src/proto_ipv4.h

   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 #ifndef PROTO_IPV4_H
  10 #define PROTO_IPV4_H
  11
  12 #include <stdio.h>
  13 #include <stdint.h>
  14 #include <netinet/in.h>    /* for ntohs() */
  15 #include <arpa/inet.h>     /* for inet_ntop() */
  16 #include <asm/byteorder.h>
  17
  18 #include "csum.h"
  19 #include "proto_struct.h"
  20 #include "dissector_eth.h"
  21 #include "pkt_buff.h"
  22 #include "built_in.h"
  23
  24 struct ipv4hdr {
  25 #if defined(__LITTLE_ENDIAN_BITFIELD)
  26         __extension__ uint8_t h_ihl:4,
  27                               h_version:4;
  28 #elif defined (__BIG_ENDIAN_BITFIELD)
  29         __extension__ uint8_t h_version:4,
  30                               h_ihl:4;
  31 #else
  32 # error "Please fix <asm/byteorder.h>"
  33 #endif
  34         uint8_t h_tos;
  35         uint16_t h_tot_len;
  36         uint16_t h_id;
  37         uint16_t h_frag_off;
  38         uint8_t h_ttl;
  39         uint8_t h_protocol;
  40         uint16_t h_check;
  41         uint32_t h_saddr;
  42         uint32_t h_daddr;
  43 } __packed;
  44
  45 #define FRAG_OFF_RESERVED_FLAG(x)      ((x) & 0x8000)
  46 #define FRAG_OFF_NO_FRAGMENT_FLAG(x)   ((x) & 0x4000)
  47 #define FRAG_OFF_MORE_FRAGMENT_FLAG(x) ((x) & 0x2000)
  48 #define FRAG_OFF_FRAGMENT_OFFSET(x)    ((x) & 0x1fff)
  49
  50 /* IP Option Numbers (http://www.iana.org/assignments/ip-parameters) */
  51 #define IP_OPT_EOOL 0x00
  52 #define IP_OPT_NOP  0x01
  53
  54 #define IP_OPT_COPIED_FLAG(x)  ((x) & 0x80)
  55 #define IP_OPT_CLASS(x)       (((x) & 0x60) >> 5)
  56 #define IP_OPT_NUMBER(x)       ((x) & 0x1F)
  57
  58 static inline void ipv4(struct pkt_buff *pkt)
  59 {
  60         uint16_t csum, frag_off;
  61         char src_ip[INET_ADDRSTRLEN];
  62         char dst_ip[INET_ADDRSTRLEN];
  63         struct ipv4hdr *ip = (struct ipv4hdr *) pkt_pull(pkt, sizeof(*ip));
  64         uint8_t *opt;
  65         ssize_t opts_len, opt_len;
  66
  67         if (!ip)
  68                 return;
  69
  70         frag_off = ntohs(ip->h_frag_off);
  71         csum = calc_csum(ip, ip->h_ihl * 4, 0);
  72
  73         inet_ntop(AF_INET, &ip->h_saddr, src_ip, sizeof(src_ip));
  74         inet_ntop(AF_INET, &ip->h_daddr, dst_ip, sizeof(dst_ip));
  75
  76         tprintf(" [ IPv4 ");
  77         tprintf("Addr (%s => %s), ", src_ip, dst_ip);
  78         tprintf("Proto (%u), ", ip->h_protocol);
  79         tprintf("TTL (%u), ", ip->h_ttl);
  80         tprintf("TOS (%u), ", ip->h_tos);
  81         tprintf("Ver (%u), ", ip->h_version);
  82         tprintf("IHL (%u), ", ip->h_ihl);
  83         tprintf("Tlen (%u), ", ntohs(ip->h_tot_len));
  84         tprintf("ID (%u), ", ntohs(ip->h_id));
  85         tprintf("Res (%u), NoFrag (%u), MoreFrag (%u), FragOff (%u), ",
  86                 FRAG_OFF_RESERVED_FLAG(frag_off) ? 1 : 0,
  87                 FRAG_OFF_NO_FRAGMENT_FLAG(frag_off) ? 1 : 0,
  88                 FRAG_OFF_MORE_FRAGMENT_FLAG(frag_off) ? 1 : 0,
  89                 FRAG_OFF_FRAGMENT_OFFSET(frag_off));
  90         tprintf("CSum (0x%.4x) is %s", ntohs(ip->h_check),
  91                 csum ? colorize_start_full(black, red) "bogus (!)"
  92                        colorize_end() : "ok");
  93         if (csum)
  94                 tprintf("%s should be 0x%.4x%s", colorize_start_full(black, red),
  95                         csum_expected(ip->h_check, csum), colorize_end());
  96         tprintf(" ]\n");
  97
  98         opts_len = max((uint8_t) ip->h_ihl, sizeof(*ip) / sizeof(uint32_t)) *
  99                    sizeof(uint32_t) - sizeof(*ip);
 100
 101         for (opt = pkt_pull(pkt, opts_len); opt && opts_len > 0; opt++) {
 102                 tprintf("   [ Option  Copied (%u), Class (%u), Number (%u)",
 103                         IP_OPT_COPIED_FLAG(*opt) ? 1 : 0, IP_OPT_CLASS(*opt),
 104                         IP_OPT_NUMBER(*opt));
 105
 106                 switch (*opt) {
 107                 case IP_OPT_EOOL:
 108                 case IP_OPT_NOP:
 109                         tprintf(" ]\n");
 110                         opts_len--;
 111                         break;
 112                 default:
 113                         /*
 114                          * Assuming that EOOL and NOP are the only single-byte
 115                          * options, treat all other options as variable in
 116                          * length with a minimum of 2.
 117                          *
 118                          * TODO: option length might be incorrect in malformed packets,
 119                          *       check and handle that
 120                          */
 121                         opt_len = *(++opt);
 122                         if (opt_len > opts_len) {
 123                                 tprintf(", Len (%u, invalid) ]\n", opt_len);
 124                                 goto out;
 125                         } else
 126                                 tprintf(", Len (%u) ]\n", opt_len);
 127                         opts_len -= opt_len;
 128                         tprintf("     [ Data hex ");
 129                         for (opt_len -= 2; opt_len > 0; opt_len--)
 130                                 tprintf(" %.2x", *(++opt));
 131                         tprintf(" ]\n");
 132                         break;
 133                 }
 134         }
 135 out:
 136         /* cut off everything that is not part of IPv4 payload */
 137         pkt_trim(pkt, pkt_len(pkt) - min(pkt_len(pkt), (ntohs(ip->h_tot_len) - ip->h_ihl * sizeof(uint32_t))));
 138         pkt_set_proto(pkt, &eth_lay3, ip->h_protocol);
 139 }
 140
 141 static inline void ipv4_less(struct pkt_buff *pkt)
 142 {
 143         char src_ip[INET_ADDRSTRLEN];
 144         char dst_ip[INET_ADDRSTRLEN];
 145         struct ipv4hdr *ip = (struct ipv4hdr *) pkt_pull(pkt, sizeof(*ip));
 146
 147         if (!ip)
 148                 return;
 149
 150         inet_ntop(AF_INET, &ip->h_saddr, src_ip, sizeof(src_ip));
 151         inet_ntop(AF_INET, &ip->h_daddr, dst_ip, sizeof(dst_ip));
 152
 153         tprintf(" %s/%s Len %u", src_ip, dst_ip,
 154                 ntohs(ip->h_tot_len));
 155
 156         /* cut off IP options and everything that is not part of IPv4 payload */
 157         pkt_pull(pkt, max((uint8_t) ip->h_ihl, sizeof(*ip) / sizeof(uint32_t))
 158                 * sizeof(uint32_t) - sizeof(*ip));
 159         pkt_trim(pkt, pkt_len(pkt) - min(pkt_len(pkt), (ntohs(ip->h_tot_len) - ip->h_ihl * sizeof(uint32_t))));
 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 };
 168
 169 #endif /* PROTO_IPV4_H */