ipc: cache windows lookups to avoid O(n^2) with nested lookups

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

src/ipc-uapi-windows.h

@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <fcntl.h>
+#include <hashtable.h>
 
 static FILE *userspace_interface_file(const char *iface)
 {
@@ -113,6 +114,9 @@ err:
 	return NULL;
 }
 
+static bool have_cached_interfaces;
+static struct hashtable cached_interfaces;
+
 static bool userspace_has_wireguard_interface(const char *iface)
 {
 	char fname[MAX_PATH];
@@ -120,10 +124,13 @@ static bool userspace_has_wireguard_interface(const char *iface)
 	HANDLE find_handle;
 	bool ret = false;
 
+	if (have_cached_interfaces)
+		return hashtable_find_entry(&cached_interfaces, iface) != NULL;
+
 	snprintf(fname, sizeof(fname), "ProtectedPrefix\\Administrators\\WireGuard\\%s", iface);
 	find_handle = FindFirstFile("\\\\.\\pipe\\*", &find_data);
 	if (find_handle == INVALID_HANDLE_VALUE)
-		return -GetLastError();
+		return -EIO;
 	do {
 		if (!strcmp(fname, find_data.cFileName)) {
 			ret = true;
@@ -139,18 +146,25 @@ static int userspace_get_wireguard_interfaces(struct string_list *list)
 	static const char prefix[] = "ProtectedPrefix\\Administrators\\WireGuard\\";
 	WIN32_FIND_DATA find_data;
 	HANDLE find_handle;
+	char *iface;
 	int ret = 0;
 
 	find_handle = FindFirstFile("\\\\.\\pipe\\*", &find_data);
 	if (find_handle == INVALID_HANDLE_VALUE)
-		return -GetLastError();
+		return -EIO;
 	do {
 		if (strncmp(prefix, find_data.cFileName, strlen(prefix)))
 			continue;
-		ret = string_list_add(list, find_data.cFileName + strlen(prefix));
+		iface = find_data.cFileName + strlen(prefix);
+		ret = string_list_add(list, iface);
 		if (ret < 0)
 			goto out;
+		if (!hashtable_find_or_insert_entry(&cached_interfaces, iface)) {
+			ret = -errno;
+			goto out;
+		}
 	} while (FindNextFile(find_handle, &find_data));
+	have_cached_interfaces = true;
 
 out:
 	FindClose(find_handle);

src/ipc-windows.h

@@ -13,12 +13,17 @@
 #include <ddk/ndisguid.h>
 #include <nci.h>
 #include <wireguard.h>
+#include <hashtable.h>
 
 #define IPC_SUPPORTS_KERNEL_INTERFACE
 
+static bool have_cached_kernel_interfaces;
+static struct hashtable cached_kernel_interfaces;
+
 static int kernel_get_wireguard_interfaces(struct string_list *list)
 {
 	HDEVINFO dev_info = SetupDiGetClassDevsExW(&GUID_DEVCLASS_NET, NULL, NULL, DIGCF_PRESENT, NULL, NULL, NULL);
+	bool will_have_cached_kernel_interfaces = true;
 
 	if (dev_info == INVALID_HANDLE_VALUE) {
 		errno = EACCES;
@@ -33,6 +38,7 @@ static int kernel_get_wireguard_interfaces(struct string_list *list)
 		HKEY key;
 		GUID instance_id;
 		char *interface_name;
+		struct hashtable_entry *entry;
 
 		if (!SetupDiEnumDeviceInfo(dev_info, i, &dev_info_data)) {
 			if (GetLastError() == ERROR_NO_MORE_ITEMS)
@@ -105,7 +111,25 @@ static int kernel_get_wireguard_interfaces(struct string_list *list)
 		}
 
 		string_list_add(list, interface_name);
+
+		entry = hashtable_find_or_insert_entry(&cached_kernel_interfaces, interface_name);
 		free(interface_name);
+		if (!entry)
+			goto cleanup_entry;
+
+		if (SetupDiGetDeviceInstanceIdW(dev_info, &dev_info_data, NULL, 0, &buf_len) || GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+			goto cleanup_entry;
+		entry->value = calloc(sizeof(WCHAR), buf_len);
+		if (!entry->value)
+			goto cleanup_entry;
+		if (!SetupDiGetDeviceInstanceIdW(dev_info, &dev_info_data, entry->value, buf_len, &buf_len)) {
+			free(entry->value);
+			entry->value = NULL;
+			goto cleanup_entry;
+		}
+
+cleanup_entry:
+		will_have_cached_kernel_interfaces |= entry != NULL && entry->value != NULL;
 cleanup_buf:
 		free(buf);
 cleanup_key:
@@ -113,15 +137,48 @@ cleanup_key:
 skip:;
 	}
 	SetupDiDestroyDeviceInfoList(dev_info);
+	have_cached_kernel_interfaces = will_have_cached_kernel_interfaces;
 	return 0;
 }
 
 static HANDLE kernel_interface_handle(const char *iface)
 {
-	HDEVINFO dev_info = SetupDiGetClassDevsExW(&GUID_DEVCLASS_NET, NULL, NULL, DIGCF_PRESENT, NULL, NULL, NULL);
+	HDEVINFO dev_info;
 	WCHAR *interfaces = NULL;
 	HANDLE handle;
 
+	if (have_cached_kernel_interfaces) {
+		struct hashtable_entry *entry = hashtable_find_entry(&cached_kernel_interfaces, iface);
+		if (entry) {
+			DWORD buf_len;
+			if (CM_Get_Device_Interface_List_SizeW(
+				&buf_len, (GUID *)&GUID_DEVINTERFACE_NET, (DEVINSTID_W)entry->value,
+				CM_GET_DEVICE_INTERFACE_LIST_PRESENT) != CR_SUCCESS)
+				goto err_hash;
+			interfaces = calloc(buf_len, sizeof(*interfaces));
+			if (!interfaces)
+				goto err_hash;
+			if (CM_Get_Device_Interface_ListW(
+				(GUID *)&GUID_DEVINTERFACE_NET, (DEVINSTID_W)entry->value, interfaces, buf_len,
+				CM_GET_DEVICE_INTERFACE_LIST_PRESENT) != CR_SUCCESS || !interfaces[0]) {
+				free(interfaces);
+				interfaces = NULL;
+				goto err_hash;
+			}
+			handle = CreateFileW(interfaces, GENERIC_READ | GENERIC_WRITE,
+					     FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL,
+					     OPEN_EXISTING, 0, NULL);
+			free(interfaces);
+			if (handle == INVALID_HANDLE_VALUE)
+				goto err_hash;
+			return handle;
+err_hash:
+			errno = EACCES;
+			return NULL;
+		}
+	}
+
+	dev_info = SetupDiGetClassDevsExW(&GUID_DEVCLASS_NET, NULL, NULL, DIGCF_PRESENT, NULL, NULL, NULL);
 	if (dev_info == INVALID_HANDLE_VALUE)
 		return NULL;
 

src/wincompat/include/hashtable.h

@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2018-2021 WireGuard LLC. All Rights Reserved.
+ */
+
+#ifndef _HASHTABLE_H
+#define _HASHTABLE_H
+
+#include <string.h>
+
+enum { HASHTABLE_ENTRY_BUCKETS_POW2 = 1 << 10 };
+
+struct hashtable_entry {
+	char *key;
+	void *value;
+	struct hashtable_entry *next;
+};
+
+struct hashtable {
+	struct hashtable_entry *entry_buckets[HASHTABLE_ENTRY_BUCKETS_POW2];
+};
+
+static unsigned int hashtable_bucket(const char *str)
+{
+	unsigned long hash = 5381;
+	char c;
+	while ((c = *str++))
+		hash = ((hash << 5) + hash) ^ c;
+	return hash & (HASHTABLE_ENTRY_BUCKETS_POW2 - 1);
+}
+
+static struct hashtable_entry *hashtable_find_entry(struct hashtable *hashtable, const char *key)
+{
+	struct hashtable_entry *entry;
+	for (entry = hashtable->entry_buckets[hashtable_bucket(key)]; entry; entry = entry->next) {
+		if (!strcmp(entry->key, key))
+			return entry;
+	}
+	return NULL;
+}
+
+static struct hashtable_entry *hashtable_find_or_insert_entry(struct hashtable *hashtable, const char *key)
+{
+	struct hashtable_entry **entry;
+	for (entry = &hashtable->entry_buckets[hashtable_bucket(key)]; *entry; entry = &(*entry)->next) {
+		if (!strcmp((*entry)->key, key))
+			return *entry;
+	}
+	*entry = calloc(1, sizeof(**entry));
+	if (!*entry)
+		return NULL;
+	(*entry)->key = strdup(key);
+	if (!(*entry)->key) {
+		free(*entry);
+		*entry = NULL;
+		return NULL;
+	}
+	return *entry;
+}
+
+#endif