1 /* 2 * Copyright 2011 Daniel Drown 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 * 16 * ipv6.c - takes ipv6 packets, finds their headers, and then calls translation functions on them 17 */ 18 #include <string.h> 19 20 #include <arpa/inet.h> 21 22 #include "translate.h" 23 #include "checksum.h" 24 #include "logging.h" 25 #include "dump.h" 26 #include "config.h" 27 #include "debug.h" 28 29 /* function: icmp6_packet 30 * takes an icmp6 packet and sets it up for translation 31 * out - output packet 32 * icmp6 - pointer to icmp6 header in packet 33 * checksum - pseudo-header checksum (unused) 34 * len - size of ip payload 35 * returns: the highest position in the output clat_packet that's filled in 36 */ 37 int icmp6_packet(clat_packet out, int pos, const struct icmp6_hdr *icmp6, size_t len) { 38 const char *payload; 39 size_t payload_size; 40 41 if(len < sizeof(struct icmp6_hdr)) { 42 logmsg_dbg(ANDROID_LOG_ERROR, "icmp6_packet/(too small)"); 43 return 0; 44 } 45 46 payload = (const char *) (icmp6 + 1); 47 payload_size = len - sizeof(struct icmp6_hdr); 48 49 return icmp6_to_icmp(out, pos, icmp6, payload, payload_size); 50 } 51 52 /* function: log_bad_address 53 * logs a bad address to android's log buffer if debugging is turned on 54 * fmt - printf-style format, use %s to place the address 55 * badaddr - the bad address in question 56 */ 57 #if CLAT_DEBUG 58 void log_bad_address(const char *fmt, const struct in6_addr *src, const struct in6_addr *dst) { 59 char srcstr[INET6_ADDRSTRLEN]; 60 char dststr[INET6_ADDRSTRLEN]; 61 62 inet_ntop(AF_INET6, src, srcstr, sizeof(srcstr)); 63 inet_ntop(AF_INET6, dst, dststr, sizeof(dststr)); 64 logmsg_dbg(ANDROID_LOG_ERROR, fmt, srcstr, dststr); 65 } 66 #else 67 #define log_bad_address(fmt, src, dst) 68 #endif 69 70 /* function: ipv6_packet 71 * takes an ipv6 packet and hands it off to the layer 4 protocol function 72 * out - output packet 73 * packet - packet data 74 * len - size of packet 75 * returns: the highest position in the output clat_packet that's filled in 76 */ 77 int ipv6_packet(clat_packet out, int pos, const char *packet, size_t len) { 78 const struct ip6_hdr *ip6 = (struct ip6_hdr *) packet; 79 struct iphdr *ip_targ = (struct iphdr *) out[pos].iov_base; 80 struct ip6_frag *frag_hdr = NULL; 81 uint8_t protocol; 82 const char *next_header; 83 size_t len_left; 84 uint32_t old_sum, new_sum; 85 int iov_len; 86 87 if(len < sizeof(struct ip6_hdr)) { 88 logmsg_dbg(ANDROID_LOG_ERROR, "ipv6_packet/too short for an ip6 header: %d", len); 89 return 0; 90 } 91 92 if(IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) { 93 log_bad_address("ipv6_packet/multicast %s->%s", &ip6->ip6_src, &ip6->ip6_dst); 94 return 0; // silently ignore 95 } 96 97 // If the packet is not from the plat subnet to the local subnet, or vice versa, drop it, unless 98 // it's an ICMP packet (which can come from anywhere). We do not send IPv6 packets from the plat 99 // subnet to the local subnet, but these can appear as inner packets in ICMP errors, so we need 100 // to translate them. We accept third-party ICMPv6 errors, even though their source addresses 101 // cannot be translated, so that things like unreachables and traceroute will work. fill_ip_header 102 // takes care of faking a source address for them. 103 if (!(is_in_plat_subnet(&ip6->ip6_src) && 104 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &Global_Clatd_Config.ipv6_local_subnet)) && 105 !(is_in_plat_subnet(&ip6->ip6_dst) && 106 IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &Global_Clatd_Config.ipv6_local_subnet)) && 107 ip6->ip6_nxt != IPPROTO_ICMPV6) { 108 log_bad_address("ipv6_packet/wrong source address: %s->%s", &ip6->ip6_src, &ip6->ip6_dst); 109 return 0; 110 } 111 112 next_header = packet + sizeof(struct ip6_hdr); 113 len_left = len - sizeof(struct ip6_hdr); 114 115 protocol = ip6->ip6_nxt; 116 117 /* Fill in the IPv4 header. We need to do this before we translate the packet because TCP and 118 * UDP include parts of the IP header in the checksum. Set the length to zero because we don't 119 * know it yet. 120 */ 121 fill_ip_header(ip_targ, 0, protocol, ip6); 122 out[pos].iov_len = sizeof(struct iphdr); 123 124 // If there's a Fragment header, parse it and decide what the next header is. 125 // Do this before calculating the pseudo-header checksum because it updates the next header value. 126 if (protocol == IPPROTO_FRAGMENT) { 127 frag_hdr = (struct ip6_frag *) next_header; 128 if (len_left < sizeof(*frag_hdr)) { 129 logmsg_dbg(ANDROID_LOG_ERROR, "ipv6_packet/too short for fragment header: %d", len); 130 return 0; 131 } 132 133 next_header += sizeof(*frag_hdr); 134 len_left -= sizeof(*frag_hdr); 135 136 protocol = parse_frag_header(frag_hdr, ip_targ); 137 } 138 139 // ICMP and ICMPv6 have different protocol numbers. 140 if (protocol == IPPROTO_ICMPV6) { 141 protocol = IPPROTO_ICMP; 142 ip_targ->protocol = IPPROTO_ICMP; 143 } 144 145 /* Calculate the pseudo-header checksum. 146 * Technically, the length that is used in the pseudo-header checksum is the transport layer 147 * length, which is not the same as len_left in the case of fragmented packets. But since 148 * translation does not change the transport layer length, the checksum is unaffected. 149 */ 150 old_sum = ipv6_pseudo_header_checksum(ip6, len_left, protocol); 151 new_sum = ipv4_pseudo_header_checksum(ip_targ, len_left); 152 153 // Does not support IPv6 extension headers except Fragment. 154 if (frag_hdr && (frag_hdr->ip6f_offlg & IP6F_OFF_MASK)) { 155 iov_len = generic_packet(out, pos + 2, next_header, len_left); 156 } else if (protocol == IPPROTO_ICMP) { 157 iov_len = icmp6_packet(out, pos + 2, (const struct icmp6_hdr *) next_header, len_left); 158 } else if (protocol == IPPROTO_TCP) { 159 iov_len = tcp_packet(out, pos + 2, (const struct tcphdr *) next_header, old_sum, new_sum, 160 len_left); 161 } else if (protocol == IPPROTO_UDP) { 162 iov_len = udp_packet(out, pos + 2, (const struct udphdr *) next_header, old_sum, new_sum, 163 len_left); 164 } else if (protocol == IPPROTO_GRE) { 165 iov_len = generic_packet(out, pos + 2, next_header, len_left); 166 } else { 167 #if CLAT_DEBUG 168 logmsg(ANDROID_LOG_ERROR, "ipv6_packet/unknown next header type: %x", ip6->ip6_nxt); 169 logcat_hexdump("ipv6/nxthdr", packet, len); 170 #endif 171 return 0; 172 } 173 174 // Set the length and calculate the checksum. 175 ip_targ->tot_len = htons(ntohs(ip_targ->tot_len) + packet_length(out, pos)); 176 ip_targ->check = ip_checksum(ip_targ, sizeof(struct iphdr)); 177 return iov_len; 178 } 179
