From 96ce3c9e052b27c2b5f85320dff5f0cc52defa9a Mon Sep 17 00:00:00 2001
From: Fufu Fang <fangfufu2003@gmail.com>
Date: Sun, 8 Aug 2021 23:39:03 +0100
Subject: [PATCH] Use libvdeplug.h instead of libvdeplug_dyn.h

Fix https://github.com/gsliepen/tinc/issues/300

The libvdeplug.h from Debian Unstable is almost identical to the
one from Debian Buster. My making this change, the task of linking
the libvdeplug library is passed to the system dynamic linker at
tincd start time, instead of doing it manually with
libvdeplug_dynopen when vde functionality is actually needed.

This fixes the compilation issue in Ubuntu 21.04 and Debian
Unstable.
---
 configure.ac     |  8 ++++++--
 src/vde_device.c | 36 ++++++++++++++++++------------------
 2 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/configure.ac b/configure.ac
index 944e63a0..db7d1aa2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -90,8 +90,12 @@ AC_ARG_ENABLE(uml,
 AC_ARG_ENABLE(vde,
   AS_HELP_STRING([--enable-vde], [enable support for Virtual Distributed Ethernet]),
   [ AS_IF([test "x$enable_vde" = "xyes"],
-      [ AC_CHECK_HEADERS(libvdeplug_dyn.h, [], [AC_MSG_ERROR([VDE plug header files not found.]); break])
-        AC_CHECK_LIB(dl, dlopen, [LIBS="$LIBS -ldl"], [AC_MSG_ERROR([VDE plug depends on libdl.]); break])
+      [ AC_CHECK_HEADERS(libvdeplug.h,
+        [AC_CHECK_LIB(vdeplug, vde_close,
+                      [LIBS="$LIBS -lvdeplug"],
+                      [AC_MSG_ERROR("VDE plug library files not found.")]
+        )],
+        [AC_MSG_ERROR([VDE plug header files not found.]); break])
         AC_DEFINE(ENABLE_VDE, 1, [Support for VDE])
         vde=true
       ],
diff --git a/src/vde_device.c b/src/vde_device.c
index b5f0785e..f30c3e32 100644
--- a/src/vde_device.c
+++ b/src/vde_device.c
@@ -19,7 +19,7 @@
 
 #include "system.h"
 
-#include <libvdeplug_dyn.h>
+#include <libvdeplug.h>
 
 #include "conf.h"
 #include "device.h"
@@ -29,20 +29,12 @@
 #include "route.h"
 #include "xalloc.h"
 
-static struct vdepluglib plug;
 static struct vdeconn *conn = NULL;
 static int port = 0;
 static char *group = NULL;
 static const char *device_info = "VDE socket";
 
 static bool setup_device(void) {
-	libvdeplug_dynopen(plug);
-
-	if(!plug.dl_handle) {
-		logger(DEBUG_ALWAYS, LOG_ERR, "Could not open libvdeplug library!");
-		return false;
-	}
-
 	if(!get_config_string(lookup_config(config_tree, "Device"), &device)) {
 		xasprintf(&device, RUNSTATEDIR "/vde.ctl");
 	}
@@ -59,14 +51,14 @@ static bool setup_device(void) {
 		.mode = 0700,
 	};
 
-	conn = plug.vde_open(device, identname, &args);
+	conn = vde_open(device, identname, &args);
 
 	if(!conn) {
 		logger(DEBUG_ALWAYS, LOG_ERR, "Could not open VDE socket %s", device);
 		return false;
 	}
 
-	device_fd = plug.vde_datafd(conn);
+	device_fd = vde_datafd(conn);
 
 #ifdef FD_CLOEXEC
 	fcntl(device_fd, F_SETFD, FD_CLOEXEC);
@@ -83,14 +75,10 @@ static bool setup_device(void) {
 
 static void close_device(void) {
 	if(conn) {
-		plug.vde_close(conn);
+		vde_close(conn);
 		conn = NULL;
 	}
 
-	if(plug.dl_handle) {
-		libvdeplug_dynclose(plug);
-	}
-
 	free(device);
 	device = NULL;
 
@@ -101,7 +89,7 @@ static void close_device(void) {
 }
 
 static bool read_packet(vpn_packet_t *packet) {
-	ssize_t lenin = (ssize_t) plug.vde_recv(conn, DATA(packet), MTU, 0);
+	ssize_t lenin = vde_recv(conn, DATA(packet), MTU, 0);
 
 	if(lenin <= 0) {
 		logger(DEBUG_ALWAYS, LOG_ERR, "Error while reading from %s %s: %s", device_info, device, strerror(errno));
@@ -109,6 +97,18 @@ static bool read_packet(vpn_packet_t *packet) {
 		return false;
 	}
 
+	if(lenin == 1) {
+		logger(DEBUG_TRAFFIC, LOG_DEBUG,
+		       "Dropped a packet received from %s - the sender was not allowed to send that packet.", device_info);
+		return false;
+	}
+
+	if(lenin < 14) {
+		logger(DEBUG_TRAFFIC, LOG_DEBUG,
+		       "Received an invalid packet from %s - packet shorter than an ethernet header).", device_info);
+		return false;
+	}
+
 	packet->len = lenin;
 
 	logger(DEBUG_TRAFFIC, LOG_DEBUG, "Read packet of %d bytes from %s", packet->len, device_info);
@@ -117,7 +117,7 @@ static bool read_packet(vpn_packet_t *packet) {
 }
 
 static bool write_packet(vpn_packet_t *packet) {
-	if((ssize_t)plug.vde_send(conn, DATA(packet), packet->len, 0) < 0) {
+	if(vde_send(conn, DATA(packet), packet->len, 0) < 0) {
 		if(errno != EINTR && errno != EAGAIN) {
 			logger(DEBUG_ALWAYS, LOG_ERR, "Can't write to %s %s: %s", device_info, device, strerror(errno));
 			event_exit();
-- 
2.20.1