net/netfilter/nf_tables_trace.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * (C) 2015 Red Hat GmbH
   4  * Author: Florian Westphal <fw@strlen.de>
   5  */
   6
   7 #include <linux/module.h>
   8 #include <linux/static_key.h>
   9 #include <linux/hash.h>
  10 #include <linux/siphash.h>
  11 #include <linux/if_vlan.h>
  12 #include <linux/init.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/netlink.h>
  15 #include <linux/netfilter.h>
  16 #include <linux/netfilter/nfnetlink.h>
  17 #include <linux/netfilter/nf_tables.h>
  18 #include <net/netfilter/nf_tables_core.h>
  19 #include <net/netfilter/nf_tables.h>
  20
  21 #define NFT_TRACETYPE_LL_HSIZE          20
  22 #define NFT_TRACETYPE_NETWORK_HSIZE     40
  23 #define NFT_TRACETYPE_TRANSPORT_HSIZE   20
  24
  25 DEFINE_STATIC_KEY_FALSE(nft_trace_enabled);
  26 EXPORT_SYMBOL_GPL(nft_trace_enabled);
  27
  28 static int trace_fill_header(struct sk_buff *nlskb, u16 type,
  29                              const struct sk_buff *skb,
  30                              int off, unsigned int len)
  31 {
  32         struct nlattr *nla;
  33
  34         if (len == 0)
  35                 return 0;
  36
  37         nla = nla_reserve(nlskb, type, len);
  38         if (!nla || skb_copy_bits(skb, off, nla_data(nla), len))
  39                 return -1;
  40
  41         return 0;
  42 }
  43
  44 static int nf_trace_fill_ll_header(struct sk_buff *nlskb,
  45                                    const struct sk_buff *skb)
  46 {
  47         struct vlan_ethhdr veth;
  48         int off;
  49
  50         BUILD_BUG_ON(sizeof(veth) > NFT_TRACETYPE_LL_HSIZE);
  51
  52         off = skb_mac_header(skb) - skb->data;
  53         if (off != -ETH_HLEN)
  54                 return -1;
  55
  56         if (skb_copy_bits(skb, off, &veth, ETH_HLEN))
  57                 return -1;
  58
  59         veth.h_vlan_proto = skb->vlan_proto;
  60         veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb));
  61         veth.h_vlan_encapsulated_proto = skb->protocol;
  62
  63         return nla_put(nlskb, NFTA_TRACE_LL_HEADER, sizeof(veth), &veth);
  64 }
  65
  66 static int nf_trace_fill_dev_info(struct sk_buff *nlskb,
  67                                   const struct net_device *indev,
  68                                   const struct net_device *outdev)
  69 {
  70         if (indev) {
  71                 if (nla_put_be32(nlskb, NFTA_TRACE_IIF,
  72                                  htonl(indev->ifindex)))
  73                         return -1;
  74
  75                 if (nla_put_be16(nlskb, NFTA_TRACE_IIFTYPE,
  76                                  htons(indev->type)))
  77                         return -1;
  78         }
  79
  80         if (outdev) {
  81                 if (nla_put_be32(nlskb, NFTA_TRACE_OIF,
  82                                  htonl(outdev->ifindex)))
  83                         return -1;
  84
  85                 if (nla_put_be16(nlskb, NFTA_TRACE_OIFTYPE,
  86                                  htons(outdev->type)))
  87                         return -1;
  88         }
  89
  90         return 0;
  91 }
  92
  93 static int nf_trace_fill_pkt_info(struct sk_buff *nlskb,
  94                                   const struct nft_pktinfo *pkt)
  95 {
  96         const struct sk_buff *skb = pkt->skb;
  97         int off = skb_network_offset(skb);
  98         unsigned int len, nh_end;
  99
 100         nh_end = pkt->flags & NFT_PKTINFO_L4PROTO ? nft_thoff(pkt) : skb->len;
 101         len = min_t(unsigned int, nh_end - skb_network_offset(skb),
 102                     NFT_TRACETYPE_NETWORK_HSIZE);
 103         if (trace_fill_header(nlskb, NFTA_TRACE_NETWORK_HEADER, skb, off, len))
 104                 return -1;
 105
 106         if (pkt->flags & NFT_PKTINFO_L4PROTO) {
 107                 len = min_t(unsigned int, skb->len - nft_thoff(pkt),
 108                             NFT_TRACETYPE_TRANSPORT_HSIZE);
 109                 if (trace_fill_header(nlskb, NFTA_TRACE_TRANSPORT_HEADER, skb,
 110                                       nft_thoff(pkt), len))
 111                         return -1;
 112         }
 113
 114         if (!skb_mac_header_was_set(skb))
 115                 return 0;
 116
 117         if (skb_vlan_tag_get(skb))
 118                 return nf_trace_fill_ll_header(nlskb, skb);
 119
 120         off = skb_mac_header(skb) - skb->data;
 121         len = min_t(unsigned int, -off, NFT_TRACETYPE_LL_HSIZE);
 122         return trace_fill_header(nlskb, NFTA_TRACE_LL_HEADER,
 123                                  skb, off, len);
 124 }
 125
 126 static int nf_trace_fill_rule_info(struct sk_buff *nlskb,
 127                                    const struct nft_traceinfo *info)
 128 {
 129         if (!info->rule || info->rule->is_last)
 130                 return 0;
 131
 132         /* a continue verdict with ->type == RETURN means that this is
 133          * an implicit return (end of chain reached).
 134          *
 135          * Since no rule matched, the ->rule pointer is invalid.
 136          */
 137         if (info->type == NFT_TRACETYPE_RETURN &&
 138             info->verdict->code == NFT_CONTINUE)
 139                 return 0;
 140
 141         return nla_put_be64(nlskb, NFTA_TRACE_RULE_HANDLE,
 142                             cpu_to_be64(info->rule->handle),
 143                             NFTA_TRACE_PAD);
 144 }
 145
 146 static bool nft_trace_have_verdict_chain(struct nft_traceinfo *info)
 147 {
 148         switch (info->type) {
 149         case NFT_TRACETYPE_RETURN:
 150         case NFT_TRACETYPE_RULE:
 151                 break;
 152         default:
 153                 return false;
 154         }
 155
 156         switch (info->verdict->code) {
 157         case NFT_JUMP:
 158         case NFT_GOTO:
 159                 break;
 160         default:
 161                 return false;
 162         }
 163
 164         return true;
 165 }
 166
 167 void nft_trace_notify(struct nft_traceinfo *info)
 168 {
 169         const struct nft_pktinfo *pkt = info->pkt;
 170         struct nlmsghdr *nlh;
 171         struct sk_buff *skb;
 172         unsigned int size;
 173         u32 mark = 0;
 174         u16 event;
 175
 176         if (!nfnetlink_has_listeners(nft_net(pkt), NFNLGRP_NFTRACE))
 177                 return;
 178
 179         size = nlmsg_total_size(sizeof(struct nfgenmsg)) +
 180                 nla_total_size(strlen(info->chain->table->name)) +
 181                 nla_total_size(strlen(info->chain->name)) +
 182                 nla_total_size_64bit(sizeof(__be64)) +  /* rule handle */
 183                 nla_total_size(sizeof(__be32)) +        /* trace type */
 184                 nla_total_size(0) +                     /* VERDICT, nested */
 185                         nla_total_size(sizeof(u32)) +   /* verdict code */
 186                 nla_total_size(sizeof(u32)) +           /* id */
 187                 nla_total_size(NFT_TRACETYPE_LL_HSIZE) +
 188                 nla_total_size(NFT_TRACETYPE_NETWORK_HSIZE) +
 189                 nla_total_size(NFT_TRACETYPE_TRANSPORT_HSIZE) +
 190                 nla_total_size(sizeof(u32)) +           /* iif */
 191                 nla_total_size(sizeof(__be16)) +        /* iiftype */
 192                 nla_total_size(sizeof(u32)) +           /* oif */
 193                 nla_total_size(sizeof(__be16)) +        /* oiftype */
 194                 nla_total_size(sizeof(u32)) +           /* mark */
 195                 nla_total_size(sizeof(u32)) +           /* nfproto */
 196                 nla_total_size(sizeof(u32));            /* policy */
 197
 198         if (nft_trace_have_verdict_chain(info))
 199                 size += nla_total_size(strlen(info->verdict->chain->name)); /* jump target */
 200
 201         skb = nlmsg_new(size, GFP_ATOMIC);
 202         if (!skb)
 203                 return;
 204
 205         event = nfnl_msg_type(NFNL_SUBSYS_NFTABLES, NFT_MSG_TRACE);
 206         nlh = nfnl_msg_put(skb, 0, 0, event, 0, info->basechain->type->family,
 207                            NFNETLINK_V0, 0);
 208         if (!nlh)
 209                 goto nla_put_failure;
 210
 211         if (nla_put_be32(skb, NFTA_TRACE_NFPROTO, htonl(nft_pf(pkt))))
 212                 goto nla_put_failure;
 213
 214         if (nla_put_be32(skb, NFTA_TRACE_TYPE, htonl(info->type)))
 215                 goto nla_put_failure;
 216
 217         if (nla_put_u32(skb, NFTA_TRACE_ID, info->skbid))
 218                 goto nla_put_failure;
 219
 220         if (nla_put_string(skb, NFTA_TRACE_CHAIN, info->chain->name))
 221                 goto nla_put_failure;
 222
 223         if (nla_put_string(skb, NFTA_TRACE_TABLE, info->chain->table->name))
 224                 goto nla_put_failure;
 225
 226         if (nf_trace_fill_rule_info(skb, info))
 227                 goto nla_put_failure;
 228
 229         switch (info->type) {
 230         case NFT_TRACETYPE_UNSPEC:
 231         case __NFT_TRACETYPE_MAX:
 232                 break;
 233         case NFT_TRACETYPE_RETURN:
 234         case NFT_TRACETYPE_RULE:
 235                 if (nft_verdict_dump(skb, NFTA_TRACE_VERDICT, info->verdict))
 236                         goto nla_put_failure;
 237
 238                 /* pkt->skb undefined iff NF_STOLEN, disable dump */
 239                 if (info->verdict->code == NF_STOLEN)
 240                         info->packet_dumped = true;
 241                 else
 242                         mark = pkt->skb->mark;
 243
 244                 break;
 245         case NFT_TRACETYPE_POLICY:
 246                 mark = pkt->skb->mark;
 247
 248                 if (nla_put_be32(skb, NFTA_TRACE_POLICY,
 249                                  htonl(info->basechain->policy)))
 250                         goto nla_put_failure;
 251                 break;
 252         }
 253
 254         if (mark && nla_put_be32(skb, NFTA_TRACE_MARK, htonl(mark)))
 255                 goto nla_put_failure;
 256
 257         if (!info->packet_dumped) {
 258                 if (nf_trace_fill_dev_info(skb, nft_in(pkt), nft_out(pkt)))
 259                         goto nla_put_failure;
 260
 261                 if (nf_trace_fill_pkt_info(skb, pkt))
 262                         goto nla_put_failure;
 263                 info->packet_dumped = true;
 264         }
 265
 266         nlmsg_end(skb, nlh);
 267         nfnetlink_send(skb, nft_net(pkt), 0, NFNLGRP_NFTRACE, 0, GFP_ATOMIC);
 268         return;
 269
 270  nla_put_failure:
 271         WARN_ON_ONCE(1);
 272         kfree_skb(skb);
 273 }
 274
 275 void nft_trace_init(struct nft_traceinfo *info, const struct nft_pktinfo *pkt,
 276                     const struct nft_verdict *verdict,
 277                     const struct nft_chain *chain)
 278 {
 279         static siphash_key_t trace_key __read_mostly;
 280         struct sk_buff *skb = pkt->skb;
 281
 282         info->basechain = nft_base_chain(chain);
 283         info->trace = true;
 284         info->nf_trace = pkt->skb->nf_trace;
 285         info->packet_dumped = false;
 286         info->pkt = pkt;
 287         info->verdict = verdict;
 288
 289         net_get_random_once(&trace_key, sizeof(trace_key));
 290
 291         info->skbid = (u32)siphash_3u32(hash32_ptr(skb),
 292                                         skb_get_hash(skb),
 293                                         skb->skb_iif,
 294                                         &trace_key);
 295 }