aboutsummaryrefslogtreecommitdiffstats
path: root/src/vnet/ip/ip_sas.c
blob: 7d3632d95ed22a81a860570704ded67aeca8f4fe (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
/*
 * Copyright (c) 2021 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "ip_sas.h"
#include <vppinfra/types.h>
#include <vnet/ip/ip_interface.h>
#include <vnet/fib/fib_table.h>
#include <vnet/ip/ip6_link.h>
#include <vppinfra/byte_order.h>

/*
 * This file implement source address selection for VPP applications
 * (e.g. ping, DNS, ICMP)
 * It does not yet implement full fledged RFC6724 SAS.
 * SAS assumes every IP enabled interface has an address. The algorithm will
 * not go and hunt for a suitable IP address on other interfaces than the
 * output interface or the specified preferred sw_if_index.
 * That means that an interface with just an IPv6 link-local address must also
 * be configured with an unnumbered configuration pointing to a numbered
 * interface.
 */

static int
ip6_sas_commonlen (const ip6_address_t *a1, const ip6_address_t *a2)
{
  u64 fa = clib_net_to_host_u64 (a1->as_u64[0]) ^
	   clib_net_to_host_u64 (a2->as_u64[0]);
  if (fa == 0)
    {
      u64 la = clib_net_to_host_u64 (a1->as_u64[1]) ^
	       clib_net_to_host_u64 (a2->as_u64[1]);
      if (la == 0)
	return 128;
      return 64 + __builtin_clzll (la);
    }
  else
    {
      return __builtin_clzll (fa);
    }
}

static int
ip4_sas_commonlen (const ip4_address_t *a1, const ip4_address_t *a2)
{
  u64 a =
    clib_net_to_host_u32 (a1->as_u32) ^ clib_net_to_host_u32 (a2->as_u32);
  if (a == 0)
    return 32;
  return __builtin_clz (a);
}

/*
 * walk all addresses on an interface:
 *  - prefer a source matching the scope of the destination address.
 *  - last resort pick the source address with the longest
 *    common prefix with destination
 * NOTE: This should at some point implement RFC6724.
 */
bool
ip6_sas_by_sw_if_index (u32 sw_if_index, const ip6_address_t *dst,
			ip6_address_t *src)
{
  ip_interface_address_t *ia = 0;
  ip_lookup_main_t *lm6 = &ip6_main.lookup_main;
  ip6_address_t *tmp, *bestsrc = 0;
  int bestlen = 0, l;

  if (ip6_address_is_link_local_unicast (dst) ||
      dst->as_u32[0] == clib_host_to_net_u32 (0xff020000))
    {
      ip6_address_copy (src, ip6_get_link_local_address (sw_if_index));
      return true;
    }

  foreach_ip_interface_address (
    lm6, ia, sw_if_index, 1, ({
      if (ia->flags & IP_INTERFACE_ADDRESS_FLAG_STALE)
	continue;
      tmp = ip_interface_address_get_address (lm6, ia);
      l = ip6_sas_commonlen (tmp, dst);
      if (l > bestlen || bestsrc == 0)
	{
	  bestsrc = tmp;
	  bestlen = l;
	}
    }));
  if (bestsrc)
    {
      ip6_address_copy (src, bestsrc);
      return true;
    }
  return false;
}

/*
 * walk all addresses on an interface and pick the source address with the
 * longest common prefix with destination.
 */
bool
ip4_sas_by_sw_if_index (u32 sw_if_index, const ip4_address_t *dst,
			ip4_address_t *src)
{
  ip_interface_address_t *ia = 0;
  ip_lookup_main_t *lm4 = &ip4_main.lookup_main;
  ip4_address_t *tmp, *bestsrc = 0;
  int bestlen = 0, l;

  foreach_ip_interface_address (
    lm4, ia, sw_if_index, 1, ({
      if (ia->flags & IP_INTERFACE_ADDRESS_FLAG_STALE)
	continue;
      tmp = ip_interface_address_get_address (lm4, ia);
      l = ip4_sas_commonlen (tmp, dst);
      if (l > bestlen || bestsrc == 0)
	{
	  bestsrc = tmp;
	  bestlen = l;
	}
    }));
  if (bestsrc)
    {
      src->as_u32 = bestsrc->as_u32;
      return true;
    }
  return false;
}

/*
 * table_id must be set. Default = 0.
 * sw_if_index is the interface to pick SA from otherwise ~0 will pick from
 * outbound interface.
 *
 * NOTE: What to do if multiple output interfaces?
 *
 */
bool
ip6_sas (u32 table_id, u32 sw_if_index, const ip6_address_t *dst,
	 ip6_address_t *src)
{
  fib_prefix_t prefix;
  u32 if_index = sw_if_index;

  /* If sw_if_index is not specified use the output interface. */
  if (sw_if_index == ~0)
    {
      clib_memcpy (&prefix.fp_addr.ip6, dst, sizeof (*dst));
      prefix.fp_proto = FIB_PROTOCOL_IP6;
      prefix.fp_len = 128;

      u32 fib_index = fib_table_find (prefix.fp_proto, table_id);
      if (fib_index == (u32) ~0)
	return false;

      fib_node_index_t fei = fib_table_lookup (fib_index, &prefix);
      if (fei == FIB_NODE_INDEX_INVALID)
	return false;

      u32 output_sw_if_index = fib_entry_get_resolving_interface (fei);
      if (output_sw_if_index == ~0)
	return false;
      if_index = output_sw_if_index;
    }
  return ip6_sas_by_sw_if_index (if_index, dst, src);
}

/*
 * table_id must be set. Default = 0.
 * sw_if_index is the interface to pick SA from otherwise ~0 will pick from
 * outbound interface.
 *
 * NOTE: What to do if multiple output interfaces?
 *
 */
bool
ip4_sas (u32 table_id, u32 sw_if_index, const ip4_address_t *dst,
	 ip4_address_t *src)
{
  fib_prefix_t prefix;
  u32 if_index = sw_if_index;

  /* If sw_if_index is not specified use the output interface. */
  if (sw_if_index == ~0)
    {
      clib_memcpy (&prefix.fp_addr.ip4, dst, sizeof (*dst));
      prefix.fp_proto = FIB_PROTOCOL_IP4;
      prefix.fp_len = 32;

      u32 fib_index = fib_table_find (prefix.fp_proto, table_id);
      if (fib_index == (u32) ~0)
	return false;

      fib_node_index_t fei = fib_table_lookup (fib_index, &prefix);
      if (fei == FIB_NODE_INDEX_INVALID)
	return false;

      u32 output_sw_if_index = fib_entry_get_resolving_interface (fei);
      if (output_sw_if_index == ~0)
	return false;
      if_index = output_sw_if_index;
    }
  return ip4_sas_by_sw_if_index (if_index, dst, src);
}