trafgen_l4.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * Subject to the GPL, version 2.
   4  */
   5
   6 #include <stdbool.h>
   7 #include <netinet/in.h>
   8
   9 #include "die.h"
  10 #include "csum.h"
  11 #include "built_in.h"
  12 #include "trafgen_l3.h"
  13 #include "trafgen_l4.h"
  14 #include "trafgen_conf.h"
  15 #include "trafgen_proto.h"
  16
  17 static struct proto_field udp_fields[] = {
  18         { .id = UDP_SPORT,      .len = 2,       .offset = 0 },
  19         { .id = UDP_DPORT,      .len = 2,       .offset = 2 },
  20         { .id = UDP_LEN,        .len = 2,       .offset = 4 },
  21         { .id = UDP_CSUM,       .len = 2,       .offset = 6 },
  22 };
  23
  24 static struct proto_field tcp_fields[] = {
  25         { .id = TCP_SPORT,   .len = 2, .offset = 0 },
  26         { .id = TCP_DPORT,   .len = 2, .offset = 2 },
  27         { .id = TCP_SEQ,     .len = 4, .offset = 4 },
  28         { .id = TCP_ACK_SEQ, .len = 4, .offset = 8 },
  29         { .id = TCP_DOFF,    .len = 2, .offset = 12, .shift = 12, .mask = 0xf000 },
  30         /* reserved (4 bits) */
  31         { .id = TCP_CWR,     .len = 2, .offset = 12, .shift = 7, .mask = 0x0080 },
  32         { .id = TCP_ECE,     .len = 2, .offset = 12, .shift = 6, .mask = 0x0040 },
  33         { .id = TCP_URG,     .len = 2, .offset = 12, .shift = 5, .mask = 0x0020 },
  34         { .id = TCP_ACK,     .len = 2, .offset = 12, .shift = 4, .mask = 0x0010 },
  35         { .id = TCP_PSH,     .len = 2, .offset = 12, .shift = 3, .mask = 0x0008 },
  36         { .id = TCP_RST,     .len = 2, .offset = 12, .shift = 2, .mask = 0x0004 },
  37         { .id = TCP_SYN,     .len = 2, .offset = 12, .shift = 1, .mask = 0x0002 },
  38         { .id = TCP_FIN,     .len = 2, .offset = 12, .shift = 0, .mask = 0x0001 },
  39         { .id = TCP_WINDOW,  .len = 2, .offset = 14 },
  40         { .id = TCP_CSUM,    .len = 2, .offset = 16 },
  41         { .id = TCP_URG_PTR, .len = 2, .offset = 18 },
  42 };
  43
  44 static void udp_header_init(struct proto_hdr *hdr)
  45 {
  46         proto_lower_default_add(hdr, PROTO_IP4);
  47
  48         proto_header_fields_add(hdr, udp_fields, array_size(udp_fields));
  49 }
  50
  51 static void udp_packet_finish(struct proto_hdr *hdr)
  52 {
  53         struct proto_hdr *lower = proto_lower_header(hdr);
  54         struct packet *pkt = current_packet();
  55         uint16_t total_len;
  56         uint16_t csum;
  57
  58         total_len = pkt->len - hdr->pkt_offset;
  59         proto_field_set_default_be16(hdr, UDP_LEN, total_len);
  60
  61         if (proto_field_is_set(hdr, UDP_CSUM))
  62                 return;
  63
  64         if (!lower || lower->id != PROTO_IP4)
  65                 return;
  66
  67         total_len = proto_field_get_u16(hdr, UDP_LEN);
  68         csum = p4_csum((void *) proto_header_ptr(lower), proto_header_ptr(hdr),
  69                         total_len, IPPROTO_UDP);
  70
  71         proto_field_set_be16(hdr, UDP_CSUM, bswap_16(csum));
  72 }
  73
  74 static struct proto_hdr udp_hdr = {
  75         .id             = PROTO_UDP,
  76         .layer          = PROTO_L4,
  77         .header_init    = udp_header_init,
  78         .packet_finish  = udp_packet_finish,
  79 };
  80
  81 static void tcp_header_init(struct proto_hdr *hdr)
  82 {
  83         proto_lower_default_add(hdr, PROTO_IP4);
  84
  85         proto_header_fields_add(hdr, tcp_fields, array_size(tcp_fields));
  86
  87         proto_field_set_default_be16(hdr, TCP_DOFF, 5);
  88 }
  89
  90 static void tcp_packet_finish(struct proto_hdr *hdr)
  91 {
  92         struct proto_hdr *lower = proto_lower_header(hdr);
  93         struct packet *pkt = current_packet();
  94         uint16_t total_len;
  95         uint16_t csum;
  96
  97         if (proto_field_is_set(hdr, TCP_CSUM))
  98                 return;
  99
 100         if (!lower || lower->id != PROTO_IP4)
 101                 return;
 102
 103         total_len = pkt->len - hdr->pkt_offset;
 104         csum = p4_csum((void *) proto_header_ptr(lower), proto_header_ptr(hdr),
 105                         total_len, IPPROTO_TCP);
 106
 107         proto_field_set_be16(hdr, TCP_CSUM, bswap_16(csum));
 108 }
 109
 110 static struct proto_hdr tcp_hdr = {
 111         .id             = PROTO_TCP,
 112         .layer          = PROTO_L4,
 113         .header_init    = tcp_header_init,
 114         .packet_finish  = tcp_packet_finish,
 115 };
 116
 117 void protos_l4_init(void)
 118 {
 119         proto_header_register(&udp_hdr);
 120         proto_header_register(&tcp_hdr);
 121 }