blob: f304b29a9f6e2cdd3386f018113977a58bba939a [file] [log] [blame]
/*
*
* Connection Manager
*
* Copyright (C) 2007-2014 Intel Corporation. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdint.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <netdb.h>
#include <resolv.h>
#include <gweb/gresolv.h>
#include <glib.h>
#include "connman.h"
#if __BYTE_ORDER == __LITTLE_ENDIAN
struct domain_hdr {
uint16_t id;
uint8_t rd:1;
uint8_t tc:1;
uint8_t aa:1;
uint8_t opcode:4;
uint8_t qr:1;
uint8_t rcode:4;
uint8_t z:3;
uint8_t ra:1;
uint16_t qdcount;
uint16_t ancount;
uint16_t nscount;
uint16_t arcount;
} __attribute__ ((packed));
#elif __BYTE_ORDER == __BIG_ENDIAN
struct domain_hdr {
uint16_t id;
uint8_t qr:1;
uint8_t opcode:4;
uint8_t aa:1;
uint8_t tc:1;
uint8_t rd:1;
uint8_t ra:1;
uint8_t z:3;
uint8_t rcode:4;
uint16_t qdcount;
uint16_t ancount;
uint16_t nscount;
uint16_t arcount;
} __attribute__ ((packed));
#else
#error "Unknown byte order"
#endif
struct partial_reply {
uint16_t len;
uint16_t received;
unsigned char buf[];
};
struct server_data {
int index;
GList *domains;
char *server;
struct sockaddr *server_addr;
socklen_t server_addr_len;
int protocol;
GIOChannel *channel;
guint watch;
guint timeout;
bool enabled;
bool connected;
struct partial_reply *incoming_reply;
};
struct request_data {
union {
struct sockaddr_in6 __sin6; /* Only for the length */
struct sockaddr sa;
};
socklen_t sa_len;
int client_sk;
int protocol;
int family;
guint16 srcid;
guint16 dstid;
guint16 altid;
guint timeout;
guint watch;
guint numserv;
guint numresp;
gpointer request;
gsize request_len;
gpointer name;
gpointer resp;
gsize resplen;
struct listener_data *ifdata;
bool append_domain;
};
struct listener_data {
int index;
GIOChannel *udp4_listener_channel;
GIOChannel *tcp4_listener_channel;
guint udp4_listener_watch;
guint tcp4_listener_watch;
GIOChannel *udp6_listener_channel;
GIOChannel *tcp6_listener_channel;
guint udp6_listener_watch;
guint tcp6_listener_watch;
};
/*
* The TCP client requires some extra handling as we need to
* be prepared to receive also partial DNS requests.
*/
struct tcp_partial_client_data {
int family;
struct listener_data *ifdata;
GIOChannel *channel;
guint watch;
unsigned char *buf;
unsigned int buf_end;
guint timeout;
};
struct cache_data {
time_t inserted;
time_t valid_until;
time_t cache_until;
int timeout;
uint16_t type;
uint16_t answers;
unsigned int data_len;
unsigned char *data; /* contains DNS header + body */
};
struct cache_entry {
char *key;
bool want_refresh;
int hits;
struct cache_data *ipv4;
struct cache_data *ipv6;
};
struct domain_question {
uint16_t type;
uint16_t class;
} __attribute__ ((packed));
struct domain_rr {
uint16_t type;
uint16_t class;
uint32_t ttl;
uint16_t rdlen;
} __attribute__ ((packed));
/*
* Max length of the DNS TCP packet.
*/
#define TCP_MAX_BUF_LEN 4096
/*
* We limit how long the cached DNS entry stays in the cache.
* By default the TTL (time-to-live) of the DNS response is used
* when setting the cache entry life time. The value is in seconds.
*/
#define MAX_CACHE_TTL (60 * 30)
/*
* Also limit the other end, cache at least for 30 seconds.
*/
#define MIN_CACHE_TTL (30)
/*
* We limit the cache size to some sane value so that cached data does
* not occupy too much memory. Each cached entry occupies on average
* about 100 bytes memory (depending on DNS name length).
* Example: caching www.connman.net uses 97 bytes memory.
* The value is the max amount of cached DNS responses (count).
*/
#define MAX_CACHE_SIZE 256
static int cache_size;
static GHashTable *cache;
static int cache_refcount;
static GSList *server_list = NULL;
static GSList *request_list = NULL;
static GHashTable *listener_table = NULL;
static time_t next_refresh;
static GHashTable *partial_tcp_req_table;
static guint cache_timer = 0;
static guint16 get_id(void)
{
uint64_t rand;
__connman_util_get_random(&rand);
return rand;
}
static int protocol_offset(int protocol)
{
switch (protocol) {
case IPPROTO_UDP:
return 0;
case IPPROTO_TCP:
return 2;
default:
return -EINVAL;
}
}
/*
* There is a power and efficiency benefit to have entries
* in our cache expire at the same time. To this extend,
* we round down the cache valid time to common boundaries.
*/
static time_t round_down_ttl(time_t end_time, int ttl)
{
if (ttl < 15)
return end_time;
/* Less than 5 minutes, round to 10 second boundary */
if (ttl < 300) {
end_time = end_time / 10;
end_time = end_time * 10;
} else { /* 5 or more minutes, round to 30 seconds */
end_time = end_time / 30;
end_time = end_time * 30;
}
return end_time;
}
static struct request_data *find_request(guint16 id)
{
GSList *list;
for (list = request_list; list; list = list->next) {
struct request_data *req = list->data;
if (req->dstid == id || req->altid == id)
return req;
}
return NULL;
}
static struct server_data *find_server(int index,
const char *server,
int protocol)
{
GSList *list;
DBG("index %d server %s proto %d", index, server, protocol);
for (list = server_list; list; list = list->next) {
struct server_data *data = list->data;
if (index < 0 && data->index < 0 &&
g_str_equal(data->server, server) &&
data->protocol == protocol)
return data;
if (index < 0 ||
data->index < 0 || !data->server)
continue;
if (data->index == index &&
g_str_equal(data->server, server) &&
data->protocol == protocol)
return data;
}
return NULL;
}
/* we can keep using the same resolve's */
static GResolv *ipv4_resolve;
static GResolv *ipv6_resolve;
static void dummy_resolve_func(GResolvResultStatus status,
char **results, gpointer user_data)
{
}
/*
* Refresh a DNS entry, but also age the hit count a bit */
static void refresh_dns_entry(struct cache_entry *entry, char *name)
{
int age = 1;
if (!ipv4_resolve) {
ipv4_resolve = g_resolv_new(0);
g_resolv_set_address_family(ipv4_resolve, AF_INET);
g_resolv_add_nameserver(ipv4_resolve, "127.0.0.1", 53, 0);
}
if (!ipv6_resolve) {
ipv6_resolve = g_resolv_new(0);
g_resolv_set_address_family(ipv6_resolve, AF_INET6);
g_resolv_add_nameserver(ipv6_resolve, "::1", 53, 0);
}
if (!entry->ipv4) {
DBG("Refresing A record for %s", name);
g_resolv_lookup_hostname(ipv4_resolve, name,
dummy_resolve_func, NULL);
age = 4;
}
if (!entry->ipv6) {
DBG("Refresing AAAA record for %s", name);
g_resolv_lookup_hostname(ipv6_resolve, name,
dummy_resolve_func, NULL);
age = 4;
}
entry->hits -= age;
if (entry->hits < 0)
entry->hits = 0;
}
static int dns_name_length(unsigned char *buf)
{
if ((buf[0] & NS_CMPRSFLGS) == NS_CMPRSFLGS) /* compressed name */
return 2;
return strlen((char *)buf);
}
static void update_cached_ttl(unsigned char *buf, int len, int new_ttl)
{
unsigned char *c;
uint16_t w;
int l;
/* skip the header */
c = buf + 12;
len -= 12;
/* skip the query, which is a name and 2 16 bit words */
l = dns_name_length(c);
c += l;
len -= l;
c += 4;
len -= 4;
/* now we get the answer records */
while (len > 0) {
/* first a name */
l = dns_name_length(c);
c += l;
len -= l;
if (len < 0)
break;
/* then type + class, 2 bytes each */
c += 4;
len -= 4;
if (len < 0)
break;
/* now the 4 byte TTL field */
c[0] = new_ttl >> 24 & 0xff;
c[1] = new_ttl >> 16 & 0xff;
c[2] = new_ttl >> 8 & 0xff;
c[3] = new_ttl & 0xff;
c += 4;
len -= 4;
if (len < 0)
break;
/* now the 2 byte rdlen field */
w = c[0] << 8 | c[1];
c += w + 2;
len -= w + 2;
}
}
static void send_cached_response(int sk, unsigned char *buf, int len,
const struct sockaddr *to, socklen_t tolen,
int protocol, int id, uint16_t answers, int ttl)
{
struct domain_hdr *hdr;
unsigned char *ptr = buf;
int err, offset, dns_len, adj_len = len - 2;
/*
* The cached packet contains always the TCP offset (two bytes)
* so skip them for UDP.
*/
switch (protocol) {
case IPPROTO_UDP:
ptr += 2;
len -= 2;
dns_len = len;
offset = 0;
break;
case IPPROTO_TCP:
offset = 2;
dns_len = ptr[0] * 256 + ptr[1];
break;
default:
return;
}
if (len < 12)
return;
hdr = (void *) (ptr + offset);
hdr->id = id;
hdr->qr = 1;
hdr->rcode = ns_r_noerror;
hdr->ancount = htons(answers);
hdr->nscount = 0;
hdr->arcount = 0;
/* if this is a negative reply, we are authorative */
if (answers == 0)
hdr->aa = 1;
else
update_cached_ttl((unsigned char *)hdr, adj_len, ttl);
DBG("sk %d id 0x%04x answers %d ptr %p length %d dns %d",
sk, hdr->id, answers, ptr, len, dns_len);
err = sendto(sk, ptr, len, MSG_NOSIGNAL, to, tolen);
if (err < 0) {
connman_error("Cannot send cached DNS response: %s",
strerror(errno));
return;
}
if (err != len || (dns_len != (len - 2) && protocol == IPPROTO_TCP) ||
(dns_len != len && protocol == IPPROTO_UDP))
DBG("Packet length mismatch, sent %d wanted %d dns %d",
err, len, dns_len);
}
static void send_response(int sk, unsigned char *buf, int len,
const struct sockaddr *to, socklen_t tolen,
int protocol)
{
struct domain_hdr *hdr;
int err, offset = protocol_offset(protocol);
DBG("sk %d", sk);
if (offset < 0)
return;
if (len < 12)
return;
hdr = (void *) (buf + offset);
DBG("id 0x%04x qr %d opcode %d", hdr->id, hdr->qr, hdr->opcode);
hdr->qr = 1;
hdr->rcode = ns_r_servfail;
hdr->ancount = 0;
hdr->nscount = 0;
hdr->arcount = 0;
err = sendto(sk, buf, len, MSG_NOSIGNAL, to, tolen);
if (err < 0) {
connman_error("Failed to send DNS response to %d: %s",
sk, strerror(errno));
return;
}
}
static int get_req_udp_socket(struct request_data *req)
{
GIOChannel *channel;
if (req->family == AF_INET)
channel = req->ifdata->udp4_listener_channel;
else
channel = req->ifdata->udp6_listener_channel;
if (!channel)
return -1;
return g_io_channel_unix_get_fd(channel);
}
static void destroy_request_data(struct request_data *req)
{
if (req->timeout > 0)
g_source_remove(req->timeout);
g_free(req->resp);
g_free(req->request);
g_free(req->name);
g_free(req);
}
static gboolean request_timeout(gpointer user_data)
{
struct request_data *req = user_data;
struct sockaddr *sa;
int sk;
if (!req)
return FALSE;
DBG("id 0x%04x", req->srcid);
request_list = g_slist_remove(request_list, req);
if (req->protocol == IPPROTO_UDP) {
sk = get_req_udp_socket(req);
sa = &req->sa;
} else if (req->protocol == IPPROTO_TCP) {
sk = req->client_sk;
sa = NULL;
} else
goto out;
if (req->resplen > 0 && req->resp) {
/*
* Here we have received at least one reply (probably telling
* "not found" result), so send that back to client instead
* of more fatal server failed error.
*/
connman_error("DNS response received but name was not resolved");
if (sk >= 0)
sendto(sk, req->resp, req->resplen, MSG_NOSIGNAL,
sa, req->sa_len);
} else if (req->request) {
/*
* There was not reply from server at all.
*/
struct domain_hdr *hdr;
connman_error("DNS query timeout %d", req->timeout);
hdr = (void *)(req->request + protocol_offset(req->protocol));
hdr->id = req->srcid;
if (sk >= 0)
send_response(sk, req->request, req->request_len,
sa, req->sa_len, req->protocol);
}
/*
* We cannot leave TCP client hanging so just kick it out
* if we get a request timeout from server.
*/
if (req->protocol == IPPROTO_TCP) {
DBG("client %d removed", req->client_sk);
g_hash_table_remove(partial_tcp_req_table,
GINT_TO_POINTER(req->client_sk));
}
out:
req->timeout = 0;
destroy_request_data(req);
return FALSE;
}
static int append_query(unsigned char *buf, unsigned int size,
const char *query, const char *domain)
{
unsigned char *ptr = buf;
int len;
DBG("query %s domain %s", query, domain);
while (query) {
const char *tmp;
tmp = strchr(query, '.');
if (!tmp) {
len = strlen(query);
if (len == 0)
break;
*ptr = len;
memcpy(ptr + 1, query, len);
ptr += len + 1;
break;
}
*ptr = tmp - query;
memcpy(ptr + 1, query, tmp - query);
ptr += tmp - query + 1;
query = tmp + 1;
}
while (domain) {
const char *tmp;
tmp = strchr(domain, '.');
if (!tmp) {
len = strlen(domain);
if (len == 0)
break;
*ptr = len;
memcpy(ptr + 1, domain, len);
ptr += len + 1;
break;
}
*ptr = tmp - domain;
memcpy(ptr + 1, domain, tmp - domain);
ptr += tmp - domain + 1;
domain = tmp + 1;
}
*ptr++ = 0x00;
return ptr - buf;
}
static bool cache_check_is_valid(struct cache_data *data,
time_t current_time)
{
if (!data)
return false;
if (data->cache_until < current_time)
return false;
return true;
}
/*
* remove stale cached entries so that they can be refreshed
*/
static void cache_enforce_validity(struct cache_entry *entry)
{
time_t current_time = time(NULL);
if (!cache_check_is_valid(entry->ipv4, current_time)
&& entry->ipv4) {
DBG("cache timeout \"%s\" type A", entry->key);
g_free(entry->ipv4->data);
g_free(entry->ipv4);
entry->ipv4 = NULL;
}
if (!cache_check_is_valid(entry->ipv6, current_time)
&& entry->ipv6) {
DBG("cache timeout \"%s\" type AAAA", entry->key);
g_free(entry->ipv6->data);
g_free(entry->ipv6);
entry->ipv6 = NULL;
}
}
static uint16_t cache_check_validity(char *question, uint16_t type,
struct cache_entry *entry)
{
time_t current_time = time(NULL);
bool want_refresh = false;
/*
* if we have a popular entry, we want a refresh instead of
* total destruction of the entry.
*/
if (entry->hits > 2)
want_refresh = true;
cache_enforce_validity(entry);
switch (type) {
case 1: /* IPv4 */
if (!cache_check_is_valid(entry->ipv4, current_time)) {
DBG("cache %s \"%s\" type A", entry->ipv4 ?
"timeout" : "entry missing", question);
if (want_refresh)
entry->want_refresh = true;
/*
* We do not remove cache entry if there is still
* valid IPv6 entry found in the cache.
*/
if (!cache_check_is_valid(entry->ipv6, current_time) && !want_refresh) {
g_hash_table_remove(cache, question);
type = 0;
}
}
break;
case 28: /* IPv6 */
if (!cache_check_is_valid(entry->ipv6, current_time)) {
DBG("cache %s \"%s\" type AAAA", entry->ipv6 ?
"timeout" : "entry missing", question);
if (want_refresh)
entry->want_refresh = true;
if (!cache_check_is_valid(entry->ipv4, current_time) && !want_refresh) {
g_hash_table_remove(cache, question);
type = 0;
}
}
break;
}
return type;
}
static void cache_element_destroy(gpointer value)
{
struct cache_entry *entry = value;
if (!entry)
return;
if (entry->ipv4) {
g_free(entry->ipv4->data);
g_free(entry->ipv4);
}
if (entry->ipv6) {
g_free(entry->ipv6->data);
g_free(entry->ipv6);
}
g_free(entry->key);
g_free(entry);
if (--cache_size < 0)
cache_size = 0;
}
static gboolean try_remove_cache(gpointer user_data)
{
cache_timer = 0;
if (__sync_fetch_and_sub(&cache_refcount, 1) == 1) {
DBG("No cache users, removing it.");
g_hash_table_destroy(cache);
cache = NULL;
}
return FALSE;
}
static void create_cache(void)
{
if (__sync_fetch_and_add(&cache_refcount, 1) == 0)
cache = g_hash_table_new_full(g_str_hash,
g_str_equal,
NULL,
cache_element_destroy);
}
static struct cache_entry *cache_check(gpointer request, int *qtype, int proto)
{
char *question;
struct cache_entry *entry;
struct domain_question *q;
uint16_t type;
int offset, proto_offset;
if (!request)
return NULL;
proto_offset = protocol_offset(proto);
if (proto_offset < 0)
return NULL;
question = request + proto_offset + 12;
offset = strlen(question) + 1;
q = (void *) (question + offset);
type = ntohs(q->type);
/* We only cache either A (1) or AAAA (28) requests */
if (type != 1 && type != 28)
return NULL;
if (!cache) {
create_cache();
return NULL;
}
entry = g_hash_table_lookup(cache, question);
if (!entry)
return NULL;
type = cache_check_validity(question, type, entry);
if (type == 0)
return NULL;
*qtype = type;
return entry;
}
/*
* Get a label/name from DNS resource record. The function decompresses the
* label if necessary. The function does not convert the name to presentation
* form. This means that the result string will contain label lengths instead
* of dots between labels. We intentionally do not want to convert to dotted
* format so that we can cache the wire format string directly.
*/
static int get_name(int counter,
unsigned char *pkt, unsigned char *start, unsigned char *max,
unsigned char *output, int output_max, int *output_len,
unsigned char **end, char *name, int *name_len)
{
unsigned char *p;
/* Limit recursion to 10 (this means up to 10 labels in domain name) */
if (counter > 10)
return -EINVAL;
p = start;
while (*p) {
if ((*p & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
uint16_t offset = (*p & 0x3F) * 256 + *(p + 1);
if (offset >= max - pkt)
return -ENOBUFS;
if (!*end)
*end = p + 2;
return get_name(counter + 1, pkt, pkt + offset, max,
output, output_max, output_len, end,
name, name_len);
} else {
unsigned label_len = *p;
if (pkt + label_len > max)
return -ENOBUFS;
if (*output_len > output_max)
return -ENOBUFS;
/*
* We need the original name in order to check
* if this answer is the correct one.
*/
name[(*name_len)++] = label_len;
memcpy(name + *name_len, p + 1, label_len + 1);
*name_len += label_len;
/* We compress the result */
output[0] = NS_CMPRSFLGS;
output[1] = 0x0C;
*output_len = 2;
p += label_len + 1;
if (!*end)
*end = p;
if (p >= max)
return -ENOBUFS;
}
}
return 0;
}
static int parse_rr(unsigned char *buf, unsigned char *start,
unsigned char *max,
unsigned char *response, unsigned int *response_size,
uint16_t *type, uint16_t *class, int *ttl, int *rdlen,
unsigned char **end,
char *name)
{
struct domain_rr *rr;
int err, offset;
int name_len = 0, output_len = 0, max_rsp = *response_size;
err = get_name(0, buf, start, max, response, max_rsp,
&output_len, end, name, &name_len);
if (err < 0)
return err;
offset = output_len;
if ((unsigned int) offset > *response_size)
return -ENOBUFS;
rr = (void *) (*end);
if (!rr)
return -EINVAL;
*type = ntohs(rr->type);
*class = ntohs(rr->class);
*ttl = ntohl(rr->ttl);
*rdlen = ntohs(rr->rdlen);
if (*ttl < 0)
return -EINVAL;
memcpy(response + offset, *end, sizeof(struct domain_rr));
offset += sizeof(struct domain_rr);
*end += sizeof(struct domain_rr);
if ((unsigned int) (offset + *rdlen) > *response_size)
return -ENOBUFS;
memcpy(response + offset, *end, *rdlen);
*end += *rdlen;
*response_size = offset + *rdlen;
return 0;
}
static bool check_alias(GSList *aliases, char *name)
{
GSList *list;
if (aliases) {
for (list = aliases; list; list = list->next) {
int len = strlen((char *)list->data);
if (strncmp((char *)list->data, name, len) == 0)
return true;
}
}
return false;
}
static int parse_response(unsigned char *buf, int buflen,
char *question, int qlen,
uint16_t *type, uint16_t *class, int *ttl,
unsigned char *response, unsigned int *response_len,
uint16_t *answers)
{
struct domain_hdr *hdr = (void *) buf;
struct domain_question *q;
unsigned char *ptr;
uint16_t qdcount = ntohs(hdr->qdcount);
uint16_t ancount = ntohs(hdr->ancount);
int err, i;
uint16_t qtype, qclass;
unsigned char *next = NULL;
unsigned int maxlen = *response_len;
GSList *aliases = NULL, *list;
char name[NS_MAXDNAME + 1];
if (buflen < 12)
return -EINVAL;
DBG("qr %d qdcount %d", hdr->qr, qdcount);
/* We currently only cache responses where question count is 1 */
if (hdr->qr != 1 || qdcount != 1)
return -EINVAL;
ptr = buf + sizeof(struct domain_hdr);
strncpy(question, (char *) ptr, qlen);
qlen = strlen(question);
ptr += qlen + 1; /* skip \0 */
q = (void *) ptr;
qtype = ntohs(q->type);
/* We cache only A and AAAA records */
if (qtype != 1 && qtype != 28)
return -ENOMSG;
qclass = ntohs(q->class);
ptr += 2 + 2; /* ptr points now to answers */
err = -ENOMSG;
*response_len = 0;
*answers = 0;
memset(name, 0, sizeof(name));
/*
* We have a bunch of answers (like A, AAAA, CNAME etc) to
* A or AAAA question. We traverse the answers and parse the
* resource records. Only A and AAAA records are cached, all
* the other records in answers are skipped.
*/
for (i = 0; i < ancount; i++) {
/*
* Get one address at a time to this buffer.
* The max size of the answer is
* 2 (pointer) + 2 (type) + 2 (class) +
* 4 (ttl) + 2 (rdlen) + addr (16 or 4) = 28
* for A or AAAA record.
* For CNAME the size can be bigger.
*/
unsigned char rsp[NS_MAXCDNAME];
unsigned int rsp_len = sizeof(rsp) - 1;
int ret, rdlen;
memset(rsp, 0, sizeof(rsp));
ret = parse_rr(buf, ptr, buf + buflen, rsp, &rsp_len,
type, class, ttl, &rdlen, &next, name);
if (ret != 0) {
err = ret;
goto out;
}
/*
* Now rsp contains compressed or uncompressed resource
* record. Next we check if this record answers the question.
* The name var contains the uncompressed label.
* One tricky bit is the CNAME records as they alias
* the name we might be interested in.
*/
/*
* Go to next answer if the class is not the one we are
* looking for.
*/
if (*class != qclass) {
ptr = next;
next = NULL;
continue;
}
/*
* Try to resolve aliases also, type is CNAME(5).
* This is important as otherwise the aliased names would not
* be cached at all as the cache would not contain the aliased
* question.
*
* If any CNAME is found in DNS packet, then we cache the alias
* IP address instead of the question (as the server
* said that question has only an alias).
* This means in practice that if e.g., ipv6.google.com is
* queried, DNS server returns CNAME of that name which is
* ipv6.l.google.com. We then cache the address of the CNAME
* but return the question name to client. So the alias
* status of the name is not saved in cache and thus not
* returned to the client. We do not return DNS packets from
* cache to client saying that ipv6.google.com is an alias to
* ipv6.l.google.com but we return instead a DNS packet that
* says ipv6.google.com has address xxx which is in fact the
* address of ipv6.l.google.com. For caching purposes this
* should not cause any issues.
*/
if (*type == 5 && strncmp(question, name, qlen) == 0) {
/*
* So now the alias answered the question. This is
* not very useful from caching point of view as
* the following A or AAAA records will not match the
* question. We need to find the real A/AAAA record
* of the alias and cache that.
*/
unsigned char *end = NULL;
int name_len = 0, output_len = 0;
memset(rsp, 0, sizeof(rsp));
rsp_len = sizeof(rsp) - 1;
/*
* Alias is in rdata part of the message,
* and next-rdlen points to it. So we need to get
* the real name of the alias.
*/
ret = get_name(0, buf, next - rdlen, buf + buflen,
rsp, rsp_len, &output_len, &end,
name, &name_len);
if (ret != 0) {
/* just ignore the error at this point */
ptr = next;
next = NULL;
continue;
}
/*
* We should now have the alias of the entry we might
* want to cache. Just remember it for a while.
* We check the alias list when we have parsed the
* A or AAAA record.
*/
aliases = g_slist_prepend(aliases, g_strdup(name));
ptr = next;
next = NULL;
continue;
}
if (*type == qtype) {
/*
* We found correct type (A or AAAA)
*/
if (check_alias(aliases, name) ||
(!aliases && strncmp(question, name,
qlen) == 0)) {
/*
* We found an alias or the name of the rr
* matches the question. If so, we append
* the compressed label to the cache.
* The end result is a response buffer that
* will contain one or more cached and
* compressed resource records.
*/
if (*response_len + rsp_len > maxlen) {
err = -ENOBUFS;
goto out;
}
memcpy(response + *response_len, rsp, rsp_len);
*response_len += rsp_len;
(*answers)++;
err = 0;
}
}
ptr = next;
next = NULL;
}
out:
for (list = aliases; list; list = list->next)
g_free(list->data);
g_slist_free(aliases);
return err;
}
struct cache_timeout {
time_t current_time;
int max_timeout;
int try_harder;
};
static gboolean cache_check_entry(gpointer key, gpointer value,
gpointer user_data)
{
struct cache_timeout *data = user_data;
struct cache_entry *entry = value;
int max_timeout;
/* Scale the number of hits by half as part of cache aging */
entry->hits /= 2;
/*
* If either IPv4 or IPv6 cached entry has expired, we
* remove both from the cache.
*/
if (entry->ipv4 && entry->ipv4->timeout > 0) {
max_timeout = entry->ipv4->cache_until;
if (max_timeout > data->max_timeout)
data->max_timeout = max_timeout;
if (entry->ipv4->cache_until < data->current_time)
return TRUE;
}
if (entry->ipv6 && entry->ipv6->timeout > 0) {
max_timeout = entry->ipv6->cache_until;
if (max_timeout > data->max_timeout)
data->max_timeout = max_timeout;
if (entry->ipv6->cache_until < data->current_time)
return TRUE;
}
/*
* if we're asked to try harder, also remove entries that have
* few hits
*/
if (data->try_harder && entry->hits < 4)
return TRUE;
return FALSE;
}
static void cache_cleanup(void)
{
static int max_timeout;
struct cache_timeout data;
int count = 0;
data.current_time = time(NULL);
data.max_timeout = 0;
data.try_harder = 0;
/*
* In the first pass, we only remove entries that have timed out.
* We use a cache of the first time to expire to do this only
* when it makes sense.
*/
if (max_timeout <= data.current_time) {
count = g_hash_table_foreach_remove(cache, cache_check_entry,
&data);
}
DBG("removed %d in the first pass", count);
/*
* In the second pass, if the first pass turned up blank,
* we also expire entries with a low hit count,
* while aging the hit count at the same time.
*/
data.try_harder = 1;
if (count == 0)
count = g_hash_table_foreach_remove(cache, cache_check_entry,
&data);
if (count == 0)
/*
* If we could not remove anything, then remember
* what is the max timeout and do nothing if we
* have not yet reached it. This will prevent
* constant traversal of the cache if it is full.
*/
max_timeout = data.max_timeout;
else
max_timeout = 0;
}
static gboolean cache_invalidate_entry(gpointer key, gpointer value,
gpointer user_data)
{
struct cache_entry *entry = value;
/* first, delete any expired elements */
cache_enforce_validity(entry);
/* if anything is not expired, mark the entry for refresh */
if (entry->hits > 0 && (entry->ipv4 || entry->ipv6))
entry->want_refresh = true;
/* delete the cached data */
if (entry->ipv4) {
g_free(entry->ipv4->data);
g_free(entry->ipv4);
entry->ipv4 = NULL;
}
if (entry->ipv6) {
g_free(entry->ipv6->data);
g_free(entry->ipv6);
entry->ipv6 = NULL;
}
/* keep the entry if we want it refreshed, delete it otherwise */
if (entry->want_refresh)
return FALSE;
else
return TRUE;
}
/*
* cache_invalidate is called from places where the DNS landscape
* has changed, say because connections are added or we entered a VPN.
* The logic is to wipe all cache data, but mark all non-expired
* parts of the cache for refresh rather than deleting the whole cache.
*/
static void cache_invalidate(void)
{
DBG("Invalidating the DNS cache %p", cache);
if (!cache)
return;
g_hash_table_foreach_remove(cache, cache_invalidate_entry, NULL);
}
static void cache_refresh_entry(struct cache_entry *entry)
{
cache_enforce_validity(entry);
if (entry->hits > 2 && !entry->ipv4)
entry->want_refresh = true;
if (entry->hits > 2 && !entry->ipv6)
entry->want_refresh = true;
if (entry->want_refresh) {
char *c;
char dns_name[NS_MAXDNAME + 1];
entry->want_refresh = false;
/* turn a DNS name into a hostname with dots */
strncpy(dns_name, entry->key, NS_MAXDNAME);
c = dns_name;
while (c && *c) {
int jump;
jump = *c;
*c = '.';
c += jump + 1;
}
DBG("Refreshing %s\n", dns_name);
/* then refresh the hostname */
refresh_dns_entry(entry, &dns_name[1]);
}
}
static void cache_refresh_iterator(gpointer key, gpointer value,
gpointer user_data)
{
struct cache_entry *entry = value;
cache_refresh_entry(entry);
}
static void cache_refresh(void)
{
if (!cache)
return;
g_hash_table_foreach(cache, cache_refresh_iterator, NULL);
}
static int reply_query_type(unsigned char *msg, int len)
{
unsigned char *c;
int l;
int type;
/* skip the header */
c = msg + sizeof(struct domain_hdr);
len -= sizeof(struct domain_hdr);
if (len < 0)
return 0;
/* now the query, which is a name and 2 16 bit words */
l = dns_name_length(c) + 1;
c += l;
type = c[0] << 8 | c[1];
return type;
}
static int cache_update(struct server_data *srv, unsigned char *msg,
unsigned int msg_len)
{
int offset = protocol_offset(srv->protocol);
int err, qlen, ttl = 0;
uint16_t answers = 0, type = 0, class = 0;
struct domain_hdr *hdr = (void *)(msg + offset);
struct domain_question *q;
struct cache_entry *entry;
struct cache_data *data;
char question[NS_MAXDNAME + 1];
unsigned char response[NS_MAXDNAME + 1];
unsigned char *ptr;
unsigned int rsplen;
bool new_entry = true;
time_t current_time;
if (cache_size >= MAX_CACHE_SIZE) {
cache_cleanup();
if (cache_size >= MAX_CACHE_SIZE)
return 0;
}
current_time = time(NULL);
/* don't do a cache refresh more than twice a minute */
if (next_refresh < current_time) {
cache_refresh();
next_refresh = current_time + 30;
}
if (offset < 0)
return 0;
DBG("offset %d hdr %p msg %p rcode %d", offset, hdr, msg, hdr->rcode);
/* Continue only if response code is 0 (=ok) */
if (hdr->rcode != ns_r_noerror)
return 0;
if (!cache)
create_cache();
rsplen = sizeof(response) - 1;
question[sizeof(question) - 1] = '\0';
err = parse_response(msg + offset, msg_len - offset,
question, sizeof(question) - 1,
&type, &class, &ttl,
response, &rsplen, &answers);
/*
* special case: if we do a ipv6 lookup and get no result
* for a record that's already in our ipv4 cache.. we want
* to cache the negative response.
*/
if ((err == -ENOMSG || err == -ENOBUFS) &&
reply_query_type(msg + offset,
msg_len - offset) == 28) {
entry = g_hash_table_lookup(cache, question);
if (entry && entry->ipv4 && !entry->ipv6) {
int cache_offset = 0;
data = g_try_new(struct cache_data, 1);
if (!data)
return -ENOMEM;
data->inserted = entry->ipv4->inserted;
data->type = type;
data->answers = ntohs(hdr->ancount);
data->timeout = entry->ipv4->timeout;
if (srv->protocol == IPPROTO_UDP)
cache_offset = 2;
data->data_len = msg_len + cache_offset;
data->data = ptr = g_malloc(data->data_len);
ptr[0] = (data->data_len - 2) / 256;
ptr[1] = (data->data_len - 2) - ptr[0] * 256;
if (srv->protocol == IPPROTO_UDP)
ptr += 2;
data->valid_until = entry->ipv4->valid_until;
data->cache_until = entry->ipv4->cache_until;
memcpy(ptr, msg, msg_len);
entry->ipv6 = data;
/*
* we will get a "hit" when we serve the response
* out of the cache
*/
entry->hits--;
if (entry->hits < 0)
entry->hits = 0;
return 0;
}
}
if (err < 0 || ttl == 0)
return 0;
qlen = strlen(question);
/*
* If the cache contains already data, check if the
* type of the cached data is the same and do not add
* to cache if data is already there.
* This is needed so that we can cache both A and AAAA
* records for the same name.
*/
entry = g_hash_table_lookup(cache, question);
if (!entry) {
entry = g_try_new(struct cache_entry, 1);
if (!entry)
return -ENOMEM;
data = g_try_new(struct cache_data, 1);
if (!data) {
g_free(entry);
return -ENOMEM;
}
entry->key = g_strdup(question);
entry->ipv4 = entry->ipv6 = NULL;
entry->want_refresh = false;
entry->hits = 0;
if (type == 1)
entry->ipv4 = data;
else
entry->ipv6 = data;
} else {
if (type == 1 && entry->ipv4)
return 0;
if (type == 28 && entry->ipv6)
return 0;
data = g_try_new(struct cache_data, 1);
if (!data)
return -ENOMEM;
if (type == 1)
entry->ipv4 = data;
else
entry->ipv6 = data;
/*
* compensate for the hit we'll get for serving
* the response out of the cache
*/
entry->hits--;
if (entry->hits < 0)
entry->hits = 0;
new_entry = false;
}
if (ttl < MIN_CACHE_TTL)
ttl = MIN_CACHE_TTL;
data->inserted = current_time;
data->type = type;
data->answers = answers;
data->timeout = ttl;
/*
* The "2" in start of the length is the TCP offset. We allocate it
* here even for UDP packet because it simplifies the sending
* of cached packet.
*/
data->data_len = 2 + 12 + qlen + 1 + 2 + 2 + rsplen;
data->data = ptr = g_malloc(data->data_len);
data->valid_until = current_time + ttl;
/*
* Restrict the cached DNS record TTL to some sane value
* in order to prevent data staying in the cache too long.
*/
if (ttl > MAX_CACHE_TTL)
ttl = MAX_CACHE_TTL;
data->cache_until = round_down_ttl(current_time + ttl, ttl);
if (!data->data) {
g_free(entry->key);
g_free(data);
g_free(entry);
return -ENOMEM;
}
/*
* We cache the two extra bytes at the start of the message
* in a TCP packet. When sending UDP packet, we skip the first
* two bytes. This way we do not need to know the format
* (UDP/TCP) of the cached message.
*/
if (srv->protocol == IPPROTO_UDP)
memcpy(ptr + 2, msg, offset + 12);
else
memcpy(ptr, msg, offset + 12);
ptr[0] = (data->data_len - 2) / 256;
ptr[1] = (data->data_len - 2) - ptr[0] * 256;
if (srv->protocol == IPPROTO_UDP)
ptr += 2;
memcpy(ptr + offset + 12, question, qlen + 1); /* copy also the \0 */
q = (void *) (ptr + offset + 12 + qlen + 1);
q->type = htons(type);
q->class = htons(class);
memcpy(ptr + offset + 12 + qlen + 1 + sizeof(struct domain_question),
response, rsplen);
if (new_entry) {
g_hash_table_replace(cache, entry->key, entry);
cache_size++;
}
DBG("cache %d %squestion \"%s\" type %d ttl %d size %zd packet %u "
"dns len %u",
cache_size, new_entry ? "new " : "old ",
question, type, ttl,
sizeof(*entry) + sizeof(*data) + data->data_len + qlen,
data->data_len,
srv->protocol == IPPROTO_TCP ?
(unsigned int)(data->data[0] * 256 + data->data[1]) :
data->data_len);
return 0;
}
static int ns_resolv(struct server_data *server, struct request_data *req,
gpointer request, gpointer name)
{
GList *list;
int sk, err, type = 0;
char *dot, *lookup = (char *) name;
struct cache_entry *entry;
entry = cache_check(request, &type, req->protocol);
if (entry) {
int ttl_left = 0;
struct cache_data *data;
DBG("cache hit %s type %s", lookup, type == 1 ? "A" : "AAAA");
if (type == 1)
data = entry->ipv4;
else
data = entry->ipv6;
if (data) {
ttl_left = data->valid_until - time(NULL);
entry->hits++;
}
if (data && req->protocol == IPPROTO_TCP) {
send_cached_response(req->client_sk, data->data,
data->data_len, NULL, 0, IPPROTO_TCP,
req->srcid, data->answers, ttl_left);
return 1;
}
if (data && req->protocol == IPPROTO_UDP) {
int udp_sk = get_req_udp_socket(req);
if (udp_sk < 0)
return -EIO;
send_cached_response(udp_sk, data->data,
data->data_len, &req->sa, req->sa_len,
IPPROTO_UDP, req->srcid, data->answers,
ttl_left);
return 1;
}
}
sk = g_io_channel_unix_get_fd(server->channel);
err = sendto(sk, request, req->request_len, MSG_NOSIGNAL,
server->server_addr, server->server_addr_len);
if (err < 0) {
DBG("Cannot send message to server %s sock %d "
"protocol %d (%s/%d)",
server->server, sk, server->protocol,
strerror(errno), errno);
return -EIO;
}
req->numserv++;
/* If we have more than one dot, we don't add domains */
dot = strchr(lookup, '.');
if (dot && dot != lookup + strlen(lookup) - 1)
return 0;
if (server->domains && server->domains->data)
req->append_domain = true;
for (list = server->domains; list; list = list->next) {
char *domain;
unsigned char alt[1024];
struct domain_hdr *hdr = (void *) &alt;
int altlen, domlen, offset;
domain = list->data;
if (!domain)
continue;
offset = protocol_offset(server->protocol);
if (offset < 0)
return offset;
domlen = strlen(domain) + 1;
if (domlen < 5)
return -EINVAL;
alt[offset] = req->altid & 0xff;
alt[offset + 1] = req->altid >> 8;
memcpy(alt + offset + 2, request + offset + 2, 10);
hdr->qdcount = htons(1);
altlen = append_query(alt + offset + 12, sizeof(alt) - 12,
name, domain);
if (altlen < 0)
return -EINVAL;
altlen += 12;
memcpy(alt + offset + altlen,
request + offset + altlen - domlen,
req->request_len - altlen - offset + domlen);
if (server->protocol == IPPROTO_TCP) {
int req_len = req->request_len + domlen - 2;
alt[0] = (req_len >> 8) & 0xff;
alt[1] = req_len & 0xff;
}
DBG("req %p dstid 0x%04x altid 0x%04x", req, req->dstid,
req->altid);
err = send(sk, alt, req->request_len + domlen, MSG_NOSIGNAL);
if (err < 0)
return -EIO;
req->numserv++;
}
return 0;
}
static char *convert_label(char *start, char *end, char *ptr, char *uptr,
int remaining_len, int *used_comp, int *used_uncomp)
{
int pos, comp_pos;
char name[NS_MAXLABEL];
pos = dn_expand((u_char *)start, (u_char *)end, (u_char *)ptr,
name, NS_MAXLABEL);
if (pos < 0) {
DBG("uncompress error [%d/%s]", errno, strerror(errno));
goto out;
}
/*
* We need to compress back the name so that we get back to internal
* label presentation.
*/
comp_pos = dn_comp(name, (u_char *)uptr, remaining_len, NULL, NULL);
if (comp_pos < 0) {
DBG("compress error [%d/%s]", errno, strerror(errno));
goto out;
}
*used_comp = pos;
*used_uncomp = comp_pos;
return ptr;
out:
return NULL;
}
static char *uncompress(int16_t field_count, char *start, char *end,
char *ptr, char *uncompressed, int uncomp_len,
char **uncompressed_ptr)
{
char *uptr = *uncompressed_ptr; /* position in result buffer */
DBG("count %d ptr %p end %p uptr %p", field_count, ptr, end, uptr);
while (field_count-- > 0 && ptr < end) {
int dlen; /* data field length */
int ulen; /* uncompress length */
int pos; /* position in compressed string */
char name[NS_MAXLABEL]; /* tmp label */
uint16_t dns_type, dns_class;
int comp_pos;
if (!convert_label(start, end, ptr, name, NS_MAXLABEL,
&pos, &comp_pos))
goto out;
/*
* Copy the uncompressed resource record, type, class and \0 to
* tmp buffer.
*/
ulen = strlen(name);
strncpy(uptr, name, uncomp_len - (uptr - uncompressed));
DBG("pos %d ulen %d left %d name %s", pos, ulen,
(int)(uncomp_len - (uptr - uncompressed)), uptr);
uptr += ulen;
*uptr++ = '\0';
ptr += pos;
/*
* We copy also the fixed portion of the result (type, class,
* ttl, address length and the address)
*/
memcpy(uptr, ptr, NS_RRFIXEDSZ);
dns_type = uptr[0] << 8 | uptr[1];
dns_class = uptr[2] << 8 | uptr[3];
if (dns_class != ns_c_in)
goto out;
ptr += NS_RRFIXEDSZ;
uptr += NS_RRFIXEDSZ;
/*
* Then the variable portion of the result (data length).
* Typically this portion is also compressed
* so we need to uncompress it also when necessary.
*/
if (dns_type == ns_t_cname) {
if (!convert_label(start, end, ptr, uptr,
uncomp_len - (uptr - uncompressed),
&pos, &comp_pos))
goto out;
uptr[-2] = comp_pos << 8;
uptr[-1] = comp_pos & 0xff;
uptr += comp_pos;
ptr += pos;
} else if (dns_type == ns_t_a || dns_type == ns_t_aaaa) {
dlen = uptr[-2] << 8 | uptr[-1];
if (ptr + dlen > end) {
DBG("data len %d too long", dlen);
goto out;
}
memcpy(uptr, ptr, dlen);
uptr += dlen;
ptr += dlen;
} else if (dns_type == ns_t_soa) {
int total_len = 0;
char *len_ptr;
/* Primary name server expansion */
if (!convert_label(start, end, ptr, uptr,
uncomp_len - (uptr - uncompressed),
&pos, &comp_pos))
goto out;
total_len += comp_pos;
len_ptr = &uptr[-2];
ptr += pos;
uptr += comp_pos;
/* Responsible authority's mailbox */
if (!convert_label(start, end, ptr, uptr,
uncomp_len - (uptr - uncompressed),
&pos, &comp_pos))
goto out;
total_len += comp_pos;
ptr += pos;
uptr += comp_pos;
/*
* Copy rest of the soa fields (serial number,
* refresh interval, retry interval, expiration
* limit and minimum ttl). They are 20 bytes long.
*/
memcpy(uptr, ptr, 20);
uptr += 20;
ptr += 20;
total_len += 20;
/*
* Finally fix the length of the data part
*/
len_ptr[0] = total_len << 8;
len_ptr[1] = total_len & 0xff;
}
*uncompressed_ptr = uptr;
}
return ptr;
out:
return NULL;
}
static int strip_domains(char *name, char *answers, int maxlen)
{
uint16_t data_len;
int name_len = strlen(name);
char *ptr, *start = answers, *end = answers + maxlen;
while (maxlen > 0) {
ptr = strstr(answers, name);
if (ptr) {
char *domain = ptr + name_len;
if (*domain) {
int domain_len = strlen(domain);
memmove(answers + name_len,
domain + domain_len,
end - (domain + domain_len));
end -= domain_len;
maxlen -= domain_len;
}
}
answers += strlen(answers) + 1;
answers += 2 + 2 + 4; /* skip type, class and ttl fields */
data_len = answers[0] << 8 | answers[1];
answers += 2; /* skip the length field */
if (answers + data_len > end)
return -EINVAL;
answers += data_len;
maxlen -= answers - ptr;
}
return end - start;
}
static int forward_dns_reply(unsigned char *reply, int reply_len, int protocol,
struct server_data *data)
{
struct domain_hdr *hdr;
struct request_data *req;
int dns_id, sk, err, offset = protocol_offset(protocol);
if (offset < 0)
return offset;
hdr = (void *)(reply + offset);
dns_id = reply[offset] | reply[offset + 1] << 8;
DBG("Received %d bytes (id 0x%04x)", reply_len, dns_id);
req = find_request(dns_id);
if (!req)
return -EINVAL;
DBG("req %p dstid 0x%04x altid 0x%04x rcode %d",
req, req->dstid, req->altid, hdr->rcode);
reply[offset] = req->srcid & 0xff;
reply[offset + 1] = req->srcid >> 8;
req->numresp++;
if (hdr->rcode == ns_r_noerror || !req->resp) {
unsigned char *new_reply = NULL;
/*
* If the domain name was append
* remove it before forwarding the reply.
* If there were more than one question, then this
* domain name ripping can be hairy so avoid that
* and bail out in that that case.
*
* The reason we are doing this magic is that if the
* user's DNS client tries to resolv hostname without
* domain part, it also expects to get the result without
* a domain name part.
*/
if (req->append_domain && ntohs(hdr->qdcount) == 1) {
uint16_t domain_len = 0;
uint16_t header_len;
uint16_t dns_type, dns_class;
uint8_t host_len, dns_type_pos;
char uncompressed[NS_MAXDNAME], *uptr;
char *ptr, *eom = (char *)reply + reply_len;
/*
* ptr points to the first char of the hostname.
* ->hostname.domain.net
*/
header_len = offset + sizeof(struct domain_hdr);
ptr = (char *)reply + header_len;
host_len = *ptr;
if (host_len > 0)
domain_len = strnlen(ptr + 1 + host_len,
reply_len - header_len);
/*
* If the query type is anything other than A or AAAA,
* then bail out and pass the message as is.
* We only want to deal with IPv4 or IPv6 addresses.
*/
dns_type_pos = host_len + 1 + domain_len + 1;
dns_type = ptr[dns_type_pos] << 8 |
ptr[dns_type_pos + 1];
dns_class = ptr[dns_type_pos + 2] << 8 |
ptr[dns_type_pos + 3];
if (dns_type != ns_t_a && dns_type != ns_t_aaaa &&
dns_class != ns_c_in) {
DBG("Pass msg dns type %d class %d",
dns_type, dns_class);
goto pass;
}
/*
* Remove the domain name and replace it by the end
* of reply. Check if the domain is really there
* before trying to copy the data. We also need to
* uncompress the answers if necessary.
* The domain_len can be 0 because if the original
* query did not contain a domain name, then we are
* sending two packets, first without the domain name
* and the second packet with domain name.
* The append_domain is set to true even if we sent
* the first packet without domain name. In this
* case we end up in this branch.
*/
if (domain_len > 0) {
int len = host_len + 1;
int new_len, fixed_len;
char *answers;
/*
* First copy host (without domain name) into
* tmp buffer.
*/
uptr = &uncompressed[0];
memcpy(uptr, ptr, len);
uptr[len] = '\0'; /* host termination */
uptr += len + 1;
/*
* Copy type and class fields of the question.
*/
ptr += len + domain_len + 1;
memcpy(uptr, ptr, NS_QFIXEDSZ);
/*
* ptr points to answers after this
*/
ptr += NS_QFIXEDSZ;
uptr += NS_QFIXEDSZ;
answers = uptr;
fixed_len = answers - uncompressed;
/*
* We then uncompress the result to buffer
* so that we can rip off the domain name
* part from the question. First answers,
* then name server (authority) information,
* and finally additional record info.
*/
ptr = uncompress(ntohs(hdr->ancount),
(char *)reply + offset, eom,
ptr, uncompressed, NS_MAXDNAME,
&uptr);
if (ptr == NULL)
goto out;
ptr = uncompress(ntohs(hdr->nscount),
(char *)reply + offset, eom,
ptr, uncompressed, NS_MAXDNAME,
&uptr);
if (ptr == NULL)
goto out;
ptr = uncompress(ntohs(hdr->arcount),
(char *)reply + offset, eom,
ptr, uncompressed, NS_MAXDNAME,
&uptr);
if (ptr == NULL)
goto out;
/*
* The uncompressed buffer now contains almost
* valid response. Final step is to get rid of
* the domain name because at least glibc
* gethostbyname() implementation does extra
* checks and expects to find an answer without
* domain name if we asked a query without
* domain part. Note that glibc getaddrinfo()
* works differently and accepts FQDN in answer
*/
new_len = strip_domains(uncompressed, answers,
uptr - answers);
if (new_len < 0) {
DBG("Corrupted packet");
return -EINVAL;
}
/*
* Because we have now uncompressed the answers
* we might have to create a bigger buffer to
* hold all that data.
*/
reply_len = header_len + new_len + fixed_len;
new_reply = g_try_malloc(reply_len);
if (!new_reply)
return -ENOMEM;
memcpy(new_reply, reply, header_len);
memcpy(new_reply + header_len, uncompressed,
new_len + fixed_len);
reply = new_reply;
}
}
pass:
g_free(req->resp);
req->resplen = 0;
req->resp = g_try_malloc(reply_len);
if (!req->resp)
return -ENOMEM;
memcpy(req->resp, reply, reply_len);
req->resplen = reply_len;
cache_update(data, reply, reply_len);
g_free(new_reply);
}
out:
if (req->numresp < req->numserv) {
if (hdr->rcode > ns_r_noerror) {
return -EINVAL;
} else if (hdr->ancount == 0 && req->append_domain) {
return -EINVAL;
}
}
request_list = g_slist_remove(request_list, req);
if (protocol == IPPROTO_UDP) {
sk = get_req_udp_socket(req);
if (sk < 0) {
errno = -EIO;
err = -EIO;
} else
err = sendto(sk, req->resp, req->resplen, 0,
&req->sa, req->sa_len);
} else {
sk = req->client_sk;
err = send(sk, req->resp, req->resplen, MSG_NOSIGNAL);
}
if (err < 0)
DBG("Cannot send msg, sk %d proto %d errno %d/%s", sk,
protocol, errno, strerror(errno));
else
DBG("proto %d sent %d bytes to %d", protocol, err, sk);
destroy_request_data(req);
return err;
}
static void server_destroy_socket(struct server_data *data)
{
DBG("index %d server %s proto %d", data->index,
data->server, data->protocol);
if (data->watch > 0) {
g_source_remove(data->watch);
data->watch = 0;
}
if (data->timeout > 0) {
g_source_remove(data->timeout);
data->timeout = 0;
}
if (data->channel) {
g_io_channel_shutdown(data->channel, TRUE, NULL);
g_io_channel_unref(data->channel);
data->channel = NULL;
}
g_free(data->incoming_reply);
data->incoming_reply = NULL;
}
static void destroy_server(struct server_data *server)
{
DBG("index %d server %s sock %d", server->index, server->server,
server->channel ?
g_io_channel_unix_get_fd(server->channel): -1);
server_list = g_slist_remove(server_list, server);
server_destroy_socket(server);
if (server->protocol == IPPROTO_UDP && server->enabled)
DBG("Removing DNS server %s", server->server);
g_free(server->server);
g_list_free_full(server->domains, g_free);
g_free(server->server_addr);
/*
* We do not remove cache right away but delay it few seconds.
* The idea is that when IPv6 DNS server is added via RDNSS, it has a
* lifetime. When the lifetime expires we decrease the refcount so it
* is possible that the cache is then removed. Because a new DNS server
* is usually created almost immediately we would then loose the cache
* without any good reason. The small delay allows the new RDNSS to
* create a new DNS server instance and the refcount does not go to 0.
*/
if (cache && !cache_timer)
cache_timer = g_timeout_add_seconds(3, try_remove_cache, NULL);
g_free(server);
}
static gboolean udp_server_event(GIOChannel *channel, GIOCondition condition,
gpointer user_data)
{
unsigned char buf[4096];
int sk, err, len;
struct server_data *data = user_data;
if (condition & (G_IO_NVAL | G_IO_ERR | G_IO_HUP)) {
connman_error("Error with UDP server %s", data->server);
server_destroy_socket(data);
return FALSE;
}
sk = g_io_channel_unix_get_fd(channel);
len = recv(sk, buf, sizeof(buf), 0);
if (len < 12)
return TRUE;
err = forward_dns_reply(buf, len, IPPROTO_UDP, data);
if (err < 0)
return TRUE;
return TRUE;
}
static gboolean tcp_server_event(GIOChannel *channel, GIOCondition condition,
gpointer user_data)
{
int sk;
struct server_data *server = user_data;
sk = g_io_channel_unix_get_fd(channel);
if (sk == 0)
return FALSE;
if (condition & (G_IO_NVAL | G_IO_ERR | G_IO_HUP)) {
GSList *list;
hangup:
DBG("TCP server channel closed, sk %d", sk);
/*
* Discard any partial response which is buffered; better
* to get a proper response from a working server.
*/
g_free(server->incoming_reply);
server->incoming_reply = NULL;
for (list = request_list; list; list = list->next) {
struct request_data *req = list->data;
struct domain_hdr *hdr;
if (req->protocol == IPPROTO_UDP)
continue;
if (!req->request)
continue;
/*
* If we're not waiting for any further response
* from another name server, then we send an error
* response to the client.
*/
if (req->numserv && --(req->numserv))
continue;
hdr = (void *) (req->request + 2);
hdr->id = req->srcid;
send_response(req->client_sk, req->request,
req->request_len, NULL, 0, IPPROTO_TCP);
request_list = g_slist_remove(request_list, req);
}
destroy_server(server);
return FALSE;
}
if ((condition & G_IO_OUT) && !server->connected) {
GSList *list;
GList *domains;
bool no_request_sent = true;
struct server_data *udp_server;
udp_server = find_server(server->index, server->server,
IPPROTO_UDP);
if (udp_server) {
for (domains = udp_server->domains; domains;
domains = domains->next) {
char *dom = domains->data;
DBG("Adding domain %s to %s",
dom, server->server);
server->domains = g_list_append(server->domains,
g_strdup(dom));
}
}
server->connected = true;
server_list = g_slist_append(server_list, server);
if (server->timeout > 0) {
g_source_remove(server->timeout);
server->timeout = 0;
}
for (list = request_list; list; ) {
struct request_data *req = list->data;
int status;
if (req->protocol == IPPROTO_UDP) {
list = list->next;
continue;
}
DBG("Sending req %s over TCP", (char *)req->name);
status = ns_resolv(server, req,
req->request, req->name);
if (status > 0) {
/*
* A cached result was sent,
* so the request can be released
*/
list = list->next;
request_list = g_slist_remove(request_list, req);
destroy_request_data(req);
continue;
}
if (status < 0) {
list = list->next;
continue;
}
no_request_sent = false;
if (req->timeout > 0)
g_source_remove(req->timeout);
req->timeout = g_timeout_add_seconds(30,
request_timeout, req);
list = list->next;
}
if (no_request_sent) {
destroy_server(server);
return FALSE;
}
} else if (condition & G_IO_IN) {
struct partial_reply *reply = server->incoming_reply;
int bytes_recv;
if (!reply) {
unsigned char reply_len_buf[2];
uint16_t reply_len;
bytes_recv = recv(sk, reply_len_buf, 2, MSG_PEEK);
if (!bytes_recv) {
goto hangup;
} else if (bytes_recv < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK)
return TRUE;
connman_error("DNS proxy error %s",
strerror(errno));
goto hangup;
} else if (bytes_recv < 2)
return TRUE;
reply_len = reply_len_buf[1] | reply_len_buf[0] << 8;
reply_len += 2;
DBG("TCP reply %d bytes from %d", reply_len, sk);
reply = g_try_malloc(sizeof(*reply) + reply_len + 2);
if (!reply)
return TRUE;
reply->len = reply_len;
reply->received = 0;
server->incoming_reply = reply;
}
while (reply->received < reply->len) {
bytes_recv = recv(sk, reply->buf + reply->received,
reply->len - reply->received, 0);
if (!bytes_recv) {
connman_error("DNS proxy TCP disconnect");
break;
} else if (bytes_recv < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK)
return TRUE;
connman_error("DNS proxy error %s",
strerror(errno));
break;
}
reply->received += bytes_recv;
}
forward_dns_reply(reply->buf, reply->received, IPPROTO_TCP,
server);
g_free(reply);
server->incoming_reply = NULL;
destroy_server(server);
return FALSE;
}
return TRUE;
}
static gboolean tcp_idle_timeout(gpointer user_data)
{
struct server_data *server = user_data;
DBG("");
if (!server)
return FALSE;
destroy_server(server);
return FALSE;
}
static int server_create_socket(struct server_data *data)
{
int sk, err;
char *interface;
DBG("index %d server %s proto %d", data->index,
data->server, data->protocol);
sk = socket(data->server_addr->sa_family,
data->protocol == IPPROTO_TCP ? SOCK_STREAM : SOCK_DGRAM,
data->protocol);
if (sk < 0) {
err = errno;
connman_error("Failed to create server %s socket",
data->server);
server_destroy_socket(data);
return -err;
}
DBG("sk %d", sk);
interface = connman_inet_ifname(data->index);
if (interface) {
if (setsockopt(sk, SOL_SOCKET, SO_BINDTODEVICE,
interface,
strlen(interface) + 1) < 0) {
err = errno;
connman_error("Failed to bind server %s "
"to interface %s",
data->server, interface);
close(sk);
server_destroy_socket(data);
g_free(interface);
return -err;
}
g_free(interface);
}
data->channel = g_io_channel_unix_new(sk);
if (!data->channel) {
connman_error("Failed to create server %s channel",
data->server);
close(sk);
server_destroy_socket(data);
return -ENOMEM;
}
g_io_channel_set_close_on_unref(data->channel, TRUE);
if (data->protocol == IPPROTO_TCP) {
g_io_channel_set_flags(data->channel, G_IO_FLAG_NONBLOCK, NULL);
data->watch = g_io_add_watch(data->channel,
G_IO_OUT | G_IO_IN | G_IO_HUP | G_IO_NVAL | G_IO_ERR,
tcp_server_event, data);
data->timeout = g_timeout_add_seconds(30, tcp_idle_timeout,
data);
} else
data->watch = g_io_add_watch(data->channel,
G_IO_IN | G_IO_NVAL | G_IO_ERR | G_IO_HUP,
udp_server_event, data);
if (connect(sk, data->server_addr, data->server_addr_len) < 0) {
err = errno;
if ((data->protocol == IPPROTO_TCP && errno != EINPROGRESS) ||
data->protocol == IPPROTO_UDP) {
connman_error("Failed to connect to server %s",
data->server);
server_destroy_socket(data);
return -err;
}
}
create_cache();
return 0;
}
static struct server_data *create_server(int index,
const char *domain, const char *server,
int protocol)
{
struct server_data *data;
struct addrinfo hints, *rp;
int ret;
DBG("index %d server %s", index, server);
data = g_try_new0(struct server_data, 1);
if (!data) {
connman_error("Failed to allocate server %s data", server);
return NULL;
}
data->index = index;
if (domain)
data->domains = g_list_append(data->domains, g_strdup(domain));
data->server = g_strdup(server);
data->protocol = protocol;
memset(&hints, 0, sizeof(hints));
switch (protocol) {
case IPPROTO_UDP:
hints.ai_socktype = SOCK_DGRAM;
break;
case IPPROTO_TCP:
hints.ai_socktype = SOCK_STREAM;
break;
default:
destroy_server(data);
return NULL;
}
hints.ai_family = AF_UNSPEC;
hints.ai_flags = AI_NUMERICSERV | AI_NUMERICHOST;
ret = getaddrinfo(data->server, "53", &hints, &rp);
if (ret) {
connman_error("Failed to parse server %s address: %s\n",
data->server, gai_strerror(ret));
destroy_server(data);
return NULL;
}
/* Do not blindly copy this code elsewhere; it doesn't loop over the
results using ->ai_next as it should. That's OK in *this* case
because it was a numeric lookup; we *know* there's only one. */
data->server_addr_len = rp->ai_addrlen;
switch (rp->ai_family) {
case AF_INET:
data->server_addr = (struct sockaddr *)
g_try_new0(struct sockaddr_in, 1);
break;
case AF_INET6:
data->server_addr = (struct sockaddr *)
g_try_new0(struct sockaddr_in6, 1);
break;
default:
connman_error("Wrong address family %d", rp->ai_family);
break;
}
if (!data->server_addr) {
freeaddrinfo(rp);
destroy_server(data);
return NULL;
}
memcpy(data->server_addr, rp->ai_addr, rp->ai_addrlen);
freeaddrinfo(rp);
if (server_create_socket(data) != 0) {
destroy_server(data);
return NULL;
}
if (protocol == IPPROTO_UDP) {
if (__connman_service_index_is_default(data->index) ||
__connman_service_index_is_split_routing(
data->index)) {
data->enabled = true;
DBG("Adding DNS server %s", data->server);
}
server_list = g_slist_append(server_list, data);
}
return data;
}
static bool resolv(struct request_data *req,
gpointer request, gpointer name)
{
GSList *list;
for (list = server_list; list; list = list->next) {
struct server_data *data = list->data;
if (data->protocol == IPPROTO_TCP) {
DBG("server %s ignored proto TCP", data->server);
continue;
}
DBG("server %s enabled %d", data->server, data->enabled);
if (!data->enabled)
continue;
if (!data->channel && data->protocol == IPPROTO_UDP) {
if (server_create_socket(data) < 0) {
DBG("socket creation failed while resolving");
continue;
}
}
if (ns_resolv(data, req, request, name) > 0)
return true;
}
return false;
}
static void append_domain(int index, const char *domain)
{
GSList *list;
DBG("index %d domain %s", index, domain);
if (!domain)
return;
for (list = server_list; list; list = list->next) {
struct server_data *data = list->data;
GList *dom_list;
char *dom;
bool dom_found = false;
if (data->index < 0)
continue;
if (data->index != index)
continue;
for (dom_list = data->domains; dom_list;
dom_list = dom_list->next) {
dom = dom_list->data;
if (g_str_equal(dom, domain)) {
dom_found = true;
break;
}
}
if (!dom_found) {
data->domains =
g_list_append(data->domains, g_strdup(domain));
}
}
}
static void flush_requests(struct server_data *server)
{
GSList *list;
list = request_list;
while (list) {
struct request_data *req = list->data;
list = list->next;
if (ns_resolv(server, req, req->request, req->name)) {
/*
* A cached result was sent,
* so the request can be released
*/
request_list =
g_slist_remove(request_list, req);
destroy_request_data(req);
continue;
}
if (req->timeout > 0)
g_source_remove(req->timeout);
req->timeout = g_timeout_add_seconds(5, request_timeout, req);
}
}
int __connman_dnsproxy_append(int index, const char *domain,
const char *server)
{
struct server_data *data;
DBG("index %d server %s", index, server);
if (!server && !domain)
return -EINVAL;
if (!server) {
append_domain(index, domain);
return 0;
}
if (g_str_equal(server, "127.0.0.1"))
return -ENODEV;
if (g_str_equal(server, "::1"))
return -ENODEV;
data = find_server(index, server, IPPROTO_UDP);
if (data) {
append_domain(index, domain);
return 0;
}
data = create_server(index, domain, server, IPPROTO_UDP);
if (!data)
return -EIO;
flush_requests(data);
return 0;
}
static void remove_server(int index, const char *domain,
const char *server, int protocol)
{
struct server_data *data;
data = find_server(index, server, protocol);
if (!data)
return;
destroy_server(data);
}
int __connman_dnsproxy_remove(int index, const char *domain,
const char *server)
{
DBG("index %d server %s", index, server);
if (!server)
return -EINVAL;
if (g_str_equal(server, "127.0.0.1"))
return -ENODEV;
if (g_str_equal(server, "::1"))
return -ENODEV;
remove_server(index, domain, server, IPPROTO_UDP);
remove_server(index, domain, server, IPPROTO_TCP);
return 0;
}
static void dnsproxy_offline_mode(bool enabled)
{
GSList *list;
DBG("enabled %d", enabled);
for (list = server_list; list; list = list->next) {
struct server_data *data = list->data;
if (!enabled) {
DBG("Enabling DNS server %s", data->server);
data->enabled = true;
cache_invalidate();
cache_refresh();
} else {
DBG("Disabling DNS server %s", data->server);
data->enabled = false;
cache_invalidate();
}
}
}
static void dnsproxy_default_changed(struct connman_service *service)
{
GSList *list;
int index;
DBG("service %p", service);
/* DNS has changed, invalidate the cache */
cache_invalidate();
if (!service) {
/* When no services are active, then disable DNS proxying */
dnsproxy_offline_mode(true);
return;
}
index = __connman_service_get_index(service);
if (index < 0)
return;
for (list = server_list; list; list = list->next) {
struct server_data *data = list->data;
if (data->index == index) {
DBG("Enabling DNS server %s", data->server);
data->enabled = true;
} else {
DBG("Disabling DNS server %s", data->server);
data->enabled = false;
}
}
cache_refresh();
}
static struct connman_notifier dnsproxy_notifier = {
.name = "dnsproxy",
.default_changed = dnsproxy_default_changed,
.offline_mode = dnsproxy_offline_mode,
};
static unsigned char opt_edns0_type[2] = { 0x00, 0x29 };
static int parse_request(unsigned char *buf, int len,
char *name, unsigned int size)
{
struct domain_hdr *hdr = (void *) buf;
uint16_t qdcount = ntohs(hdr->qdcount);
uint16_t arcount = ntohs(hdr->arcount);
unsigned char *ptr;
char *last_label = NULL;
unsigned int remain, used = 0;
if (len < 12)
return -EINVAL;
DBG("id 0x%04x qr %d opcode %d qdcount %d arcount %d",
hdr->id, hdr->qr, hdr->opcode,
qdcount, arcount);
if (hdr->qr != 0 || qdcount != 1)
return -EINVAL;
name[0] = '\0';
ptr = buf + sizeof(struct domain_hdr);
remain = len - sizeof(struct domain_hdr);
while (remain > 0) {
uint8_t label_len = *ptr;
if (label_len == 0x00) {
last_label = (char *) (ptr + 1);
break;
}
if (used + label_len + 1 > size)
return -ENOBUFS;
strncat(name, (char *) (ptr + 1), label_len);
strcat(name, ".");
used += label_len + 1;
ptr += label_len + 1;
remain -= label_len + 1;
}
if (last_label && arcount && remain >= 9 && last_label[4] == 0 &&
!memcmp(last_label + 5, opt_edns0_type, 2)) {
uint16_t edns0_bufsize;
edns0_bufsize = last_label[7] << 8 | last_label[8];
DBG("EDNS0 buffer size %u", edns0_bufsize);
/* This is an evil hack until full TCP support has been
* implemented.
*
* Somtimes the EDNS0 request gets send with a too-small
* buffer size. Since glibc doesn't seem to crash when it
* gets a response biffer then it requested, just bump
* the buffer size up to 4KiB.
*/
if (edns0_bufsize < 0x1000) {
last_label[7] = 0x10;
last_label[8] = 0x00;
}
}
DBG("query %s", name);
return 0;
}
static void client_reset(struct tcp_partial_client_data *client)
{
if (!client)
return;
if (client->channel) {
DBG("client %d closing",
g_io_channel_unix_get_fd(client->channel));
g_io_channel_unref(client->channel);
client->channel = NULL;
}
if (client->watch > 0) {
g_source_remove(client->watch);
client->watch = 0;
}
if (client->timeout > 0) {
g_source_remove(client->timeout);
client->timeout = 0;
}
g_free(client->buf);
client->buf = NULL;
client->buf_end = 0;
}
static unsigned int get_msg_len(unsigned char *buf)
{
return buf[0]<<8 | buf[1];
}
static bool read_tcp_data(struct tcp_partial_client_data *client,
void *client_addr, socklen_t client_addr_len,
int read_len)
{
char query[TCP_MAX_BUF_LEN];
struct request_data *req;
int client_sk, err;
unsigned int msg_len;
GSList *list;
bool waiting_for_connect = false;
int qtype = 0;
struct cache_entry *entry;
client_sk = g_io_channel_unix_get_fd(client->channel);
if (read_len == 0) {
DBG("client %d closed, pending %d bytes",
client_sk, client->buf_end);
g_hash_table_remove(partial_tcp_req_table,
GINT_TO_POINTER(client_sk));
return false;
}
DBG("client %d received %d bytes", client_sk, read_len);
client->buf_end += read_len;
if (client->buf_end < 2)
return true;
msg_len = get_msg_len(client->buf);
if (msg_len > TCP_MAX_BUF_LEN) {
DBG("client %d sent too much data %d", client_sk, msg_len);
g_hash_table_remove(partial_tcp_req_table,
GINT_TO_POINTER(client_sk));
return false;
}
read_another:
DBG("client %d msg len %d end %d past end %d", client_sk, msg_len,
client->buf_end, client->buf_end - (msg_len + 2));
if (client->buf_end < (msg_len + 2)) {
DBG("client %d still missing %d bytes",
client_sk,
msg_len + 2 - client->buf_end);
return true;
}
DBG("client %d all data %d received", client_sk, msg_len);
err = parse_request(client->buf + 2, msg_len,
query, sizeof(query));
if (err < 0 || (g_slist_length(server_list) == 0)) {
send_response(client_sk, client->buf, msg_len + 2,
NULL, 0, IPPROTO_TCP);
return true;
}
req = g_try_new0(struct request_data, 1);
if (!req)
return true;
memcpy(&req->sa, client_addr, client_addr_len);
req->sa_len = client_addr_len;
req->client_sk = client_sk;
req->protocol = IPPROTO_TCP;
req->family = client->family;
req->srcid = client->buf[2] | (client->buf[3] << 8);
req->dstid = get_id();
req->altid = get_id();
req->request_len = msg_len + 2;
client->buf[2] = req->dstid & 0xff;
client->buf[3] = req->dstid >> 8;
req->numserv = 0;
req->ifdata = client->ifdata;
req->append_domain = false;
/*
* Check if the answer is found in the cache before
* creating sockets to the server.
*/
entry = cache_check(client->buf, &qtype, IPPROTO_TCP);
if (entry) {
int ttl_left = 0;
struct cache_data *data;
DBG("cache hit %s type %s", query, qtype == 1 ? "A" : "AAAA");
if (qtype == 1)
data = entry->ipv4;
else
data = entry->ipv6;
if (data) {
ttl_left = data->valid_until - time(NULL);
entry->hits++;
send_cached_response(client_sk, data->data,
data->data_len, NULL, 0, IPPROTO_TCP,
req->srcid, data->answers, ttl_left);
g_free(req);
goto out;
} else
DBG("data missing, ignoring cache for this query");
}
for (list = server_list; list; list = list->next) {
struct server_data *data = list->data;
if (data->protocol != IPPROTO_UDP || !data->enabled)
continue;
if (!create_server(data->index, NULL, data->server,
IPPROTO_TCP))
continue;
waiting_for_connect = true;
}
if (!waiting_for_connect) {
/* No server is waiting for connect */
send_response(client_sk, client->buf,
req->request_len, NULL, 0, IPPROTO_TCP);
g_free(req);
return true;
}
/*
* The server is not connected yet.
* Copy the relevant buffers.
* The request will actually be sent once we're
* properly connected over TCP to the nameserver.
*/
req->request = g_try_malloc0(req->request_len);
if (!req->request) {
send_response(client_sk, client->buf,
req->request_len, NULL, 0, IPPROTO_TCP);
g_free(req);
goto out;
}
memcpy(req->request, client->buf, req->request_len);
req->name = g_try_malloc0(sizeof(query));
if (!req->name) {
send_response(client_sk, client->buf,
req->request_len, NULL, 0, IPPROTO_TCP);
g_free(req->request);
g_free(req);
goto out;
}
memcpy(req->name, query, sizeof(query));
req->timeout = g_timeout_add_seconds(30, request_timeout, req);
request_list = g_slist_append(request_list, req);
out:
if