Merge pull request #158 from iovisor/bblanco_dev

Fix map.clear() usage for array type maps

src/cc/bpf_common.cc

@@ -122,6 +122,18 @@ int bpf_table_fd_id(void *program, size_t id) {
   return mod->table_fd(id);
 }
 
+int bpf_table_type(void *program, const char *table_name) {
+  auto mod = static_cast<ebpf::BPFModule *>(program);
+  if (!mod) return -1;
+  return mod->table_type(table_name);
+}
+
+int bpf_table_type_id(void *program, size_t id) {
+  auto mod = static_cast<ebpf::BPFModule *>(program);
+  if (!mod) return -1;
+  return mod->table_type(id);
+}
+
 const char * bpf_table_name(void *program, size_t id) {
   auto mod = static_cast<ebpf::BPFModule *>(program);
   if (!mod) return nullptr;

src/cc/bpf_common.h

@@ -40,6 +40,8 @@ size_t bpf_num_tables(void *program);
 size_t bpf_table_id(void *program, const char *table_name);
 int bpf_table_fd(void *program, const char *table_name);
 int bpf_table_fd_id(void *program, size_t id);
+int bpf_table_type(void *program, const char *table_name);
+int bpf_table_type_id(void *program, size_t id);
 const char * bpf_table_name(void *program, size_t id);
 const char * bpf_table_key_desc(void *program, const char *table_name);
 const char * bpf_table_key_desc_id(void *program, size_t id);

src/cc/bpf_module.cc

@@ -488,6 +488,15 @@ int BPFModule::table_fd(size_t id) const {
   return (*tables_)[id].fd;
 }
 
+int BPFModule::table_type(const string &name) const {
+  return table_type(table_id(name));
+}
+
+int BPFModule::table_type(size_t id) const {
+  if (id >= tables_->size()) return -1;
+  return (*tables_)[id].type;
+}
+
 const char * BPFModule::table_name(size_t id) const {
   if (id >= tables_->size()) return nullptr;
   return (*tables_)[id].name.c_str();

src/cc/bpf_module.h

@@ -68,6 +68,8 @@ class BPFModule {
   int table_fd(size_t id) const;
   int table_fd(const std::string &name) const;
   const char * table_name(size_t id) const;
+  int table_type(const std::string &name) const;
+  int table_type(size_t id) const;
   const char * table_key_desc(size_t id) const;
   const char * table_key_desc(const std::string &name) const;
   size_t table_key_size(size_t id) const;

src/cc/frontends/b/codegen_llvm.cc

@@ -1232,9 +1232,15 @@ StatusTuple CodegenLLVM::visit(Node* root, vector<TableDesc> &tables) {
   //TRY2(print_parser());
 
   for (auto table : tables_) {
+    bpf_map_type map_type = BPF_MAP_TYPE_UNSPEC;
+    if (table.first->type_id()->name_ == "FIXED_MATCH")
+      map_type = BPF_MAP_TYPE_HASH;
+    else if (table.first->type_id()->name_ == "INDEXED")
+      map_type = BPF_MAP_TYPE_ARRAY;
     tables.push_back({
       table.first->id_->name_,
       table_fds_[table.first],
+      map_type,
       table.first->key_type_->bit_width_ >> 3,
       table.first->leaf_type_->bit_width_ >> 3,
       table.first->size_,

src/cc/frontends/clang/b_frontend_action.cc

@@ -408,6 +408,7 @@ bool BTypeVisitor::VisitVarDecl(VarDecl *Decl) {
         return false;
       }
     }
+    table.type = map_type;
     table.fd = bpf_create_map(map_type, table.key_size, table.leaf_size, table.max_entries);
     if (table.fd < 0) {
       C.getDiagnostics().Report(Decl->getLocStart(), diag::err_expected)

src/cc/table_desc.h

@@ -26,6 +26,7 @@ namespace ebpf {
 struct TableDesc {
   std::string name;
   int fd;
+  int type;
   size_t key_size;  // sizes are in bytes
   size_t leaf_size;
   size_t max_entries;

src/python/bpf/__init__.py

@@ -44,6 +44,8 @@ lib.bpf_table_id.restype = ct.c_ulonglong
 lib.bpf_table_id.argtypes = [ct.c_void_p, ct.c_char_p]
 lib.bpf_table_fd.restype = ct.c_int
 lib.bpf_table_fd.argtypes = [ct.c_void_p, ct.c_char_p]
+lib.bpf_table_type_id.restype = ct.c_int
+lib.bpf_table_type_id.argtypes = [ct.c_void_p, ct.c_ulonglong]
 lib.bpf_table_key_desc.restype = ct.c_char_p
 lib.bpf_table_key_desc.argtypes = [ct.c_void_p, ct.c_char_p]
 lib.bpf_table_leaf_desc.restype = ct.c_char_p
@@ -103,6 +105,10 @@ class BPF(object):
     SCHED_CLS = 3
     SCHED_ACT = 4
 
+    HASH = 1
+    ARRAY = 2
+    PROG_ARRAY = 3
+
     class Function(object):
         def __init__(self, bpf, name, fd):
             self.bpf = bpf
@@ -116,6 +122,7 @@ class BPF(object):
             self.map_fd = map_fd
             self.Key = keytype
             self.Leaf = leaftype
+            self.ttype = lib.bpf_table_type_id(self.bpf.module, self.map_id)
 
         def key_sprintf(self, key):
             key_p = ct.pointer(key)
@@ -180,9 +187,33 @@ class BPF(object):
 
         def __delitem__(self, key):
             key_p = ct.pointer(key)
-            res = lib.bpf_delete_elem(self.map_fd, ct.cast(key_p, ct.c_void_p))
-            if res < 0:
-                raise KeyError
+            ttype = lib.bpf_table_type_id(self.bpf.module, self.map_id)
+            # Deleting from array type maps does not have an effect, so
+            # zero out the entry instead.
+            if ttype in (BPF.ARRAY, BPF.PROG_ARRAY):
+                leaf = self.Leaf()
+                leaf_p = ct.pointer(leaf)
+                res = lib.bpf_update_elem(self.map_fd,
+                        ct.cast(key_p, ct.c_void_p),
+                        ct.cast(leaf_p, ct.c_void_p), 0)
+                if res < 0:
+                    raise Exception("Could not clear item")
+            else:
+                res = lib.bpf_delete_elem(self.map_fd,
+                        ct.cast(key_p, ct.c_void_p))
+                if res < 0:
+                    raise KeyError
+
+        def clear(self):
+            if self.ttype in (BPF.ARRAY, BPF.PROG_ARRAY):
+                # Special case clear, since this class is currently behaving
+                # like a dict but popitem on an array causes an infinite loop.
+                # TODO: derive Table from array.array instead
+                for k in self.keys():
+                    self.__delitem__(k)
+            else:
+                super(BPF.Table, self).clear()
+
 
         def __iter__(self):
             return BPF.Table.Iter(self, self.Key)

tools/pidpersec

 #!/usr/bin/python
+# vim: ts=8 noet sw=8
 #
 # pidpersec	Count new processes (via fork).
 #		For Linux, uses BCC, eBPF. See .c file.
@@ -32,8 +33,8 @@ while (1):
 	try:
 		sleep(1)
 	except KeyboardInterrupt:
-		pass; exit()
+		exit()
 
 	print("%s: PIDs/sec: %d" % (strftime("%H:%M:%S"),
-	    (b["stats"][S_COUNT].value - last)))
-	last = b["stats"][S_COUNT].value
+	    (b["stats"][S_COUNT].value)))
+	b["stats"].clear()