BCC macro for the creation of LPM trie maps (#1359)

LPM trie maps require the BPF_F_NO_PREALLOC flag on creation. The
need for this flag is not obvious at first; this new macro should
help avoid the mistake.

docs/reference_guide.md

@@ -34,14 +34,15 @@ This guide is incomplete. If something feels missing, check the bcc and kernel s
         - [5. BPF_STACK_TRACE](#5-bpf_stack_trace)
         - [6. BPF_PERF_ARRAY](#6-bpf_perf_array)
         - [7. BPF_PERCPU_ARRAY](#7-bpf_percpu_array)
-        - [8. map.lookup()](#8-maplookup)
-        - [9. map.lookup_or_init()](#9-maplookup_or_init)
-        - [10. map.delete()](#10-mapdelete)
-        - [11. map.update()](#11-mapupdate)
-        - [12. map.insert()](#12-mapinsert)
-        - [13. map.increment()](#13-mapincrement)
-        - [14. map.get_stackid()](#14-mapget_stackid)
-        - [15. map.perf_read()](#15-mapperf_read)
+        - [8. BPF_LPM_TRIE](#8-bpf_lpm_trie)
+        - [9. map.lookup()](#9-maplookup)
+        - [10. map.lookup_or_init()](#10-maplookup_or_init)
+        - [11. map.delete()](#11-mapdelete)
+        - [12. map.update()](#12-mapupdate)
+        - [13. map.insert()](#13-mapinsert)
+        - [14. map.increment()](#14-mapincrement)
+        - [15. map.get_stackid()](#15-mapget_stackid)
+        - [16. map.perf_read()](#16-mapperf_read)
 
 - [bcc Python](#bcc-python)
     - [Initialization](#initialization)
@@ -532,7 +533,29 @@ Examples in situ:
 [search /examples](https://github.com/iovisor/bcc/search?q=BPF_PERCPU_ARRAY+path%3Aexamples&type=Code),
 [search /tools](https://github.com/iovisor/bcc/search?q=BPF_PERCPU_ARRAY+path%3Atools&type=Code)
 
-### 8. map.lookup()
+### 8. BPF_LPM_TRIE
+
+Syntax: `BPF_LPM_TRIE(name [, key_type [, leaf_type [, size]]])`
+
+Creates a longest prefix match trie map named `name`, with optional parameters.
+
+Defaults: `BPF_LPM_TRIE(name, key_type=u64, leaf_type=u64, size=10240)`
+
+For example:
+
+```c
+BPF_LPM_TRIE(trie, struct key_v6);
+```
+
+This creates an LPM trie map named `trie` where the key is a `struct key_v6`, and the value defaults to u64.
+
+Methods (covered later): map.lookup(), map.lookup_or_init(), map.delete(), map.update(), map.insert(), map.increment().
+
+Examples in situ:
+[search /examples](https://github.com/iovisor/bcc/search?q=BPF_LPM_TRIE+path%3Aexamples&type=Code),
+[search /tools](https://github.com/iovisor/bcc/search?q=BPF_LPM_TRIE+path%3Atools&type=Code)
+
+### 9. map.lookup()
 
 Syntax: ```*val map.lookup(&key)```
 
@@ -542,7 +565,7 @@ Examples in situ:
 [search /examples](https://github.com/iovisor/bcc/search?q=lookup+path%3Aexamples&type=Code),
 [search /tools](https://github.com/iovisor/bcc/search?q=lookup+path%3Atools&type=Code)
 
-### 9. map.lookup_or_init()
+### 10. map.lookup_or_init()
 
 Syntax: ```*val map.lookup_or_init(&key, &zero)```
 
@@ -552,7 +575,7 @@ Examples in situ:
 [search /examples](https://github.com/iovisor/bcc/search?q=lookup_or_init+path%3Aexamples&type=Code),
 [search /tools](https://github.com/iovisor/bcc/search?q=lookup_or_init+path%3Atools&type=Code)
 
-### 10. map.delete()
+### 11. map.delete()
 
 Syntax: ```map.delete(&key)```
 
@@ -562,7 +585,7 @@ Examples in situ:
 [search /examples](https://github.com/iovisor/bcc/search?q=delete+path%3Aexamples&type=Code),
 [search /tools](https://github.com/iovisor/bcc/search?q=delete+path%3Atools&type=Code)
 
-### 11. map.update()
+### 12. map.update()
 
 Syntax: ```map.update(&key, &val)```
 
@@ -572,7 +595,7 @@ Examples in situ:
 [search /examples](https://github.com/iovisor/bcc/search?q=update+path%3Aexamples&type=Code),
 [search /tools](https://github.com/iovisor/bcc/search?q=update+path%3Atools&type=Code)
 
-### 12. map.insert()
+### 13. map.insert()
 
 Syntax: ```map.insert(&key, &val)```
 
@@ -581,7 +604,7 @@ Associate the value in the second argument to the key, only if there was no prev
 Examples in situ:
 [search /examples](https://github.com/iovisor/bcc/search?q=insert+path%3Aexamples&type=Code)
 
-### 13. map.increment()
+### 14. map.increment()
 
 Syntax: ```map.increment(key)```
 
@@ -591,7 +614,7 @@ Examples in situ:
 [search /examples](https://github.com/iovisor/bcc/search?q=increment+path%3Aexamples&type=Code),
 [search /tools](https://github.com/iovisor/bcc/search?q=increment+path%3Atools&type=Code)
 
-### 14. map.get_stackid()
+### 15. map.get_stackid()
 
 Syntax: ```int map.get_stackid(void *ctx, u64 flags)```
 
@@ -601,7 +624,7 @@ Examples in situ:
 [search /examples](https://github.com/iovisor/bcc/search?q=get_stackid+path%3Aexamples&type=Code),
 [search /tools](https://github.com/iovisor/bcc/search?q=get_stackid+path%3Atools&type=Code)
 
-### 15. map.perf_read()
+### 16. map.perf_read()
 
 Syntax: ```u64 map.perf_read(u32 cpu)```
 

src/cc/export/helpers.h

@@ -163,6 +163,21 @@ struct _name##_table_t _name = { .max_entries = (_max_entries) }
 #define BPF_HISTOGRAM(...) \
   BPF_HISTX(__VA_ARGS__, BPF_HIST3, BPF_HIST2, BPF_HIST1)(__VA_ARGS__)
 
+#define BPF_LPM_TRIE1(_name) \
+  BPF_F_TABLE("lpm_trie", u64, u64, _name, 10240, BPF_F_NO_PREALLOC)
+#define BPF_LPM_TRIE2(_name, _key_type) \
+  BPF_F_TABLE("lpm_trie", _key_type, u64, _name, 10240, BPF_F_NO_PREALLOC)
+#define BPF_LPM_TRIE3(_name, _key_type, _leaf_type) \
+  BPF_F_TABLE("lpm_trie", _key_type, _leaf_type, _name, 10240, BPF_F_NO_PREALLOC)
+#define BPF_LPM_TRIE4(_name, _key_type, _leaf_type, _size) \
+  BPF_F_TABLE("lpm_trie", _key_type, _leaf_type, _name, _size, BPF_F_NO_PREALLOC)
+#define BPF_LPM_TRIEX(_1, _2, _3, _4, NAME, ...) NAME
+
+// Define a LPM trie function, some arguments optional
+// BPF_LPM_TRIE(name, key_type=u64, leaf_type=u64, size=10240)
+#define BPF_LPM_TRIE(...) \
+  BPF_LPM_TRIEX(__VA_ARGS__, BPF_LPM_TRIE4, BPF_LPM_TRIE3, BPF_LPM_TRIE2, BPF_LPM_TRIE1)(__VA_ARGS__)
+
 struct bpf_stacktrace {
   u64 ip[BPF_MAX_STACK_DEPTH];
 };

tests/python/test_lpm_trie.py

@@ -18,7 +18,7 @@ class KeyV6(ct.Structure):
 class TestLpmTrie(unittest.TestCase):
     def test_lpm_trie_v4(self):
         test_prog1 = """
-        BPF_F_TABLE("lpm_trie", u64, int, trie, 16, BPF_F_NO_PREALLOC);
+        BPF_LPM_TRIE(trie, u64, int, 16);
         """
         b = BPF(text=test_prog1)
         t = b["trie"]
@@ -47,7 +47,7 @@ class TestLpmTrie(unittest.TestCase):
             u32 prefixlen;
             u32 data[4];
         };
-        BPF_F_TABLE("lpm_trie", struct key_v6, int, trie, 16, BPF_F_NO_PREALLOC);
+        BPF_LPM_TRIE(trie, struct key_v6, int, 16);
         """
         b = BPF(text=test_prog1)
         t = b["trie"]