fib: Source Address Selection

Type: feature

Use the FIB to provide SAS (in so far as it is today)
 - Use the glean adjacency as the record of the connected prefixes
 = there's a glean per-{interface, protocol, connected-prefix}
 - Keep the glean up to date with whatever the recieve host prefix is
(since it can change)

Signed-off-by: Neale Ranns <neale.ranns@cisco.com>
Change-Id: I0f3dd1edb1f3fc965af1c7c586709028eb9cdeac

1 files changed, 121 insertions, 0 deletions

diff --git a/src/vnet/fib/fib_sas.c b/src/vnet/fib/fib_sas.c
new file mode 100644
index 00000000000..b607a0b5be8
--- /dev/null
+++ b/src/vnet/fib/fib_sas.c
@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2020 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.
+ */
+
+/**
+ * @brief FIB Source Address selection
+ *
+ * Use the FIB for source address selection on an interface
+ */
+
+#include <vnet/fib/fib_sas.h>
+#include <vnet/adj/adj_glean.h>
+#include <vnet/ip/ip6_link.h>
+
+
+bool
+fib_sas_get (u32 sw_if_index,
+             ip_address_family_t af,
+             const ip46_address_t *dst,
+             ip46_address_t *src)
+{
+    switch (af)
+    {
+    case AF_IP4:
+        if (dst)
+            return (fib_sas4_get(sw_if_index, &dst->ip4, &src->ip4));
+        else
+            return (fib_sas4_get(sw_if_index, NULL, &src->ip4));
+    case AF_IP6:
+        if (dst)
+            return (fib_sas6_get(sw_if_index, &dst->ip6, &src->ip6));
+        else
+            return (fib_sas6_get(sw_if_index, NULL, &src->ip6));
+    }
+    return (false);
+}
+
+bool
+fib_sas4_get (u32 sw_if_index,
+              const ip4_address_t *dst,
+              ip4_address_t *src)
+{
+    ip46_address_t d_tmp, *d_tmpp = NULL;
+    const ip46_address_t *s_tmp;
+    vnet_sw_interface_t *swif;
+
+    if (dst)
+    {
+        d_tmpp = &d_tmp;
+        d_tmp.ip4 = *dst;
+    }
+
+    /*
+     * If the interface is unnumbered then use the IP interface
+     */
+    swif = vnet_get_sw_interface (vnet_get_main(), sw_if_index);
+
+    if (swif->flags & VNET_SW_INTERFACE_FLAG_UNNUMBERED)
+        sw_if_index = swif->unnumbered_sw_if_index;
+
+    /*
+     * get the source address from the glean adjacency
+     */
+    s_tmp = adj_glean_get_src (FIB_PROTOCOL_IP4, sw_if_index, d_tmpp);
+
+    if (NULL != s_tmp)
+    {
+        src->as_u32 = s_tmp->ip4.as_u32;
+        return (true);
+    }
+
+    return (false);
+}
+
+bool
+fib_sas6_get (u32 sw_if_index,
+              const ip6_address_t *dst,
+              ip6_address_t *src)
+{
+    ip46_address_t d_tmp, *d_tmpp = NULL;
+    const ip46_address_t *s_tmp;
+
+    if (dst)
+    {
+        d_tmpp = &d_tmp;
+        d_tmp.ip6 = *dst;
+    }
+
+    /*
+     * if the dst is v6 and link local, use the source link local
+     */
+    if (ip6_address_is_link_local_unicast (dst))
+    {
+        ip6_address_copy (src, ip6_get_link_local_address (sw_if_index));
+        return (true);
+    }
+
+    /*
+     * get the source address from the glean adjacency
+     */
+    s_tmp = adj_glean_get_src (FIB_PROTOCOL_IP6, sw_if_index, d_tmpp);
+
+    if (NULL != s_tmp)
+    {
+        ip6_address_copy(src, &s_tmp->ip6);
+        return (true);
+    }
+
+    return (false);
+}