/* function: tcp6_to_tcp
* translate ipv6 tcp to ipv4 tcp
* fd - tun interface fd
* ip6 - source packet ipv6 header
* tcp - source packet tcp header
* payload - tcp payload
* payload_size - size of payload
* options - tcp options
* options_size - size of options
*/
void tcp6_to_tcp(int fd,const struct ip6_hdr *ip6, const struct tcphdr *tcp, const char *payload, size_t payload_size, const char *options, size_t options_size) {
struct iphdr ip_targ;
struct iovec io_targ[5];
struct tun_pi tun_header;
uint32_t checksum;
fill_tun_header(&tun_header,ETH_P_IP);
fill_ip_header(&ip_targ,payload_size+options_size+sizeof(struct tcphdr),IPPROTO_TCP,ip6);
checksum = ipv4_pseudo_header_checksum(0, &ip_targ);
io_targ[0].iov_base = &tun_header;
io_targ[0].iov_len = sizeof(tun_header);
io_targ[1].iov_base = &ip_targ;
io_targ[1].iov_len = sizeof(ip_targ);
tcp_translate(fd,tcp,payload,payload_size,io_targ,checksum,options,options_size);
}
/* function: udp6_to_udp
* translate ipv6 udp to ipv4 udp
* fd - tun interface fd
* ip6 - source packet ipv6 header
* udp - source packet udp header
* payload - udp payload
* payload_size - size of payload
*/
void udp6_to_udp(int fd, const struct ip6_hdr *ip6, const struct udphdr *udp, const char *payload, size_t payload_size) {
struct iphdr ip_targ;
struct iovec io_targ[4];
struct tun_pi tun_header;
uint32_t checksum;
fill_tun_header(&tun_header,ETH_P_IP);
fill_ip_header(&ip_targ,payload_size + sizeof(struct udphdr),IPPROTO_UDP,ip6);
checksum = ipv4_pseudo_header_checksum(0, &ip_targ);
io_targ[0].iov_base = &tun_header;
io_targ[0].iov_len = sizeof(tun_header);
io_targ[1].iov_base = &ip_targ;
io_targ[1].iov_len = sizeof(ip_targ);
udp_translate(fd,udp,payload,payload_size,io_targ,checksum);
}
/* function: icmp6_to_icmp
* translate ipv6 icmp to ipv4 icmp
* fd - tun interface fd
* ip6 - source packet ipv6 header
* icmp6 - source packet icmp6 header
* payload - icmp6 payload
* payload_size - size of payload
*/
void icmp6_to_icmp(int fd, const struct ip6_hdr *ip6, const struct icmp6_hdr *icmp6, const char *payload, size_t payload_size) {
struct iphdr ip_targ;
struct icmphdr icmp_targ;
struct iovec io_targ[4];
struct tun_pi tun_header;
uint32_t temp_icmp_checksum;
if((icmp6->icmp6_type != ICMP6_ECHO_REQUEST) && (icmp6->icmp6_type != ICMP6_ECHO_REPLY)) {
#if CLAT_DEBUG
logmsg(ANDROID_LOG_WARN,"icmp6_to_icmp/unhandled icmp6 type: 0x%x",icmp6->icmp6_type);
#endif
return;
}
memset(&icmp_targ, 0, sizeof(icmp_targ));
fill_tun_header(&tun_header,ETH_P_IP);
fill_ip_header(&ip_targ,sizeof(icmp_targ) + payload_size, IPPROTO_ICMP, ip6);
icmp_targ.type = (icmp6->icmp6_type == ICMP6_ECHO_REQUEST) ? ICMP_ECHO : ICMP_ECHOREPLY;
icmp_targ.code = 0x0;
icmp_targ.checksum = 0;
icmp_targ.un.echo.id = icmp6->icmp6_id;
icmp_targ.un.echo.sequence = icmp6->icmp6_seq;
temp_icmp_checksum = ip_checksum_add(0,(void *)&icmp_targ,sizeof(icmp_targ));
temp_icmp_checksum = ip_checksum_add(temp_icmp_checksum, (void *)payload, payload_size);
icmp_targ.checksum = ip_checksum_finish(temp_icmp_checksum);
io_targ[0].iov_base = &tun_header;
io_targ[0].iov_len = sizeof(tun_header);
io_targ[1].iov_base = &ip_targ;
io_targ[1].iov_len = sizeof(ip_targ);
io_targ[2].iov_base = &icmp_targ;
io_targ[2].iov_len = sizeof(icmp_targ);
io_targ[3].iov_base = (char *)payload;
io_targ[3].iov_len = payload_size;
writev(fd, io_targ, 4);
}
/* function: ipv6_packet
* takes an ipv6 packet and hands it off to the layer 4 protocol function
* out - output packet
* packet - packet data
* len - size of packet
* returns: the highest position in the output clat_packet that's filled in
*/
int ipv6_packet(clat_packet out, clat_packet_index pos, const uint8_t *packet, size_t len) {
const struct ip6_hdr *ip6 = (struct ip6_hdr *) packet;
struct iphdr *ip_targ = (struct iphdr *) out[pos].iov_base;
struct ip6_frag *frag_hdr = NULL;
uint8_t protocol;
const uint8_t *next_header;
size_t len_left;
uint32_t old_sum, new_sum;
int iov_len;
if(len < sizeof(struct ip6_hdr)) {
logmsg_dbg(ANDROID_LOG_ERROR, "ipv6_packet/too short for an ip6 header: %d", len);
return 0;
}
if(IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
log_bad_address("ipv6_packet/multicast %s->%s", &ip6->ip6_src, &ip6->ip6_dst);
return 0; // silently ignore
}
// If the packet is not from the plat subnet to the local subnet, or vice versa, drop it, unless
// it's an ICMP packet (which can come from anywhere). We do not send IPv6 packets from the plat
// subnet to the local subnet, but these can appear as inner packets in ICMP errors, so we need
// to translate them. We accept third-party ICMPv6 errors, even though their source addresses
// cannot be translated, so that things like unreachables and traceroute will work. fill_ip_header
// takes care of faking a source address for them.
if (!(is_in_plat_subnet(&ip6->ip6_src) &&
IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &Global_Clatd_Config.ipv6_local_subnet)) &&
!(is_in_plat_subnet(&ip6->ip6_dst) &&
IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &Global_Clatd_Config.ipv6_local_subnet)) &&
ip6->ip6_nxt != IPPROTO_ICMPV6) {
log_bad_address("ipv6_packet/wrong source address: %s->%s", &ip6->ip6_src, &ip6->ip6_dst);
return 0;
}
next_header = packet + sizeof(struct ip6_hdr);
len_left = len - sizeof(struct ip6_hdr);
protocol = ip6->ip6_nxt;
/* Fill in the IPv4 header. We need to do this before we translate the packet because TCP and
* UDP include parts of the IP header in the checksum. Set the length to zero because we don't
* know it yet.
*/
fill_ip_header(ip_targ, 0, protocol, ip6);
out[pos].iov_len = sizeof(struct iphdr);
// If there's a Fragment header, parse it and decide what the next header is.
// Do this before calculating the pseudo-header checksum because it updates the next header value.
if (protocol == IPPROTO_FRAGMENT) {
frag_hdr = (struct ip6_frag *) next_header;
if (len_left < sizeof(*frag_hdr)) {
logmsg_dbg(ANDROID_LOG_ERROR, "ipv6_packet/too short for fragment header: %d", len);
return 0;
}
next_header += sizeof(*frag_hdr);
len_left -= sizeof(*frag_hdr);
protocol = parse_frag_header(frag_hdr, ip_targ);
}
// ICMP and ICMPv6 have different protocol numbers.
if (protocol == IPPROTO_ICMPV6) {
protocol = IPPROTO_ICMP;
ip_targ->protocol = IPPROTO_ICMP;
}
/* Calculate the pseudo-header checksum.
* Technically, the length that is used in the pseudo-header checksum is the transport layer
* length, which is not the same as len_left in the case of fragmented packets. But since
* translation does not change the transport layer length, the checksum is unaffected.
*/
old_sum = ipv6_pseudo_header_checksum(ip6, len_left, protocol);
new_sum = ipv4_pseudo_header_checksum(ip_targ, len_left);
// Does not support IPv6 extension headers except Fragment.
if (frag_hdr && (frag_hdr->ip6f_offlg & IP6F_OFF_MASK)) {
iov_len = generic_packet(out, pos + 2, next_header, len_left);
} else if (protocol == IPPROTO_ICMP) {
iov_len = icmp6_packet(out, pos + 2, (const struct icmp6_hdr *) next_header, len_left);
} else if (protocol == IPPROTO_TCP) {
iov_len = tcp_packet(out, pos + 2, (const struct tcphdr *) next_header, old_sum, new_sum,
len_left);
} else if (protocol == IPPROTO_UDP) {
iov_len = udp_packet(out, pos + 2, (const struct udphdr *) next_header, old_sum, new_sum,
len_left);
} else if (protocol == IPPROTO_GRE) {
iov_len = generic_packet(out, pos + 2, next_header, len_left);
} else {
#if CLAT_DEBUG
logmsg(ANDROID_LOG_ERROR, "ipv6_packet/unknown next header type: %x", ip6->ip6_nxt);
logcat_hexdump("ipv6/nxthdr", packet, len);
#endif
return 0;
}
// Set the length and calculate the checksum.
ip_targ->tot_len = htons(ntohs(ip_targ->tot_len) + packet_length(out, pos));
ip_targ->check = ip_checksum(ip_targ, sizeof(struct iphdr));
return iov_len;
}
