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Diffstat (limited to 'src/vnet/ip/ip_sas.c')
| -rw-r--r-- | src/vnet/ip/ip_sas.c | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/src/vnet/ip/ip_sas.c b/src/vnet/ip/ip_sas.c new file mode 100644 index 00000000000..0fc261724f1 --- /dev/null +++ b/src/vnet/ip/ip_sas.c @@ -0,0 +1,219 @@ +/* + * 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)) + { + const ip6_address_t *ll = ip6_get_link_local_address (sw_if_index); + if (NULL == ll) + { + return false; + } + ip6_address_copy (src, ll); + 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); +} |