proto_ipv4.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>.
   4  * Copyright (C) 2009, 2010 Daniel Borkmann
   5  * Copyright (C) 2012 Christoph Jaeger <christoph@netsniff-ng.org>
   6  * Subject to the GPL, version 2.
   7  */
   8
   9 #include <stdio.h>
  10 #include <stdint.h>
  11 #include <netinet/in.h>    /* for ntohs() */
  12 #include <arpa/inet.h>     /* for inet_ntop() */
  13
  14 #include "proto.h"
  15 #include "protos.h"
  16 #include "csum.h"
  17 #include "dissector_eth.h"
  18 #include "ipv4.h"
  19 #include "pkt_buff.h"
  20 #include "built_in.h"
  21
  22 #define FRAG_OFF_RESERVED_FLAG(x)      ((x) & 0x8000)
  23 #define FRAG_OFF_NO_FRAGMENT_FLAG(x)   ((x) & 0x4000)
  24 #define FRAG_OFF_MORE_FRAGMENT_FLAG(x) ((x) & 0x2000)
  25 #define FRAG_OFF_FRAGMENT_OFFSET(x)    ((x) & 0x1fff)
  26
  27 /* IP Option Numbers (http://www.iana.org/assignments/ip-parameters) */
  28 #define IP_OPT_EOOL 0x00
  29 #define IP_OPT_NOP  0x01
  30
  31 #define IP_OPT_COPIED_FLAG(x)  ((x) & 0x80)
  32 #define IP_OPT_CLASS(x)       (((x) & 0x60) >> 5)
  33 #define IP_OPT_NUMBER(x)       ((x) & 0x1F)
  34
  35 static void ipv4(struct pkt_buff *pkt)
  36 {
  37         uint16_t csum, frag_off, h_tot_len;
  38         char src_ip[INET_ADDRSTRLEN];
  39         char dst_ip[INET_ADDRSTRLEN];
  40         struct ipv4hdr *ip = (struct ipv4hdr *) pkt_pull(pkt, sizeof(*ip));
  41         uint8_t *opt, *trailer;
  42         unsigned int trailer_len = 0;
  43         ssize_t opts_len, opt_len;
  44
  45         if (!ip)
  46                 return;
  47
  48         frag_off = ntohs(ip->h_frag_off);
  49         h_tot_len = ntohs(ip->h_tot_len);
  50         csum = calc_csum(ip, ip->h_ihl * 4, 0);
  51
  52         inet_ntop(AF_INET, &ip->h_saddr, src_ip, sizeof(src_ip));
  53         inet_ntop(AF_INET, &ip->h_daddr, dst_ip, sizeof(dst_ip));
  54
  55         if ((pkt_len(pkt) + sizeof(*ip)) > h_tot_len) {
  56                 trailer_len = pkt_len(pkt) + sizeof(*ip) - h_tot_len;
  57                 trailer = pkt->data + h_tot_len + trailer_len;
  58         }
  59
  60         if (trailer_len) {
  61                  tprintf(" [ Eth trailer ");
  62                  while (trailer_len--) {
  63                         tprintf("%x", *(trailer - trailer_len));
  64                  }
  65                  tprintf(" ]\n");
  66         }
  67
  68         tprintf(" [ IPv4 ");
  69         tprintf("Addr (%s => %s), ", src_ip, dst_ip);
  70         tprintf("Proto (%u), ", ip->h_protocol);
  71         tprintf("TTL (%u), ", ip->h_ttl);
  72         tprintf("TOS (%u), ", ip->h_tos);
  73         tprintf("Ver (%u), ", ip->h_version);
  74         tprintf("IHL (%u), ", ip->h_ihl);
  75         tprintf("Tlen (%u), ", ntohs(ip->h_tot_len));
  76         tprintf("ID (%u), ", ntohs(ip->h_id));
  77         tprintf("Res (%u), NoFrag (%u), MoreFrag (%u), FragOff (%u), ",
  78                 FRAG_OFF_RESERVED_FLAG(frag_off) ? 1 : 0,
  79                 FRAG_OFF_NO_FRAGMENT_FLAG(frag_off) ? 1 : 0,
  80                 FRAG_OFF_MORE_FRAGMENT_FLAG(frag_off) ? 1 : 0,
  81                 FRAG_OFF_FRAGMENT_OFFSET(frag_off));
  82         tprintf("CSum (0x%.4x) is %s", ntohs(ip->h_check),
  83                 csum ? colorize_start_full(black, red) "bogus (!)"
  84                        colorize_end() : "ok");
  85         if (csum)
  86                 tprintf("%s should be 0x%.4x%s", colorize_start_full(black, red),
  87                         csum_expected(ip->h_check, csum), colorize_end());
  88         tprintf(" ]\n");
  89
  90         opts_len = max((uint8_t) ip->h_ihl, sizeof(*ip) / sizeof(uint32_t)) *
  91                    sizeof(uint32_t) - sizeof(*ip);
  92
  93         for (opt = pkt_pull(pkt, opts_len); opt && opts_len > 0; opt++) {
  94                 tprintf("   [ Option  Copied (%u), Class (%u), Number (%u)",
  95                         IP_OPT_COPIED_FLAG(*opt) ? 1 : 0, IP_OPT_CLASS(*opt),
  96                         IP_OPT_NUMBER(*opt));
  97
  98                 switch (*opt) {
  99                 case IP_OPT_EOOL:
 100                 case IP_OPT_NOP:
 101                         tprintf(" ]\n");
 102                         opts_len--;
 103                         break;
 104                 default:
 105                         /*
 106                          * Assuming that EOOL and NOP are the only single-byte
 107                          * options, treat all other options as variable in
 108                          * length with a minimum of 2.
 109                          *
 110                          * TODO: option length might be incorrect in malformed packets,
 111                          *       check and handle that
 112                          */
 113                         opt_len = *(++opt);
 114                         if (opt_len > opts_len) {
 115                                 tprintf(", Len (%zd, invalid) ]\n", opt_len);
 116                                 goto out;
 117                         } else
 118                                 tprintf(", Len (%zd) ]\n", opt_len);
 119                         opts_len -= opt_len;
 120                         tprintf("     [ Data hex ");
 121                         for (opt_len -= 2; opt_len > 0; opt_len--)
 122                                 tprintf(" %.2x", *(++opt));
 123                         tprintf(" ]\n");
 124                         break;
 125                 }
 126         }
 127 out:
 128         /* cut off everything that is not part of IPv4 payload */
 129         /* XXX there could still be an Ethernet trailer included or others */
 130
 131         pkt_trim(pkt, pkt_len(pkt) - min(pkt_len(pkt),
 132                  (ntohs(ip->h_tot_len) - ip->h_ihl * sizeof(uint32_t))));
 133
 134         pkt_set_proto(pkt, &eth_lay3, ip->h_protocol);
 135 }
 136
 137 static void ipv4_less(struct pkt_buff *pkt)
 138 {
 139         char src_ip[INET_ADDRSTRLEN];
 140         char dst_ip[INET_ADDRSTRLEN];
 141         struct ipv4hdr *ip = (struct ipv4hdr *) pkt_pull(pkt, sizeof(*ip));
 142
 143         if (!ip)
 144                 return;
 145
 146         inet_ntop(AF_INET, &ip->h_saddr, src_ip, sizeof(src_ip));
 147         inet_ntop(AF_INET, &ip->h_daddr, dst_ip, sizeof(dst_ip));
 148
 149         tprintf(" %s/%s Len %u", src_ip, dst_ip,
 150                 ntohs(ip->h_tot_len));
 151
 152         /* cut off IP options and everything that is not part of IPv4 payload */
 153         pkt_pull(pkt, max((uint8_t) ip->h_ihl, sizeof(*ip) / sizeof(uint32_t))
 154                 * sizeof(uint32_t) - sizeof(*ip));
 155         /* XXX there coul still be an Ethernet trailer included or others */
 156 #if 0
 157         pkt_trim(pkt, pkt_len(pkt) - min(pkt_len(pkt),
 158                  (ntohs(ip->h_tot_len) - ip->h_ihl * sizeof(uint32_t))));
 159 #endif
 160         pkt_set_proto(pkt, &eth_lay3, ip->h_protocol);
 161 }
 162
 163 struct protocol ipv4_ops = {
 164         .key = 0x0800,
 165         .print_full = ipv4,
 166         .print_less = ipv4_less,
 167 };