unix4lyfe git - darkstat/blob - decode.c

   1 /* darkstat 3
   2  * copyright (c) 2001-2009 Emil Mikulic.
   3  *
   4  * decode.c: packet decoding.
   5  *
   6  * Given a captured packet, decode it and fill out a pktsummary struct which
   7  * will be sent to the accounting code in acct.c
   8  *
   9  * You may use, modify and redistribute this file under the terms of the
  10  * GNU General Public License version 2. (see COPYING.GPL)
  11  */
  12
  13 #include "darkstat.h"
  14 #include "acct.h"
  15 #include "cap.h"
  16 #include "decode.h"
  17 #include "err.h"
  18
  19 #include <sys/ioctl.h>
  20 #include <sys/socket.h>
  21 #include <assert.h>
  22 #include <pcap.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <arpa/inet.h> /* inet_ntoa() */
  26
  27 /* need struct ether_header */
  28 #if defined(__NetBSD__) || defined(__OpenBSD__)
  29 # include <sys/queue.h>
  30 # include <net/if.h>
  31 # include <net/if_arp.h>
  32 # include <netinet/if_ether.h>
  33 #else
  34 # ifdef __sun
  35 #  include <sys/ethernet.h>
  36 #  define ETHER_HDR_LEN 14
  37 # else
  38 #  ifdef _AIX
  39 #   include <netinet/if_ether.h>
  40 #   define ETHER_HDR_LEN 14
  41 #  else
  42 #   include <net/ethernet.h>
  43 #  endif
  44 # endif
  45 #endif
  46 #ifndef ETHERTYPE_PPPOE
  47 #define ETHERTYPE_PPPOE 0x8864
  48 #endif
  49
  50 #ifndef ETHERTYPE_IPV6
  51 # ifdef HAVE_NET_IF_ETHER_H
  52 #  include <net/if_ether.h>     /* ETH_P_IPV6 for GNU/kfreebsd */
  53 # endif
  54 # ifdef ETH_P_IPV6
  55 #  define ETHERTYPE_IPV6 ETH_P_IPV6
  56 # endif
  57 #endif
  58
  59 #include <net/if.h> /* struct ifreq */
  60 #include <netinet/in_systm.h> /* n_long */
  61 #include <netinet/ip.h> /* struct ip */
  62 #include <netinet/ip6.h> /* struct ip6_hdr */
  63 #define __FAVOR_BSD
  64 #include <netinet/tcp.h> /* struct tcphdr */
  65 #include <netinet/udp.h> /* struct udphdr */
  66
  67 extern int want_pppoe;
  68
  69 static void decode_ether(u_char *, const struct pcap_pkthdr *,
  70    const u_char *);
  71 static void decode_loop(u_char *, const struct pcap_pkthdr *,
  72    const u_char *);
  73 static void decode_ppp(u_char *, const struct pcap_pkthdr *,
  74    const u_char *);
  75 static void decode_pppoe(u_char *, const struct pcap_pkthdr *,
  76    const u_char *);
  77 static void decode_pppoe_real(const u_char *pdata, const uint32_t len,
  78    struct pktsummary *sm);
  79 static void decode_linux_sll(u_char *, const struct pcap_pkthdr *,
  80    const u_char *);
  81 static void decode_raw(u_char *, const struct pcap_pkthdr *,
  82    const u_char *);
  83 static void decode_ip(const u_char *pdata, const uint32_t len,
  84    struct pktsummary *sm);
  85 static void decode_ipv6(const u_char *pdata, const uint32_t len,
  86    struct pktsummary *sm);
  87
  88 /* Link-type header information */
  89 static const struct linkhdr linkhdrs[] = {
  90   /* linktype       hdrlen         handler       */
  91    { DLT_EN10MB,    ETHER_HDR_LEN, decode_ether  },
  92    { DLT_LOOP,      NULL_HDR_LEN,  decode_loop  },
  93    { DLT_NULL,      NULL_HDR_LEN,  decode_loop  },
  94    { DLT_PPP,       PPP_HDR_LEN,   decode_ppp },
  95 #if defined(__NetBSD__)
  96    { DLT_PPP_SERIAL, PPP_HDR_LEN,  decode_ppp },
  97 #endif
  98    { DLT_FDDI,      FDDI_HDR_LEN,  NULL },
  99    { DLT_PPP_ETHER, PPPOE_HDR_LEN, decode_pppoe },
 100 #ifdef DLT_LINUX_SLL
 101    { DLT_LINUX_SLL, SLL_HDR_LEN,   decode_linux_sll },
 102 #endif
 103    { DLT_RAW,       RAW_HDR_LEN,   decode_raw },
 104    { -1, 0, NULL }
 105 };
 106
 107 /*
 108  * Returns a pointer to the linkhdr record matching the given linktype, or
 109  * NULL if no matching entry found.
 110  */
 111 const struct linkhdr *
 112 getlinkhdr(const int linktype)
 113 {
 114    size_t i;
 115
 116    for (i=0; linkhdrs[i].linktype != -1; i++)
 117       if (linkhdrs[i].linktype == linktype)
 118          return (&(linkhdrs[i]));
 119    return (NULL);
 120 }
 121
 122 /*
 123  * Returns the minimum snaplen needed to decode everything up to the TCP/UDP
 124  * packet headers.  The IPv6 header is normative.  The argument lh is not
 125  * allowed to be NULL.
 126  */
 127 int
 128 getsnaplen(const struct linkhdr *lh)
 129 {
 130    return (int)(lh->hdrlen + IPV6_HDR_LEN + max(TCP_HDR_LEN, UDP_HDR_LEN));
 131 }
 132
 133 /* Decoding functions. */
 134 static void
 135 decode_ether(u_char *user _unused_,
 136       const struct pcap_pkthdr *pheader,
 137       const u_char *pdata)
 138 {
 139    u_short type;
 140    const struct ether_header *hdr = (const struct ether_header *)pdata;
 141    struct pktsummary sm;
 142    memset(&sm, 0, sizeof(sm));
 143    sm.time = pheader->ts.tv_sec;
 144
 145    if (pheader->caplen < ETHER_HDR_LEN) {
 146       verbosef("ether: packet too short (%u bytes)", pheader->caplen);
 147       return;
 148    }
 149
 150 #ifdef __sun
 151    memcpy(sm.src_mac, hdr->ether_shost.ether_addr_octet, sizeof(sm.src_mac));
 152    memcpy(sm.dst_mac, hdr->ether_dhost.ether_addr_octet, sizeof(sm.dst_mac));
 153 #else
 154    memcpy(sm.src_mac, hdr->ether_shost, sizeof(sm.src_mac));
 155    memcpy(sm.dst_mac, hdr->ether_dhost, sizeof(sm.dst_mac));
 156 #endif
 157
 158    type = ntohs( hdr->ether_type );
 159    switch (type) {
 160    case ETHERTYPE_IP:
 161    case ETHERTYPE_IPV6:
 162       if (!want_pppoe) {
 163          decode_ip(pdata + ETHER_HDR_LEN,
 164                    pheader->caplen - ETHER_HDR_LEN, &sm);
 165          acct_for(&sm);
 166       } else
 167          verbosef("ether: discarded IP packet, expecting PPPoE instead");
 168       break;
 169    case ETHERTYPE_ARP:
 170       /* known protocol, don't complain about it. */
 171       break;
 172    case ETHERTYPE_PPPOE:
 173       if (want_pppoe)
 174          decode_pppoe_real(pdata + ETHER_HDR_LEN,
 175                            pheader->caplen - ETHER_HDR_LEN, &sm);
 176       else
 177          verbosef("ether: got PPPoE frame: maybe you want --pppoe");
 178       break;
 179    default:
 180       verbosef("ether: unknown protocol (0x%04x)", type);
 181    }
 182 }
 183
 184 static void
 185 decode_loop(u_char *user _unused_,
 186       const struct pcap_pkthdr *pheader,
 187       const u_char *pdata)
 188 {
 189    uint32_t family;
 190    struct pktsummary sm;
 191    memset(&sm, 0, sizeof(sm));
 192
 193    if (pheader->caplen < NULL_HDR_LEN) {
 194       verbosef("loop: packet too short (%u bytes)", pheader->caplen);
 195       return;
 196    }
 197    family = *(const uint32_t *)pdata;
 198 #ifdef __OpenBSD__
 199    family = ntohl(family);
 200 #endif
 201    if (family == AF_INET) {
 202       /* OpenBSD tun or FreeBSD tun or FreeBSD lo */
 203       decode_ip(pdata + NULL_HDR_LEN, pheader->caplen - NULL_HDR_LEN, &sm);
 204       sm.time = pheader->ts.tv_sec;
 205       acct_for(&sm);
 206    }
 207    else if (family == AF_INET6) {
 208       /* XXX: Check this! */
 209       decode_ip(pdata + NULL_HDR_LEN, pheader->caplen - NULL_HDR_LEN, &sm);
 210       sm.time = pheader->ts.tv_sec;
 211       acct_for(&sm);
 212    }
 213    else
 214       verbosef("loop: unknown family (%x)", family);
 215 }
 216
 217 static void
 218 decode_ppp(u_char *user _unused_,
 219       const struct pcap_pkthdr *pheader,
 220       const u_char *pdata)
 221 {
 222    struct pktsummary sm;
 223    memset(&sm, 0, sizeof(sm));
 224
 225    if (pheader->caplen < PPPOE_HDR_LEN) {
 226       verbosef("ppp: packet too short (%u bytes)", pheader->caplen);
 227       return;
 228    }
 229
 230    if (pdata[2] == 0x00 && pdata[3] == 0x21) {
 231          decode_ip(pdata + PPP_HDR_LEN, pheader->caplen - PPP_HDR_LEN, &sm);
 232          sm.time = pheader->ts.tv_sec;
 233          acct_for(&sm);
 234    } else
 235       verbosef("non-IP PPP packet; ignoring.");
 236 }
 237
 238 static void
 239 decode_pppoe(u_char *user _unused_,
 240       const struct pcap_pkthdr *pheader,
 241       const u_char *pdata)
 242 {
 243    struct pktsummary sm;
 244    memset(&sm, 0, sizeof(sm));
 245    sm.time = pheader->ts.tv_sec;
 246    decode_pppoe_real(pdata, pheader->caplen, &sm);
 247 }
 248
 249 static void
 250 decode_pppoe_real(const u_char *pdata, const uint32_t len,
 251    struct pktsummary *sm)
 252 {
 253    if (len < PPPOE_HDR_LEN) {
 254       verbosef("pppoe: packet too short (%u bytes)", len);
 255       return;
 256    }
 257
 258    if (pdata[1] != 0x00) {
 259       verbosef("pppoe: code = 0x%02x, expecting 0; ignoring.", pdata[1]);
 260       return;
 261    }
 262
 263    if ((pdata[6] == 0xc0) && (pdata[7] == 0x21)) return; /* LCP */
 264    if ((pdata[6] == 0xc0) && (pdata[7] == 0x25)) return; /* LQR */
 265
 266    if ((pdata[6] == 0x00) && (pdata[7] == 0x21)) {
 267       decode_ip(pdata + PPPOE_HDR_LEN, len - PPPOE_HDR_LEN, sm);
 268       acct_for(sm);
 269    } else
 270       verbosef("pppoe: non-IP PPPoE packet (0x%02x%02x); ignoring.",
 271          pdata[6], pdata[7]);
 272 }
 273
 274 /* very similar to decode_ether ... */
 275 static void
 276 decode_linux_sll(u_char *user _unused_,
 277       const struct pcap_pkthdr *pheader,
 278       const u_char *pdata)
 279 {
 280    const struct sll_header {
 281       uint16_t packet_type;
 282       uint16_t device_type;
 283       uint16_t addr_length;
 284 #define SLL_MAX_ADDRLEN 8
 285       uint8_t addr[SLL_MAX_ADDRLEN];
 286       uint16_t ether_type;
 287    } *hdr = (const struct sll_header *)pdata;
 288    u_short type;
 289    struct pktsummary sm;
 290    memset(&sm, 0, sizeof(sm));
 291
 292    if (pheader->caplen < SLL_HDR_LEN) {
 293       verbosef("linux_sll: packet too short (%u bytes)", pheader->caplen);
 294       return;
 295    }
 296
 297    type = ntohs( hdr->ether_type );
 298    switch (type) {
 299    case ETHERTYPE_IP:
 300    case ETHERTYPE_IPV6:
 301       decode_ip(pdata + SLL_HDR_LEN, pheader->caplen - SLL_HDR_LEN, &sm);
 302       sm.time = pheader->ts.tv_sec;
 303       acct_for(&sm);
 304       break;
 305    case ETHERTYPE_ARP:
 306       /* known protocol, don't complain about it. */
 307       break;
 308    default:
 309       verbosef("linux_sll: unknown protocol (%04x)", type);
 310    }
 311 }
 312
 313 static void
 314 decode_raw(u_char *user _unused_,
 315       const struct pcap_pkthdr *pheader,
 316       const u_char *pdata)
 317 {
 318    struct pktsummary sm;
 319    memset(&sm, 0, sizeof(sm));
 320
 321    decode_ip(pdata, pheader->caplen, &sm);
 322    sm.time = pheader->ts.tv_sec;
 323    acct_for(&sm);
 324 }
 325
 326 static void decode_ip_payload(const u_char *pdata, const uint32_t len,
 327       struct pktsummary *sm);
 328
 329 static void
 330 decode_ip(const u_char *pdata, const uint32_t len, struct pktsummary *sm)
 331 {
 332    const struct ip *hdr = (const struct ip *)pdata;
 333
 334    if (hdr->ip_v == 6) {
 335       /* Redirect parsing of IPv6 packets. */
 336       decode_ipv6(pdata, len, sm);
 337       return;
 338    }
 339    if (len < IP_HDR_LEN) {
 340       verbosef("ip: packet too short (%u bytes)", len);
 341       return;
 342    }
 343    if (hdr->ip_v != 4) {
 344       verbosef("ip: version %d (expecting 4 or 6)", hdr->ip_v);
 345       return;
 346    }
 347
 348    sm->len = ntohs(hdr->ip_len);
 349    sm->proto = hdr->ip_p;
 350
 351    sm->src.family = IPv4;
 352    sm->src.ip.v4 = hdr->ip_src.s_addr;
 353
 354    sm->dst.family = IPv4;
 355    sm->dst.ip.v4 = hdr->ip_dst.s_addr;
 356
 357    decode_ip_payload(pdata + IP_HDR_LEN, len - IP_HDR_LEN, sm);
 358 }
 359
 360 static void
 361 decode_ipv6(const u_char *pdata, const uint32_t len, struct pktsummary *sm)
 362 {
 363    const struct ip6_hdr *hdr = (const struct ip6_hdr *)pdata;
 364
 365    if (len < IPV6_HDR_LEN) {
 366       verbosef("ipv6: packet too short (%u bytes)", len);
 367       return;
 368    }
 369
 370    sm->len = ntohs(hdr->ip6_plen) + IPV6_HDR_LEN;
 371    sm->proto = hdr->ip6_nxt;
 372
 373    sm->src.family = IPv6;
 374    memcpy(&sm->src.ip.v6, &hdr->ip6_src, sizeof(sm->src.ip.v6));
 375
 376    sm->dst.family = IPv6;
 377    memcpy(&sm->dst.ip.v6, &hdr->ip6_dst, sizeof(sm->dst.ip.v6));
 378
 379    decode_ip_payload(pdata + IPV6_HDR_LEN, len - IPV6_HDR_LEN, sm);
 380 }
 381
 382 static void
 383 decode_ip_payload(const u_char *pdata, const uint32_t len,
 384       struct pktsummary *sm)
 385 {
 386    switch (sm->proto) {
 387       case IPPROTO_TCP: {
 388          const struct tcphdr *thdr = (const struct tcphdr *)pdata;
 389          if (len < TCP_HDR_LEN) {
 390             verbosef("tcp: packet too short (%u bytes)", len);
 391             sm->proto = IPPROTO_INVALID; /* don't do accounting! */
 392             return;
 393          }
 394          sm->src_port = ntohs(thdr->th_sport);
 395          sm->dst_port = ntohs(thdr->th_dport);
 396          sm->tcp_flags = thdr->th_flags &
 397             (TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG);
 398          break;
 399       }
 400
 401       case IPPROTO_UDP: {
 402          const struct udphdr *uhdr = (const struct udphdr *)pdata;
 403          if (len < UDP_HDR_LEN) {
 404             verbosef("udp: packet too short (%u bytes)", len);
 405             sm->proto = IPPROTO_INVALID; /* don't do accounting! */
 406             return;
 407          }
 408          sm->src_port = ntohs(uhdr->uh_sport);
 409          sm->dst_port = ntohs(uhdr->uh_dport);
 410          break;
 411       }
 412
 413       case IPPROTO_ICMP:
 414       case IPPROTO_ICMPV6:
 415       case IPPROTO_AH:
 416       case IPPROTO_ESP:
 417       case IPPROTO_OSPF:
 418          /* known protocol, don't complain about it */
 419          break;
 420
 421       default:
 422          verbosef("ip: unknown protocol %d", sm->proto);
 423    }
 424 }
 425
 426 /* vim:set ts=3 sw=3 tw=78 expandtab: */