2 This file is part of GNUnet.
3 (C) 2010, 2011, 2012 Christian Grothoff
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6 it under the terms of the GNU General Public License as published
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
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23 * @brief standard IP calculations for TUN interaction
24 * @author Philipp Toelke
25 * @author Christian Grothoff
28 #include "gnunet_tun_lib.h"
31 * IP TTL we use for packets that we assemble (8 bit unsigned integer)
37 * Initialize an IPv4 header.
39 * @param ip header to initialize
40 * @param protocol protocol to use (i.e. IPPROTO_UDP)
41 * @param payload_length number of bytes of payload that follow (excluding IPv4 header)
42 * @param src source IP address to use
43 * @param dst destination IP address to use
46 GNUNET_TUN_initialize_ipv4_header (struct GNUNET_TUN_IPv4Header *ip,
48 uint16_t payload_length,
49 const struct in_addr *src,
50 const struct in_addr *dst)
52 GNUNET_assert (payload_length <= UINT16_MAX - sizeof (struct GNUNET_TUN_IPv4Header));
53 memset (ip, 0, sizeof (struct GNUNET_TUN_IPv4Header));
54 ip->header_length = sizeof (struct GNUNET_TUN_IPv4Header) / 4;
56 ip->total_length = htons (sizeof (struct GNUNET_TUN_IPv4Header) + payload_length);
57 ip->identification = (uint16_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
60 ip->protocol = protocol;
61 ip->source_address = *src;
62 ip->destination_address = *dst;
63 ip->checksum = GNUNET_CRYPTO_crc16_n (ip, sizeof (struct GNUNET_TUN_IPv4Header));
68 * Initialize an IPv6 header.
70 * @param ip header to initialize
71 * @param protocol protocol to use (i.e. IPPROTO_UDP), technically "next_header" for IPv6
72 * @param payload_length number of bytes of payload that follow (excluding IPv4 header)
73 * @param src source IP address to use
74 * @param dst destination IP address to use
77 GNUNET_TUN_initialize_ipv6_header (struct GNUNET_TUN_IPv6Header *ip,
79 uint16_t payload_length,
80 const struct in6_addr *src,
81 const struct in6_addr *dst)
83 GNUNET_assert (payload_length <= UINT16_MAX - sizeof (struct GNUNET_TUN_IPv6Header));
84 memset (ip, 0, sizeof (struct GNUNET_TUN_IPv6Header));
86 ip->next_header = protocol;
87 ip->payload_length = htons ((uint16_t) payload_length);
88 ip->hop_limit = FRESH_TTL;
89 ip->destination_address = *dst;
90 ip->source_address = *src;
95 * Calculate IPv4 TCP checksum.
97 * @param ip ipv4 header fully initialized
98 * @param tcp TCP header (initialized except for CRC)
99 * @param payload the TCP payload
100 * @param payload_length number of bytes of TCP payload
103 GNUNET_TUN_calculate_tcp4_checksum (const struct GNUNET_TUN_IPv4Header *ip,
104 struct GNUNET_TUN_TcpHeader *tcp,
106 uint16_t payload_length)
111 GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_IPv4Header) + sizeof (struct GNUNET_TUN_TcpHeader) ==
112 ntohs (ip->total_length));
113 GNUNET_assert (IPPROTO_TCP == ip->protocol);
116 sum = GNUNET_CRYPTO_crc16_step (0,
118 sizeof (struct in_addr) * 2);
119 tmp = htons (IPPROTO_TCP);
120 sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint16_t));
121 tmp = htons (payload_length + sizeof (struct GNUNET_TUN_TcpHeader));
122 sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint16_t));
123 sum = GNUNET_CRYPTO_crc16_step (sum, tcp, sizeof (struct GNUNET_TUN_TcpHeader));
124 sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
125 tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
130 * Calculate IPv6 TCP checksum.
132 * @param ip ipv6 header fully initialized
133 * @param tcp header (initialized except for CRC)
134 * @param payload the TCP payload
135 * @param payload_length number of bytes of TCP payload
138 GNUNET_TUN_calculate_tcp6_checksum (const struct GNUNET_TUN_IPv6Header *ip,
139 struct GNUNET_TUN_TcpHeader *tcp,
141 uint16_t payload_length)
146 GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_TcpHeader) ==
147 ntohs (ip->payload_length));
148 GNUNET_assert (IPPROTO_TCP == ip->next_header);
150 sum = GNUNET_CRYPTO_crc16_step (0, &ip->source_address, 2 * sizeof (struct in6_addr));
151 tmp = htonl (sizeof (struct GNUNET_TUN_TcpHeader) + payload_length);
152 sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
153 tmp = htonl (IPPROTO_TCP);
154 sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
155 sum = GNUNET_CRYPTO_crc16_step (sum, tcp,
156 sizeof (struct GNUNET_TUN_TcpHeader));
157 sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
158 tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
163 * Calculate IPv4 UDP checksum.
165 * @param ip ipv4 header fully initialized
166 * @param udp UDP header (initialized except for CRC)
167 * @param payload the UDP payload
168 * @param payload_length number of bytes of UDP payload
171 GNUNET_TUN_calculate_udp4_checksum (const struct GNUNET_TUN_IPv4Header *ip,
172 struct GNUNET_TUN_UdpHeader *udp,
174 uint16_t payload_length)
179 GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_IPv4Header) + sizeof (struct GNUNET_TUN_UdpHeader) ==
180 ntohs (ip->total_length));
181 GNUNET_assert (IPPROTO_UDP == ip->protocol);
183 udp->crc = 0; /* technically optional, but we calculate it anyway, just to be sure */
184 sum = GNUNET_CRYPTO_crc16_step (0,
186 sizeof (struct in_addr) * 2);
187 tmp = htons (IPPROTO_UDP);
188 sum = GNUNET_CRYPTO_crc16_step (sum,
191 tmp = htons (sizeof (struct GNUNET_TUN_UdpHeader) + payload_length);
192 sum = GNUNET_CRYPTO_crc16_step (sum,
195 sum = GNUNET_CRYPTO_crc16_step (sum,
197 sizeof (struct GNUNET_TUN_UdpHeader));
198 sum = GNUNET_CRYPTO_crc16_step (sum,
201 udp->crc = GNUNET_CRYPTO_crc16_finish (sum);
206 * Calculate IPv6 UDP checksum.
208 * @param ip ipv6 header fully initialized
209 * @param udp UDP header (initialized except for CRC)
210 * @param payload the UDP payload
211 * @param payload_length number of bytes of UDP payload
214 GNUNET_TUN_calculate_udp6_checksum (const struct GNUNET_TUN_IPv6Header *ip,
215 struct GNUNET_TUN_UdpHeader *udp,
217 uint16_t payload_length)
222 GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_UdpHeader) ==
223 ntohs (ip->payload_length));
224 GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_UdpHeader) ==
226 GNUNET_assert (IPPROTO_UDP == ip->next_header);
229 sum = GNUNET_CRYPTO_crc16_step (0,
231 sizeof (struct in6_addr) * 2);
232 tmp = htons (sizeof (struct GNUNET_TUN_UdpHeader) + payload_length); /* aka udp->len */
233 sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
234 tmp = htons (ip->next_header);
235 sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
236 sum = GNUNET_CRYPTO_crc16_step (sum, udp, sizeof (struct GNUNET_TUN_UdpHeader));
237 sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
238 udp->crc = GNUNET_CRYPTO_crc16_finish (sum);
243 * Calculate ICMP checksum.
245 * @param icmp IMCP header (initialized except for CRC)
246 * @param payload the ICMP payload
247 * @param payload_length number of bytes of ICMP payload
250 GNUNET_TUN_calculate_icmp_checksum (struct GNUNET_TUN_IcmpHeader *icmp,
252 uint16_t payload_length)
257 sum = GNUNET_CRYPTO_crc16_step (0,
259 sizeof (struct GNUNET_TUN_IcmpHeader));
260 sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
261 icmp->crc = GNUNET_CRYPTO_crc16_finish (sum);