protocol: add udpgw_proto

protocol/udpgw_proto.h

@@ -0,0 +1,59 @@
+/**
+ * @file udpgw_proto.h
+ * @author Ambroz Bizjak <ambrop7@gmail.com>
+ * 
+ * @section LICENSE
+ * 
+ * This file is part of BadVPN.
+ * 
+ * BadVPN is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ * 
+ * BadVPN is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * 
+ * @section DESCRIPTION
+ * 
+ * Protocol for forwarding UDP over TCP. Messages should be carried with PacketProto.
+ */
+
+#ifndef BADVPN_PROTOCOL_UDPGW_PROTO_H
+#define BADVPN_PROTOCOL_UDPGW_PROTO_H
+
+#include <stdint.h>
+
+#include <misc/bsize.h>
+
+#define UDPGW_CLIENT_FLAG_KEEPALIVE (1 << 0)
+#define UDPGW_CLIENT_FLAG_REBIND (1 << 1)
+
+struct udpgw_header {
+    uint8_t flags;
+    uint16_t conid;
+    uint32_t addr_ip;
+    uint16_t addr_port;
+} __attribute__((packed));
+
+static int udpgw_compute_mtu (int dgram_mtu)
+{
+    bsize_t bs = bsize_add(
+        bsize_fromsize(sizeof(struct udpgw_header)),
+        bsize_fromint(dgram_mtu)
+    );
+    
+    int s;
+    if (!bsize_toint(bs, &s)) {
+        return -1;
+    }
+    
+    return s;
+}
+
+#endif