net_buffer: prevent modules from messing with metadata too much

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@21211 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/kernel/network/stack/net_buffer.cpp

@@ -17,6 +17,7 @@
 #include <KernelExport.h>
 #include <util/AutoLock.h>
 
+#include <algorithm>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/uio.h>
@@ -1174,6 +1175,13 @@ count_iovecs(net_buffer *_buffer)
 }
 
 
+static void
+swap_addresses(net_buffer *buffer)
+{
+	std::swap(buffer->source, buffer->destination);
+}
+
+
 status_t
 init_net_buffers()
 {
@@ -1257,6 +1265,8 @@ net_buffer_module_info gNetBufferModule = {
 	get_iovecs,
 	count_iovecs,
 
+	swap_addresses,
+
 	dump_buffer,	// dump
 };