-move IPv4 header initialization to tun library

diff --git a/src/tun/tun.c b/src/tun/tun.c
new file mode 100644 (file)
index 0000000..97b7a73
--- /dev/null
+++ b/src/tun/tun.c
@@ -0,0 +1,69 @@
+/*
+     This file is part of GNUnet.
+     (C) 2010, 2011, 2012 Christian Grothoff
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet 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 GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file tun/tun.
+ * @brief standard IP calculations for TUN interaction
+ * @author Philipp Toelke
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "gnunet_tun_lib.h"
+
+/**
+ * IP TTL we use for packets that we assemble (8 bit unsigned integer)
+ */
+#define FRESH_TTL 255
+
+/**
+ * Initialize an IPv4 header.
+ *
+ * @param ip header to initialize
+ * @param protocol protocol to use (i.e. IPPROTO_UDP)
+ * @param payload_length number of bytes of payload that follow (excluding IPv4 header)
+ * @param src source IP address to use
+ * @param dst destination IP address to use
+ */
+void
+GNUNET_TUN_initialize_ipv4_header (struct GNUNET_TUN_IPv4Header *ip,
+                                  uint8_t protocol,
+                                  uint16_t payload_length,
+                                  const struct in_addr *src,
+                                  const struct in_addr *dst)
+{
+  ip->header_length =  sizeof (struct GNUNET_TUN_IPv4Header) / 4;
+  ip->version = 4;
+  ip->diff_serv = 0;
+  ip->total_length = htons (sizeof (struct GNUNET_TUN_IPv4Header) + payload_length);
+  ip->identification = (uint16_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, 
+                                                           65536);
+  ip->flags = 0;
+  ip->fragmentation_offset = 0;
+  ip->ttl = FRESH_TTL;
+  ip->protocol = protocol;
+  ip->checksum = 0;
+  ip->source_address = *src;
+  ip->destination_address = *dst;
+  ip->checksum = GNUNET_CRYPTO_crc16_n (ip, sizeof (struct GNUNET_TUN_IPv4Header));
+}
+
+
+
+/* end of tun.c */