| /* |
| * 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 "netutils/checksum.h" |
| |
| #include "debug.h" |
| #include "dump.h" |
| #include "logging.h" |
| #include "translate.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, clat_packet_index pos, const struct icmphdr *icmp, |
| uint32_t checksum, size_t len) { |
| const uint8_t *payload; |
| size_t payload_size; |
| |
| if (len < sizeof(struct icmphdr)) { |
| logmsg_dbg(ANDROID_LOG_ERROR, "icmp_packet/(too small)"); |
| return 0; |
| } |
| |
| payload = (const uint8_t *)(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, clat_packet_index pos, const uint8_t *packet, size_t len) { |
| const struct iphdr *header = (struct iphdr *)packet; |
| struct ip6_hdr *ip6_targ = (struct ip6_hdr *)out[pos].iov_base; |
| struct ip6_frag *frag_hdr; |
| size_t frag_hdr_len; |
| uint8_t nxthdr; |
| const uint8_t *next_header; |
| size_t len_left; |
| uint32_t old_sum, new_sum; |
| int iov_len; |
| |
| if (len < sizeof(struct iphdr)) { |
| logmsg_dbg(ANDROID_LOG_ERROR, "ip_packet/too short for an ip header"); |
| 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. |
| * 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 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 + 2, (const struct tcphdr *)next_header, old_sum, new_sum, len_left); |
| } else if (nxthdr == IPPROTO_UDP) { |
| iov_len = |
| udp_packet(out, pos + 2, (const struct udphdr *)next_header, old_sum, new_sum, len_left); |
| } else if (nxthdr == IPPROTO_GRE || nxthdr == IPPROTO_ESP) { |
| 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); |
| logcat_hexdump("ipv4/protocol", packet, len); |
| #endif |
| return 0; |
| } |
| |
| // Set the length. |
| ip6_targ->ip6_plen = htons(packet_length(out, pos)); |
| return iov_len; |
| } |