new(scap): introduce linux hostinfo platform

This is a minimal Linux platformm intended to be useful with source
plugins that do not handle syscall data but still want access to some
info about the machine they're running on. Currently collected data
includes:
- machine info
- agent info
- interface list

Signed-off-by: Grzegorz Nosek <[email protected]>

userspace/libscap/linux/CMakeLists.txt

@@ -14,7 +14,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-add_library(scap_platform STATIC scap_linux_platform.c scap_procs.c scap_fds.c scap_userlist.c scap_iflist.c scap_cgroup.c scap_machine_info.c)
+add_library(scap_platform
+	STATIC
+	scap_linux_platform.c
+	scap_linux_hostinfo_platform.c
+	scap_procs.c
+	scap_fds.c
+	scap_userlist.c
+	scap_iflist.c
+	scap_cgroup.c
+	scap_machine_info.c)
 target_include_directories(scap_platform PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>)
 target_link_libraries(scap_platform PRIVATE scap_error scap_platform_util)
 add_dependencies(scap_platform uthash)

userspace/libscap/linux/scap_linux_hostinfo_platform.c

@@ -0,0 +1,73 @@
+/*
+Copyright (C) 2024 The Falco Authors.
+
+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 <libscap/linux/scap_linux_platform.h>
+
+#include <libscap/scap.h>
+#include <libscap/scap-int.h>
+#include <libscap/scap_machine_info.h>
+#include <libscap/linux/scap_linux_int.h>
+
+#include <stdlib.h>
+#include <unistd.h>
+
+static void scap_linux_hostinfo_free_platform(struct scap_platform* platform)
+{
+	free(platform);
+}
+
+int32_t scap_linux_hostinfo_init_platform(struct scap_platform* platform, char* lasterr, struct scap_engine_handle engine, struct scap_open_args* oargs)
+{
+	int rc;
+
+	if(scap_os_get_machine_info(&platform->m_machine_info, lasterr) != SCAP_SUCCESS)
+	{
+		return SCAP_FAILURE;
+	}
+
+	scap_os_get_agent_info(&platform->m_agent_info);
+
+	rc = scap_linux_create_iflist(platform);
+	if(rc != SCAP_SUCCESS)
+	{
+		scap_linux_hostinfo_free_platform(platform);
+		return rc;
+	}
+
+	return SCAP_SUCCESS;
+}
+
+static const struct scap_platform_vtable scap_linux_hostinfo_platform_vtable = {
+	.init_platform = scap_linux_hostinfo_init_platform,
+	.refresh_addr_list = scap_linux_create_iflist,
+	.free_platform = scap_linux_hostinfo_free_platform,
+};
+
+struct scap_platform* scap_linux_hostinfo_alloc_platform()
+{
+	struct scap_linux_platform* platform = calloc(1, sizeof(*platform));
+
+	if(platform == NULL)
+	{
+		return NULL;
+	}
+
+	struct scap_platform* generic = &platform->m_generic;
+	generic->m_vtable = &scap_linux_hostinfo_platform_vtable;
+
+	return generic;
+}

userspace/libscap/linux/scap_linux_platform.h

@@ -103,6 +103,22 @@ struct scap_linux_platform
 
 struct scap_platform* scap_linux_alloc_platform(proc_entry_callback proc_callback, void* proc_callback_context);
 
+/**
+ * @brief A lightweight Linux platform that only collects static host information
+ *
+ * This is useful with source plugins that do not handle syscall data but still want access
+ * to some info about the machine they're running on. Currently collected data includes:
+ * - machine info
+ * - agent info
+ * - interface list
+ */
+struct scap_linux_hostinfo_platform
+{
+	struct scap_platform m_generic;
+};
+
+struct scap_platform* scap_linux_hostinfo_alloc_platform();
+
 #ifdef __cplusplus
 };
 #endif

userspace/libscap/scap.c

@@ -35,12 +35,16 @@ limitations under the License.
 // The test_input and source_plugin engines can optionally use a linux_platform
 // but only on an actual Linux system.
 //
-// Still, to compile properly on non-Linux, provide an implementation
-// of scap_linux_alloc_platform() that always fails at runtime.
+// Still, to compile properly on non-Linux, provide implementations
+// of scap_linux_alloc_platform() and scap_linux_hostinfo_alloc_platform() that always fail at runtime.
 struct scap_platform* scap_linux_alloc_platform(proc_entry_callback proc_callback, void* proc_callback_context)
 {
 	return NULL;
 }
+struct scap_platform* scap_linux_hostinfo_alloc_platform()
+{
+	return NULL;
+}
 #endif
 
 const char* scap_getlasterr(scap_t* handle)