FIB: optimise for src memory allocations

Most FIB entries will only ever have one source providing forwarding
information. Currently the source infom is stored in a vector of sources
on the FIB entry. Change this to a union of one source inline and a vector.
This saves the need to alloc a vector of sources for each FIB entry.

before:
vpp# ip route add count 1500000 1.0.0.1/32 via 10.10.10.2 loop0
4.392857e5 routes/sec
vpp# ip route del count 1500000 1.0.0.1/32 via 10.10.10.2 loop0
9.175464e5 routes/sec
vpp# ip route add count 1500000 1.0.0.1/32 via 10.10.10.2 loop0
5.193375e5 routes/sec
vpp# sh fib mem
FIB memory
             Name               Size  in-use /allocated   totals
             Entry               72   1500011/ 1500011    108000792/108000792
         Entry Source            32   1500011/ 1500011    48000352/48000352

after:
vpp# ip route add count 1500000 1.0.0.1/32 via 10.10.10.2 loop0
4.726560e5 routes/sec
vpp# ip route del count 1500000 1.0.0.1/32 via 10.10.10.2 loop0
1.041629e6 routes/sec
vpp# ip route add count 1500000 1.0.0.1/32 via 10.10.10.2 loop0
5.702895e5 routes/sec
vpp# sh fib mem
FIB memory
             Name               Size  in-use /allocated   totals
             Entry               96   1500011/ 1500011    144001056/144001056
         Entry Source            32      0   /    0       0/0

Change-Id: Ic71e413eaff1ec152656beda3b94186f7894ea49
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/fib/fib_entry_src.h b/src/vnet/fib/fib_entry_src.h
index 35c4393..a19fae1 100644
--- a/src/vnet/fib/fib_entry_src.h
+++ b/src/vnet/fib/fib_entry_src.h
@@ -105,15 +105,6 @@
     const fib_entry_t *fib_entry);
 
 /**
- * Forwarding updated. Notification that the forwarding information for the
- * entry has been updated. This notification is sent to all sources, not just
- * the active best.
- */
-typedef void (*fib_entry_src_fwd_update_t)(fib_entry_src_t *src,
-					   const fib_entry_t *fib_entry,
-					   fib_source_t best_source);
-
-/**
  * Installed. Notification that the source is now installed as
  * the entry's forwarding source.
  */
@@ -182,22 +173,56 @@
     fib_entry_src_cover_update_t fesv_cover_update;
     fib_entry_src_format_t fesv_format;
     fib_entry_src_installed_t fesv_installed;
-    fib_entry_src_fwd_update_t fesv_fwd_update;
     fib_entry_src_get_data_t fesv_get_data;
     fib_entry_src_set_data_t fesv_set_data;
 } fib_entry_src_vft_t;
 
-#define FOR_EACH_SRC_ADDED(_entry, _src, _source, action)	\
-{								\
-    vec_foreach(_src, _entry->fe_srcs)				\
-    {								\
-	if (_src->fes_flags & FIB_ENTRY_SRC_FLAG_ADDED) {	\
-	    _source = _src->fes_src;				\
-	    do {						\
-		action;						\
-	    } while(0);						\
-	}							\
-    }								\
+#define FOR_EACH_SRC_ADDED(_entry, _src, _source, action)        \
+{                                                                \
+    if (fib_entry_has_multiple_srcs(_entry))                     \
+    {                                                            \
+        vec_foreach(_src, _entry->fe_u_src.fe_srcs)              \
+        {                                                        \
+            if (_src->fes_flags & FIB_ENTRY_SRC_FLAG_ADDED) {    \
+                _source = _src->fes_src;                         \
+                do {                                             \
+                    action;                                      \
+                } while(0);                                      \
+            }                                                    \
+        }                                                        \
+    }                                                            \
+    else                                                         \
+    {                                                            \
+        _src = &_entry->fe_u_src.fe_src;                         \
+        if (_src->fes_flags & FIB_ENTRY_SRC_FLAG_ADDED) {        \
+            _source = _src->fes_src;                             \
+            do {                                                 \
+                action;                                          \
+            } while(0);                                          \
+        }                                                        \
+    }                                                            \
+}
+
+#define FOR_EACH_SRC(_entry, _src, _source, action)              \
+{                                                                \
+    if (fib_entry_has_multiple_srcs(_entry))                     \
+    {                                                            \
+        vec_foreach(_src, _entry->fe_u_src.fe_srcs)              \
+        {                                                        \
+            _source = _src->fes_src;                             \
+            do {                                                 \
+                action;                                          \
+            } while(0);                                          \
+        }                                                        \
+    }                                                            \
+    else                                                         \
+    {                                                            \
+        _src = &_entry->fe_u_src.fe_src;                         \
+        _source = _src->fes_src;                                 \
+        do {                                                     \
+            action;                                              \
+        } while(0);                                              \
+    }                                                            \
 }
 
 extern u8* fib_entry_src_format(fib_entry_t *entry,
@@ -260,7 +285,7 @@
 							     fib_source_t source,
 							     const fib_route_path_t *path);
 
-extern void fib_entry_src_action_installed(const fib_entry_t *fib_entry,
+extern void fib_entry_src_action_installed(fib_entry_t *fib_entry,
 					   fib_source_t source);
 
 extern fib_forward_chain_type_t fib_entry_get_default_chain_type(
@@ -279,6 +304,7 @@
 
 extern fib_protocol_t fib_entry_get_proto(const fib_entry_t * fib_entry);
 extern dpo_proto_t fib_entry_get_dpo_proto(const fib_entry_t * fib_entry);
+extern u32 fib_entry_has_multiple_srcs(const fib_entry_t * fib_entry);
 
 /*
  * Per-source registration. declared here so we save a separate .h file for each