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Diffstat (limited to 'translate.c')
| -rw-r--r-- | translate.c | 529 |
1 files changed, 0 insertions, 529 deletions
diff --git a/translate.c b/translate.c deleted file mode 100644 index 22830d8..0000000 --- a/translate.c +++ /dev/null @@ -1,529 +0,0 @@ -/* - * Copyright 2011 Daniel Drown - * - * Licensed under the Apache License, Version 2.0 (the "License"); - * you may not use this file except in compliance with the License. - * You may obtain a copy of the License at - * - * http://www.apache.org/licenses/LICENSE-2.0 - * - * Unless required by applicable law or agreed to in writing, software - * distributed under the License is distributed on an "AS IS" BASIS, - * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. - * See the License for the specific language governing permissions and - * limitations under the License. - * - * translate.c - CLAT functions / partial implementation of rfc6145 - */ -#include "translate.h" - -#include <string.h> - -#include "checksum.h" -#include "clatd.h" -#include "common.h" -#include "config.h" -#include "debug.h" -#include "icmp.h" -#include "logging.h" - -/* function: packet_checksum - * calculates the checksum over all the packet components starting from pos - * checksum - checksum of packet components before pos - * packet - packet to calculate the checksum of - * pos - position to start counting from - * returns - the completed 16-bit checksum, ready to write into a checksum header field - */ -uint16_t packet_checksum(uint32_t checksum, clat_packet packet, clat_packet_index pos) { - int i; - for (i = pos; i < CLAT_POS_MAX; i++) { - if (packet[i].iov_len > 0) { - checksum = ip_checksum_add(checksum, packet[i].iov_base, packet[i].iov_len); - } - } - return ip_checksum_finish(checksum); -} - -/* function: packet_length - * returns the total length of all the packet components after pos - * packet - packet to calculate the length of - * pos - position to start counting after - * returns: the total length of the packet components after pos - */ -uint16_t packet_length(clat_packet packet, clat_packet_index pos) { - size_t len = 0; - int i; - for (i = pos + 1; i < CLAT_POS_MAX; i++) { - len += packet[i].iov_len; - } - return len; -} - -/* function: is_in_plat_subnet - * returns true iff the given IPv6 address is in the plat subnet. - * addr - IPv6 address - */ -int is_in_plat_subnet(const struct in6_addr *addr6) { - // Assumes a /96 plat subnet. - return (addr6 != NULL) && (memcmp(addr6, &Global_Clatd_Config.plat_subnet, 12) == 0); -} - -/* function: ipv6_addr_to_ipv4_addr - * return the corresponding ipv4 address for the given ipv6 address - * addr6 - ipv6 address - * returns: the IPv4 address - */ -uint32_t ipv6_addr_to_ipv4_addr(const struct in6_addr *addr6) { - if (is_in_plat_subnet(addr6)) { - // Assumes a /96 plat subnet. - return addr6->s6_addr32[3]; - } else if (IN6_ARE_ADDR_EQUAL(addr6, &Global_Clatd_Config.ipv6_local_subnet)) { - // Special-case our own address. - return Global_Clatd_Config.ipv4_local_subnet.s_addr; - } else { - // Third party packet. Let the caller deal with it. - return INADDR_NONE; - } -} - -/* function: ipv4_addr_to_ipv6_addr - * return the corresponding ipv6 address for the given ipv4 address - * addr4 - ipv4 address - */ -struct in6_addr ipv4_addr_to_ipv6_addr(uint32_t addr4) { - struct in6_addr addr6; - // Both addresses are in network byte order (addr4 comes from a network packet, and the config - // file entry is read using inet_ntop). - if (addr4 == Global_Clatd_Config.ipv4_local_subnet.s_addr) { - return Global_Clatd_Config.ipv6_local_subnet; - } else { - // Assumes a /96 plat subnet. - addr6 = Global_Clatd_Config.plat_subnet; - addr6.s6_addr32[3] = addr4; - return addr6; - } -} - -/* function: fill_tun_header - * fill in the header for the tun fd - * tun_header - tunnel header, already allocated - * proto - ethernet protocol id: ETH_P_IP(ipv4) or ETH_P_IPV6(ipv6) - */ -void fill_tun_header(struct tun_pi *tun_header, uint16_t proto) { - tun_header->flags = 0; - tun_header->proto = htons(proto); -} - -/* function: fill_ip_header - * generate an ipv4 header from an ipv6 header - * ip_targ - (ipv4) target packet header, source: original ipv4 addr, dest: local subnet addr - * payload_len - length of other data inside packet - * protocol - protocol number (tcp, udp, etc) - * old_header - (ipv6) source packet header, source: nat64 prefix, dest: local subnet prefix - */ -void fill_ip_header(struct iphdr *ip, uint16_t payload_len, uint8_t protocol, - const struct ip6_hdr *old_header) { - int ttl_guess; - memset(ip, 0, sizeof(struct iphdr)); - - ip->ihl = 5; - ip->version = 4; - ip->tos = 0; - ip->tot_len = htons(sizeof(struct iphdr) + payload_len); - ip->id = 0; - ip->frag_off = htons(IP_DF); - ip->ttl = old_header->ip6_hlim; - ip->protocol = protocol; - ip->check = 0; - - ip->saddr = ipv6_addr_to_ipv4_addr(&old_header->ip6_src); - ip->daddr = ipv6_addr_to_ipv4_addr(&old_header->ip6_dst); - - // Third-party ICMPv6 message. This may have been originated by an native IPv6 address. - // In that case, the source IPv6 address can't be translated and we need to make up an IPv4 - // source address. For now, use 255.0.0.<ttl>, which at least looks useful in traceroute. - if ((uint32_t)ip->saddr == INADDR_NONE) { - ttl_guess = icmp_guess_ttl(old_header->ip6_hlim); - ip->saddr = htonl((0xff << 24) + ttl_guess); - } -} - -/* function: fill_ip6_header - * generate an ipv6 header from an ipv4 header - * ip6 - (ipv6) target packet header, source: local subnet prefix, dest: nat64 prefix - * payload_len - length of other data inside packet - * protocol - protocol number (tcp, udp, etc) - * old_header - (ipv4) source packet header, source: local subnet addr, dest: internet's ipv4 addr - */ -void fill_ip6_header(struct ip6_hdr *ip6, uint16_t payload_len, uint8_t protocol, - const struct iphdr *old_header) { - memset(ip6, 0, sizeof(struct ip6_hdr)); - - ip6->ip6_vfc = 6 << 4; - ip6->ip6_plen = htons(payload_len); - ip6->ip6_nxt = protocol; - ip6->ip6_hlim = old_header->ttl; - - ip6->ip6_src = ipv4_addr_to_ipv6_addr(old_header->saddr); - ip6->ip6_dst = ipv4_addr_to_ipv6_addr(old_header->daddr); -} - -/* function: maybe_fill_frag_header - * fills a fragmentation header - * generate an ipv6 fragment header from an ipv4 header - * frag_hdr - target (ipv6) fragmentation header - * ip6_targ - target (ipv6) header - * old_header - (ipv4) source packet header - * returns: the length of the fragmentation header if present, or zero if not present - */ -size_t maybe_fill_frag_header(struct ip6_frag *frag_hdr, struct ip6_hdr *ip6_targ, - const struct iphdr *old_header) { - uint16_t frag_flags = ntohs(old_header->frag_off); - uint16_t frag_off = frag_flags & IP_OFFMASK; - if (frag_off == 0 && (frag_flags & IP_MF) == 0) { - // Not a fragment. - return 0; - } - - frag_hdr->ip6f_nxt = ip6_targ->ip6_nxt; - frag_hdr->ip6f_reserved = 0; - // In IPv4, the offset is the bottom 13 bits; in IPv6 it's the top 13 bits. - frag_hdr->ip6f_offlg = htons(frag_off << 3); - if (frag_flags & IP_MF) { - frag_hdr->ip6f_offlg |= IP6F_MORE_FRAG; - } - frag_hdr->ip6f_ident = htonl(ntohs(old_header->id)); - ip6_targ->ip6_nxt = IPPROTO_FRAGMENT; - - return sizeof(*frag_hdr); -} - -/* function: parse_frag_header - * return the length of the fragmentation header if present, or zero if not present - * generate an ipv6 fragment header from an ipv4 header - * frag_hdr - (ipv6) fragmentation header - * ip_targ - target (ipv4) header - * returns: the next header value - */ -uint8_t parse_frag_header(const struct ip6_frag *frag_hdr, struct iphdr *ip_targ) { - uint16_t frag_off = (ntohs(frag_hdr->ip6f_offlg & IP6F_OFF_MASK) >> 3); - if (frag_hdr->ip6f_offlg & IP6F_MORE_FRAG) { - frag_off |= IP_MF; - } - ip_targ->frag_off = htons(frag_off); - ip_targ->id = htons(ntohl(frag_hdr->ip6f_ident) & 0xffff); - ip_targ->protocol = frag_hdr->ip6f_nxt; - return frag_hdr->ip6f_nxt; -} - -/* function: icmp_to_icmp6 - * translate ipv4 icmp to ipv6 icmp - * out - output packet - * icmp - source packet icmp header - * checksum - pseudo-header checksum - * payload - icmp payload - * payload_size - size of payload - * returns: the highest position in the output clat_packet that's filled in - */ -int icmp_to_icmp6(clat_packet out, clat_packet_index pos, const struct icmphdr *icmp, - uint32_t checksum, const uint8_t *payload, size_t payload_size) { - struct icmp6_hdr *icmp6_targ = out[pos].iov_base; - uint8_t icmp6_type; - int clat_packet_len; - - memset(icmp6_targ, 0, sizeof(struct icmp6_hdr)); - - icmp6_type = icmp_to_icmp6_type(icmp->type, icmp->code); - icmp6_targ->icmp6_type = icmp6_type; - icmp6_targ->icmp6_code = icmp_to_icmp6_code(icmp->type, icmp->code); - - out[pos].iov_len = sizeof(struct icmp6_hdr); - - if (pos == CLAT_POS_TRANSPORTHDR && is_icmp_error(icmp->type) && icmp6_type != ICMP6_PARAM_PROB) { - // An ICMP error we understand, one level deep. - // Translate the nested packet (the one that caused the error). - clat_packet_len = ipv4_packet(out, pos + 1, payload, payload_size); - - // The pseudo-header checksum was calculated on the transport length of the original IPv4 - // packet that we were asked to translate. This transport length is 20 bytes smaller than it - // needs to be, because the ICMP error contains an IPv4 header, which we will be translating to - // an IPv6 header, which is 20 bytes longer. Fix it up here. - // We only need to do this for ICMP->ICMPv6, not ICMPv6->ICMP, because ICMP does not use the - // pseudo-header when calculating its checksum (as the IPv4 header has its own checksum). - checksum = checksum + htons(20); - } else if (icmp6_type == ICMP6_ECHO_REQUEST || icmp6_type == ICMP6_ECHO_REPLY) { - // Ping packet. - icmp6_targ->icmp6_id = icmp->un.echo.id; - icmp6_targ->icmp6_seq = icmp->un.echo.sequence; - out[CLAT_POS_PAYLOAD].iov_base = (uint8_t *)payload; - out[CLAT_POS_PAYLOAD].iov_len = payload_size; - clat_packet_len = CLAT_POS_PAYLOAD + 1; - } else { - // Unknown type/code. The type/code conversion functions have already logged an error. - return 0; - } - - icmp6_targ->icmp6_cksum = 0; // Checksum field must be 0 when calculating checksum. - icmp6_targ->icmp6_cksum = packet_checksum(checksum, out, pos); - - return clat_packet_len; -} - -/* function: icmp6_to_icmp - * translate ipv6 icmp to ipv4 icmp - * out - output packet - * icmp6 - source packet icmp6 header - * payload - icmp6 payload - * payload_size - size of payload - * returns: the highest position in the output clat_packet that's filled in - */ -int icmp6_to_icmp(clat_packet out, clat_packet_index pos, const struct icmp6_hdr *icmp6, - const uint8_t *payload, size_t payload_size) { - struct icmphdr *icmp_targ = out[pos].iov_base; - uint8_t icmp_type; - int clat_packet_len; - - memset(icmp_targ, 0, sizeof(struct icmphdr)); - - icmp_type = icmp6_to_icmp_type(icmp6->icmp6_type, icmp6->icmp6_code); - icmp_targ->type = icmp_type; - icmp_targ->code = icmp6_to_icmp_code(icmp6->icmp6_type, icmp6->icmp6_code); - - out[pos].iov_len = sizeof(struct icmphdr); - - if (pos == CLAT_POS_TRANSPORTHDR && is_icmp6_error(icmp6->icmp6_type) && - icmp_type != ICMP_PARAMETERPROB) { - // An ICMPv6 error we understand, one level deep. - // Translate the nested packet (the one that caused the error). - clat_packet_len = ipv6_packet(out, pos + 1, payload, payload_size); - } else if (icmp_type == ICMP_ECHO || icmp_type == ICMP_ECHOREPLY) { - // Ping packet. - icmp_targ->un.echo.id = icmp6->icmp6_id; - icmp_targ->un.echo.sequence = icmp6->icmp6_seq; - out[CLAT_POS_PAYLOAD].iov_base = (uint8_t *)payload; - out[CLAT_POS_PAYLOAD].iov_len = payload_size; - clat_packet_len = CLAT_POS_PAYLOAD + 1; - } else { - // Unknown type/code. The type/code conversion functions have already logged an error. - return 0; - } - - icmp_targ->checksum = 0; // Checksum field must be 0 when calculating checksum. - icmp_targ->checksum = packet_checksum(0, out, pos); - - return clat_packet_len; -} - -/* function: generic_packet - * takes a generic IP packet and sets it up for translation - * out - output packet - * pos - position in the output packet of the transport header - * payload - pointer to IP payload - * len - size of ip payload - * returns: the highest position in the output clat_packet that's filled in - */ -int generic_packet(clat_packet out, clat_packet_index pos, const uint8_t *payload, size_t len) { - out[pos].iov_len = 0; - out[CLAT_POS_PAYLOAD].iov_base = (uint8_t *)payload; - out[CLAT_POS_PAYLOAD].iov_len = len; - - return CLAT_POS_PAYLOAD + 1; -} - -/* function: udp_packet - * takes a udp packet and sets it up for translation - * out - output packet - * udp - pointer to udp header in packet - * old_sum - pseudo-header checksum of old header - * new_sum - pseudo-header checksum of new header - * len - size of ip payload - */ -int udp_packet(clat_packet out, clat_packet_index pos, const struct udphdr *udp, uint32_t old_sum, - uint32_t new_sum, size_t len) { - const uint8_t *payload; - size_t payload_size; - - if (len < sizeof(struct udphdr)) { - logmsg_dbg(ANDROID_LOG_ERROR, "udp_packet/(too small)"); - return 0; - } - - payload = (const uint8_t *)(udp + 1); - payload_size = len - sizeof(struct udphdr); - - return udp_translate(out, pos, udp, old_sum, new_sum, payload, payload_size); -} - -/* function: tcp_packet - * takes a tcp packet and sets it up for translation - * out - output packet - * tcp - pointer to tcp header in packet - * checksum - pseudo-header checksum - * len - size of ip payload - * returns: the highest position in the output clat_packet that's filled in - */ -int tcp_packet(clat_packet out, clat_packet_index pos, const struct tcphdr *tcp, uint32_t old_sum, - uint32_t new_sum, size_t len) { - const uint8_t *payload; - size_t payload_size, header_size; - - if (len < sizeof(struct tcphdr)) { - logmsg_dbg(ANDROID_LOG_ERROR, "tcp_packet/(too small)"); - return 0; - } - - if (tcp->doff < 5) { - logmsg_dbg(ANDROID_LOG_ERROR, "tcp_packet/tcp header length set to less than 5: %x", tcp->doff); - return 0; - } - - if ((size_t)tcp->doff * 4 > len) { - logmsg_dbg(ANDROID_LOG_ERROR, "tcp_packet/tcp header length set too large: %x", tcp->doff); - return 0; - } - - header_size = tcp->doff * 4; - payload = ((const uint8_t *)tcp) + header_size; - payload_size = len - header_size; - - return tcp_translate(out, pos, tcp, header_size, old_sum, new_sum, payload, payload_size); -} - -/* function: udp_translate - * common between ipv4/ipv6 - setup checksum and send udp packet - * out - output packet - * udp - udp header - * old_sum - pseudo-header checksum of old header - * new_sum - pseudo-header checksum of new header - * payload - tcp payload - * payload_size - size of payload - * returns: the highest position in the output clat_packet that's filled in - */ -int udp_translate(clat_packet out, clat_packet_index pos, const struct udphdr *udp, - uint32_t old_sum, uint32_t new_sum, const uint8_t *payload, size_t payload_size) { - struct udphdr *udp_targ = out[pos].iov_base; - - memcpy(udp_targ, udp, sizeof(struct udphdr)); - - out[pos].iov_len = sizeof(struct udphdr); - out[CLAT_POS_PAYLOAD].iov_base = (uint8_t *)payload; - out[CLAT_POS_PAYLOAD].iov_len = payload_size; - - if (udp_targ->check) { - udp_targ->check = ip_checksum_adjust(udp->check, old_sum, new_sum); - } else { - // Zero checksums are special. RFC 768 says, "An all zero transmitted checksum value means that - // the transmitter generated no checksum (for debugging or for higher level protocols that - // don't care)." However, in IPv6 zero UDP checksums were only permitted by RFC 6935 (2013). So - // for safety we recompute it. - udp_targ->check = 0; // Checksum field must be 0 when calculating checksum. - udp_targ->check = packet_checksum(new_sum, out, pos); - } - - // RFC 768: "If the computed checksum is zero, it is transmitted as all ones (the equivalent - // in one's complement arithmetic)." - if (!udp_targ->check) { - udp_targ->check = 0xffff; - } - - return CLAT_POS_PAYLOAD + 1; -} - -/* function: tcp_translate - * common between ipv4/ipv6 - setup checksum and send tcp packet - * out - output packet - * tcp - tcp header - * header_size - size of tcp header including options - * checksum - partial checksum covering ipv4/ipv6 header - * payload - tcp payload - * payload_size - size of payload - * returns: the highest position in the output clat_packet that's filled in - */ -int tcp_translate(clat_packet out, clat_packet_index pos, const struct tcphdr *tcp, - size_t header_size, uint32_t old_sum, uint32_t new_sum, const uint8_t *payload, - size_t payload_size) { - struct tcphdr *tcp_targ = out[pos].iov_base; - out[pos].iov_len = header_size; - - if (header_size > MAX_TCP_HDR) { - // A TCP header cannot be more than MAX_TCP_HDR bytes long because it's a 4-bit field that - // counts in 4-byte words. So this can never happen unless there is a bug in the caller. - logmsg(ANDROID_LOG_ERROR, "tcp_translate: header too long %d > %d, truncating", header_size, - MAX_TCP_HDR); - header_size = MAX_TCP_HDR; - } - - memcpy(tcp_targ, tcp, header_size); - - out[CLAT_POS_PAYLOAD].iov_base = (uint8_t *)payload; - out[CLAT_POS_PAYLOAD].iov_len = payload_size; - - tcp_targ->check = ip_checksum_adjust(tcp->check, old_sum, new_sum); - - return CLAT_POS_PAYLOAD + 1; -} - -// Weak symbol so we can override it in the unit test. -void send_rawv6(int fd, clat_packet out, int iov_len) __attribute__((weak)); - -void send_rawv6(int fd, clat_packet out, int iov_len) { - // A send on a raw socket requires a destination address to be specified even if the socket's - // protocol is IPPROTO_RAW. This is the address that will be used in routing lookups; the - // destination address in the packet header only affects what appears on the wire, not where the - // packet is sent to. - static struct sockaddr_in6 sin6 = { AF_INET6, 0, 0, { { { 0, 0, 0, 0 } } }, 0 }; - static struct msghdr msg = { - .msg_name = &sin6, - .msg_namelen = sizeof(sin6), - }; - - msg.msg_iov = out, msg.msg_iovlen = iov_len, - sin6.sin6_addr = ((struct ip6_hdr *)out[CLAT_POS_IPHDR].iov_base)->ip6_dst; - sendmsg(fd, &msg, 0); -} - -/* function: translate_packet - * takes a packet, translates it, and writes it to fd - * fd - fd to write translated packet to - * to_ipv6 - true if translating to ipv6, false if translating to ipv4 - * packet - packet - * packetsize - size of packet - */ -void translate_packet(int fd, int to_ipv6, const uint8_t *packet, size_t packetsize) { - int iov_len = 0; - - // Allocate buffers for all packet headers. - struct tun_pi tun_targ; - char iphdr[sizeof(struct ip6_hdr)]; - char fraghdr[sizeof(struct ip6_frag)]; - char transporthdr[MAX_TCP_HDR]; - char icmp_iphdr[sizeof(struct ip6_hdr)]; - char icmp_fraghdr[sizeof(struct ip6_frag)]; - char icmp_transporthdr[MAX_TCP_HDR]; - - // iovec of the packets we'll send. This gets passed down to the translation functions. - clat_packet out = { - { &tun_targ, 0 }, // Tunnel header. - { iphdr, 0 }, // IP header. - { fraghdr, 0 }, // Fragment header. - { transporthdr, 0 }, // Transport layer header. - { icmp_iphdr, 0 }, // ICMP error inner IP header. - { icmp_fraghdr, 0 }, // ICMP error fragmentation header. - { icmp_transporthdr, 0 }, // ICMP error transport layer header. - { NULL, 0 }, // Payload. No buffer, it's a pointer to the original payload. - }; - - if (to_ipv6) { - iov_len = ipv4_packet(out, CLAT_POS_IPHDR, packet, packetsize); - if (iov_len > 0) { - send_rawv6(fd, out, iov_len); - } - } else { - iov_len = ipv6_packet(out, CLAT_POS_IPHDR, packet, packetsize); - if (iov_len > 0) { - fill_tun_header(&tun_targ, ETH_P_IP); - out[CLAT_POS_TUNHDR].iov_len = sizeof(tun_targ); - writev(fd, out, iov_len); - } - } -} |