trafgen_l3.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * Subject to the GPL, version 2.
   4  */
   5
   6 #include <linux/if_ether.h>
   7
   8 #include "csum.h"
   9 #include "built_in.h"
  10 #include "trafgen_l2.h"
  11 #include "trafgen_l3.h"
  12 #include "trafgen_proto.h"
  13 #include "trafgen_conf.h"
  14
  15 static struct proto_field ipv4_fields[] = {
  16         { .id = IP4_VER,       .len = 1, .offset = 0, .shift = 4, .mask = 0xf0 },
  17         { .id = IP4_IHL,       .len = 1, .offset = 0, .shift = 0, .mask = 0x0f },
  18         { .id = IP4_DSCP,      .len = 1, .offset = 1, .shift = 2, .mask = 0xfc },
  19         { .id = IP4_ECN,       .len = 1, .offset = 1, .shift = 0, .mask = 0x03 },
  20         { .id = IP4_TOS,       .len = 1, .offset = 1 },
  21         { .id = IP4_LEN,       .len = 2, .offset = 2 },
  22         { .id = IP4_ID,        .len = 2, .offset = 4 },
  23         { .id = IP4_FLAGS,     .len = 2, .offset = 6, .shift = 13, .mask = 0xe000 },
  24         { .id = IP4_MF,        .len = 2, .offset = 6, .shift = 13, .mask = 0x2000 },
  25         { .id = IP4_DF,        .len = 2, .offset = 6, .shift = 14, .mask = 0x4000 },
  26         { .id = IP4_FRAG_OFFS, .len = 2, .offset = 6, .shift = 0,  .mask = 0x1fff },
  27         { .id = IP4_TTL,       .len = 1, .offset = 8 },
  28         { .id = IP4_PROTO,     .len = 1, .offset = 9 },
  29         { .id = IP4_CSUM,      .len = 2, .offset = 10 },
  30         { .id = IP4_SADDR,     .len = 4, .offset = 12 },
  31         { .id = IP4_DADDR,     .len = 4, .offset = 16 },
  32 };
  33
  34 static void ipv4_header_init(struct proto_hdr *hdr)
  35 {
  36         struct proto_hdr *lower;
  37
  38         proto_lower_default_add(PROTO_ETH);
  39
  40         lower = proto_current_header();
  41
  42         if (lower->id == PROTO_ETH)
  43                 proto_field_set_default_be16(lower, ETH_PROTO_ID, ETH_P_IP);
  44         else if (lower->id == PROTO_IP4)
  45                 proto_field_set_default_u8(lower, IP4_PROTO, IPPROTO_IPIP);
  46
  47         proto_header_fields_add(hdr, ipv4_fields, array_size(ipv4_fields));
  48
  49         proto_field_set_default_u8(hdr, IP4_VER, 4);
  50         proto_field_set_default_u8(hdr, IP4_IHL, 5);
  51         proto_field_set_default_dev_ipv4(hdr, IP4_SADDR);
  52 }
  53
  54 static void ipv4_packet_finish(struct proto_hdr *hdr)
  55 {
  56         struct packet *pkt = current_packet();
  57         uint16_t total_len;
  58
  59         total_len = pkt->len - hdr->pkt_offset;
  60         proto_field_set_default_be16(hdr, IP4_LEN, total_len);
  61
  62         if (!proto_field_is_set(hdr, IP4_CSUM)) {
  63                 uint16_t csum;
  64                 uint8_t ihl;
  65
  66                 ihl = proto_field_get_u8(hdr, IP4_IHL);
  67                 csum = htons(calc_csum(&pkt->payload[hdr->pkt_offset], ihl * 4));
  68                 proto_field_set_u16(hdr, IP4_CSUM, bswap_16(csum));
  69         }
  70 }
  71
  72 static struct proto_hdr ipv4_hdr = {
  73         .id             = PROTO_IP4,
  74         .layer          = PROTO_L3,
  75         .header_init    = ipv4_header_init,
  76         .packet_finish  = ipv4_packet_finish,
  77 };
  78
  79 void protos_l3_init(void)
  80 {
  81         proto_header_register(&ipv4_hdr);
  82 }