tools: ynl: add sample for wireguard

Add a sample application for WireGuard, using the generated C library.

The main benefit of this is to exercise the generated library,
which might be useful for future selftests.

In order to support usage with a pre-YNL wireguard.h in /usr/include,
the former header guard is added to Makefile.deps as well.

Example:
  $ make -C tools/net/ynl/lib
  $ make -C tools/net/ynl/generated
  $ make -C tools/net/ynl/samples wireguard
  $ ./tools/net/ynl/samples/wireguard
  usage: ./tools/net/ynl/samples/wireguard <ifindex|ifname>
  $ sudo ./tools/net/ynl/samples/wireguard wg-test
  Interface 3: wg-test
      Peer 6adfb183a4a2c94a2f92dab5ade762a4788[...]:
          Data: rx: 42 / tx: 42 bytes
          Allowed IPs:
              0.0.0.0/0
              ::/0

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/tools/net/ynl/samples/wireguard.c b/tools/net/ynl/samples/wireguard.c
new file mode 100644
index 000000000000..43f3551eb101
--- /dev/null
+++ b/tools/net/ynl/samples/wireguard.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <arpa/inet.h>
+#include <string.h>
+#include <stdio.h>
+#include <errno.h>
+#include <ynl.h>
+
+#include "wireguard-user.h"
+
+static void print_allowed_ip(const struct wireguard_wgallowedip *aip)
+{
+	char addr_out[INET6_ADDRSTRLEN];
+
+	if (!inet_ntop(aip->family, aip->ipaddr, addr_out, sizeof(addr_out))) {
+		addr_out[0] = '?';
+		addr_out[1] = '\0';
+	}
+	printf("\t\t\t%s/%u\n", addr_out, aip->cidr_mask);
+}
+
+/* Only printing public key in this demo. For better key formatting,
+ * use the constant-time implementation as found in wireguard-tools.
+ */
+static void print_peer_header(const struct wireguard_wgpeer *peer)
+{
+	unsigned int i;
+	uint8_t *key = peer->public_key;
+	unsigned int len = peer->_len.public_key;
+
+	if (len != 32)
+		return;
+	printf("\tPeer ");
+	for (i = 0; i < len; i++)
+		printf("%02x", key[i]);
+	printf(":\n");
+}
+
+static void print_peer(const struct wireguard_wgpeer *peer)
+{
+	unsigned int i;
+
+	print_peer_header(peer);
+	printf("\t\tData: rx: %llu / tx: %llu bytes\n",
+	       peer->rx_bytes, peer->tx_bytes);
+	printf("\t\tAllowed IPs:\n");
+	for (i = 0; i < peer->_count.allowedips; i++)
+		print_allowed_ip(&peer->allowedips[i]);
+}
+
+static void build_request(struct wireguard_get_device_req *req, char *arg)
+{
+	char *endptr;
+	int ifindex;
+
+	ifindex = strtol(arg, &endptr, 0);
+	if (endptr != arg + strlen(arg) || errno != 0)
+		ifindex = 0;
+	if (ifindex > 0)
+		wireguard_get_device_req_set_ifindex(req, ifindex);
+	else
+		wireguard_get_device_req_set_ifname(req, arg);
+}
+
+int main(int argc, char **argv)
+{
+	struct wireguard_get_device_list *devs;
+	struct wireguard_get_device_req *req;
+	struct ynl_sock *ys;
+
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s <ifindex|ifname>\n", argv[0]);
+		return 1;
+	}
+
+	req = wireguard_get_device_req_alloc();
+	build_request(req, argv[1]);
+
+	ys = ynl_sock_create(&ynl_wireguard_family, NULL);
+	if (!ys)
+		return 2;
+
+	devs = wireguard_get_device_dump(ys, req);
+	if (!devs)
+		goto err_close;
+
+	ynl_dump_foreach(devs, d) {
+		unsigned int i;
+
+		printf("Interface %d: %s\n", d->ifindex, d->ifname);
+		for (i = 0; i < d->_count.peers; i++)
+			print_peer(&d->peers[i]);
+	}
+	wireguard_get_device_list_free(devs);
+	wireguard_get_device_req_free(req);
+	ynl_sock_destroy(ys);
+
+	return 0;
+
+err_close:
+	fprintf(stderr, "YNL (%d): %s\n", ys->err.code, ys->err.msg);
+	wireguard_get_device_req_free(req);
+	ynl_sock_destroy(ys);
+	return 3;
+}