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 * ipv4.c - takes ipv4 packets, finds their headers, and then calls translation functions on them 17 */ 18 #include <string.h> 19 20 #include "translate.h" 21 #include "checksum.h" 22 #include "logging.h" 23 #include "debug.h" 24 #include "dump.h" 25 26 /* function: icmp_packet 27 * translates an icmp packet 28 * out - output packet 29 * icmp - pointer to icmp header in packet 30 * checksum - pseudo-header checksum 31 * len - size of ip payload 32 * returns: the highest position in the output clat_packet that's filled in 33 */ 34 int icmp_packet(clat_packet out, clat_packet_index pos, const struct icmphdr *icmp, 35 uint32_t checksum, size_t len) { 36 const uint8_t *payload; 37 size_t payload_size; 38 39 if(len < sizeof(struct icmphdr)) { 40 logmsg_dbg(ANDROID_LOG_ERROR, "icmp_packet/(too small)"); 41 return 0; 42 } 43 44 payload = (const uint8_t *) (icmp + 1); 45 payload_size = len - sizeof(struct icmphdr); 46 47 return icmp_to_icmp6(out, pos, icmp, checksum, payload, payload_size); 48 } 49 50 /* function: ipv4_packet 51 * translates an ipv4 packet 52 * out - output packet 53 * packet - packet data 54 * len - size of packet 55 * returns: the highest position in the output clat_packet that's filled in 56 */ 57 int ipv4_packet(clat_packet out, clat_packet_index pos, const uint8_t *packet, size_t len) { 58 const struct iphdr *header = (struct iphdr *) packet; 59 struct ip6_hdr *ip6_targ = (struct ip6_hdr *) out[pos].iov_base; 60 struct ip6_frag *frag_hdr; 61 size_t frag_hdr_len; 62 uint8_t nxthdr; 63 const uint8_t *next_header; 64 size_t len_left; 65 uint32_t old_sum, new_sum; 66 int iov_len; 67 68 if(len < sizeof(struct iphdr)) { 69 logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/too short for an ip header"); 70 return 0; 71 } 72 73 if(header->ihl < 5) { 74 logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/ip header length set to less than 5: %x", header->ihl); 75 return 0; 76 } 77 78 if((size_t) header->ihl * 4 > len) { // ip header length larger than entire packet 79 logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/ip header length set too large: %x", header->ihl); 80 return 0; 81 } 82 83 if(header->version != 4) { 84 logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/ip header version not 4: %x", header->version); 85 return 0; 86 } 87 88 /* rfc6145 - If any IPv4 options are present in the IPv4 packet, they MUST be 89 * ignored and the packet translated normally; there is no attempt to 90 * translate the options. 91 */ 92 93 next_header = packet + header->ihl*4; 94 len_left = len - header->ihl * 4; 95 96 nxthdr = header->protocol; 97 if (nxthdr == IPPROTO_ICMP) { 98 // ICMP and ICMPv6 have different protocol numbers. 99 nxthdr = IPPROTO_ICMPV6; 100 } 101 102 /* Fill in the IPv6 header. We need to do this before we translate the packet because TCP and 103 * UDP include parts of the IP header in the checksum. Set the length to zero because we don't 104 * know it yet. 105 */ 106 fill_ip6_header(ip6_targ, 0, nxthdr, header); 107 out[pos].iov_len = sizeof(struct ip6_hdr); 108 109 /* Calculate the pseudo-header checksum. 110 * Technically, the length that is used in the pseudo-header checksum is the transport layer 111 * length, which is not the same as len_left in the case of fragmented packets. But since 112 * translation does not change the transport layer length, the checksum is unaffected. 113 */ 114 old_sum = ipv4_pseudo_header_checksum(header, len_left); 115 new_sum = ipv6_pseudo_header_checksum(ip6_targ, len_left, nxthdr); 116 117 // If the IPv4 packet is fragmented, add a Fragment header. 118 frag_hdr = (struct ip6_frag *) out[pos + 1].iov_base; 119 frag_hdr_len = maybe_fill_frag_header(frag_hdr, ip6_targ, header); 120 out[pos + 1].iov_len = frag_hdr_len; 121 122 if (frag_hdr_len && frag_hdr->ip6f_offlg & IP6F_OFF_MASK) { 123 // Non-first fragment. Copy the rest of the packet as is. 124 iov_len = generic_packet(out, pos + 2, next_header, len_left); 125 } else if (nxthdr == IPPROTO_ICMPV6) { 126 iov_len = icmp_packet(out, pos + 2, (const struct icmphdr *) next_header, new_sum, len_left); 127 } else if (nxthdr == IPPROTO_TCP) { 128 iov_len = tcp_packet(out, pos + 2, (const struct tcphdr *) next_header, old_sum, new_sum, 129 len_left); 130 } else if (nxthdr == IPPROTO_UDP) { 131 iov_len = udp_packet(out, pos + 2, (const struct udphdr *) next_header, old_sum, new_sum, 132 len_left); 133 } else if (nxthdr == IPPROTO_GRE) { 134 iov_len = generic_packet(out, pos + 2, next_header, len_left); 135 } else { 136 #if CLAT_DEBUG 137 logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/unknown protocol: %x",header->protocol); 138 logcat_hexdump("ipv4/protocol", packet, len); 139 #endif 140 return 0; 141 } 142 143 // Set the length. 144 ip6_targ->ip6_plen = htons(packet_length(out, pos)); 145 return iov_len; 146 } 147
