| /* |
| * 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. |
| * |
| * ipv4.c - takes ipv4 packets, finds their headers, and then calls translation functions on them |
| */ |
| #include <string.h> |
| |
| #include <netinet/in.h> |
| #include <netinet/ip.h> |
| #include <netinet/ip_icmp.h> |
| #include <netinet/udp.h> |
| #include <netinet/tcp.h> |
| #include <netinet/ip6.h> |
| #include <netinet/icmp6.h> |
| #include <linux/icmp.h> |
| |
| #include "translate.h" |
| #include "checksum.h" |
| #include "logging.h" |
| #include "debug.h" |
| #include "dump.h" |
| |
| /* function: icmp_packet |
| * translates an icmp packet |
| * out - output packet |
| * icmp - pointer to icmp 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 icmp_packet(clat_packet out, int pos, const struct icmphdr *icmp, uint32_t checksum, |
| size_t len) { |
| const char *payload; |
| size_t payload_size; |
| |
| if(len < sizeof(struct icmphdr)) { |
| logmsg_dbg(ANDROID_LOG_ERROR, "icmp_packet/(too small)"); |
| return 0; |
| } |
| |
| payload = (const char *) (icmp + 1); |
| payload_size = len - sizeof(struct icmphdr); |
| |
| return icmp_to_icmp6(out, pos, icmp, checksum, payload, payload_size); |
| } |
| |
| /* function: ipv4_packet |
| * translates an ipv4 packet |
| * out - output packet |
| * packet - packet data |
| * len - size of packet |
| * returns: the highest position in the output clat_packet that's filled in |
| */ |
| 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; |
| uint8_t nxthdr; |
| const char *next_header; |
| size_t len_left; |
| uint32_t checksum; |
| int iov_len; |
| |
| if(len < sizeof(struct iphdr)) { |
| logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/too short for an ip header"); |
| 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; |
| } |
| |
| if((size_t) header->ihl * 4 > len) { // ip header length larger than entire packet |
| logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/ip header length set too large: %x", header->ihl); |
| return 0; |
| } |
| |
| if(header->version != 4) { |
| logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/ip header version not 4: %x", header->version); |
| return 0; |
| } |
| |
| /* rfc6145 - If any IPv4 options are present in the IPv4 packet, they MUST be |
| * ignored and the packet translated normally; there is no attempt to |
| * translate the options. |
| */ |
| |
| next_header = packet + header->ihl*4; |
| len_left = len - header->ihl * 4; |
| |
| nxthdr = header->protocol; |
| if (nxthdr == IPPROTO_ICMP) { |
| // ICMP and ICMPv6 have different protocol numbers. |
| nxthdr = IPPROTO_ICMPV6; |
| } |
| |
| /* Fill in the IPv6 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_ip6_header(ip6_targ, 0, nxthdr, header); |
| out[pos].iov_len = sizeof(struct ip6_hdr); |
| |
| // Calculate the pseudo-header checksum. |
| checksum = ipv6_pseudo_header_checksum(0, ip6_targ, len_left); |
| |
| if(nxthdr == IPPROTO_ICMPV6) { |
| iov_len = icmp_packet(out, pos + 1, (const struct icmphdr *) next_header, checksum, len_left); |
| } else if(nxthdr == IPPROTO_TCP) { |
| iov_len = tcp_packet(out, pos + 1, (const struct tcphdr *) next_header, checksum, len_left); |
| } else if(nxthdr == IPPROTO_UDP) { |
| iov_len = udp_packet(out, pos + 1, (const struct udphdr *) next_header, checksum, len_left); |
| } else { |
| #if CLAT_DEBUG |
| logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/unknown protocol: %x",header->protocol); |
| logcat_hexdump("ipv4/protocol", packet, len); |
| #endif |
| return 0; |
| } |
| |
| // Set the length. |
| ip6_targ->ip6_plen = htons(packet_length(out, pos)); |
| return iov_len; |
| } |