diff options
-rw-r--r-- | clatd.c | 8 | ||||
-rw-r--r-- | dump.c | 1 | ||||
-rw-r--r-- | ipv4.c | 33 | ||||
-rw-r--r-- | ipv6.c | 52 | ||||
-rw-r--r-- | translate.c | 54 | ||||
-rw-r--r-- | translate.h | 13 |
6 files changed, 126 insertions, 35 deletions
@@ -51,6 +51,9 @@ #define DEVICENAME6 "clat" #define DEVICENAME4 "clat4" +/* 40 bytes IPv6 header - 20 bytes IPv4 header + 8 bytes fragment header */ +#define MTU_DELTA 28 + int forwarding_fd = -1; volatile sig_atomic_t running = 1; @@ -271,8 +274,9 @@ void configure_interface(const char *uplink_interface, const char *plat_prefix, Global_Clatd_Config.mtu = 1280; } - if(Global_Clatd_Config.ipv4mtu <= 0 || (Global_Clatd_Config.ipv4mtu > Global_Clatd_Config.mtu - 20)) { - Global_Clatd_Config.ipv4mtu = Global_Clatd_Config.mtu-20; + if(Global_Clatd_Config.ipv4mtu <= 0 || + Global_Clatd_Config.ipv4mtu > Global_Clatd_Config.mtu - MTU_DELTA) { + Global_Clatd_Config.ipv4mtu = Global_Clatd_Config.mtu - MTU_DELTA; logmsg(ANDROID_LOG_WARN,"ipv4mtu now set to = %d",Global_Clatd_Config.ipv4mtu); } @@ -220,6 +220,7 @@ void logcat_hexdump(const char *info, const char *data, size_t len) { char output[PACKETLEN*3+2]; size_t i; + output[0] = '\0'; for(i = 0; i < len && i < PACKETLEN; i++) { snprintf(output + i*3, 4, " %02x", (uint8_t)data[i]); } @@ -57,7 +57,8 @@ int icmp_packet(clat_packet out, int pos, const struct icmphdr *icmp, uint32_t c int ipv4_packet(clat_packet out, int pos, const char *packet, size_t len) { const struct iphdr *header = (struct iphdr *) packet; struct ip6_hdr *ip6_targ = (struct ip6_hdr *) out[pos].iov_base; - uint16_t frag_flags; + struct ip6_frag *frag_hdr; + size_t frag_hdr_len; uint8_t nxthdr; const char *next_header; size_t len_left; @@ -69,12 +70,6 @@ int ipv4_packet(clat_packet out, int pos, const char *packet, size_t len) { return 0; } - frag_flags = ntohs(header->frag_off); - if(frag_flags & IP_MF) { // this could theoretically be supported, but isn't - logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/more fragments set, dropping"); - return 0; - } - if(header->ihl < 5) { logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/ip header length set to less than 5: %x", header->ihl); return 0; @@ -111,20 +106,32 @@ int ipv4_packet(clat_packet out, int pos, const char *packet, size_t len) { fill_ip6_header(ip6_targ, 0, nxthdr, header); out[pos].iov_len = sizeof(struct ip6_hdr); - // Calculate the pseudo-header checksum. + /* 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 = ipv4_pseudo_header_checksum(header, len_left); new_sum = ipv6_pseudo_header_checksum(ip6_targ, len_left, nxthdr); - if (nxthdr == IPPROTO_ICMPV6) { - iov_len = icmp_packet(out, pos + 1, (const struct icmphdr *) next_header, new_sum, len_left); + // If the IPv4 packet is fragmented, add a Fragment header. + frag_hdr = (struct ip6_frag *) out[pos + 1].iov_base; + frag_hdr_len = maybe_fill_frag_header(frag_hdr, ip6_targ, header); + out[pos + 1].iov_len = frag_hdr_len; + + if (frag_hdr_len && frag_hdr->ip6f_offlg & IP6F_OFF_MASK) { + // Non-first fragment. Copy the rest of the packet as is. + iov_len = generic_packet(out, pos + 2, next_header, len_left); + } else if (nxthdr == IPPROTO_ICMPV6) { + iov_len = icmp_packet(out, pos + 2, (const struct icmphdr *) next_header, new_sum, len_left); } else if (nxthdr == IPPROTO_TCP) { - iov_len = tcp_packet(out, pos + 1, (const struct tcphdr *) next_header, old_sum, new_sum, + iov_len = tcp_packet(out, pos + 2, (const struct tcphdr *) next_header, old_sum, new_sum, len_left); } else if (nxthdr == IPPROTO_UDP) { - iov_len = udp_packet(out, pos + 1, (const struct udphdr *) next_header, old_sum, new_sum, + iov_len = udp_packet(out, pos + 2, (const struct udphdr *) next_header, old_sum, new_sum, len_left); } else if (nxthdr == IPPROTO_GRE) { - iov_len = generic_packet(out, pos + 1, next_header, len_left); + iov_len = generic_packet(out, pos + 2, next_header, len_left); } else { #if CLAT_DEBUG logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/unknown protocol: %x",header->protocol); @@ -77,6 +77,7 @@ void log_bad_address(const char *fmt, const struct in6_addr *src, const struct i int ipv6_packet(clat_packet out, int pos, const char *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 char *next_header; size_t len_left; @@ -112,10 +113,6 @@ int ipv6_packet(clat_packet out, int pos, const char *packet, size_t len) { len_left = len - sizeof(struct ip6_hdr); protocol = ip6->ip6_nxt; - if (protocol == IPPROTO_ICMPV6) { - // ICMP and ICMPv6 have different protocol numbers. - protocol = IPPROTO_ICMP; - } /* 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 @@ -124,21 +121,48 @@ int ipv6_packet(clat_packet out, int pos, const char *packet, size_t len) { fill_ip_header(ip_targ, 0, protocol, ip6); out[pos].iov_len = sizeof(struct iphdr); - // Calculate the pseudo-header checksum. + // 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, this will drop any packet with them - if (protocol == IPPROTO_ICMP) { - iov_len = icmp6_packet(out, pos + 1, (const struct icmp6_hdr *) next_header, len_left); - } else if (ip6->ip6_nxt == IPPROTO_TCP) { - iov_len = tcp_packet(out, pos + 1, (const struct tcphdr *) next_header, old_sum, new_sum, + // 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 (ip6->ip6_nxt == IPPROTO_UDP) { - iov_len = udp_packet(out, pos + 1, (const struct udphdr *) next_header, old_sum, new_sum, + } 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 (ip6->ip6_nxt == IPPROTO_GRE) { - iov_len = generic_packet(out, pos + 1, next_header, 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); diff --git a/translate.c b/translate.c index f7f09cb..7585092 100644 --- a/translate.c +++ b/translate.c @@ -167,6 +167,53 @@ void fill_ip6_header(struct ip6_hdr *ip6, uint16_t payload_len, uint8_t protocol 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 @@ -393,9 +440,6 @@ int udp_translate(clat_packet out, int pos, const struct udphdr *udp, uint32_t o * payload - tcp payload * payload_size - size of payload * returns: the highest position in the output clat_packet that's filled in - * - * TODO: mss rewrite - * TODO: hosts without pmtu discovery - non DF packets will rely on fragmentation (unimplemented) */ int tcp_translate(clat_packet out, int pos, const struct tcphdr *tcp, size_t header_size, uint32_t old_sum, uint32_t new_sum, const char *payload, size_t payload_size) { @@ -435,16 +479,20 @@ void translate_packet(const struct tun_data *tunnel, struct tun_pi *tun_header, // 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, sizeof(tun_targ) }, // 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. }; diff --git a/translate.h b/translate.h index 3378254..5efa817 100644 --- a/translate.h +++ b/translate.h @@ -36,9 +36,11 @@ // The CLAT_POS_XXX constants represent the array indices within the clat_packet that contain // specific parts of the packet. The packet_* functions operate on all the packet segments past a // given position. -enum clat_packet_index { CLAT_POS_TUNHDR, CLAT_POS_IPHDR, CLAT_POS_TRANSPORTHDR, - CLAT_POS_ICMPERR_IPHDR, CLAT_POS_ICMPERR_TRANSPORTHDR, - CLAT_POS_PAYLOAD, CLAT_POS_MAX }; +enum clat_packet_index { + CLAT_POS_TUNHDR, CLAT_POS_IPHDR, CLAT_POS_FRAGHDR, CLAT_POS_TRANSPORTHDR, + CLAT_POS_ICMPERR_IPHDR, CLAT_POS_ICMPERR_FRAGHDR, CLAT_POS_ICMPERR_TRANSPORTHDR, + CLAT_POS_PAYLOAD, CLAT_POS_MAX +}; typedef struct iovec clat_packet[CLAT_POS_MAX]; // Calculates the checksum over all the packet components starting from pos. @@ -65,6 +67,11 @@ void translate_packet(const struct tun_data *tunnel, struct tun_pi *tun_header, int ipv4_packet(clat_packet out, int pos, const char *packet, size_t len); int ipv6_packet(clat_packet out, int pos, const char *packet, size_t len); +// Deal with fragmented packets. +size_t maybe_fill_frag_header(struct ip6_frag *frag_hdr, struct ip6_hdr *ip6_targ, + const struct iphdr *old_header); +uint8_t parse_frag_header(const struct ip6_frag *frag_hdr, struct iphdr *ip_targ); + // Translate ICMP packets. int icmp_to_icmp6(clat_packet out, int pos, const struct icmphdr *icmp, uint32_t checksum, const char *payload, size_t payload_size); |