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 <netinet/in.h>
21 #include <netinet/ip.h>
22 #include <netinet/ip_icmp.h>
23 #include <netinet/udp.h>
24 #include <netinet/tcp.h>
25 #include <netinet/ip6.h>
26 #include <netinet/icmp6.h>
27 #include <linux/icmp.h>
28 #include <arpa/inet.h>
29
30 #include "translate.h"
31 #include "checksum.h"
32 #include "ipv6.h"
33 #include "logging.h"
34 #include "dump.h"
35 #include "config.h"
36 #include "debug.h"
37
38 /* function: icmp6_packet
39 * takes an icmp6 packet and sets it up for translation
40 * out - output packet
41 * icmp6 - pointer to icmp6 header in packet
42 * checksum - pseudo-header checksum (unused)
43 * len - size of ip payload
44 * returns: the highest position in the output clat_packet that's filled in
45 */
icmp6_packet(clat_packet out,int pos,const struct icmp6_hdr * icmp6,uint32_t checksum,size_t len)46 int icmp6_packet(clat_packet out, int pos, const struct icmp6_hdr *icmp6, uint32_t checksum,
47 size_t len) {
48 const char *payload;
49 size_t payload_size;
50
51 if(len < sizeof(struct icmp6_hdr)) {
52 logmsg_dbg(ANDROID_LOG_ERROR, "icmp6_packet/(too small)");
53 return 0;
54 }
55
56 payload = (const char *) (icmp6 + 1);
57 payload_size = len - sizeof(struct icmp6_hdr);
58
59 return icmp6_to_icmp(out, pos, icmp6, checksum, payload, payload_size);
60 }
61
62 /* function: log_bad_address
63 * logs a bad address to android's log buffer if debugging is turned on
64 * fmt - printf-style format, use %s to place the address
65 * badaddr - the bad address in question
66 */
log_bad_address(const char * fmt,const struct in6_addr * src,const struct in6_addr * dst)67 void log_bad_address(const char *fmt, const struct in6_addr *src, const struct in6_addr *dst) {
68 #if CLAT_DEBUG
69 char srcstr[INET6_ADDRSTRLEN];
70 char dststr[INET6_ADDRSTRLEN];
71
72 inet_ntop(AF_INET6, src, srcstr, sizeof(srcstr));
73 inet_ntop(AF_INET6, dst, dststr, sizeof(dststr));
74 logmsg_dbg(ANDROID_LOG_ERROR, fmt, srcstr, dststr);
75 #endif
76 }
77
78 /* function: ipv6_packet
79 * takes an ipv6 packet and hands it off to the layer 4 protocol function
80 * out - output packet
81 * packet - packet data
82 * len - size of packet
83 * returns: the highest position in the output clat_packet that's filled in
84 */
ipv6_packet(clat_packet out,int pos,const char * packet,size_t len)85 int ipv6_packet(clat_packet out, int pos, const char *packet, size_t len) {
86 const struct ip6_hdr *ip6 = (struct ip6_hdr *) packet;
87 struct iphdr *ip_targ = (struct iphdr *) out[pos].iov_base;
88 uint8_t protocol;
89 const char *next_header;
90 size_t len_left;
91 uint32_t checksum;
92 int iov_len;
93 int i;
94
95 if(len < sizeof(struct ip6_hdr)) {
96 logmsg_dbg(ANDROID_LOG_ERROR, "ipv6_packet/too short for an ip6 header: %d", len);
97 return 0;
98 }
99
100 if(IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
101 log_bad_address("ipv6_packet/multicast %s->%s", &ip6->ip6_src, &ip6->ip6_dst);
102 return 0; // silently ignore
103 }
104
105 // If the packet is not from the plat subnet to the local subnet, or vice versa, drop it, unless
106 // it's an ICMP packet (which can come from anywhere). We do not send IPv6 packets from the plat
107 // subnet to the local subnet, but these can appear as inner packets in ICMP errors, so we need
108 // to translate them. We accept third-party ICMPv6 errors, even though their source addresses
109 // cannot be translated, so that things like unreachables and traceroute will work. fill_ip_header
110 // takes care of faking a source address for them.
111 if (!(is_in_plat_subnet(&ip6->ip6_src) &&
112 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &Global_Clatd_Config.ipv6_local_subnet)) &&
113 !(is_in_plat_subnet(&ip6->ip6_dst) &&
114 IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &Global_Clatd_Config.ipv6_local_subnet)) &&
115 ip6->ip6_nxt != IPPROTO_ICMPV6) {
116 log_bad_address("ipv6_packet/wrong source address: %s->%s", &ip6->ip6_src, &ip6->ip6_dst);
117 return 0;
118 }
119
120 next_header = packet + sizeof(struct ip6_hdr);
121 len_left = len - sizeof(struct ip6_hdr);
122
123 protocol = ip6->ip6_nxt;
124 if (protocol == IPPROTO_ICMPV6) {
125 // ICMP and ICMPv6 have different protocol numbers.
126 protocol = IPPROTO_ICMP;
127 }
128
129 /* Fill in the IPv4 header. We need to do this before we translate the packet because TCP and
130 * UDP include parts of the IP header in the checksum. Set the length to zero because we don't
131 * know it yet.
132 */
133 fill_ip_header(ip_targ, 0, protocol, ip6);
134 out[pos].iov_len = sizeof(struct iphdr);
135
136 // Calculate the pseudo-header checksum.
137 checksum = ipv4_pseudo_header_checksum(0, ip_targ, len_left);
138
139 // does not support IPv6 extension headers, this will drop any packet with them
140 if(protocol == IPPROTO_ICMP) {
141 iov_len = icmp6_packet(out, pos + 1, (const struct icmp6_hdr *) next_header, checksum,
142 len_left);
143 } else if(ip6->ip6_nxt == IPPROTO_TCP) {
144 iov_len = tcp_packet(out, pos + 1, (const struct tcphdr *) next_header, checksum,
145 len_left);
146 } else if(ip6->ip6_nxt == IPPROTO_UDP) {
147 iov_len = udp_packet(out, pos + 1, (const struct udphdr *) next_header, checksum,
148 len_left);
149 } else {
150 #if CLAT_DEBUG
151 logmsg(ANDROID_LOG_ERROR, "ipv6_packet/unknown next header type: %x", ip6->ip6_nxt);
152 logcat_hexdump("ipv6/nxthdr", packet, len);
153 #endif
154 return 0;
155 }
156
157 // Set the length and calculate the checksum.
158 ip_targ->tot_len = htons(ntohs(ip_targ->tot_len) + packet_length(out, pos));
159 ip_targ->check = ip_checksum(ip_targ, sizeof(struct iphdr));
160 return iov_len;
161 }
162