf_tables_core.h>
  22 #include <net/netfilter/nf_tables.h>
  23
  24 #define NFT_TRACETYPE_LL_HSIZE          20
  25 #define NFT_TRACETYPE_NETWORK_HSIZE     40
  26 #define NFT_TRACETYPE_TRANSPORT_HSIZE   20
  27
  28 DEFINE_STATIC_KEY_FALSE(nft_trace_enabled);
  29 EXPORT_SYMBOL_GPL(nft_trace_enabled);
  30
  31 static int trace_fill_id(struct sk_buff *nlskb, struct sk_buff *skb)
  32 {
  33         __be32 id;
  34
  35         /* using skb address as ID results in a limited number of
  36          * values (and quick reuse).
  37          *
  38          * So we attempt to use as many skb members that will not
  39          * change while skb is with netfilter.
  40          */
  41         id = (__be32)jhash_2words(hash32_ptr(skb), skb_get_hash(skb),
  42                                   skb->skb_iif);
  43
  44         return nla_put_be32(nlskb, NFTA_TRACE_ID, id);
  45 }
  46
  47 static int trace_fill_header(struct sk_buff *nlskb, u16 type,
  48                              const struct sk_buff *skb,
  49                              int off, unsigned int len)
  50 {
  51         struct nlattr *nla;
  52
  53         if (len == 0)
  54                 return 0;
  55
  56         nla = nla_reserve(nlskb, type, len);
  57         if (!nla || skb_copy_bits(skb, off, nla_data(nla), len))
  58                 return -1;
  59
  60         return 0;
  61 }
  62
  63 static int nf_trace_fill_ll_header(struct sk_buff *nlskb,
  64                                    const struct sk_buff *skb)
  65 {
  66         struct vlan_ethhdr veth;
  67         int off;
  68
  69         BUILD_BUG_ON(sizeof(veth) > NFT_TRACETYPE_LL_HSIZE);
  70
  71         off = skb_mac_header(skb) - skb->data;
  72         if (off != -ETH_HLEN)
  73                 return -1;
  74
  75         if (skb_copy_bits(skb, off, &veth, ETH_HLEN))
  76                 return -1;
  77
  78         veth.h_vlan_proto = skb->vlan_proto;
  79         veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
  80         veth.h_vlan_encapsulated_proto = skb->protocol;
  81
  82         return nla_put(nlskb, NFTA_TRACE_LL_HEADER, sizeof(veth), &veth);
  83 }
  84
  85 static int nf_trace_fill_dev_info(struct sk_buff *nlskb,
  86                                   const struct net_device *indev,
  87                                   const struct net_device *outdev)
  88 {
  89         if (indev) {
  90                 if (nla_put_be32(nlskb, NFTA_TRACE_IIF,
  91                                  htonl(indev->ifindex)))
  92                         return -1;
  93
  94                 if (nla_put_be16(nlskb, NFTA_TRACE_IIFTYPE,
  95                                  htons(indev->type)))
  96                         return -1;
  97         }
  98
  99         if (outdev) {
 100                 if (nla_put_be32(nlskb, NFTA_TRACE_OIF,
 101                                  htonl(outdev->ifindex)))
 102                         return -1;
 103
 104                 if (nla_put_be16(nlskb, NFTA_TRACE_OIFTYPE,
 105                                  htons(outdev->type)))
 106                         return -1;
 107         }
 108
 109         return 0;
 110 }
 111
 112 static int nf_trace_fill_pkt_info(struct sk_buff *nlskb,
 113                                   const struct nft_pktinfo *pkt)
 114 {
 115         const struct sk_buff *skb = pkt->skb;
 116         int off = skb_network_offset(skb);
 117         unsigned int len, nh_end;
 118
 119         nh_end = pkt->tprot_set ? pkt->xt.thoff : skb->len;
 120         len = min_t(unsigned int, nh_end - skb_network_offset(skb),
 121                     NFT_TRACETYPE_NETWORK_HSIZE);
 122         if (trace_fill_header(nlskb, NFTA_TRACE_NETWORK_HEADER, skb, off, len))
 123                 return -1;
 124
 125         if (pkt->tprot_set) {
 126                 len = min_t(unsigned int, skb->len - pkt->xt.thoff,
 127                             NFT_TRACETYPE_TRANSPORT_HSIZE);
 128                 if (trace_fill_header(nlskb, NFTA_TRACE_TRANSPORT_HEADER, skb,
 129                                       pkt->xt.thoff, len))
 130                         return -1;
 131         }
 132
 133         if (!skb_mac_header_was_set(skb))
 134                 return 0;
 135
 136         if (skb_vlan_tag_get(skb))
 137                 return nf_trace_fill_ll_header(nlskb, skb);
 138
 139         off = skb_mac_header(skb) - skb->data;
 140         len = min_t(unsigned int, -off, NFT_TRACETYPE_LL_HSIZE);
 141         return trace_fill_header(nlskb, NFTA_TRACE_LL_HEADER,
 142                                  skb, off, len);
 143 }
 144
 145 static int nf_trace_fill_rule_info(struct sk_buff *nlskb,
 146                                    const struct nft_traceinfo *info)
 147 {
 148         if (!info->rule)
 149                 return 0;
 150
 151         /* a continue verdict with ->type == RETURN means that this is
 152          * an implicit return (end of chain reached).
 153          *
 154          * Since no rule matched, the ->rule pointer is invalid.
 155          */
 156         if (info->type == NFT_TRACETYPE_RETURN &&
 157             info->verdict->code == NFT_CONTINUE)
 158                 return 0;
 159
 160         return nla_put_be64(nlskb, NFTA_TRACE_RULE_HANDLE,
 161                             cpu_to_be64(info->rule->handle),
 162                             NFTA_TRACE_PAD);
 163 }
 164
 165 static bool nft_trace_have_verdict_chain(struct nft_traceinfo *info)
 166 {
 167         switch (info->type) {
 168         case NFT_TRACETYPE_RETURN:
 169         case NFT_TRACETYPE_RULE:
 170                 break;
 171         default:
 172                 return false;
 173         }
 174
 175         switch (info->verdict->code) {
 176         case NFT_JUMP:
 177         case NFT_GOTO:
 178                 break;
 179         default:
 180                 return false;
 181         }
 182
 183         return true;
 184 }
 185
 186 void nft_trace_notify(struct nft_traceinfo *info)
 187 {
 188         const struct nft_pktinfo *pkt = info->pkt;
 189         struct nfgenmsg *nfmsg;
 190         struct nlmsghdr *nlh;
 191         struct sk_buff *skb;
 192         unsigned int size;
 193         u16 event;
 194
 195         if (!nfnetlink_has_listeners(nft_net(pkt), NFNLGRP_NFTRACE))
 196                 return;
 197
 198         size = nlmsg_total_size(sizeof(struct nfgenmsg)) +
 199                 nla_total_size(strlen(info->chain->table->name)) +
 200                 nla_total_size(strlen(info->chain->name)) +
 201                 nla_total_size_64bit(sizeof(__be64)) +  /* rule handle */
 202                 nla_total_size(sizeof(__be32)) +        /* trace type */
 203                 nla_total_size(0) +                     /* VERDICT, nested */
 204                         nla_total_size(sizeof(u32)) +   /* verdict code */
 205                 nla_total_size(sizeof(u32)) +           /* id */
 206                 nla_total_size(NFT_TRACETYPE_LL_HSIZE) +
 207                 nla_total_size(NFT_TRACETYPE_NETWORK_HSIZE) +
 208                 nla_total_size(NFT_TRACETYPE_TRANSPORT_HSIZE) +
 209                 nla_total_size(sizeof(u32)) +           /* iif */
 210                 nla_total_size(sizeof(__be16)) +        /* iiftype */
 211                 nla_total_size(sizeof(u32)) +           /* oif */
 212                 nla_total_size(sizeof(__be16)) +        /* oiftype */
 213                 nla_total_size(sizeof(u32)) +           /* mark */
 214                 nla_total_size(sizeof(u32)) +           /* nfproto */
 215                 nla_total_size(sizeof(u32));            /* policy */
 216
 217         if (nft_trace_have_verdict_chain(info))
 218                 size += nla_total_size(strlen(info->verdict->chain->name)); /* jump target */
 219
 220         skb = nlmsg_new(size, GFP_ATOMIC);
 221         if (!skb)
 222                 return;
 223
 224         event = nfnl_msg_type(NFNL_SUBSYS_NFTABLES, NFT_MSG_TRACE);
 225         nlh = nlmsg_put(skb, 0, 0, event, sizeof(struct nfgenmsg), 0);
 226         if (!nlh)
 227                 goto nla_put_failure;
 228
 229         nfmsg = nlmsg_data(nlh);
 230         nfmsg->nfgen_family     = info->basechain->type->family;
 231         nfmsg->version          = NFNETLINK_V0;
 232         nfmsg->res_id           = 0;
 233
 234         if (nla_put_be32(skb, NFTA_TRACE_NFPROTO, htonl(nft_pf(pkt))))
 235                 goto nla_put_failure;
 236
 237         if (nla_put_be32(skb, NFTA_TRACE_TYPE, htonl(info->type)))
 238                 goto nla_put_failure;
 239
 240         if (trace_fill_id(skb, pkt->skb))
 241                 goto nla_put_failure;
 242
 243         if (nla_put_string(skb, NFTA_TRACE_CHAIN, info->chain->name))
 244                 goto nla_put_failure;
 245
 246         if (nla_put_string(skb, NFTA_TRACE_TABLE, info->chain->table->name))
 247                 goto nla_put_failure;
 248
 249         if (nf_trace_fill_rule_info(skb, info))
 250                 goto nla_put_failure;
 251
 252         switch (info->type) {
 253         case NFT_TRACETYPE_UNSPEC:
 254         case __NFT_TRACETYPE_MAX:
 255                 break;
 256         case NFT_TRACETYPE_RETURN:
 257         case NFT_TRACETYPE_RULE:
 258                 if (nft_verdict_dump(skb, NFTA_TRACE_VERDICT, info->verdict))
 259                         goto nla_put_failure;
 260                 break;
 261         case NFT_TRACETYPE_POLICY:
 262                 if (nla_put_be32(skb, NFTA_TRACE_POLICY,
 263                                  htonl(info->basechain->policy)))
 264                         goto nla_put_failure;
 265                 break;
 266         }
 267
 268         if (pkt->skb->mark &&
 269             nla_put_be32(skb, NFTA_TRACE_MARK, htonl(pkt->skb->mark)))
 270                 goto nla_put_failure;
 271
 272         if (!info->packet_dumped) {
 273                 if (nf_trace_fill_dev_info(skb, nft_in(pkt), nft_out(pkt)))
 274                         goto nla_put_failure;
 275
 276                 if (nf_trace_fill_pkt_info(skb, pkt))
 277                         goto nla_put_failure;
 278                 info->packet_dumped = true;
 279         }
 280
 281         nlmsg_end(skb, nlh);
 282         nfnetlink_send(skb, nft_net(pkt), 0, NFNLGRP_NFTRACE, 0, GFP_ATOMIC);
 283         return;
 284
 285  nla_put_failure:
 286         WARN_ON_ONCE(1);
 287         kfree_skb(skb);
 288 }
 289
 290 void nft_trace_init(struct nft_traceinfo *info, const struct nft_pktinfo *pkt,
 291                     const struct nft_verdict *verdict,
 292                     const struct nft_chain *chain)
 293 {
 294         info->basechain = nft_base_chain(chain);
 295         info->trace = true;
 296         info->packet_dumped = false;
 297         info->pkt = pkt;
 298         info->verdict = verdict;
 299 }