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/*
* 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 "ipv4.h"
#include "logging.h"
#include "debug.h"
/* function: icmp_packet
* takes an icmp packet and sets it up for translation
* fd - tun interface fd
* packet - ip payload
* len - size of ip payload
* ip - ip header
*/
void icmp_packet(int fd, const char *packet, size_t len, struct iphdr *ip) {
struct icmphdr icmp;
const char *payload;
size_t payload_size;
if(len < sizeof(icmp)) {
logmsg_dbg(ANDROID_LOG_ERROR,"icmp_packet/(too small)");
return;
}
memcpy(&icmp, packet, sizeof(icmp));
payload = packet + sizeof(icmp);
payload_size = len - sizeof(icmp);
icmp_to_icmp6(fd,ip,&icmp,payload,payload_size);
}
/* function: tcp_packet
* takes a tcp packet and sets it up for translation
* fd - tun interface fd
* packet - ip payload
* len - size of ip payload
* ip - ip header
*/
void tcp_packet(int fd, const char *packet, size_t len, struct iphdr *ip) {
struct tcphdr tcp;
const char *payload;
const char *options;
size_t payload_size, options_size;
if(len < sizeof(tcp)) {
logmsg_dbg(ANDROID_LOG_ERROR,"tcp_packet/(too small)");
return;
}
memcpy(&tcp, packet, sizeof(tcp));
if(tcp.doff < 5) {
logmsg_dbg(ANDROID_LOG_ERROR,"tcp_packet/tcp header length set to less than 5: %x",tcp.doff);
return;
}
if((size_t)tcp.doff*4 > len) {
logmsg_dbg(ANDROID_LOG_ERROR,"tcp_packet/tcp header length set too large: %x",tcp.doff);
return;
}
if(tcp.doff > 5) {
options = packet + sizeof(tcp);
options_size = tcp.doff*4 - sizeof(tcp);
} else {
options = NULL;
options_size = 0;
}
payload = packet + tcp.doff*4;
payload_size = len - tcp.doff*4;
tcp_to_tcp6(fd,ip,&tcp,payload,payload_size,options,options_size);
}
/* function: udp_packet
* takes a udp packet and sets it up for translation
* fd - tun interface fd
* packet - ip payload
* len - size of ip payload
* ip - ip header
*/
void udp_packet(int fd, const char *packet, size_t len, const struct iphdr *ip) {
struct udphdr udp;
const char *payload;
size_t payload_size;
if(len < sizeof(udp)) {
logmsg_dbg(ANDROID_LOG_ERROR,"udp_packet/(too small)");
return;
}
memcpy(&udp, packet, sizeof(udp));
payload = packet + sizeof(udp);
payload_size = len - sizeof(udp);
udp_to_udp6(fd,ip,&udp,payload,payload_size);
}
/* function: ip_packet
* takes an ip packet and hands it off to the layer 4 protocol function
* fd - tun interface fd
* packet - packet data
* len - size of packet
*/
void ip_packet(int fd, const char *packet, size_t len) {
struct iphdr header;
uint16_t frag_flags;
const char *next_header;
size_t len_left;
if(len < sizeof(header)) {
logmsg_dbg(ANDROID_LOG_ERROR,"ip_packet/too short for an ip header");
return;
}
memcpy(&header, packet, sizeof(header));
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;
}
if(header.ihl < 5) {
logmsg_dbg(ANDROID_LOG_ERROR,"ip_packet/ip header length set to less than 5: %x",header.ihl);
return;
}
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;
}
if(header.version != 4) {
logmsg_dbg(ANDROID_LOG_ERROR,"ip_packet/ip header version not 4: %x",header.version);
return;
}
/* 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;
if(header.protocol == IPPROTO_ICMP) {
icmp_packet(fd,next_header,len_left,&header);
} else if(header.protocol == IPPROTO_TCP) {
tcp_packet(fd,next_header,len_left,&header);
} else if(header.protocol == IPPROTO_UDP) {
udp_packet(fd,next_header,len_left,&header);
} else {
#if CLAT_DEBUG
logmsg_dbg(ANDROID_LOG_ERROR,"ip_packet/unknown protocol: %x",header.protocol);
logcat_hexdump("ipv4/protocol", packet, len);
#endif
}
}
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