FD.io VPP  v20.05-21-gb1500e9ff
Vector Packet Processing
tcp_packet.h
Go to the documentation of this file.
1 /*
2  * Copyright (c) 2016-2019 Cisco and/or its affiliates.
3  * Licensed under the Apache License, Version 2.0 (the "License");
4  * you may not use this file except in compliance with the License.
5  * You may obtain a copy of the License at:
6  *
7  * http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software
10  * distributed under the License is distributed on an "AS IS" BASIS,
11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  * See the License for the specific language governing permissions and
13  * limitations under the License.
14  */
15 
16 #ifndef included_tcp_packet_h
17 #define included_tcp_packet_h
18 
19 #include <vnet/vnet.h>
20 
21 /* TCP flags bit 0 first. */
22 #define foreach_tcp_flag \
23  _ (FIN) /**< No more data from sender. */ \
24  _ (SYN) /**< Synchronize sequence numbers. */ \
25  _ (RST) /**< Reset the connection. */ \
26  _ (PSH) /**< Push function. */ \
27  _ (ACK) /**< Ack field significant. */ \
28  _ (URG) /**< Urgent pointer field significant. */ \
29  _ (ECE) /**< ECN-echo. Receiver got CE packet */ \
30  _ (CWR) /**< Sender reduced congestion window */
31 
32 enum
33 {
34 #define _(f) TCP_FLAG_BIT_##f,
36 #undef _
38 };
39 
40 enum
41 {
42 #define _(f) TCP_FLAG_##f = 1 << TCP_FLAG_BIT_##f,
44 #undef _
45 };
46 
47 typedef struct _tcp_header
48 {
49  union
50  {
51  struct
52  {
53  u16 src_port; /**< Source port. */
54  u16 dst_port; /**< Destination port. */
55  };
56  struct
57  {
58  u16 src, dst;
59  };
60  };
61 
62  u32 seq_number; /**< Sequence number of the first data octet in this
63  * segment, except when SYN is present. If SYN
64  * is present the seq number is is the ISN and the
65  * first data octet is ISN+1 */
66  u32 ack_number; /**< Acknowledgement number if ACK is set. It contains
67  * the value of the next sequence number the sender
68  * of the segment is expecting to receive. */
69  u8 data_offset_and_reserved;
70  u8 flags; /**< Flags: see the macro above */
71  u16 window; /**< Number of bytes sender is willing to receive. */
72 
73  u16 checksum; /**< Checksum of TCP pseudo header and data. */
74  u16 urgent_pointer; /**< Seq number of the byte after the urgent data. */
75 } __attribute__ ((packed)) tcp_header_t;
76 
77 /* Flag tests that return 0 or !0 */
78 #define tcp_doff(_th) ((_th)->data_offset_and_reserved >> 4)
79 #define tcp_fin(_th) ((_th)->flags & TCP_FLAG_FIN)
80 #define tcp_syn(_th) ((_th)->flags & TCP_FLAG_SYN)
81 #define tcp_rst(_th) ((_th)->flags & TCP_FLAG_RST)
82 #define tcp_psh(_th) ((_th)->flags & TCP_FLAG_PSH)
83 #define tcp_ack(_th) ((_th)->flags & TCP_FLAG_ACK)
84 #define tcp_urg(_th) ((_th)->flags & TCP_FLAG_URG)
85 #define tcp_ece(_th) ((_th)->flags & TCP_FLAG_ECE)
86 #define tcp_cwr(_th) ((_th)->flags & TCP_FLAG_CWR)
87 
88 /* Flag tests that return 0 or 1 */
89 #define tcp_is_syn(_th) !!((_th)->flags & TCP_FLAG_SYN)
90 #define tcp_is_fin(_th) !!((_th)->flags & TCP_FLAG_FIN)
91 
92 always_inline int
94 {
95  return tcp_doff (t) * sizeof (u32);
96 }
97 
98 /*
99  * TCP options.
100  */
101 
102 typedef enum tcp_option_type
103 {
104  TCP_OPTION_EOL = 0, /**< End of options. */
105  TCP_OPTION_NOOP = 1, /**< No operation. */
106  TCP_OPTION_MSS = 2, /**< Limit MSS. */
107  TCP_OPTION_WINDOW_SCALE = 3, /**< Window scale. */
108  TCP_OPTION_SACK_PERMITTED = 4, /**< Selective Ack permitted. */
109  TCP_OPTION_SACK_BLOCK = 5, /**< Selective Ack block. */
110  TCP_OPTION_TIMESTAMP = 8, /**< Timestamps. */
111  TCP_OPTION_UTO = 28, /**< User timeout. */
112  TCP_OPTION_AO = 29, /**< Authentication Option. */
114 
115 #define foreach_tcp_options_flag \
116  _ (MSS) /**< MSS advertised in SYN */ \
117  _ (TSTAMP) /**< Timestamp capability advertised in SYN */ \
118  _ (WSCALE) /**< Wnd scale capability advertised in SYN */ \
119  _ (SACK_PERMITTED) /**< SACK capability advertised in SYN */ \
120  _ (SACK) /**< SACK present */
121 
122 enum
123 {
124 #define _(f) TCP_OPTS_FLAG_BIT_##f,
126 #undef _
128 };
129 
130 enum
131 {
132 #define _(f) TCP_OPTS_FLAG_##f = 1 << TCP_OPTS_FLAG_BIT_##f,
134 #undef _
135 };
136 
137 typedef struct _sack_block
138 {
139  u32 start; /**< Start sequence number */
140  u32 end; /**< End sequence number (first outside) */
141 } sack_block_t;
142 
143 typedef struct
144 {
145  u8 flags; /** Option flags, see above */
146  u8 wscale; /**< Window scale advertised */
147  u16 mss; /**< Maximum segment size advertised */
148  u32 tsval; /**< Timestamp value */
149  u32 tsecr; /**< Echoed/reflected time stamp */
150  sack_block_t *sacks; /**< SACK blocks */
151  u8 n_sack_blocks; /**< Number of SACKs blocks */
152 } tcp_options_t;
153 
154 /* Flag tests that return 0 or !0 */
155 #define tcp_opts_mss(_to) ((_to)->flags & TCP_OPTS_FLAG_MSS)
156 #define tcp_opts_tstamp(_to) ((_to)->flags & TCP_OPTS_FLAG_TSTAMP)
157 #define tcp_opts_wscale(_to) ((_to)->flags & TCP_OPTS_FLAG_WSCALE)
158 #define tcp_opts_sack(_to) ((_to)->flags & TCP_OPTS_FLAG_SACK)
159 #define tcp_opts_sack_permitted(_to) ((_to)->flags & TCP_OPTS_FLAG_SACK_PERMITTED)
160 
161 /* TCP option lengths */
162 #define TCP_OPTION_LEN_EOL 1
163 #define TCP_OPTION_LEN_NOOP 1
164 #define TCP_OPTION_LEN_MSS 4
165 #define TCP_OPTION_LEN_WINDOW_SCALE 3
166 #define TCP_OPTION_LEN_SACK_PERMITTED 2
167 #define TCP_OPTION_LEN_TIMESTAMP 10
168 #define TCP_OPTION_LEN_SACK_BLOCK 8
169 
170 #define TCP_HDR_LEN_MAX 60
171 #define TCP_WND_MAX 65535U
172 #define TCP_MAX_WND_SCALE 14 /* See RFC 1323 */
173 #define TCP_OPTS_ALIGN 4
174 #define TCP_OPTS_MAX_SACK_BLOCKS 3
175 
176 /* Modulo arithmetic for TCP sequence numbers */
177 #define seq_lt(_s1, _s2) ((i32)((_s1)-(_s2)) < 0)
178 #define seq_leq(_s1, _s2) ((i32)((_s1)-(_s2)) <= 0)
179 #define seq_gt(_s1, _s2) ((i32)((_s1)-(_s2)) > 0)
180 #define seq_geq(_s1, _s2) ((i32)((_s1)-(_s2)) >= 0)
181 #define seq_max(_s1, _s2) (seq_gt((_s1), (_s2)) ? (_s1) : (_s2))
182 
183 /* Modulo arithmetic for timestamps */
184 #define timestamp_lt(_t1, _t2) ((i32)((_t1)-(_t2)) < 0)
185 #define timestamp_leq(_t1, _t2) ((i32)((_t1)-(_t2)) <= 0)
186 
187 /**
188  * Parse TCP header options.
189  *
190  * @param th TCP header
191  * @param to TCP options data structure to be populated
192  * @param is_syn set if packet is syn
193  * @return -1 if parsing failed
194  */
195 always_inline int
197 {
198  const u8 *data;
199  u8 opt_len, opts_len, kind;
200  int j;
201  sack_block_t b;
202 
203  opts_len = (tcp_doff (th) << 2) - sizeof (tcp_header_t);
204  data = (const u8 *) (th + 1);
205 
206  /* Zero out all flags but those set in SYN */
207  to->flags &= (TCP_OPTS_FLAG_SACK_PERMITTED | TCP_OPTS_FLAG_WSCALE
208  | TCP_OPTS_FLAG_TSTAMP | TCP_OPTS_FLAG_MSS);
209 
210  for (; opts_len > 0; opts_len -= opt_len, data += opt_len)
211  {
212  kind = data[0];
213 
214  /* Get options length */
215  if (kind == TCP_OPTION_EOL)
216  break;
217  else if (kind == TCP_OPTION_NOOP)
218  {
219  opt_len = 1;
220  continue;
221  }
222  else
223  {
224  /* broken options */
225  if (opts_len < 2)
226  return -1;
227  opt_len = data[1];
228 
229  /* weird option length */
230  if (opt_len < 2 || opt_len > opts_len)
231  return -1;
232  }
233 
234  /* Parse options */
235  switch (kind)
236  {
237  case TCP_OPTION_MSS:
238  if (!is_syn)
239  break;
240  if ((opt_len == TCP_OPTION_LEN_MSS) && tcp_syn (th))
241  {
242  to->flags |= TCP_OPTS_FLAG_MSS;
243  to->mss = clib_net_to_host_u16 (*(u16 *) (data + 2));
244  }
245  break;
247  if (!is_syn)
248  break;
249  if ((opt_len == TCP_OPTION_LEN_WINDOW_SCALE) && tcp_syn (th))
250  {
251  to->flags |= TCP_OPTS_FLAG_WSCALE;
252  to->wscale = data[2];
253  if (to->wscale > TCP_MAX_WND_SCALE)
255  }
256  break;
258  if (is_syn)
259  to->flags |= TCP_OPTS_FLAG_TSTAMP;
260  if ((to->flags & TCP_OPTS_FLAG_TSTAMP)
261  && opt_len == TCP_OPTION_LEN_TIMESTAMP)
262  {
263  to->tsval = clib_net_to_host_u32 (*(u32 *) (data + 2));
264  to->tsecr = clib_net_to_host_u32 (*(u32 *) (data + 6));
265  }
266  break;
268  if (!is_syn)
269  break;
270  if (opt_len == TCP_OPTION_LEN_SACK_PERMITTED && tcp_syn (th))
271  to->flags |= TCP_OPTS_FLAG_SACK_PERMITTED;
272  break;
274  /* If SACK permitted was not advertised or a SYN, break */
275  if ((to->flags & TCP_OPTS_FLAG_SACK_PERMITTED) == 0 || tcp_syn (th))
276  break;
277 
278  /* If too short or not correctly formatted, break */
279  if (opt_len < 10 || ((opt_len - 2) % TCP_OPTION_LEN_SACK_BLOCK))
280  break;
281 
282  to->flags |= TCP_OPTS_FLAG_SACK;
283  to->n_sack_blocks = (opt_len - 2) / TCP_OPTION_LEN_SACK_BLOCK;
284  vec_reset_length (to->sacks);
285  for (j = 0; j < to->n_sack_blocks; j++)
286  {
287  b.start = clib_net_to_host_u32 (*(u32 *) (data + 2 + 8 * j));
288  b.end = clib_net_to_host_u32 (*(u32 *) (data + 6 + 8 * j));
289  vec_add1 (to->sacks, b);
290  }
291  break;
292  default:
293  /* Nothing to see here */
294  continue;
295  }
296  }
297  return 0;
298 }
299 
300 /**
301  * Write TCP options to segment.
302  *
303  * @param data buffer where to write the options
304  * @param opts options to write
305  * @return length of options written
306  */
309 {
310  u32 opts_len = 0;
311  u32 buf, seq_len = 4;
312 
313  if (tcp_opts_mss (opts))
314  {
315  *data++ = TCP_OPTION_MSS;
316  *data++ = TCP_OPTION_LEN_MSS;
317  buf = clib_host_to_net_u16 (opts->mss);
318  clib_memcpy_fast (data, &buf, sizeof (opts->mss));
319  data += sizeof (opts->mss);
320  opts_len += TCP_OPTION_LEN_MSS;
321  }
322 
323  if (tcp_opts_wscale (opts))
324  {
325  *data++ = TCP_OPTION_WINDOW_SCALE;
326  *data++ = TCP_OPTION_LEN_WINDOW_SCALE;
327  *data++ = opts->wscale;
328  opts_len += TCP_OPTION_LEN_WINDOW_SCALE;
329  }
330 
331  if (tcp_opts_sack_permitted (opts))
332  {
333  *data++ = TCP_OPTION_SACK_PERMITTED;
335  opts_len += TCP_OPTION_LEN_SACK_PERMITTED;
336  }
337 
338  if (tcp_opts_tstamp (opts))
339  {
340  *data++ = TCP_OPTION_TIMESTAMP;
341  *data++ = TCP_OPTION_LEN_TIMESTAMP;
342  buf = clib_host_to_net_u32 (opts->tsval);
343  clib_memcpy_fast (data, &buf, sizeof (opts->tsval));
344  data += sizeof (opts->tsval);
345  buf = clib_host_to_net_u32 (opts->tsecr);
346  clib_memcpy_fast (data, &buf, sizeof (opts->tsecr));
347  data += sizeof (opts->tsecr);
348  opts_len += TCP_OPTION_LEN_TIMESTAMP;
349  }
350 
351  if (tcp_opts_sack (opts))
352  {
353  int i;
354 
355  if (opts->n_sack_blocks != 0)
356  {
357  *data++ = TCP_OPTION_SACK_BLOCK;
358  *data++ = 2 + opts->n_sack_blocks * TCP_OPTION_LEN_SACK_BLOCK;
359  for (i = 0; i < opts->n_sack_blocks; i++)
360  {
361  buf = clib_host_to_net_u32 (opts->sacks[i].start);
362  clib_memcpy_fast (data, &buf, seq_len);
363  data += seq_len;
364  buf = clib_host_to_net_u32 (opts->sacks[i].end);
365  clib_memcpy_fast (data, &buf, seq_len);
366  data += seq_len;
367  }
368  opts_len += 2 + opts->n_sack_blocks * TCP_OPTION_LEN_SACK_BLOCK;
369  }
370  }
371 
372  /* Terminate TCP options */
373  if (opts_len % 4)
374  {
375  *data++ = TCP_OPTION_EOL;
376  opts_len += TCP_OPTION_LEN_EOL;
377  }
378 
379  /* Pad with zeroes to a u32 boundary */
380  while (opts_len % 4)
381  {
382  *data++ = TCP_OPTION_NOOP;
383  opts_len += TCP_OPTION_LEN_NOOP;
384  }
385  return opts_len;
386 }
387 
388 #endif /* included_tcp_packet_h */
389 
390 /*
391  * fd.io coding-style-patch-verification: ON
392  *
393  * Local Variables:
394  * eval: (c-set-style "gnu")
395  * End:
396  */
End of options.
Definition: tcp_packet.h:104
#define TCP_OPTION_LEN_EOL
Definition: tcp_packet.h:162
#define TCP_OPTION_LEN_SACK_PERMITTED
Definition: tcp_packet.h:166
struct _sack_block sack_block_t
Selective Ack permitted.
Definition: tcp_packet.h:108
#define tcp_opts_tstamp(_to)
Definition: tcp_packet.h:156
#define clib_memcpy_fast(a, b, c)
Definition: string.h:81
static u32 tcp_options_write(u8 *data, tcp_options_t *opts)
Write TCP options to segment.
Definition: tcp_packet.h:308
#define tcp_doff(_th)
Definition: tcp_packet.h:78
#define vec_add1(V, E)
Add 1 element to end of vector (unspecified alignment).
Definition: vec.h:590
vl_api_address_t src
Definition: gre.api:54
#define tcp_opts_sack(_to)
Definition: tcp_packet.h:158
No operation.
Definition: tcp_packet.h:105
u8 n_sack_blocks
Number of SACKs blocks.
Definition: tcp_packet.h:151
struct _tcp_header tcp_header_t
unsigned char u8
Definition: types.h:56
u8 wscale
Option flags, see above.
Definition: tcp_packet.h:146
User timeout.
Definition: tcp_packet.h:111
#define vec_reset_length(v)
Reset vector length to zero NULL-pointer tolerant.
u16 src_port
Definition: udp.api:41
Limit MSS.
Definition: tcp_packet.h:106
static int tcp_options_parse(tcp_header_t *th, tcp_options_t *to, u8 is_syn)
Parse TCP header options.
Definition: tcp_packet.h:196
#define TCP_OPTION_LEN_SACK_BLOCK
Definition: tcp_packet.h:168
enum tcp_option_type tcp_option_type_t
sack_block_t * sacks
SACK blocks.
Definition: tcp_packet.h:150
unsigned int u32
Definition: types.h:88
#define foreach_tcp_options_flag
SACK present.
Definition: tcp_packet.h:115
#define TCP_OPTION_LEN_WINDOW_SCALE
Definition: tcp_packet.h:165
#define tcp_opts_mss(_to)
Definition: tcp_packet.h:155
unsigned short u16
Definition: types.h:57
#define always_inline
Definition: ipsec.h:28
vl_api_address_t dst
Definition: gre.api:55
#define TCP_OPTION_LEN_TIMESTAMP
Definition: tcp_packet.h:167
Selective Ack block.
Definition: tcp_packet.h:109
#define TCP_MAX_WND_SCALE
Definition: tcp_packet.h:172
u32 flags
Definition: vhost_user.h:248
sll srl srl sll sra u16x4 i
Definition: vector_sse42.h:317
u16 mss
Maximum segment size advertised.
Definition: tcp_packet.h:147
#define tcp_syn(_th)
Definition: tcp_packet.h:80
u8 data[128]
Definition: ipsec_types.api:89
#define foreach_tcp_flag
Sender reduced congestion window.
Definition: tcp_packet.h:22
#define tcp_opts_wscale(_to)
Definition: tcp_packet.h:157
u32 tsval
Timestamp value.
Definition: tcp_packet.h:148
u32 tsecr
Echoed/reflected time stamp.
Definition: tcp_packet.h:149
#define TCP_OPTION_LEN_MSS
Definition: tcp_packet.h:164
Authentication Option.
Definition: tcp_packet.h:112
static int tcp_header_bytes(tcp_header_t *t)
Definition: tcp_packet.h:93
#define TCP_OPTION_LEN_NOOP
Definition: tcp_packet.h:163
f64 end
end of the time range
Definition: mactime.api:44
Window scale.
Definition: tcp_packet.h:107
#define tcp_opts_sack_permitted(_to)
Definition: tcp_packet.h:159
u16 dst_port
Definition: udp.api:42
Timestamps.
Definition: tcp_packet.h:110
tcp_option_type
Definition: tcp_packet.h:102