gnunet-android

gnunet_tun_lib.h (20785B)

---

 /*
      This file is part of GNUnet.
      Copyright (C) 2010-2013 Christian Grothoff
 
      GNUnet is free software: you can redistribute it and/or modify it
      under the terms of the GNU Affero General Public License as published
      by the Free Software Foundation, either version 3 of the License,
      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
      Affero General Public License for more details.
 
      You should have received a copy of the GNU Affero General Public License
      along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
      SPDX-License-Identifier: AGPL3.0-or-later
  */
 
 #if ! defined (__GNUNET_UTIL_LIB_H_INSIDE__)
 #error "Only <gnunet_util_lib.h> can be included directly."
 #endif
 
 /**
  * @addtogroup vpn_suite  VPN services and libraries
  * @{
  *
  * @author Philipp Toelke
  * @author Christian Grothoff
  *
  * @file
  * Standard TCP/IP network structs and IP checksum calculations for TUN
  * interaction
  *
  * @defgroup tun  TUN library
  * Standard TCP/IP network structs and IP checksum calculations for TUN
  * interaction
  * @{
  */
 #ifndef GNUNET_TUN_LIB_H
 #define GNUNET_TUN_LIB_H
 
 
 /* see http://www.iana.org/assignments/ethernet-numbers */
 #ifndef ETH_P_IPV4
 /**
  * Number for IPv4
  */
 #define ETH_P_IPV4 0x0800
 #endif
 
 #ifndef ETH_P_IPV6
 /**
  * Number for IPv6
  */
 #define ETH_P_IPV6 0x86DD
 #endif
 
 
 /**
  * Maximum regex string length for use with #GNUNET_REGEX_ipv4toregexsearch.
  *
  * 8 bytes for IPv4, 4 bytes for port, 1 byte for "4", 2 bytes for "-",
  * one byte for 0-termination.
  */
 
 #define GNUNET_TUN_IPV4_REGEXLEN 16
 
 
 /**
  * Maximum regex string length for use with #GNUNET_REGEX_ipv6toregexsearch
  *
  * 32 bytes for IPv4, 4 bytes for port, 1 byte for "4", 2 bytes for "-",
  * one byte for 0-termination.
  */
 #define GNUNET_TUN_IPV6_REGEXLEN 40
 
 
 GNUNET_NETWORK_STRUCT_BEGIN
 
 /**
  * Header from Linux TUN interface.
  */
 struct GNUNET_TUN_Layer2PacketHeader
 {
   /**
    * Some flags (unused).
    */
   uint16_t flags GNUNET_PACKED;
 
   /**
    * Here we get an ETH_P_-number.
    */
   uint16_t proto GNUNET_PACKED;
 };
 
 
 /**
  * Standard IPv4 header.
  */
 struct GNUNET_TUN_IPv4Header
 {
 #if __BYTE_ORDER == __LITTLE_ENDIAN
   unsigned int header_length : 4 GNUNET_PACKED;
   unsigned int version : 4 GNUNET_PACKED;
 #elif __BYTE_ORDER == __BIG_ENDIAN
   unsigned int version : 4 GNUNET_PACKED;
   unsigned int header_length : 4 GNUNET_PACKED;
 #else
 #error byteorder undefined
 #endif
   uint8_t diff_serv;
 
   /**
    * Length of the packet, including this header.
    */
   uint16_t total_length GNUNET_PACKED;
 
   /**
    * Unique random ID for matching up fragments.
    */
   uint16_t identification GNUNET_PACKED;
 
   unsigned int flags : 3 GNUNET_PACKED;
 
   unsigned int fragmentation_offset : 13 GNUNET_PACKED;
 
   /**
    * How many more hops can this packet be forwarded?
    */
   uint8_t ttl;
 
   /**
    * L4-protocol, for example, IPPROTO_UDP or IPPROTO_TCP.
    */
   uint8_t protocol;
 
   /**
    * Checksum.
    */
   uint16_t checksum GNUNET_PACKED;
 
   /**
    * Origin of the packet.
    */
   struct in_addr source_address;
 
   /**
    * Destination of the packet.
    */
   struct in_addr destination_address;
 } GNUNET_GCC_STRUCT_LAYOUT;
 
 
 /**
  * Standard IPv6 header.
  */
 struct GNUNET_TUN_IPv6Header
 {
 #if __BYTE_ORDER == __LITTLE_ENDIAN
   unsigned int traffic_class_h : 4 GNUNET_PACKED;
   unsigned int version : 4 GNUNET_PACKED;
   unsigned int traffic_class_l : 4 GNUNET_PACKED;
   unsigned int flow_label : 20 GNUNET_PACKED;
 #elif __BYTE_ORDER == __BIG_ENDIAN
   unsigned int version : 4 GNUNET_PACKED;
   unsigned int traffic_class : 8 GNUNET_PACKED;
   unsigned int flow_label : 20 GNUNET_PACKED;
 #else
 #error byteorder undefined
 #endif
   /**
    * Length of the payload, excluding this header.
    */
   uint16_t payload_length GNUNET_PACKED;
 
   /**
    * For example, IPPROTO_UDP or IPPROTO_TCP.
    */
   uint8_t next_header;
 
   /**
    * How many more hops can this packet be forwarded?
    */
   uint8_t hop_limit;
 
   /**
    * Origin of the packet.
    */
   struct in6_addr source_address GNUNET_PACKED;
 
   /**
    * Destination of the packet.
    */
   struct in6_addr destination_address GNUNET_PACKED;
 } GNUNET_GCC_STRUCT_LAYOUT;
 
 
 /**
  * TCP flags.
  */
 #define GNUNET_TUN_TCP_FLAGS_FIN 1
 #define GNUNET_TUN_TCP_FLAGS_SYN 2
 #define GNUNET_TUN_TCP_FLAGS_RST 4
 #define GNUNET_TUN_TCP_FLAGS_PSH 8
 #define GNUNET_TUN_TCP_FLAGS_ACK 16
 #define GNUNET_TUN_TCP_FLAGS_URG 32
 #define GNUNET_TUN_TCP_FLAGS_ECE 64
 #define GNUNET_TUN_TCP_FLAGS_CWR 128
 
 /**
  * TCP packet header.
  */
 struct GNUNET_TUN_TcpHeader
 {
   /**
    * Source port (in NBO).
    */
   uint16_t source_port GNUNET_PACKED;
 
   /**
    * Destination port (in NBO).
    */
   uint16_t destination_port GNUNET_PACKED;
 
   /**
    * Sequence number.
    */
   uint32_t seq GNUNET_PACKED;
 
   /**
    * Acknowledgement number.
    */
   uint32_t ack GNUNET_PACKED;
 #if __BYTE_ORDER == __LITTLE_ENDIAN
   /**
    * Reserved.  Must be zero.
    */
   unsigned int reserved : 4 GNUNET_PACKED;
   /**
    * Number of 32-bit words in TCP header.
    */
   unsigned int off : 4 GNUNET_PACKED;
 #elif __BYTE_ORDER == __BIG_ENDIAN
   /**
    * Number of 32-bit words in TCP header.
    */
   unsigned int off : 4 GNUNET_PACKED;
   /**
    * Reserved.  Must be zero.
    */
   unsigned int reserved : 4 GNUNET_PACKED;
 #else
 #error byteorder undefined
 #endif
 
   /**
    * Flags (SYN, FIN, ACK, etc.)
    */
   uint8_t flags;
 
   /**
    * Window size.
    */
   uint16_t window_size GNUNET_PACKED;
 
   /**
    * Checksum.
    */
   uint16_t crc GNUNET_PACKED;
 
   /**
    * Urgent pointer.
    */
   uint16_t urgent_pointer GNUNET_PACKED;
 } GNUNET_GCC_STRUCT_LAYOUT;
 
 
 /**
  * UDP packet header.
  */
 struct GNUNET_TUN_UdpHeader
 {
   /**
    * Source port (in NBO).
    */
   uint16_t source_port GNUNET_PACKED;
 
   /**
    * Destination port (in NBO).
    */
   uint16_t destination_port GNUNET_PACKED;
 
   /**
    * Number of bytes of payload.
    */
   uint16_t len GNUNET_PACKED;
 
   /**
    * Checksum.
    */
   uint16_t crc GNUNET_PACKED;
 };
 
 
 /**
  * A few common DNS classes (ok, only one is common, but I list a
  * couple more to make it clear what we're talking about here).
  */
 #define GNUNET_TUN_DNS_CLASS_INTERNET 1
 #define GNUNET_TUN_DNS_CLASS_CHAOS 3
 #define GNUNET_TUN_DNS_CLASS_HESIOD 4
 
 #define GNUNET_TUN_DNS_OPCODE_QUERY 0
 #define GNUNET_TUN_DNS_OPCODE_INVERSE_QUERY 1
 #define GNUNET_TUN_DNS_OPCODE_STATUS 2
 
 
 /**
  * RFC 1035 codes.
  */
 #define GNUNET_TUN_DNS_RETURN_CODE_NO_ERROR 0
 #define GNUNET_TUN_DNS_RETURN_CODE_FORMAT_ERROR 1
 #define GNUNET_TUN_DNS_RETURN_CODE_SERVER_FAILURE 2
 #define GNUNET_TUN_DNS_RETURN_CODE_NAME_ERROR 3
 #define GNUNET_TUN_DNS_RETURN_CODE_NOT_IMPLEMENTED 4
 #define GNUNET_TUN_DNS_RETURN_CODE_REFUSED 5
 
 /**
  * RFC 2136 codes
  */
 #define GNUNET_TUN_DNS_RETURN_CODE_YXDOMAIN 6
 #define GNUNET_TUN_DNS_RETURN_CODE_YXRRSET 7
 #define GNUNET_TUN_DNS_RETURN_CODE_NXRRSET 8
 #define GNUNET_TUN_DNS_RETURN_CODE_NOT_AUTH 9
 #define GNUNET_TUN_DNS_RETURN_CODE_NOT_ZONE 10
 
 
 /**
  * DNS flags (largely RFC 1035 / RFC 2136).
  */
 struct GNUNET_TUN_DnsFlags
 {
 #if __BYTE_ORDER == __LITTLE_ENDIAN
   /**
    * Set to 1 if recursion is desired (client -> server)
    */
   unsigned int recursion_desired : 1 GNUNET_PACKED;
 
   /**
    * Set to 1 if message is truncated
    */
   unsigned int message_truncated : 1 GNUNET_PACKED;
 
   /**
    * Set to 1 if this is an authoritative answer
    */
   unsigned int authoritative_answer : 1 GNUNET_PACKED;
 
   /**
    * See GNUNET_TUN_DNS_OPCODE_ defines.
    */
   unsigned int opcode : 4 GNUNET_PACKED;
 
   /**
    * query:0, response:1
    */
   unsigned int query_or_response : 1 GNUNET_PACKED;
 
   /**
    * See GNUNET_TUN_DNS_RETURN_CODE_ defines.
    */
   unsigned int return_code : 4 GNUNET_PACKED;
 
   /**
    * See RFC 4035.
    */
   unsigned int checking_disabled : 1 GNUNET_PACKED;
 
   /**
    * Response has been cryptographically verified, RFC 4035.
    */
   unsigned int authenticated_data : 1 GNUNET_PACKED;
 
   /**
    * Always zero.
    */
   unsigned int zero : 1 GNUNET_PACKED;
 
   /**
    * Set to 1 if recursion is available (server -> client)
    */
   unsigned int recursion_available : 1 GNUNET_PACKED;
 #elif __BYTE_ORDER == __BIG_ENDIAN
   /**
    * query:0, response:1
    */
   unsigned int query_or_response : 1 GNUNET_PACKED;
 
   /**
    * See GNUNET_TUN_DNS_OPCODE_ defines.
    */
   unsigned int opcode : 4 GNUNET_PACKED;
 
   /**
    * Set to 1 if this is an authoritative answer
    */
   unsigned int authoritative_answer : 1 GNUNET_PACKED;
 
   /**
    * Set to 1 if message is truncated
    */
   unsigned int message_truncated : 1 GNUNET_PACKED;
 
   /**
    * Set to 1 if recursion is desired (client -> server)
    */
   unsigned int recursion_desired : 1 GNUNET_PACKED;
 
 
   /**
    * Set to 1 if recursion is available (server -> client)
    */
   unsigned int recursion_available : 1 GNUNET_PACKED;
 
   /**
    * Always zero.
    */
   unsigned int zero : 1 GNUNET_PACKED;
 
   /**
    * Response has been cryptographically verified, RFC 4035.
    */
   unsigned int authenticated_data : 1 GNUNET_PACKED;
 
   /**
    * See RFC 4035.
    */
   unsigned int checking_disabled : 1 GNUNET_PACKED;
 
   /**
    * See GNUNET_TUN_DNS_RETURN_CODE_ defines.
    */
   unsigned int return_code : 4 GNUNET_PACKED;
 #else
 #error byteorder undefined
 #endif
 } GNUNET_GCC_STRUCT_LAYOUT;
 
 
 /**
  * DNS header.
  */
 struct GNUNET_TUN_DnsHeader
 {
   /**
    * Unique identifier for the request/response.
    */
   uint16_t id GNUNET_PACKED;
 
   /**
    * Flags.
    */
   struct GNUNET_TUN_DnsFlags flags;
 
   /**
    * Number of queries.
    */
   uint16_t query_count GNUNET_PACKED;
 
   /**
    * Number of answers.
    */
   uint16_t answer_rcount GNUNET_PACKED;
 
   /**
    * Number of authoritative answers.
    */
   uint16_t authority_rcount GNUNET_PACKED;
 
   /**
    * Number of additional records.
    */
   uint16_t additional_rcount GNUNET_PACKED;
 };
 
 
 /**
  * Payload of DNS SOA record (header).
  */
 struct GNUNET_TUN_DnsSoaRecord
 {
   /**
    * The version number of the original copy of the zone.   (NBO)
    */
   uint32_t serial GNUNET_PACKED;
 
   /**
    * Time interval before the zone should be refreshed. (NBO)
    */
   uint32_t refresh GNUNET_PACKED;
 
   /**
    * Time interval that should elapse before a failed refresh should
    * be retried. (NBO)
    */
   uint32_t retry GNUNET_PACKED;
 
   /**
    * Time value that specifies the upper limit on the time interval
    * that can elapse before the zone is no longer authoritative. (NBO)
    */
   uint32_t expire GNUNET_PACKED;
 
   /**
    * The bit minimum TTL field that should be exported with any RR
    * from this zone. (NBO)
    */
   uint32_t minimum GNUNET_PACKED;
 };
 
 
 /**
  * Payload of DNS SRV record (header).
  */
 struct GNUNET_TUN_DnsSrvRecord
 {
   /**
    * Preference for this entry (lower value is higher preference).  Clients
    * will contact hosts from the lowest-priority group first and fall back
    * to higher priorities if the low-priority entries are unavailable. (NBO)
    */
   uint16_t prio GNUNET_PACKED;
 
   /**
    * Relative weight for records with the same priority.  Clients will use
    * the hosts of the same (lowest) priority with a probability proportional
    * to the weight given. (NBO)
    */
   uint16_t weight GNUNET_PACKED;
 
   /**
    * TCP or UDP port of the service. (NBO)
    */
   uint16_t port GNUNET_PACKED;
 
   /* followed by 'target' name */
 };
 
 
 /**
  * Payload of DNS URI record (header).
  */
 struct GNUNET_TUN_DnsUriRecord
 {
   /**
    * Preference for this entry (lower value is higher preference).  Clients
    * will contact hosts from the lowest-priority group first and fall back
    * to higher priorities if the low-priority entries are unavailable. (NBO)
    */
   uint16_t prio GNUNET_PACKED;
 
   /**
    * Relative weight for records with the same priority.  Clients will use
    * the hosts of the same (lowest) priority with a probability proportional
    * to the weight given. (NBO)
    */
   uint16_t weight GNUNET_PACKED;
 
   /* followed by 'target' name */
 };
 
 
 /**
  * Payload of DNS CERT record.
  */
 struct GNUNET_TUN_DnsCertRecord
 {
   /**
    * Certificate type
    */
   uint16_t cert_type;
 
   /**
    * Certificate KeyTag
    */
   uint16_t cert_tag;
 
   /**
    * Algorithm
    */
   uint8_t algorithm;
 
   /* Followed by the certificate */
 };
 
 
 /**
  * Payload of DNSSEC TLSA record.
  * http://datatracker.ietf.org/doc/draft-ietf-dane-protocol/
  */
 struct GNUNET_TUN_DnsTlsaRecord
 {
   /**
    * Certificate usage
    * 0: CA cert
    * 1: Entity cert
    * 2: Trust anchor
    * 3: domain-issued cert
    */
   uint8_t usage;
 
   /**
    * Selector
    * What part will be matched against the cert
    * presented by server
    * 0: Full cert (in binary)
    * 1: Full cert (in DER)
    */
   uint8_t selector;
 
   /**
    * Matching type (of selected content)
    * 0: exact match
    * 1: SHA-256 hash
    * 2: SHA-512 hash
    */
   uint8_t matching_type;
 
   /**
    * followed by certificate association data
    * The "certificate association data" to be matched.
    * These bytes are either raw data (that is, the full certificate or
    * its SubjectPublicKeyInfo, depending on the selector) for matching
    * type 0, or the hash of the raw data for matching types 1 and 2.
    * The data refers to the certificate in the association, not to the
    * TLS ASN.1 Certificate object.
    *
    * The data is represented as a string of hex chars
    */
 };
 
 
 /**
  * Payload of GNS VPN record
  */
 struct GNUNET_TUN_GnsVpnRecord
 {
   /**
    * The peer to contact
    */
   struct GNUNET_PeerIdentity peer;
 
   /**
    * The protocol to use
    */
   uint16_t proto;
 
   /* followed by the servicename */
 };
 
 
 /**
  * DNS query prefix.
  */
 struct GNUNET_TUN_DnsQueryLine
 {
   /**
    * Desired type (GNUNET_DNSPARSER_TYPE_XXX). (NBO)
    */
   uint16_t type GNUNET_PACKED;
 
   /**
    * Desired class (usually GNUNET_TUN_DNS_CLASS_INTERNET). (NBO)
    */
   uint16_t dns_traffic_class GNUNET_PACKED;
 };
 
 
 /**
  * General DNS record prefix.
  */
 struct GNUNET_TUN_DnsRecordLine
 {
   /**
    * Record type (GNUNET_DNSPARSER_TYPE_XXX). (NBO)
    */
   uint16_t type GNUNET_PACKED;
 
   /**
    * Record class (usually GNUNET_TUN_DNS_CLASS_INTERNET). (NBO)
    */
   uint16_t dns_traffic_class GNUNET_PACKED;
 
   /**
    * Expiration for the record (in seconds). (NBO)
    */
   uint32_t ttl GNUNET_PACKED;
 
   /**
    * Number of bytes of data that follow. (NBO)
    */
   uint16_t data_len GNUNET_PACKED;
 };
 
 
 #define GNUNET_TUN_ICMPTYPE_ECHO_REPLY 0
 #define GNUNET_TUN_ICMPTYPE_DESTINATION_UNREACHABLE 3
 #define GNUNET_TUN_ICMPTYPE_SOURCE_QUENCH 4
 #define GNUNET_TUN_ICMPTYPE_REDIRECT_MESSAGE 5
 #define GNUNET_TUN_ICMPTYPE_ECHO_REQUEST 8
 #define GNUNET_TUN_ICMPTYPE_ROUTER_ADVERTISEMENT 9
 #define GNUNET_TUN_ICMPTYPE_ROUTER_SOLICITATION 10
 #define GNUNET_TUN_ICMPTYPE_TIME_EXCEEDED 11
 
 #define GNUNET_TUN_ICMPTYPE6_DESTINATION_UNREACHABLE 1
 #define GNUNET_TUN_ICMPTYPE6_PACKET_TOO_BIG 2
 #define GNUNET_TUN_ICMPTYPE6_TIME_EXCEEDED 3
 #define GNUNET_TUN_ICMPTYPE6_PARAMETER_PROBLEM 4
 #define GNUNET_TUN_ICMPTYPE6_ECHO_REQUEST 128
 #define GNUNET_TUN_ICMPTYPE6_ECHO_REPLY 129
 
 
 /**
  * ICMP header.
  */
 struct GNUNET_TUN_IcmpHeader
 {
   uint8_t type;
   uint8_t code;
   uint16_t crc GNUNET_PACKED;
 
   union
   {
     /**
      * ICMP Echo (request/reply)
      */
     struct
     {
       uint16_t identifier GNUNET_PACKED;
       uint16_t sequence_number GNUNET_PACKED;
     } echo;
 
     /**
      * ICMP Destination Unreachable (RFC 1191)
      */
     struct ih_pmtu
     {
       uint16_t empty GNUNET_PACKED;
       uint16_t next_hop_mtu GNUNET_PACKED;
       /* followed by original IP header + first 8 bytes of original IP datagram
        */
     } destination_unreachable;
 
     /**
      * ICMP Redirect
      */
     struct in_addr redirect_gateway_address;
 
     /**
      * MTU for packets that are too big (IPv6).
      */
     uint32_t packet_too_big_mtu GNUNET_PACKED;
   } quench;
 };
 
 
 GNUNET_NETWORK_STRUCT_END
 
 
 /**
  * Initialize an IPv4 header.
  *
  * @param ip header to initialize
  * @param protocol protocol to use (e.g. 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);
 
 
 /**
  * Initialize an IPv6 header.
  *
  * @param ip header to initialize
  * @param protocol protocol to use (e.g. 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_ipv6_header (struct GNUNET_TUN_IPv6Header *ip,
                                    uint8_t protocol,
                                    uint16_t payload_length,
                                    const struct in6_addr *src,
                                    const struct in6_addr *dst);
 
 /**
  * Calculate IPv4 TCP checksum.
  *
  * @param ip ipv4 header fully initialized
  * @param tcp TCP header (initialized except for CRC)
  * @param payload the TCP payload
  * @param payload_length number of bytes of TCP @a payload
  */
 void
 GNUNET_TUN_calculate_tcp4_checksum (const struct GNUNET_TUN_IPv4Header *ip,
                                     struct GNUNET_TUN_TcpHeader *tcp,
                                     const void *payload,
                                     uint16_t payload_length);
 
 /**
  * Calculate IPv6 TCP checksum.
  *
  * @param ip ipv6 header fully initialized
  * @param tcp TCP header (initialized except for CRC)
  * @param payload the TCP payload
  * @param payload_length number of bytes of TCP payload
  */
 void
 GNUNET_TUN_calculate_tcp6_checksum (const struct GNUNET_TUN_IPv6Header *ip,
                                     struct GNUNET_TUN_TcpHeader *tcp,
                                     const void *payload,
                                     uint16_t payload_length);
 
 /**
  * Calculate IPv4 UDP checksum.
  *
  * @param ip ipv4 header fully initialized
  * @param udp UDP header (initialized except for CRC)
  * @param payload the UDP payload
  * @param payload_length number of bytes of UDP @a payload
  */
 void
 GNUNET_TUN_calculate_udp4_checksum (const struct GNUNET_TUN_IPv4Header *ip,
                                     struct GNUNET_TUN_UdpHeader *udp,
                                     const void *payload,
                                     uint16_t payload_length);
 
 
 /**
  * Calculate IPv6 UDP checksum.
  *
  * @param ip ipv6 header fully initialized
  * @param udp UDP header (initialized except for CRC)
  * @param payload the UDP payload
  * @param payload_length number of bytes of @a payload
  */
 void
 GNUNET_TUN_calculate_udp6_checksum (const struct GNUNET_TUN_IPv6Header *ip,
                                     struct GNUNET_TUN_UdpHeader *udp,
                                     const void *payload,
                                     uint16_t payload_length);
 
 
 /**
  * Calculate ICMP checksum.
  *
  * @param icmp IMCP header (initialized except for CRC)
  * @param payload the ICMP payload
  * @param payload_length number of bytes of @a payload
  */
 void
 GNUNET_TUN_calculate_icmp_checksum (struct GNUNET_TUN_IcmpHeader *icmp,
                                     const void *payload,
                                     uint16_t payload_length);
 
 
 /**
  * Hash the service name of a hosted service to the
  * hash code that is used to identify the service on
  * the network.
  *
  * @param service_name a string
  * @param[out] hc corresponding hash
  */
 void
 GNUNET_TUN_service_name_to_hash (const char *service_name,
                                  struct GNUNET_HashCode *hc);
 
 
 /**
  * Check if two sockaddrs are equal.
  *
  * @param sa one address
  * @param sb another address
  * @param include_port also check ports
  * @return #GNUNET_YES if they are equal
  */
 int
 GNUNET_TUN_sockaddr_cmp (const struct sockaddr *sa,
                          const struct sockaddr *sb,
                          int include_port);
 
 
 /**
  * Compute the CADET port given a service descriptor
  * (returned from #GNUNET_TUN_service_name_to_hash) and
  * a TCP/UDP port @a ip_port.
  *
  * @param desc service shared secret
  * @param ip_port TCP/UDP port, use 0 for ICMP
  * @param[out] cadet_port CADET port to use
  */
 void
 GNUNET_TUN_compute_service_cadet_port (const struct GNUNET_HashCode *desc,
                                        uint16_t ip_port,
                                        struct GNUNET_HashCode *cadet_port);
 
 #endif
 
 /** @} */ /* end of group */
 
 /** @} */ /* end of group addition */