*/
/**
- * @file tun/tun.
+ * @file tun/tun.c
* @brief standard IP calculations for TUN interaction
* @author Philipp Toelke
* @author Christian Grothoff
/**
* IP TTL we use for packets that we assemble (8 bit unsigned integer)
*/
-#define FRESH_TTL 255
+#define FRESH_TTL 64
+
/**
* Initialize an IPv4 header.
const struct in_addr *src,
const struct in_addr *dst)
{
+ GNUNET_assert (20 == sizeof (struct GNUNET_TUN_IPv4Header));
+ GNUNET_assert (payload_length <= UINT16_MAX - sizeof (struct GNUNET_TUN_IPv4Header));
+ memset (ip, 0, sizeof (struct GNUNET_TUN_IPv4Header));
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));
}
+/**
+ * Initialize an IPv6 header.
+ *
+ * @param ip header to initialize
+ * @param protocol protocol to use (i.e. IPPROTO_UDP), technically "next_header" for IPv6
+ * @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)
+{
+ GNUNET_assert (40 == sizeof (struct GNUNET_TUN_IPv6Header));
+ GNUNET_assert (payload_length <= UINT16_MAX - sizeof (struct GNUNET_TUN_IPv6Header));
+ memset (ip, 0, sizeof (struct GNUNET_TUN_IPv6Header));
+ ip->version = 6;
+ ip->next_header = protocol;
+ ip->payload_length = htons ((uint16_t) payload_length);
+ ip->hop_limit = FRESH_TTL;
+ ip->destination_address = *dst;
+ ip->source_address = *src;
+}
+
+
+/**
+ * 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 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)
+{
+ uint32_t sum;
+ uint16_t tmp;
+
+ GNUNET_assert (20 == sizeof (struct GNUNET_TUN_TcpHeader));
+ GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_IPv4Header) + sizeof (struct GNUNET_TUN_TcpHeader) ==
+ ntohs (ip->total_length));
+ GNUNET_assert (IPPROTO_TCP == ip->protocol);
+
+ tcp->crc = 0;
+ sum = GNUNET_CRYPTO_crc16_step (0,
+ &ip->source_address,
+ sizeof (struct in_addr) * 2);
+ tmp = htons (IPPROTO_TCP);
+ sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint16_t));
+ tmp = htons (payload_length + sizeof (struct GNUNET_TUN_TcpHeader));
+ sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint16_t));
+ sum = GNUNET_CRYPTO_crc16_step (sum, tcp, sizeof (struct GNUNET_TUN_TcpHeader));
+ sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+ tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+/**
+ * Calculate IPv6 TCP checksum.
+ *
+ * @param ip ipv6 header fully initialized
+ * @param 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)
+{
+ uint32_t sum;
+ uint32_t tmp;
+
+ GNUNET_assert (20 == sizeof (struct GNUNET_TUN_TcpHeader));
+ GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_TcpHeader) ==
+ ntohs (ip->payload_length));
+ GNUNET_assert (IPPROTO_TCP == ip->next_header);
+ tcp->crc = 0;
+ sum = GNUNET_CRYPTO_crc16_step (0, &ip->source_address, 2 * sizeof (struct in6_addr));
+ tmp = htonl (sizeof (struct GNUNET_TUN_TcpHeader) + payload_length);
+ sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+ tmp = htonl (IPPROTO_TCP);
+ sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+ sum = GNUNET_CRYPTO_crc16_step (sum, tcp,
+ sizeof (struct GNUNET_TUN_TcpHeader));
+ sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+ tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+/**
+ * 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 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)
+{
+ uint32_t sum;
+ uint16_t tmp;
+
+ GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader));
+ GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_IPv4Header) + sizeof (struct GNUNET_TUN_UdpHeader) ==
+ ntohs (ip->total_length));
+ GNUNET_assert (IPPROTO_UDP == ip->protocol);
+
+ udp->crc = 0; /* technically optional, but we calculate it anyway, just to be sure */
+ sum = GNUNET_CRYPTO_crc16_step (0,
+ &ip->source_address,
+ sizeof (struct in_addr) * 2);
+ tmp = htons (IPPROTO_UDP);
+ sum = GNUNET_CRYPTO_crc16_step (sum,
+ &tmp,
+ sizeof (uint16_t));
+ tmp = htons (sizeof (struct GNUNET_TUN_UdpHeader) + payload_length);
+ sum = GNUNET_CRYPTO_crc16_step (sum,
+ &tmp,
+ sizeof (uint16_t));
+ sum = GNUNET_CRYPTO_crc16_step (sum,
+ udp,
+ sizeof (struct GNUNET_TUN_UdpHeader));
+ sum = GNUNET_CRYPTO_crc16_step (sum,
+ payload,
+ payload_length);
+ udp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+/**
+ * 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 UDP 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)
+{
+ uint32_t sum;
+ uint32_t tmp;
+
+ GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_UdpHeader) ==
+ ntohs (ip->payload_length));
+ GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_UdpHeader) ==
+ ntohs (udp->len));
+ GNUNET_assert (IPPROTO_UDP == ip->next_header);
+
+ udp->crc = 0;
+ sum = GNUNET_CRYPTO_crc16_step (0,
+ &ip->source_address,
+ sizeof (struct in6_addr) * 2);
+ tmp = htons (sizeof (struct GNUNET_TUN_UdpHeader) + payload_length); /* aka udp->len */
+ sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+ tmp = htons (ip->next_header);
+ sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+ sum = GNUNET_CRYPTO_crc16_step (sum, udp, sizeof (struct GNUNET_TUN_UdpHeader));
+ sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+ udp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+/**
+ * Calculate ICMP checksum.
+ *
+ * @param icmp IMCP header (initialized except for CRC)
+ * @param payload the ICMP payload
+ * @param payload_length number of bytes of ICMP payload
+ */
+void
+GNUNET_TUN_calculate_icmp_checksum (struct GNUNET_TUN_IcmpHeader *icmp,
+ const void *payload,
+ uint16_t payload_length)
+{
+ uint32_t sum;
+
+ GNUNET_assert (8 == sizeof (struct GNUNET_TUN_IcmpHeader));
+ icmp->crc = 0;
+ sum = GNUNET_CRYPTO_crc16_step (0,
+ icmp,
+ sizeof (struct GNUNET_TUN_IcmpHeader));
+ sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+ icmp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
/* end of tun.c */
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