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Vector Packet Processing
nat_inlines.h
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1 /*
2  * Copyright (c) 2020 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 #include <vnet/tcp/tcp_packet.h>
17 #include <vnet/ip/ip4_packet.h>
18 
19 always_inline void
21 {
22  u8 *data;
23  u8 opt_len, opts_len, kind;
24  u16 mss;
25 
26  if (!(mss_clamping && tcp_syn (tcp)))
27  return;
28 
29  opts_len = (tcp_doff (tcp) << 2) - sizeof (tcp_header_t);
30  data = (u8 *) (tcp + 1);
31  for (; opts_len > 0; opts_len -= opt_len, data += opt_len)
32  {
33  kind = data[0];
34 
35  if (kind == TCP_OPTION_EOL)
36  break;
37  else if (kind == TCP_OPTION_NOOP)
38  {
39  opt_len = 1;
40  continue;
41  }
42  else
43  {
44  if (opts_len < 2)
45  return;
46  opt_len = data[1];
47 
48  if (opt_len < 2 || opt_len > opts_len)
49  return;
50  }
51 
52  if (kind == TCP_OPTION_MSS)
53  {
54  mss = *(u16 *) (data + 2);
55  if (clib_net_to_host_u16 (mss) > mss_clamping)
56  {
57  u16 mss_value_net = clib_host_to_net_u16(mss_clamping);
58  *sum =
59  ip_csum_update (*sum, mss, mss_value_net, ip4_header_t,
60  length);
61  clib_memcpy_fast (data + 2, &mss_value_net, 2);
62  }
63  return;
64  }
65  }
66 }
End of options.
Definition: tcp_packet.h:104
#define clib_memcpy_fast(a, b, c)
Definition: string.h:81
#define tcp_doff(_th)
Definition: tcp_packet.h:78
uword ip_csum_t
Definition: ip_packet.h:244
No operation.
Definition: tcp_packet.h:105
struct _tcp_header tcp_header_t
unsigned char u8
Definition: types.h:56
u8 data[128]
Definition: ipsec_types.api:89
Limit MSS.
Definition: tcp_packet.h:106
unsigned short u16
Definition: types.h:57
static void mss_clamping(u16 mss_clamping, tcp_header_t *tcp, ip_csum_t *sum)
Definition: nat_inlines.h:20
#define always_inline
Definition: ipsec.h:28
#define tcp_syn(_th)
Definition: tcp_packet.h:80
#define ip_csum_update(sum, old, new, type, field)
Definition: ip_packet.h:294