/*
* 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.
*
* config.c - configuration settings
*/
#include <string.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <limits.h>
#include <errno.h>
#include <unistd.h>
#include <cutils/config_utils.h>
#include <netutils/ifc.h>
#include "config.h"
#include "dns64.h"
#include "logging.h"
#include "getaddr.h"
#include "clatd.h"
#include "checksum.h"
struct clat_config Global_Clatd_Config;
/* function: config_item_str
* locates the config item and returns the pointer to a string, or NULL on failure. Caller frees pointer
* root - parsed configuration
* item_name - name of config item to locate
* defaultvar - value to use if config item isn't present
*/
char *config_item_str(cnode *root, const char *item_name, const char *defaultvar) {
const char *tmp;
if(!(tmp = config_str(root, item_name, defaultvar))) {
logmsg(ANDROID_LOG_FATAL,"%s config item needed",item_name);
return NULL;
}
return strdup(tmp);
}
/* function: config_item_int16_t
* locates the config item, parses the integer, and returns the pointer ret_val_ptr, or NULL on failure
* root - parsed configuration
* item_name - name of config item to locate
* defaultvar - value to use if config item isn't present
* ret_val_ptr - pointer for return value storage
*/
int16_t *config_item_int16_t(cnode *root, const char *item_name, const char *defaultvar, int16_t *ret_val_ptr) {
const char *tmp;
char *endptr;
long int conf_int;
if(!(tmp = config_str(root, item_name, defaultvar))) {
logmsg(ANDROID_LOG_FATAL,"%s config item needed",item_name);
return NULL;
}
errno = 0;
conf_int = strtol(tmp,&endptr,10);
if(errno > 0) {
logmsg(ANDROID_LOG_FATAL,"%s config item is not numeric: %s (error=%s)",item_name,tmp,strerror(errno));
return NULL;
}
if(endptr == tmp || *tmp == '\0') {
logmsg(ANDROID_LOG_FATAL,"%s config item is not numeric: %s",item_name,tmp);
return NULL;
}
if(*endptr != '\0') {
logmsg(ANDROID_LOG_FATAL,"%s config item contains non-numeric characters: %s",item_name,endptr);
return NULL;
}
if(conf_int > INT16_MAX || conf_int < INT16_MIN) {
logmsg(ANDROID_LOG_FATAL,"%s config item is too big/small: %d",item_name,conf_int);
return NULL;
}
*ret_val_ptr = conf_int;
return ret_val_ptr;
}
/* function: config_item_ip
* locates the config item, parses the ipv4 address, and returns the pointer ret_val_ptr, or NULL on failure
* root - parsed configuration
* item_name - name of config item to locate
* defaultvar - value to use if config item isn't present
* ret_val_ptr - pointer for return value storage
*/
struct in_addr *config_item_ip(cnode *root, const char *item_name, const char *defaultvar, struct in_addr *ret_val_ptr) {
const char *tmp;
int status;
if(!(tmp = config_str(root, item_name, defaultvar))) {
logmsg(ANDROID_LOG_FATAL,"%s config item needed",item_name);
return NULL;
}
status = inet_pton(AF_INET, tmp, ret_val_ptr);
if(status <= 0) {
logmsg(ANDROID_LOG_FATAL,"invalid IPv4 address specified for %s: %s", item_name, tmp);
return NULL;
}
return ret_val_ptr;
}
/* function: config_item_ip6
* locates the config item, parses the ipv6 address, and returns the pointer ret_val_ptr, or NULL on failure
* root - parsed configuration
* item_name - name of config item to locate
* defaultvar - value to use if config item isn't present
* ret_val_ptr - pointer for return value storage
*/
struct in6_addr *config_item_ip6(cnode *root, const char *item_name, const char *defaultvar, struct in6_addr *ret_val_ptr) {
const char *tmp;
int status;
if(!(tmp = config_str(root, item_name, defaultvar))) {
logmsg(ANDROID_LOG_FATAL,"%s config item needed",item_name);
return NULL;
}
status = inet_pton(AF_INET6, tmp, ret_val_ptr);
if(status <= 0) {
logmsg(ANDROID_LOG_FATAL,"invalid IPv6 address specified for %s: %s", item_name, tmp);
return NULL;
}
return ret_val_ptr;
}
/* function: free_config
* frees the memory used by the global config variable
*/
void free_config() {
if(Global_Clatd_Config.plat_from_dns64_hostname) {
free(Global_Clatd_Config.plat_from_dns64_hostname);
Global_Clatd_Config.plat_from_dns64_hostname = NULL;
}
}
/* function: ipv6_prefix_equal
* compares the prefixes two ipv6 addresses. assumes the prefix lengths are both /64.
* a1 - first address
* a2 - second address
* returns: 0 if the subnets are different, 1 if they are the same.
*/
int ipv6_prefix_equal(struct in6_addr *a1, struct in6_addr *a2) {
return !memcmp(a1, a2, 8);
}
/* function: dns64_detection
* does dns lookups to set the plat subnet or exits on failure, waits forever for a dns response with a query backoff timer
* net_id - (optional) netId to use, NETID_UNSET indicates use of default network
*/
void dns64_detection(unsigned net_id) {
int backoff_sleep, status;
struct in6_addr tmp_ptr;
backoff_sleep = 1;
while(1) {
status = plat_prefix(Global_Clatd_Config.plat_from_dns64_hostname,net_id,&tmp_ptr);
if(status > 0) {
memcpy(&Global_Clatd_Config.plat_subnet, &tmp_ptr, sizeof(struct in6_addr));
return;
}
logmsg(ANDROID_LOG_WARN, "dns64_detection -- error, sleeping for %d seconds", backoff_sleep);
sleep(backoff_sleep);
backoff_sleep *= 2;
if(backoff_sleep >= 120) {
backoff_sleep = 120;
}
}
}
/* function: gen_random_iid
* picks a random interface ID that is checksum neutral with the IPv4 address and the NAT64 prefix
* myaddr - IPv6 address to write to
* ipv4_local_subnet - clat IPv4 address
* plat_subnet - NAT64 prefix
*/
void gen_random_iid(struct in6_addr *myaddr, struct in_addr *ipv4_local_subnet,
struct in6_addr *plat_subnet) {
// Fill last 8 bytes of IPv6 address with random bits.
arc4random_buf(&myaddr->s6_addr[8], 8);
// Make the IID checksum-neutral. That is, make it so that:
// checksum(Local IPv4 | Remote IPv4) = checksum(Local IPv6 | Remote IPv6)
// in other words (because remote IPv6 = NAT64 prefix | Remote IPv4):
// checksum(Local IPv4) = checksum(Local IPv6 | NAT64 prefix)
// Do this by adjusting the two bytes in the middle of the IID.
uint16_t middlebytes = (myaddr->s6_addr[11] << 8) + myaddr->s6_addr[12];
uint32_t c1 = ip_checksum_add(0, ipv4_local_subnet, sizeof(*ipv4_local_subnet));
uint32_t c2 = ip_checksum_add(0, plat_subnet, sizeof(*plat_subnet)) +
ip_checksum_add(0, myaddr, sizeof(*myaddr));
uint16_t delta = ip_checksum_adjust(middlebytes, c1, c2);
myaddr->s6_addr[11] = delta >> 8;
myaddr->s6_addr[12] = delta & 0xff;
}
// Factored out to a separate function for testability.
int connect_is_ipv4_address_free(in_addr_t addr) {
int s = socket(AF_INET, SOCK_DGRAM, 0);
if (s == -1) {
return 0;
}
// Attempt to connect to the address. If the connection succeeds and getsockname returns the same
// the address then the address is already assigned to the system and we can't use it.
struct sockaddr_in sin = { .sin_family = AF_INET, .sin_addr = { addr }, .sin_port = 53 };
socklen_t len = sizeof(sin);
int inuse = connect(s, (struct sockaddr *) &sin, sizeof(sin)) == 0 &&
getsockname(s, (struct sockaddr *) &sin, &len) == 0 &&
(size_t) len >= sizeof(sin) &&
sin.sin_addr.s_addr == addr;
close(s);
return !inuse;
}
addr_free_func config_is_ipv4_address_free = connect_is_ipv4_address_free;
/* function: config_select_ipv4_address
* picks a free IPv4 address, starting from ip and trying all addresses in the prefix in order
* ip - the IP address from the configuration file
* prefixlen - the length of the prefix from which addresses may be selected.
* returns: the IPv4 address, or INADDR_NONE if no addresses were available
*/
in_addr_t config_select_ipv4_address(const struct in_addr *ip, int16_t prefixlen) {
in_addr_t chosen = INADDR_NONE;
// Don't accept prefixes that are too large because we scan addresses one by one.
if (prefixlen < 16 || prefixlen > 32) {
return chosen;
}
// All these are in host byte order.
in_addr_t mask = 0xffffffff >> (32 - prefixlen) << (32 - prefixlen);
in_addr_t ipv4 = ntohl(ip->s_addr);
in_addr_t first_ipv4 = ipv4;
in_addr_t prefix = ipv4 & mask;
// Pick the first IPv4 address in the pool, wrapping around if necessary.
// So, for example, 192.0.0.4 -> 192.0.0.5 -> 192.0.0.6 -> 192.0.0.7 -> 192.0.0.0.
do {
if (config_is_ipv4_address_free(htonl(ipv4))) {
chosen = htonl(ipv4);
break;
}
ipv4 = prefix | ((ipv4 + 1) & ~mask);
} while (ipv4 != first_ipv4);
return chosen;
}
/* function: config_generate_local_ipv6_subnet
* generates the local ipv6 subnet when given the interface ip
* requires config.ipv6_host_id
* interface_ip - in: interface ip, out: local ipv6 host address
*/
void config_generate_local_ipv6_subnet(struct in6_addr *interface_ip) {
int i;
if (Global_Clatd_Config.use_dynamic_iid) {
/* Generate a random interface ID. */
gen_random_iid(interface_ip,
&Global_Clatd_Config.ipv4_local_subnet,
&Global_Clatd_Config.plat_subnet);
} else {
/* Use the specified interface ID. */
for(i = 2; i < 4; i++) {
interface_ip->s6_addr32[i] = Global_Clatd_Config.ipv6_host_id.s6_addr32[i];
}
}
}
/* function: read_config
* reads the config file and parses it into the global variable Global_Clatd_Config. returns 0 on failure, 1 on success
* file - filename to parse
* uplink_interface - interface to use to reach the internet and supplier of address space
* plat_prefix - (optional) plat prefix to use, otherwise follow config file
* net_id - (optional) netId to use, NETID_UNSET indicates use of default network
*/
int read_config(const char *file, const char *uplink_interface, const char *plat_prefix,
unsigned net_id) {
cnode *root = config_node("", "");
void *tmp_ptr = NULL;
unsigned flags;
if(!root) {
logmsg(ANDROID_LOG_FATAL,"out of memory");
return 0;
}
memset(&Global_Clatd_Config, '\0', sizeof(Global_Clatd_Config));
config_load_file(root, file);
if(root->first_child == NULL) {
logmsg(ANDROID_LOG_FATAL,"Could not read config file %s", file);
goto failed;
}
Global_Clatd_Config.default_pdp_interface = strdup(uplink_interface);
if (!Global_Clatd_Config.default_pdp_interface)
goto failed;
if(!config_item_int16_t(root, "mtu", "-1", &Global_Clatd_Config.mtu))
goto failed;
if(!config_item_int16_t(root, "ipv4mtu", "-1", &Global_Clatd_Config.ipv4mtu))
goto failed;
if(!config_item_ip(root, "ipv4_local_subnet", DEFAULT_IPV4_LOCAL_SUBNET,
&Global_Clatd_Config.ipv4_local_subnet))
goto failed;
if(!config_item_int16_t(root, "ipv4_local_prefixlen", DEFAULT_IPV4_LOCAL_PREFIXLEN,
&Global_Clatd_Config.ipv4_local_prefixlen))
goto failed;
if(plat_prefix) { // plat subnet is coming from the command line
if(inet_pton(AF_INET6, plat_prefix, &Global_Clatd_Config.plat_subnet) <= 0) {
logmsg(ANDROID_LOG_FATAL,"invalid IPv6 address specified for plat prefix: %s", plat_prefix);
goto failed;
}
} else {
tmp_ptr = (void *)config_item_str(root, "plat_from_dns64", "yes");
if(!tmp_ptr || strcmp(tmp_ptr, "no") == 0) {
free(tmp_ptr);
if(!config_item_ip6(root, "plat_subnet", NULL, &Global_Clatd_Config.plat_subnet)) {
logmsg(ANDROID_LOG_FATAL, "plat_from_dns64 disabled, but no plat_subnet specified");
goto failed;
}
} else {
free(tmp_ptr);
if(!(Global_Clatd_Config.plat_from_dns64_hostname = config_item_str(root, "plat_from_dns64_hostname", DEFAULT_DNS64_DETECTION_HOSTNAME)))
goto failed;
dns64_detection(net_id);
}
}
if (!config_item_ip6(root, "ipv6_host_id", "::", &Global_Clatd_Config.ipv6_host_id))
goto failed;
/* In order to prevent multiple devices attempting to use the same clat address, never use a
statically-configured interface ID on a broadcast interface such as wifi. */
if (!IN6_IS_ADDR_UNSPECIFIED(&Global_Clatd_Config.ipv6_host_id)) {
ifc_init();
ifc_get_info(Global_Clatd_Config.default_pdp_interface, NULL, NULL, &flags);
ifc_close();
Global_Clatd_Config.use_dynamic_iid = (flags & IFF_BROADCAST) != 0;
} else {
Global_Clatd_Config.use_dynamic_iid = 1;
}
return 1;
failed:
free(root);
free_config();
return 0;
}
/* function; dump_config
* prints the current config
*/
void dump_config() {
char charbuffer[INET6_ADDRSTRLEN];
logmsg(ANDROID_LOG_DEBUG,"mtu = %d",Global_Clatd_Config.mtu);
logmsg(ANDROID_LOG_DEBUG,"ipv4mtu = %d",Global_Clatd_Config.ipv4mtu);
logmsg(ANDROID_LOG_DEBUG,"ipv6_local_subnet = %s",inet_ntop(AF_INET6, &Global_Clatd_Config.ipv6_local_subnet, charbuffer, sizeof(charbuffer)));
logmsg(ANDROID_LOG_DEBUG,"ipv4_local_subnet = %s",inet_ntop(AF_INET, &Global_Clatd_Config.ipv4_local_subnet, charbuffer, sizeof(charbuffer)));
logmsg(ANDROID_LOG_DEBUG,"ipv4_local_prefixlen = %d", Global_Clatd_Config.ipv4_local_prefixlen);
logmsg(ANDROID_LOG_DEBUG,"plat_subnet = %s",inet_ntop(AF_INET6, &Global_Clatd_Config.plat_subnet, charbuffer, sizeof(charbuffer)));
logmsg(ANDROID_LOG_DEBUG,"default_pdp_interface = %s",Global_Clatd_Config.default_pdp_interface);
}