1 files changed, 242 insertions, 0 deletions
diff --git a/src/tools/kernel.c b/src/tools/kernel.c
new file mode 100644
index 0000000..0448308
--- /dev/null
+++ b/src/tools/kernel.c
@@ -0,0 +1,242 @@
+/* Copyright 2015-2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
+
+#include <errno.h>
+#include <libmnl/libmnl.h>
+#include <linux/if_link.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <netinet/in.h>
+#include <net/if.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <time.h>
+
+#include "kernel.h"
+#include "../uapi.h"
+
+struct inflatable_buffer {
+	char *buffer;
+	char *next;
+	bool good;
+	size_t len;
+	size_t pos;
+};
+
+#define max(a, b) (a > b ? a : b)
+
+static int add_next_to_inflatable_buffer(struct inflatable_buffer *buffer)
+{
+	size_t len, expand_to;
+	char *new_buffer;
+
+	if (!buffer->good || !buffer->next) {
+		free(buffer->next);
+		return 0;
+	}
+
+	len = strlen(buffer->next) + 1;
+
+	if (len == 1)
+		return 0;
+
+	if (buffer->len - buffer->pos <= len) {
+		expand_to = max(buffer->len * 2, buffer->len + len + 1);
+		new_buffer = realloc(buffer->buffer, expand_to);
+		if (!new_buffer) {
+			free(buffer->next);
+			return -errno;
+		}
+		memset(&new_buffer[buffer->len], 0, expand_to - buffer->len);
+		buffer->buffer = new_buffer;
+		buffer->len = expand_to;
+	}
+	memcpy(&buffer->buffer[buffer->pos], buffer->next, len);
+	free(buffer->next);
+	buffer->pos += len;
+	return 0;
+}
+
+static int parse_linkinfo(const struct nlattr *attr, void *data)
+{
+	struct inflatable_buffer *buffer = data;
+	if (mnl_attr_get_type(attr) == IFLA_INFO_KIND && !strcmp("wireguard", mnl_attr_get_str(attr)))
+		buffer->good = true;
+	return MNL_CB_OK;
+}
+
+static int parse_infomsg(const struct nlattr *attr, void *data)
+{
+	struct inflatable_buffer *buffer = data;
+	if (mnl_attr_get_type(attr) == IFLA_LINKINFO)
+		return mnl_attr_parse_nested(attr, parse_linkinfo, data);
+	else if (mnl_attr_get_type(attr) == IFLA_IFNAME)
+		buffer->next = strdup(mnl_attr_get_str(attr));
+	return MNL_CB_OK;
+}
+
+static int read_devices_cb(const struct nlmsghdr *nlh, void *data)
+{
+	struct inflatable_buffer *buffer = data;
+	buffer->good = false;
+	buffer->next = NULL;
+	int ret = mnl_attr_parse(nlh, sizeof(struct ifinfomsg), parse_infomsg, data);
+	if (ret != MNL_CB_OK)
+		return ret;
+	ret = add_next_to_inflatable_buffer(buffer);
+	if (ret < 0)
+		return ret;
+	if (nlh->nlmsg_type != NLMSG_DONE)
+		return MNL_CB_OK + 1;
+	return MNL_CB_OK;
+}
+
+/* first\0second\0third\0forth\0last\0\0 */
+char *kernel_get_wireguard_interfaces(void)
+{
+	struct mnl_socket *nl = NULL;
+	char *rtnl_buffer = NULL;
+	size_t message_len;
+	unsigned int portid, seq;
+	ssize_t len;
+	int ret = 0;
+	struct inflatable_buffer buffer = { 0 };
+	struct nlmsghdr *nlh;
+	struct ifinfomsg *ifm;
+
+	buffer.len = 4096;
+	buffer.buffer = calloc(buffer.len, 1);
+	if (!buffer.buffer) {
+		ret = -errno;
+		goto cleanup;
+	}
+
+	rtnl_buffer = calloc(4096, 1);
+	if (!rtnl_buffer) {
+		ret = -errno;
+		goto cleanup;
+	}
+
+	nl = mnl_socket_open(NETLINK_ROUTE);
+	if (!nl) {
+		ret = -errno;
+		goto cleanup;
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		ret = -errno;
+		goto cleanup;
+	}
+
+	seq = time(NULL);
+	portid = mnl_socket_get_portid(nl);
+	nlh = mnl_nlmsg_put_header(rtnl_buffer);
+	nlh->nlmsg_type = RTM_GETLINK;
+	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP;
+	nlh->nlmsg_seq = seq;
+	ifm = mnl_nlmsg_put_extra_header(nlh, sizeof(*ifm));
+	ifm->ifi_family = AF_UNSPEC;
+	message_len = nlh->nlmsg_len;
+
+	if (mnl_socket_sendto(nl, rtnl_buffer, message_len) < 0) {
+		ret = -errno;
+		goto cleanup;
+	}
+
+another:
+	if ((len = mnl_socket_recvfrom(nl, rtnl_buffer, 4096)) < 0) {
+		ret = -errno;
+		goto cleanup;
+	}
+	if ((len = mnl_cb_run(rtnl_buffer, len, seq, portid, read_devices_cb, &buffer)) < 0) {
+		ret = -errno;
+		goto cleanup;
+	}
+	if (len == MNL_CB_OK + 1)
+		goto another;
+
+cleanup:
+	free(rtnl_buffer);
+	if (nl)
+		mnl_socket_close(nl);
+	errno = -ret;
+	if (errno) {
+		perror("Error when trying to get a list of Wireguard interfaces");
+		free(buffer.buffer);
+		return NULL;
+	}
+	return buffer.buffer;
+}
+
+bool kernel_has_wireguard_interface(const char *interface)
+{
+	char *interfaces, *this_interface;
+	this_interface = interfaces = kernel_get_wireguard_interfaces();
+	if (!interfaces)
+		return false;
+	for (size_t len = 0; (len = strlen(this_interface)); this_interface += len + 1) {
+		if (!strcmp(interface, this_interface)) {
+			free(interfaces);
+			return true;
+		}
+	}
+	free(interfaces);
+	return false;
+}
+
+static int do_ioctl(int req, struct ifreq *ifreq)
+{
+	static int fd = -1;
+	if (fd < 0) {
+		fd = socket(AF_INET, SOCK_DGRAM, 0);
+		if (fd < 0)
+			return fd;
+	}
+	return ioctl(fd, req, ifreq);
+}
+
+int kernel_set_device(struct wgdevice *dev)
+{
+	struct ifreq ifreq = { .ifr_data = (char *)dev };
+	memcpy(&ifreq.ifr_name, dev->interface, IFNAMSIZ);
+	ifreq.ifr_name[IFNAMSIZ - 1] = 0;
+	return do_ioctl(WG_SET_DEVICE, &ifreq);
+}
+
+int kernel_get_device(struct wgdevice **dev, const char *interface)
+{
+	int ret;
+	struct ifreq ifreq = { 0 };
+	memcpy(&ifreq.ifr_name, interface, IFNAMSIZ);
+	ifreq.ifr_name[IFNAMSIZ - 1] = 0;
+	*dev = NULL;
+	do {
+		free(*dev);
+		ret = do_ioctl(WG_GET_DEVICE, &ifreq);
+		if (ret < 0)
+			goto out;
+		*dev = calloc(ret + sizeof(struct wgdevice), 1);
+		if (!*dev) {
+			perror("calloc");
+			ret = -ENOMEM;
+			goto out;
+		}
+		(*dev)->peers_size = ret;
+		ifreq.ifr_data = (char *)*dev;
+		memcpy(&ifreq.ifr_name, interface, IFNAMSIZ);
+		ifreq.ifr_name[IFNAMSIZ - 1] = 0;
+		ret = do_ioctl(WG_GET_DEVICE, &ifreq);
+	} while (ret == -EMSGSIZE);
+	if (ret < 0) {
+		free(*dev);
+		*dev = NULL;
+	}
+out:
+	errno = -ret;
+	return ret;
+}