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08bbcffc0e
tor/src/feature/relay/dns.c
Neel Chauhan 32db806dfa Teach the OOM handler about the DNS cache
2018-07-17 09:19:27 -04:00

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/* Copyright (c) 2003-2004, Roger Dingledine.
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2018, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file dns.c
* \brief Implements a local cache for DNS results for Tor servers.
* This is implemented as a wrapper around Adam Langley's eventdns.c code.
* (We can't just use gethostbyname() and friends because we really need to
* be nonblocking.)
*
* There are three main cases when a Tor relay uses dns.c to launch a DNS
* request:
* <ol>
* <li>To check whether the DNS server is working more or less correctly.
* This happens via dns_launch_correctness_checks(). The answer is
* reported in the return value from later calls to
* dns_seems_to_be_broken().
* <li>When a client has asked the relay, in a RELAY_BEGIN cell, to connect
* to a given server by hostname. This happens via dns_resolve().
* <li>When a client has asked the relay, in a RELAY_RESOLVE cell, to look
* up a given server's IP address(es) by hostname. This also happens via
* dns_resolve().
* </ol>
*
* Each of these gets handled a little differently.
*
* To check for correctness, we look up some hostname we expect to exist and
* have real entries, some hostnames which we expect to definitely not exist,
* and some hostnames that we expect to probably not exist. If too many of
* the hostnames that shouldn't exist do exist, that's a DNS hijacking
* attempt. If too many of the hostnames that should exist have the same
* addresses as the ones that shouldn't exist, that's a very bad DNS hijacking
* attempt, or a very naughty captive portal. And if the hostnames that
* should exist simply don't exist, we probably have a broken nameserver.
*
* To handle client requests, we first check our cache for answers. If there
* isn't something up-to-date, we've got to launch A or AAAA requests as
* appropriate. How we handle responses to those in particular is a bit
* complex; see dns_lookup() and set_exitconn_info_from_resolve().
*
* When a lookup is finally complete, the inform_pending_connections()
* function will tell all of the streams that have been waiting for the
* resolve, by calling connection_exit_connect() if the client sent a
* RELAY_BEGIN cell, and by calling send_resolved_cell() or
* send_hostname_cell() if the client sent a RELAY_RESOLVE cell.
**/
#define DNS_PRIVATE
#include "core/or/or.h"
#include "core/or/circuitlist.h"
#include "core/or/circuituse.h"
#include "app/config/config.h"
#include "core/mainloop/connection.h"
#include "core/or/connection_edge.h"
#include "feature/control/control.h"
#include "lib/crypt_ops/crypto_rand.h"
#include "feature/relay/dns.h"
#include "core/mainloop/main.h"
#include "core/or/policies.h"
#include "core/or/relay.h"
#include "feature/relay/router.h"
#include "ht.h"
#include "lib/sandbox/sandbox.h"
#include "lib/evloop/compat_libevent.h"
#include "core/or/edge_connection_st.h"
#include "core/or/or_circuit_st.h"
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#include <event2/event.h>
#include <event2/dns.h>
/** How long will we wait for an answer from the resolver before we decide
* that the resolver is wedged? */
#define RESOLVE_MAX_TIMEOUT 300
/** Our evdns_base; this structure handles all our name lookups. */
static struct evdns_base *the_evdns_base = NULL;
/** Have we currently configured nameservers with eventdns? */
static int nameservers_configured = 0;
/** Did our most recent attempt to configure nameservers with eventdns fail? */
static int nameserver_config_failed = 0;
/** What was the resolv_conf fname we last used when configuring the
* nameservers? Used to check whether we need to reconfigure. */
static char *resolv_conf_fname = NULL;
/** What was the mtime on the resolv.conf file we last used when configuring
* the nameservers? Used to check whether we need to reconfigure. */
static time_t resolv_conf_mtime = 0;
static void purge_expired_resolves(time_t now);
static void dns_found_answer(const char *address, uint8_t query_type,
int dns_answer,
const tor_addr_t *addr,
const char *hostname,
uint32_t ttl);
static void add_wildcarded_test_address(const char *address);
static int configure_nameservers(int force);
static int answer_is_wildcarded(const char *ip);
static int evdns_err_is_transient(int err);
static void inform_pending_connections(cached_resolve_t *resolve);
static void make_pending_resolve_cached(cached_resolve_t *cached);
#ifdef DEBUG_DNS_CACHE
static void assert_cache_ok_(void);
#define assert_cache_ok() assert_cache_ok_()
#else
#define assert_cache_ok() STMT_NIL
#endif /* defined(DEBUG_DNS_CACHE) */
static void assert_resolve_ok(cached_resolve_t *resolve);
/** Hash table of cached_resolve objects. */
static HT_HEAD(cache_map, cached_resolve_t) cache_root;
/** Global: how many IPv6 requests have we made in all? */
static uint64_t n_ipv6_requests_made = 0;
/** Global: how many IPv6 requests have timed out? */
static uint64_t n_ipv6_timeouts = 0;
/** Global: Do we think that IPv6 DNS is broken? */
static int dns_is_broken_for_ipv6 = 0;
/** Function to compare hashed resolves on their addresses; used to
* implement hash tables. */
static inline int
cached_resolves_eq(cached_resolve_t *a, cached_resolve_t *b)
{
/* make this smarter one day? */
assert_resolve_ok(a); // Not b; b may be just a search.
return !strncmp(a->address, b->address, MAX_ADDRESSLEN);
}
/** Hash function for cached_resolve objects */
static inline unsigned int
cached_resolve_hash(cached_resolve_t *a)
{
return (unsigned) siphash24g((const uint8_t*)a->address, strlen(a->address));
}
HT_PROTOTYPE(cache_map, cached_resolve_t, node, cached_resolve_hash,
cached_resolves_eq)
HT_GENERATE2(cache_map, cached_resolve_t, node, cached_resolve_hash,
cached_resolves_eq, 0.6, tor_reallocarray_, tor_free_)
/** Initialize the DNS cache. */
static void
init_cache_map(void)
{
HT_INIT(cache_map, &cache_root);
}
/** Helper: called by eventdns when eventdns wants to log something. */
static void
evdns_log_cb(int warn, const char *msg)
{
const char *cp;
static int all_down = 0;
int severity = warn ? LOG_WARN : LOG_INFO;
if (!strcmpstart(msg, "Resolve requested for") &&
get_options()->SafeLogging) {
log_info(LD_EXIT, "eventdns: Resolve requested.");
return;
} else if (!strcmpstart(msg, "Search: ")) {
return;
}
if (!strcmpstart(msg, "Nameserver ") && (cp=strstr(msg, " has failed: "))) {
char *ns = tor_strndup(msg+11, cp-(msg+11));
const char *colon = strchr(cp, ':');
tor_assert(colon);
const char *err = colon+2;
/* Don't warn about a single failed nameserver; we'll warn with 'all
* nameservers have failed' if we're completely out of nameservers;
* otherwise, the situation is tolerable. */
severity = LOG_INFO;
control_event_server_status(LOG_NOTICE,
"NAMESERVER_STATUS NS=%s STATUS=DOWN ERR=%s",
ns, escaped(err));
tor_free(ns);
} else if (!strcmpstart(msg, "Nameserver ") &&
(cp=strstr(msg, " is back up"))) {
char *ns = tor_strndup(msg+11, cp-(msg+11));
severity = (all_down && warn) ? LOG_NOTICE : LOG_INFO;
all_down = 0;
control_event_server_status(LOG_NOTICE,
"NAMESERVER_STATUS NS=%s STATUS=UP", ns);
tor_free(ns);
} else if (!strcmp(msg, "All nameservers have failed")) {
control_event_server_status(LOG_WARN, "NAMESERVER_ALL_DOWN");
all_down = 1;
} else if (!strcmpstart(msg, "Address mismatch on received DNS")) {
static ratelim_t mismatch_limit = RATELIM_INIT(3600);
const char *src = strstr(msg, " Apparent source");
if (!src || get_options()->SafeLogging) {
src = "";
}
log_fn_ratelim(&mismatch_limit, severity, LD_EXIT,
"eventdns: Received a DNS packet from "
"an IP address to which we did not send a request. This "
"could be a DNS spoofing attempt, or some kind of "
"misconfiguration.%s", src);
return;
}
tor_log(severity, LD_EXIT, "eventdns: %s", msg);
}
/** Helper: passed to eventdns.c as a callback so it can generate random
* numbers for transaction IDs and 0x20-hack coding. */
static void
dns_randfn_(char *b, size_t n)
{
crypto_rand(b,n);
}
/** Initialize the DNS subsystem; called by the OR process. */
int
dns_init(void)
{
init_cache_map();
evdns_set_random_bytes_fn(dns_randfn_);
if (server_mode(get_options())) {
int r = configure_nameservers(1);
return r;
}
return 0;
}
/** Called when DNS-related options change (or may have changed). Returns -1
* on failure, 0 on success. */
int
dns_reset(void)
{
const or_options_t *options = get_options();
if (! server_mode(options)) {
if (!the_evdns_base) {
if (!(the_evdns_base = evdns_base_new(tor_libevent_get_base(), 0))) {
log_err(LD_BUG, "Couldn't create an evdns_base");
return -1;
}
}
evdns_base_clear_nameservers_and_suspend(the_evdns_base);
evdns_base_search_clear(the_evdns_base);
nameservers_configured = 0;
tor_free(resolv_conf_fname);
resolv_conf_mtime = 0;
} else {
if (configure_nameservers(0) < 0) {
return -1;
}
}
return 0;
}
/** Return true iff the most recent attempt to initialize the DNS subsystem
* failed. */
int
has_dns_init_failed(void)
{
return nameserver_config_failed;
}
/** Helper: Given a TTL from a DNS response, determine what TTL to give the
* OP that asked us to resolve it, and how long to cache that record
* ourselves. */
uint32_t
dns_clip_ttl(uint32_t ttl)
{
/* This logic is a defense against "DefectTor" DNS-based traffic
* confirmation attacks, as in https://nymity.ch/tor-dns/tor-dns.pdf .
* We only give two values: a "low" value and a "high" value.
*/
if (ttl < MIN_DNS_TTL_AT_EXIT)
return MIN_DNS_TTL_AT_EXIT;
else
return MAX_DNS_TTL_AT_EXIT;
}
/** Helper: free storage held by an entry in the DNS cache. */
static void
free_cached_resolve_(cached_resolve_t *r)
{
if (!r)
return;
while (r->pending_connections) {
pending_connection_t *victim = r->pending_connections;
r->pending_connections = victim->next;
tor_free(victim);
}
if (r->res_status_hostname == RES_STATUS_DONE_OK)
tor_free(r->result_ptr.hostname);
r->magic = 0xFF00FF00;
tor_free(r);
}
/** Compare two cached_resolve_t pointers by expiry time, and return
* less-than-zero, zero, or greater-than-zero as appropriate. Used for
* the priority queue implementation. */
static int
compare_cached_resolves_by_expiry_(const void *_a, const void *_b)
{
const cached_resolve_t *a = _a, *b = _b;
if (a->expire < b->expire)
return -1;
else if (a->expire == b->expire)
return 0;
else
return 1;
}
/** Priority queue of cached_resolve_t objects to let us know when they
* will expire. */
static smartlist_t *cached_resolve_pqueue = NULL;
static void
cached_resolve_add_answer(cached_resolve_t *resolve,
int query_type,
int dns_result,
const tor_addr_t *answer_addr,
const char *answer_hostname,
uint32_t ttl)
{
if (query_type == DNS_PTR) {
if (resolve->res_status_hostname != RES_STATUS_INFLIGHT)
return;
if (dns_result == DNS_ERR_NONE && answer_hostname) {
resolve->result_ptr.hostname = tor_strdup(answer_hostname);
resolve->res_status_hostname = RES_STATUS_DONE_OK;
} else {
resolve->result_ptr.err_hostname = dns_result;
resolve->res_status_hostname = RES_STATUS_DONE_ERR;
}
resolve->ttl_hostname = ttl;
} else if (query_type == DNS_IPv4_A) {
if (resolve->res_status_ipv4 != RES_STATUS_INFLIGHT)
return;
if (dns_result == DNS_ERR_NONE && answer_addr &&
tor_addr_family(answer_addr) == AF_INET) {
resolve->result_ipv4.addr_ipv4 = tor_addr_to_ipv4h(answer_addr);
resolve->res_status_ipv4 = RES_STATUS_DONE_OK;
} else {
resolve->result_ipv4.err_ipv4 = dns_result;
resolve->res_status_ipv4 = RES_STATUS_DONE_ERR;
}
resolve->ttl_ipv4 = ttl;
} else if (query_type == DNS_IPv6_AAAA) {
if (resolve->res_status_ipv6 != RES_STATUS_INFLIGHT)
return;
if (dns_result == DNS_ERR_NONE && answer_addr &&
tor_addr_family(answer_addr) == AF_INET6) {
memcpy(&resolve->result_ipv6.addr_ipv6,
tor_addr_to_in6(answer_addr),
sizeof(struct in6_addr));
resolve->res_status_ipv6 = RES_STATUS_DONE_OK;
} else {
resolve->result_ipv6.err_ipv6 = dns_result;
resolve->res_status_ipv6 = RES_STATUS_DONE_ERR;
}
resolve->ttl_ipv6 = ttl;
}
}
/** Return true iff there are no in-flight requests for <b>resolve</b>. */
static int
cached_resolve_have_all_answers(const cached_resolve_t *resolve)
{
return (resolve->res_status_ipv4 != RES_STATUS_INFLIGHT &&
resolve->res_status_ipv6 != RES_STATUS_INFLIGHT &&
resolve->res_status_hostname != RES_STATUS_INFLIGHT);
}
/** Set an expiry time for a cached_resolve_t, and add it to the expiry
* priority queue */
static void
set_expiry(cached_resolve_t *resolve, time_t expires)
{
tor_assert(resolve && resolve->expire == 0);
if (!cached_resolve_pqueue)
cached_resolve_pqueue = smartlist_new();
resolve->expire = expires;
smartlist_pqueue_add(cached_resolve_pqueue,
compare_cached_resolves_by_expiry_,
offsetof(cached_resolve_t, minheap_idx),
resolve);
}
/** Free all storage held in the DNS cache and related structures. */
void
dns_free_all(void)
{
cached_resolve_t **ptr, **next, *item;
assert_cache_ok();
if (cached_resolve_pqueue) {
SMARTLIST_FOREACH(cached_resolve_pqueue, cached_resolve_t *, res,
{
if (res->state == CACHE_STATE_DONE)
free_cached_resolve_(res);
});
}
for (ptr = HT_START(cache_map, &cache_root); ptr != NULL; ptr = next) {
item = *ptr;
next = HT_NEXT_RMV(cache_map, &cache_root, ptr);
free_cached_resolve_(item);
}
HT_CLEAR(cache_map, &cache_root);
smartlist_free(cached_resolve_pqueue);
cached_resolve_pqueue = NULL;
tor_free(resolv_conf_fname);
}
/** Remove every cached_resolve whose <b>expire</b> time is before or
* equal to <b>now</b> from the cache. */
static void
purge_expired_resolves(time_t now)
{
cached_resolve_t *resolve, *removed;
pending_connection_t *pend;
edge_connection_t *pendconn;
assert_cache_ok();
if (!cached_resolve_pqueue)
return;
while (smartlist_len(cached_resolve_pqueue)) {
resolve = smartlist_get(cached_resolve_pqueue, 0);
if (resolve->expire > now)
break;
smartlist_pqueue_pop(cached_resolve_pqueue,
compare_cached_resolves_by_expiry_,
offsetof(cached_resolve_t, minheap_idx));
if (resolve->state == CACHE_STATE_PENDING) {
log_debug(LD_EXIT,
"Expiring a dns resolve %s that's still pending. Forgot to "
"cull it? DNS resolve didn't tell us about the timeout?",
escaped_safe_str(resolve->address));
} else if (resolve->state == CACHE_STATE_CACHED) {
log_debug(LD_EXIT,
"Forgetting old cached resolve (address %s, expires %lu)",
escaped_safe_str(resolve->address),
(unsigned long)resolve->expire);
tor_assert(!resolve->pending_connections);
} else {
tor_assert(resolve->state == CACHE_STATE_DONE);
tor_assert(!resolve->pending_connections);
}
if (resolve->pending_connections) {
log_debug(LD_EXIT,
"Closing pending connections on timed-out DNS resolve!");
while (resolve->pending_connections) {
pend = resolve->pending_connections;
resolve->pending_connections = pend->next;
/* Connections should only be pending if they have no socket. */
tor_assert(!SOCKET_OK(pend->conn->base_.s));
pendconn = pend->conn;
/* Prevent double-remove */
pendconn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
if (!pendconn->base_.marked_for_close) {
connection_edge_end(pendconn, END_STREAM_REASON_TIMEOUT);
circuit_detach_stream(circuit_get_by_edge_conn(pendconn), pendconn);
connection_free_(TO_CONN(pendconn));
}
tor_free(pend);
}
}
if (resolve->state == CACHE_STATE_CACHED ||
resolve->state == CACHE_STATE_PENDING) {
removed = HT_REMOVE(cache_map, &cache_root, resolve);
if (removed != resolve) {
log_err(LD_BUG, "The expired resolve we purged didn't match any in"
" the cache. Tried to purge %s (%p); instead got %s (%p).",
resolve->address, (void*)resolve,
removed ? removed->address : "NULL", (void*)removed);
}
tor_assert(removed == resolve);
} else {
/* This should be in state DONE. Make sure it's not in the cache. */
cached_resolve_t *tmp = HT_FIND(cache_map, &cache_root, resolve);
tor_assert(tmp != resolve);
}
if (resolve->res_status_hostname == RES_STATUS_DONE_OK)
tor_free(resolve->result_ptr.hostname);
resolve->magic = 0xF0BBF0BB;
tor_free(resolve);
}
assert_cache_ok();
}
/* argument for send_resolved_cell only, meaning "let the answer type be ipv4
* or ipv6 depending on the connection's address". */
#define RESOLVED_TYPE_AUTO 0xff
/** Send a response to the RESOLVE request of a connection.
* <b>answer_type</b> must be one of
* RESOLVED_TYPE_(AUTO|ERROR|ERROR_TRANSIENT|).
*
* If <b>circ</b> is provided, and we have a cached answer, send the
* answer back along circ; otherwise, send the answer back along
* <b>conn</b>'s attached circuit.
*/
MOCK_IMPL(STATIC void,
send_resolved_cell,(edge_connection_t *conn, uint8_t answer_type,
const cached_resolve_t *resolved))
{
char buf[RELAY_PAYLOAD_SIZE], *cp = buf;
size_t buflen = 0;
uint32_t ttl;
buf[0] = answer_type;
ttl = dns_clip_ttl(conn->address_ttl);
switch (answer_type)
{
case RESOLVED_TYPE_AUTO:
if (resolved && resolved->res_status_ipv4 == RES_STATUS_DONE_OK) {
cp[0] = RESOLVED_TYPE_IPV4;
cp[1] = 4;
set_uint32(cp+2, htonl(resolved->result_ipv4.addr_ipv4));
set_uint32(cp+6, htonl(ttl));
cp += 10;
}
if (resolved && resolved->res_status_ipv6 == RES_STATUS_DONE_OK) {
const uint8_t *bytes = resolved->result_ipv6.addr_ipv6.s6_addr;
cp[0] = RESOLVED_TYPE_IPV6;
cp[1] = 16;
memcpy(cp+2, bytes, 16);
set_uint32(cp+18, htonl(ttl));
cp += 22;
}
if (cp != buf) {
buflen = cp - buf;
break;
} else {
answer_type = RESOLVED_TYPE_ERROR;
/* fall through. */
}
/* Falls through. */
case RESOLVED_TYPE_ERROR_TRANSIENT:
case RESOLVED_TYPE_ERROR:
{
const char *errmsg = "Error resolving hostname";
size_t msglen = strlen(errmsg);
buf[0] = answer_type;
buf[1] = msglen;
strlcpy(buf+2, errmsg, sizeof(buf)-2);
set_uint32(buf+2+msglen, htonl(ttl));
buflen = 6+msglen;
break;
}
default:
tor_assert(0);
return;
}
// log_notice(LD_EXIT, "Sending a regular RESOLVED reply: ");
connection_edge_send_command(conn, RELAY_COMMAND_RESOLVED, buf, buflen);
}
/** Send a response to the RESOLVE request of a connection for an in-addr.arpa
* address on connection <b>conn</b> which yielded the result <b>hostname</b>.
* The answer type will be RESOLVED_HOSTNAME.
*
* If <b>circ</b> is provided, and we have a cached answer, send the
* answer back along circ; otherwise, send the answer back along
* <b>conn</b>'s attached circuit.
*/
MOCK_IMPL(STATIC void,
send_resolved_hostname_cell,(edge_connection_t *conn,
const char *hostname))
{
char buf[RELAY_PAYLOAD_SIZE];
size_t buflen;
uint32_t ttl;
size_t namelen = strlen(hostname);
tor_assert(hostname);
tor_assert(namelen < 256);
ttl = dns_clip_ttl(conn->address_ttl);
buf[0] = RESOLVED_TYPE_HOSTNAME;
buf[1] = (uint8_t)namelen;
memcpy(buf+2, hostname, namelen);
set_uint32(buf+2+namelen, htonl(ttl));
buflen = 2+namelen+4;
// log_notice(LD_EXIT, "Sending a reply RESOLVED reply: %s", hostname);
connection_edge_send_command(conn, RELAY_COMMAND_RESOLVED, buf, buflen);
// log_notice(LD_EXIT, "Sent");
}
/** See if we have a cache entry for <b>exitconn</b>-\>address. If so,
* if resolve valid, put it into <b>exitconn</b>-\>addr and return 1.
* If resolve failed, free exitconn and return -1.
*
* (For EXIT_PURPOSE_RESOLVE connections, send back a RESOLVED error cell
* on returning -1. For EXIT_PURPOSE_CONNECT connections, there's no
* need to send back an END cell, since connection_exit_begin_conn will
* do that for us.)
*
* If we have a cached answer, send the answer back along <b>exitconn</b>'s
* circuit.
*
* Else, if seen before and pending, add conn to the pending list,
* and return 0.
*
* Else, if not seen before, add conn to pending list, hand to
* dns farm, and return 0.
*
* Exitconn's on_circuit field must be set, but exitconn should not
* yet be linked onto the n_streams/resolving_streams list of that circuit.
* On success, link the connection to n_streams if it's an exit connection.
* On "pending", link the connection to resolving streams. Otherwise,
* clear its on_circuit field.
*/
int
dns_resolve(edge_connection_t *exitconn)
{
or_circuit_t *oncirc = TO_OR_CIRCUIT(exitconn->on_circuit);
int is_resolve, r;
int made_connection_pending = 0;
char *hostname = NULL;
cached_resolve_t *resolve = NULL;
is_resolve = exitconn->base_.purpose == EXIT_PURPOSE_RESOLVE;
r = dns_resolve_impl(exitconn, is_resolve, oncirc, &hostname,
&made_connection_pending, &resolve);
switch (r) {
case 1:
/* We got an answer without a lookup -- either the answer was
* cached, or it was obvious (like an IP address). */
if (is_resolve) {
/* Send the answer back right now, and detach. */
if (hostname)
send_resolved_hostname_cell(exitconn, hostname);
else
send_resolved_cell(exitconn, RESOLVED_TYPE_AUTO, resolve);
exitconn->on_circuit = NULL;
} else {
/* Add to the n_streams list; the calling function will send back a
* connected cell. */
exitconn->next_stream = oncirc->n_streams;
oncirc->n_streams = exitconn;
}
break;
case 0:
/* The request is pending: add the connection into the linked list of
* resolving_streams on this circuit. */
exitconn->base_.state = EXIT_CONN_STATE_RESOLVING;
exitconn->next_stream = oncirc->resolving_streams;
oncirc->resolving_streams = exitconn;
break;
case -2:
case -1:
/* The request failed before it could start: cancel this connection,
* and stop everybody waiting for the same connection. */
if (is_resolve) {
send_resolved_cell(exitconn,
(r == -1) ? RESOLVED_TYPE_ERROR : RESOLVED_TYPE_ERROR_TRANSIENT,
NULL);
}
exitconn->on_circuit = NULL;
dns_cancel_pending_resolve(exitconn->base_.address);
if (!made_connection_pending && !exitconn->base_.marked_for_close) {
/* If we made the connection pending, then we freed it already in
* dns_cancel_pending_resolve(). If we marked it for close, it'll
* get freed from the main loop. Otherwise, can free it now. */
connection_free_(TO_CONN(exitconn));
}
break;
default:
tor_assert(0);
}
tor_free(hostname);
return r;
}
/** Helper function for dns_resolve: same functionality, but does not handle:
* - marking connections on error and clearing their on_circuit
* - linking connections to n_streams/resolving_streams,
* - sending resolved cells if we have an answer/error right away,
*
* Return -2 on a transient error. If it's a reverse resolve and it's
* successful, sets *<b>hostname_out</b> to a newly allocated string
* holding the cached reverse DNS value.
*
* Set *<b>made_connection_pending_out</b> to true if we have placed
* <b>exitconn</b> on the list of pending connections for some resolve; set it
* to false otherwise.
*
* Set *<b>resolve_out</b> to a cached resolve, if we found one.
*/
MOCK_IMPL(STATIC int,
dns_resolve_impl,(edge_connection_t *exitconn, int is_resolve,
or_circuit_t *oncirc, char **hostname_out,
int *made_connection_pending_out,
cached_resolve_t **resolve_out))
{
cached_resolve_t *resolve;
cached_resolve_t search;
pending_connection_t *pending_connection;
int is_reverse = 0;
tor_addr_t addr;
time_t now = time(NULL);
int r;
assert_connection_ok(TO_CONN(exitconn), 0);
tor_assert(!SOCKET_OK(exitconn->base_.s));
assert_cache_ok();
tor_assert(oncirc);
*made_connection_pending_out = 0;
/* first check if exitconn->base_.address is an IP. If so, we already
* know the answer. */
if (tor_addr_parse(&addr, exitconn->base_.address) >= 0) {
if (tor_addr_family(&addr) == AF_INET ||
tor_addr_family(&addr) == AF_INET6) {
tor_addr_copy(&exitconn->base_.addr, &addr);
exitconn->address_ttl = DEFAULT_DNS_TTL;
return 1;
} else {
/* XXXX unspec? Bogus? */
return -1;
}
}
/* If we're a non-exit, don't even do DNS lookups. */
if (router_my_exit_policy_is_reject_star())
return -1;
if (address_is_invalid_destination(exitconn->base_.address, 0)) {
tor_log(LOG_PROTOCOL_WARN, LD_EXIT,
"Rejecting invalid destination address %s",
escaped_safe_str(exitconn->base_.address));
return -1;
}
/* then take this opportunity to see if there are any expired
* resolves in the hash table. */
purge_expired_resolves(now);
/* lower-case exitconn->base_.address, so it's in canonical form */
tor_strlower(exitconn->base_.address);
/* Check whether this is a reverse lookup. If it's malformed, or it's a
* .in-addr.arpa address but this isn't a resolve request, kill the
* connection.
*/
if ((r = tor_addr_parse_PTR_name(&addr, exitconn->base_.address,
AF_UNSPEC, 0)) != 0) {
if (r == 1) {
is_reverse = 1;
if (tor_addr_is_internal(&addr, 0)) /* internal address? */
return -1;
}
if (!is_reverse || !is_resolve) {
if (!is_reverse)
log_info(LD_EXIT, "Bad .in-addr.arpa address \"%s\"; sending error.",
escaped_safe_str(exitconn->base_.address));
else if (!is_resolve)
log_info(LD_EXIT,
"Attempt to connect to a .in-addr.arpa address \"%s\"; "
"sending error.",
escaped_safe_str(exitconn->base_.address));
return -1;
}
//log_notice(LD_EXIT, "Looks like an address %s",
//exitconn->base_.address);
}
exitconn->is_reverse_dns_lookup = is_reverse;
/* now check the hash table to see if 'address' is already there. */
strlcpy(search.address, exitconn->base_.address, sizeof(search.address));
resolve = HT_FIND(cache_map, &cache_root, &search);
if (resolve && resolve->expire > now) { /* already there */
switch (resolve->state) {
case CACHE_STATE_PENDING:
/* add us to the pending list */
pending_connection = tor_malloc_zero(
sizeof(pending_connection_t));
pending_connection->conn = exitconn;
pending_connection->next = resolve->pending_connections;
resolve->pending_connections = pending_connection;
*made_connection_pending_out = 1;
log_debug(LD_EXIT,"Connection (fd "TOR_SOCKET_T_FORMAT") waiting "
"for pending DNS resolve of %s", exitconn->base_.s,
escaped_safe_str(exitconn->base_.address));
return 0;
case CACHE_STATE_CACHED:
log_debug(LD_EXIT,"Connection (fd "TOR_SOCKET_T_FORMAT") found "
"cached answer for %s",
exitconn->base_.s,
escaped_safe_str(resolve->address));
*resolve_out = resolve;
return set_exitconn_info_from_resolve(exitconn, resolve, hostname_out);
case CACHE_STATE_DONE:
log_err(LD_BUG, "Found a 'DONE' dns resolve still in the cache.");
tor_fragile_assert();
}
tor_assert(0);
}
tor_assert(!resolve);
/* not there, need to add it */
resolve = tor_malloc_zero(sizeof(cached_resolve_t));
resolve->magic = CACHED_RESOLVE_MAGIC;
resolve->state = CACHE_STATE_PENDING;
resolve->minheap_idx = -1;
strlcpy(resolve->address, exitconn->base_.address, sizeof(resolve->address));
/* add this connection to the pending list */
pending_connection = tor_malloc_zero(sizeof(pending_connection_t));
pending_connection->conn = exitconn;
resolve->pending_connections = pending_connection;
*made_connection_pending_out = 1;
/* Add this resolve to the cache and priority queue. */
HT_INSERT(cache_map, &cache_root, resolve);
set_expiry(resolve, now + RESOLVE_MAX_TIMEOUT);
log_debug(LD_EXIT,"Launching %s.",
escaped_safe_str(exitconn->base_.address));
assert_cache_ok();
return launch_resolve(resolve);
}
/** Given an exit connection <b>exitconn</b>, and a cached_resolve_t
* <b>resolve</b> whose DNS lookups have all either succeeded or failed,
* update the appropriate fields (address_ttl and addr) of <b>exitconn</b>.
*
* The logic can be complicated here, since we might have launched both
* an A lookup and an AAAA lookup, and since either of those might have
* succeeded or failed, and since we want to answer a RESOLVE cell with
* a full answer but answer a BEGIN cell with whatever answer the client
* would accept <i>and</i> we could still connect to.
*
* If this is a reverse lookup, set *<b>hostname_out</b> to a newly allocated
* copy of the name resulting hostname.
*
* Return -2 on a transient error, -1 on a permenent error, and 1 on
* a successful lookup.
*/
MOCK_IMPL(STATIC int,
set_exitconn_info_from_resolve,(edge_connection_t *exitconn,
const cached_resolve_t *resolve,
char **hostname_out))
{
int ipv4_ok, ipv6_ok, answer_with_ipv4, r;
uint32_t begincell_flags;
const int is_resolve = exitconn->base_.purpose == EXIT_PURPOSE_RESOLVE;
tor_assert(exitconn);
tor_assert(resolve);
if (exitconn->is_reverse_dns_lookup) {
exitconn->address_ttl = resolve->ttl_hostname;
if (resolve->res_status_hostname == RES_STATUS_DONE_OK) {
*hostname_out = tor_strdup(resolve->result_ptr.hostname);
return 1;
} else {
return -1;
}
}
/* If we're here then the connection wants one or either of ipv4, ipv6, and
* we can give it one or both. */
if (is_resolve) {
begincell_flags = BEGIN_FLAG_IPV6_OK;
} else {
begincell_flags = exitconn->begincell_flags;
}
ipv4_ok = (resolve->res_status_ipv4 == RES_STATUS_DONE_OK) &&
! (begincell_flags & BEGIN_FLAG_IPV4_NOT_OK);
ipv6_ok = (resolve->res_status_ipv6 == RES_STATUS_DONE_OK) &&
(begincell_flags & BEGIN_FLAG_IPV6_OK) &&
get_options()->IPv6Exit;
/* Now decide which one to actually give. */
if (ipv4_ok && ipv6_ok && is_resolve) {
answer_with_ipv4 = 1;
} else if (ipv4_ok && ipv6_ok) {
/* If we have both, see if our exit policy has an opinion. */
const uint16_t port = exitconn->base_.port;
int ipv4_allowed, ipv6_allowed;
tor_addr_t a4, a6;
tor_addr_from_ipv4h(&a4, resolve->result_ipv4.addr_ipv4);
tor_addr_from_in6(&a6, &resolve->result_ipv6.addr_ipv6);
ipv4_allowed = !router_compare_to_my_exit_policy(&a4, port);
ipv6_allowed = !router_compare_to_my_exit_policy(&a6, port);
if (ipv4_allowed && !ipv6_allowed) {
answer_with_ipv4 = 1;
} else if (ipv6_allowed && !ipv4_allowed) {
answer_with_ipv4 = 0;
} else {
/* Our exit policy would permit both. Answer with whichever the user
* prefers */
answer_with_ipv4 = !(begincell_flags &
BEGIN_FLAG_IPV6_PREFERRED);
}
} else {
/* Otherwise if one is okay, send it back. */
if (ipv4_ok) {
answer_with_ipv4 = 1;
} else if (ipv6_ok) {
answer_with_ipv4 = 0;
} else {
/* Neither one was okay. Choose based on user preference. */
answer_with_ipv4 = !(begincell_flags &
BEGIN_FLAG_IPV6_PREFERRED);
}
}
/* Finally, we write the answer back. */
r = 1;
if (answer_with_ipv4) {
if (resolve->res_status_ipv4 == RES_STATUS_DONE_OK) {
tor_addr_from_ipv4h(&exitconn->base_.addr,
resolve->result_ipv4.addr_ipv4);
} else {
r = evdns_err_is_transient(resolve->result_ipv4.err_ipv4) ? -2 : -1;
}
exitconn->address_ttl = resolve->ttl_ipv4;
} else {
if (resolve->res_status_ipv6 == RES_STATUS_DONE_OK) {
tor_addr_from_in6(&exitconn->base_.addr,
&resolve->result_ipv6.addr_ipv6);
} else {
r = evdns_err_is_transient(resolve->result_ipv6.err_ipv6) ? -2 : -1;
}
exitconn->address_ttl = resolve->ttl_ipv6;
}
return r;
}
/** Log an error and abort if conn is waiting for a DNS resolve.
*/
void
assert_connection_edge_not_dns_pending(edge_connection_t *conn)
{
pending_connection_t *pend;
cached_resolve_t search;
#if 1
cached_resolve_t *resolve;
strlcpy(search.address, conn->base_.address, sizeof(search.address));
resolve = HT_FIND(cache_map, &cache_root, &search);
if (!resolve)
return;
for (pend = resolve->pending_connections; pend; pend = pend->next) {
tor_assert(pend->conn != conn);
}
#else /* !(1) */
cached_resolve_t **resolve;
HT_FOREACH(resolve, cache_map, &cache_root) {
for (pend = (*resolve)->pending_connections; pend; pend = pend->next) {
tor_assert(pend->conn != conn);
}
}
#endif /* 1 */
}
/** Log an error and abort if any connection waiting for a DNS resolve is
* corrupted. */
void
assert_all_pending_dns_resolves_ok(void)
{
pending_connection_t *pend;
cached_resolve_t **resolve;
HT_FOREACH(resolve, cache_map, &cache_root) {
for (pend = (*resolve)->pending_connections;
pend;
pend = pend->next) {
assert_connection_ok(TO_CONN(pend->conn), 0);
tor_assert(!SOCKET_OK(pend->conn->base_.s));
tor_assert(!connection_in_array(TO_CONN(pend->conn)));
}
}
}
/** Remove <b>conn</b> from the list of connections waiting for conn-\>address.
*/
void
connection_dns_remove(edge_connection_t *conn)
{
pending_connection_t *pend, *victim;
cached_resolve_t search;
cached_resolve_t *resolve;
tor_assert(conn->base_.type == CONN_TYPE_EXIT);
tor_assert(conn->base_.state == EXIT_CONN_STATE_RESOLVING);
strlcpy(search.address, conn->base_.address, sizeof(search.address));
resolve = HT_FIND(cache_map, &cache_root, &search);
if (!resolve) {
log_notice(LD_BUG, "Address %s is not pending. Dropping.",
escaped_safe_str(conn->base_.address));
return;
}
tor_assert(resolve->pending_connections);
assert_connection_ok(TO_CONN(conn),0);
pend = resolve->pending_connections;
if (pend->conn == conn) {
resolve->pending_connections = pend->next;
tor_free(pend);
log_debug(LD_EXIT, "First connection (fd "TOR_SOCKET_T_FORMAT") no "
"longer waiting for resolve of %s",
conn->base_.s,
escaped_safe_str(conn->base_.address));
return;
} else {
for ( ; pend->next; pend = pend->next) {
if (pend->next->conn == conn) {
victim = pend->next;
pend->next = victim->next;
tor_free(victim);
log_debug(LD_EXIT,
"Connection (fd "TOR_SOCKET_T_FORMAT") no longer waiting "
"for resolve of %s",
conn->base_.s, escaped_safe_str(conn->base_.address));
return; /* more are pending */
}
}
log_warn(LD_BUG, "Connection (fd "TOR_SOCKET_T_FORMAT") was not waiting "
"for a resolve of %s, but we tried to remove it.",
conn->base_.s, escaped_safe_str(conn->base_.address));
}
}
/** Mark all connections waiting for <b>address</b> for close. Then cancel
* the resolve for <b>address</b> itself, and remove any cached results for
* <b>address</b> from the cache.
*/
MOCK_IMPL(void,
dns_cancel_pending_resolve,(const char *address))
{
pending_connection_t *pend;
cached_resolve_t search;
cached_resolve_t *resolve, *tmp;
edge_connection_t *pendconn;
circuit_t *circ;
strlcpy(search.address, address, sizeof(search.address));
resolve = HT_FIND(cache_map, &cache_root, &search);
if (!resolve)
return;
if (resolve->state != CACHE_STATE_PENDING) {
/* We can get into this state if we never actually created the pending
* resolve, due to finding an earlier cached error or something. Just
* ignore it. */
if (resolve->pending_connections) {
log_warn(LD_BUG,
"Address %s is not pending but has pending connections!",
escaped_safe_str(address));
tor_fragile_assert();
}
return;
}
if (!resolve->pending_connections) {
log_warn(LD_BUG,
"Address %s is pending but has no pending connections!",
escaped_safe_str(address));
tor_fragile_assert();
return;
}
tor_assert(resolve->pending_connections);
/* mark all pending connections to fail */
log_debug(LD_EXIT,
"Failing all connections waiting on DNS resolve of %s",
escaped_safe_str(address));
while (resolve->pending_connections) {
pend = resolve->pending_connections;
pend->conn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
pendconn = pend->conn;
assert_connection_ok(TO_CONN(pendconn), 0);
tor_assert(!SOCKET_OK(pendconn->base_.s));
if (!pendconn->base_.marked_for_close) {
connection_edge_end(pendconn, END_STREAM_REASON_RESOLVEFAILED);
}
circ = circuit_get_by_edge_conn(pendconn);
if (circ)
circuit_detach_stream(circ, pendconn);
if (!pendconn->base_.marked_for_close)
connection_free_(TO_CONN(pendconn));
resolve->pending_connections = pend->next;
tor_free(pend);
}
tmp = HT_REMOVE(cache_map, &cache_root, resolve);
if (tmp != resolve) {
log_err(LD_BUG, "The cancelled resolve we purged didn't match any in"
" the cache. Tried to purge %s (%p); instead got %s (%p).",
resolve->address, (void*)resolve,
tmp ? tmp->address : "NULL", (void*)tmp);
}
tor_assert(tmp == resolve);
resolve->state = CACHE_STATE_DONE;
}
/** Return true iff <b>address</b> is one of the addresses we use to verify
* that well-known sites aren't being hijacked by our DNS servers. */
static inline int
is_test_address(const char *address)
{
const or_options_t *options = get_options();
return options->ServerDNSTestAddresses &&
smartlist_contains_string_case(options->ServerDNSTestAddresses, address);
}
/** Called on the OR side when the eventdns library tells us the outcome of a
* single DNS resolve: remember the answer, and tell all pending connections
* about the result of the lookup if the lookup is now done. (<b>address</b>
* is a NUL-terminated string containing the address to look up;
* <b>query_type</b> is one of DNS_{IPv4_A,IPv6_AAAA,PTR}; <b>dns_answer</b>
* is DNS_OK or one of DNS_ERR_*, <b>addr</b> is an IPv4 or IPv6 address if we
* got one; <b>hostname</b> is a hostname fora PTR request if we got one, and
* <b>ttl</b> is the time-to-live of this answer, in seconds.)
*/
static void
dns_found_answer(const char *address, uint8_t query_type,
int dns_answer,
const tor_addr_t *addr,
const char *hostname, uint32_t ttl)
{
cached_resolve_t search;
cached_resolve_t *resolve;
assert_cache_ok();
strlcpy(search.address, address, sizeof(search.address));
resolve = HT_FIND(cache_map, &cache_root, &search);
if (!resolve) {
int is_test_addr = is_test_address(address);
if (!is_test_addr)
log_info(LD_EXIT,"Resolved unasked address %s; ignoring.",
escaped_safe_str(address));
return;
}
assert_resolve_ok(resolve);
if (resolve->state != CACHE_STATE_PENDING) {
/* XXXX Maybe update addr? or check addr for consistency? Or let
* VALID replace FAILED? */
int is_test_addr = is_test_address(address);
if (!is_test_addr)
log_notice(LD_EXIT,
"Resolved %s which was already resolved; ignoring",
escaped_safe_str(address));
tor_assert(resolve->pending_connections == NULL);
return;
}
cached_resolve_add_answer(resolve, query_type, dns_answer,
addr, hostname, ttl);
if (cached_resolve_have_all_answers(resolve)) {
inform_pending_connections(resolve);
make_pending_resolve_cached(resolve);
}
}
/** Given a pending cached_resolve_t that we just finished resolving,
* inform every connection that was waiting for the outcome of that
* resolution.
*
* Do this by sending a RELAY_RESOLVED cell (if the pending stream had sent us
* RELAY_RESOLVE cell), or by launching an exit connection (if the pending
* stream had send us a RELAY_BEGIN cell).
*/
static void
inform_pending_connections(cached_resolve_t *resolve)
{
pending_connection_t *pend;
edge_connection_t *pendconn;
int r;
while (resolve->pending_connections) {
char *hostname = NULL;
pend = resolve->pending_connections;
pendconn = pend->conn; /* don't pass complex things to the
connection_mark_for_close macro */
assert_connection_ok(TO_CONN(pendconn),time(NULL));
if (pendconn->base_.marked_for_close) {
/* prevent double-remove. */
pendconn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
resolve->pending_connections = pend->next;
tor_free(pend);
continue;
}
r = set_exitconn_info_from_resolve(pendconn,
resolve,
&hostname);
if (r < 0) {
/* prevent double-remove. */
pendconn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
if (pendconn->base_.purpose == EXIT_PURPOSE_CONNECT) {
connection_edge_end(pendconn, END_STREAM_REASON_RESOLVEFAILED);
/* This detach must happen after we send the end cell. */
circuit_detach_stream(circuit_get_by_edge_conn(pendconn), pendconn);
} else {
send_resolved_cell(pendconn, r == -1 ?
RESOLVED_TYPE_ERROR : RESOLVED_TYPE_ERROR_TRANSIENT,
NULL);
/* This detach must happen after we send the resolved cell. */
circuit_detach_stream(circuit_get_by_edge_conn(pendconn), pendconn);
}
connection_free_(TO_CONN(pendconn));
} else {
circuit_t *circ;
if (pendconn->base_.purpose == EXIT_PURPOSE_CONNECT) {
/* prevent double-remove. */
pend->conn->base_.state = EXIT_CONN_STATE_CONNECTING;
circ = circuit_get_by_edge_conn(pend->conn);
tor_assert(circ);
tor_assert(!CIRCUIT_IS_ORIGIN(circ));
/* unlink pend->conn from resolving_streams, */
circuit_detach_stream(circ, pend->conn);
/* and link it to n_streams */
pend->conn->next_stream = TO_OR_CIRCUIT(circ)->n_streams;
pend->conn->on_circuit = circ;
TO_OR_CIRCUIT(circ)->n_streams = pend->conn;
connection_exit_connect(pend->conn);
} else {
/* prevent double-remove. This isn't really an accurate state,
* but it does the right thing. */
pendconn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
if (pendconn->is_reverse_dns_lookup)
send_resolved_hostname_cell(pendconn, hostname);
else
send_resolved_cell(pendconn, RESOLVED_TYPE_AUTO, resolve);
circ = circuit_get_by_edge_conn(pendconn);
tor_assert(circ);
circuit_detach_stream(circ, pendconn);
connection_free_(TO_CONN(pendconn));
}
}
resolve->pending_connections = pend->next;
tor_free(pend);
tor_free(hostname);
}
}
/** Remove a pending cached_resolve_t from the hashtable, and add a
* corresponding cached cached_resolve_t.
*
* This function is only necessary because of the perversity of our
* cache timeout code; see inline comment for ideas on eliminating it.
**/
static void
make_pending_resolve_cached(cached_resolve_t *resolve)
{
cached_resolve_t *removed;
resolve->state = CACHE_STATE_DONE;
removed = HT_REMOVE(cache_map, &cache_root, resolve);
if (removed != resolve) {
log_err(LD_BUG, "The pending resolve we found wasn't removable from"
" the cache. Tried to purge %s (%p); instead got %s (%p).",
resolve->address, (void*)resolve,
removed ? removed->address : "NULL", (void*)removed);
}
assert_resolve_ok(resolve);
assert_cache_ok();
/* The resolve will eventually just hit the time-out in the expiry queue and
* expire. See fd0bafb0dedc7e2 for a brief explanation of how this got that
* way. XXXXX we could do better!*/
{
cached_resolve_t *new_resolve = tor_memdup(resolve,
sizeof(cached_resolve_t));
uint32_t ttl = UINT32_MAX;
new_resolve->expire = 0; /* So that set_expiry won't croak. */
if (resolve->res_status_hostname == RES_STATUS_DONE_OK)
new_resolve->result_ptr.hostname =
tor_strdup(resolve->result_ptr.hostname);
new_resolve->state = CACHE_STATE_CACHED;
assert_resolve_ok(new_resolve);
HT_INSERT(cache_map, &cache_root, new_resolve);
if ((resolve->res_status_ipv4 == RES_STATUS_DONE_OK ||
resolve->res_status_ipv4 == RES_STATUS_DONE_ERR) &&
resolve->ttl_ipv4 < ttl)
ttl = resolve->ttl_ipv4;
if ((resolve->res_status_ipv6 == RES_STATUS_DONE_OK ||
resolve->res_status_ipv6 == RES_STATUS_DONE_ERR) &&
resolve->ttl_ipv6 < ttl)
ttl = resolve->ttl_ipv6;
if ((resolve->res_status_hostname == RES_STATUS_DONE_OK ||
resolve->res_status_hostname == RES_STATUS_DONE_ERR) &&
resolve->ttl_hostname < ttl)
ttl = resolve->ttl_hostname;
set_expiry(new_resolve, time(NULL) + dns_clip_ttl(ttl));
}
assert_cache_ok();
}
/** Eventdns helper: return true iff the eventdns result <b>err</b> is
* a transient failure. */
static int
evdns_err_is_transient(int err)
{
switch (err)
{
case DNS_ERR_SERVERFAILED:
case DNS_ERR_TRUNCATED:
case DNS_ERR_TIMEOUT:
return 1;
default:
return 0;
}
}
/** Configure eventdns nameservers if force is true, or if the configuration
* has changed since the last time we called this function, or if we failed on
* our last attempt. On Unix, this reads from /etc/resolv.conf or
* options->ServerDNSResolvConfFile; on Windows, this reads from
* options->ServerDNSResolvConfFile or the registry. Return 0 on success or
* -1 on failure. */
static int
configure_nameservers(int force)
{
const or_options_t *options;
const char *conf_fname;
struct stat st;
int r, flags;
options = get_options();
conf_fname = options->ServerDNSResolvConfFile;
#ifndef _WIN32
if (!conf_fname)
conf_fname = "/etc/resolv.conf";
#endif
flags = DNS_OPTIONS_ALL;
if (!the_evdns_base) {
if (!(the_evdns_base = evdns_base_new(tor_libevent_get_base(), 0))) {
log_err(LD_BUG, "Couldn't create an evdns_base");
return -1;
}
}
evdns_set_log_fn(evdns_log_cb);
if (conf_fname) {
log_debug(LD_FS, "stat()ing %s", conf_fname);
if (stat(sandbox_intern_string(conf_fname), &st)) {
log_warn(LD_EXIT, "Unable to stat resolver configuration in '%s': %s",
conf_fname, strerror(errno));
goto err;
}
if (!force && resolv_conf_fname && !strcmp(conf_fname,resolv_conf_fname)
&& st.st_mtime == resolv_conf_mtime) {
log_info(LD_EXIT, "No change to '%s'", conf_fname);
return 0;
}
if (nameservers_configured) {
evdns_base_search_clear(the_evdns_base);
evdns_base_clear_nameservers_and_suspend(the_evdns_base);
}
#if defined(DNS_OPTION_HOSTSFILE) && defined(USE_LIBSECCOMP)
if (flags & DNS_OPTION_HOSTSFILE) {
flags ^= DNS_OPTION_HOSTSFILE;
log_debug(LD_FS, "Loading /etc/hosts");
evdns_base_load_hosts(the_evdns_base,
sandbox_intern_string("/etc/hosts"));
}
#endif /* defined(DNS_OPTION_HOSTSFILE) && defined(USE_LIBSECCOMP) */
log_info(LD_EXIT, "Parsing resolver configuration in '%s'", conf_fname);
if ((r = evdns_base_resolv_conf_parse(the_evdns_base, flags,
sandbox_intern_string(conf_fname)))) {
log_warn(LD_EXIT, "Unable to parse '%s', or no nameservers in '%s' (%d)",
conf_fname, conf_fname, r);
goto err;
}
if (evdns_base_count_nameservers(the_evdns_base) == 0) {
log_warn(LD_EXIT, "Unable to find any nameservers in '%s'.", conf_fname);
goto err;
}
tor_free(resolv_conf_fname);
resolv_conf_fname = tor_strdup(conf_fname);
resolv_conf_mtime = st.st_mtime;
if (nameservers_configured)
evdns_base_resume(the_evdns_base);
}
#ifdef _WIN32
else {
if (nameservers_configured) {
evdns_base_search_clear(the_evdns_base);
evdns_base_clear_nameservers_and_suspend(the_evdns_base);
}
if (evdns_base_config_windows_nameservers(the_evdns_base)) {
log_warn(LD_EXIT,"Could not config nameservers.");
goto err;
}
if (evdns_base_count_nameservers(the_evdns_base) == 0) {
log_warn(LD_EXIT, "Unable to find any platform nameservers in "
"your Windows configuration.");
goto err;
}
if (nameservers_configured)
evdns_base_resume(the_evdns_base);
tor_free(resolv_conf_fname);
resolv_conf_mtime = 0;
}
#endif /* defined(_WIN32) */
#define SET(k,v) evdns_base_set_option(the_evdns_base, (k), (v))
// If we only have one nameserver, it does not make sense to back off
// from it for a timeout. Unfortunately, the value for max-timeouts is
// currently clamped by libevent to 255, but it does not hurt to set
// it higher in case libevent gets a patch for this. Higher-than-
// default maximum of 3 with multiple nameservers to avoid spuriously
// marking one down on bursts of timeouts resulting from scans/attacks
// against non-responding authoritative DNS servers.
if (evdns_base_count_nameservers(the_evdns_base) == 1) {
SET("max-timeouts:", "1000000");
} else {
SET("max-timeouts:", "10");
}
// Elongate the queue of maximum inflight dns requests, so if a bunch
// remain pending at the resolver (happens commonly with Unbound) we won't
// stall every other DNS request. This potentially means some wasted
// CPU as there's a walk over a linear queue involved, but this is a
// much better tradeoff compared to just failing DNS requests because
// of a full queue.
SET("max-inflight:", "8192");
// Two retries at 5 and 10 seconds for bind9/named which relies on
// clients to handle retries. Second retry for retried circuits with
// extended 15 second timeout. Superfluous with local-system Unbound
// instance--has its own elaborate retry scheme.
SET("timeout:", "5");
SET("attempts:","3");
if (options->ServerDNSRandomizeCase)
SET("randomize-case:", "1");
else
SET("randomize-case:", "0");
#undef SET
dns_servers_relaunch_checks();
nameservers_configured = 1;
if (nameserver_config_failed) {
nameserver_config_failed = 0;
/* XXX the three calls to republish the descriptor might be producing
* descriptors that are only cosmetically different, especially on
* non-exit relays! -RD */
mark_my_descriptor_dirty("dns resolvers back");
}
return 0;
err:
nameservers_configured = 0;
if (! nameserver_config_failed) {
nameserver_config_failed = 1;
mark_my_descriptor_dirty("dns resolvers failed");
}
return -1;
}
/** For eventdns: Called when we get an answer for a request we launched.
* See eventdns.h for arguments; 'arg' holds the address we tried to resolve.
*/
static void
evdns_callback(int result, char type, int count, int ttl, void *addresses,
void *arg)
{
char *arg_ = arg;
uint8_t orig_query_type = arg_[0];
char *string_address = arg_ + 1;
tor_addr_t addr;
const char *hostname = NULL;
int was_wildcarded = 0;
tor_addr_make_unspec(&addr);
/* Keep track of whether IPv6 is working */
if (type == DNS_IPv6_AAAA) {
if (result == DNS_ERR_TIMEOUT) {
++n_ipv6_timeouts;
}
if (n_ipv6_timeouts > 10 &&
n_ipv6_timeouts > n_ipv6_requests_made / 2) {
if (! dns_is_broken_for_ipv6) {
log_notice(LD_EXIT, "More than half of our IPv6 requests seem to "
"have timed out. I'm going to assume I can't get AAAA "
"responses.");
dns_is_broken_for_ipv6 = 1;
}
}
}
if (result == DNS_ERR_NONE) {
if (type == DNS_IPv4_A && count) {
char answer_buf[INET_NTOA_BUF_LEN+1];
char *escaped_address;
uint32_t *addrs = addresses;
tor_addr_from_ipv4n(&addr, addrs[0]);
tor_addr_to_str(answer_buf, &addr, sizeof(answer_buf), 0);
escaped_address = esc_for_log(string_address);
if (answer_is_wildcarded(answer_buf)) {
log_debug(LD_EXIT, "eventdns said that %s resolves to ISP-hijacked "
"address %s; treating as a failure.",
safe_str(escaped_address),
escaped_safe_str(answer_buf));
was_wildcarded = 1;
tor_addr_make_unspec(&addr);
result = DNS_ERR_NOTEXIST;
} else {
log_debug(LD_EXIT, "eventdns said that %s resolves to %s",
safe_str(escaped_address),
escaped_safe_str(answer_buf));
}
tor_free(escaped_address);
} else if (type == DNS_IPv6_AAAA && count) {
char answer_buf[TOR_ADDR_BUF_LEN];
char *escaped_address;
struct in6_addr *addrs = addresses;
tor_addr_from_in6(&addr, &addrs[0]);
tor_inet_ntop(AF_INET6, &addrs[0], answer_buf, sizeof(answer_buf));
escaped_address = esc_for_log(string_address);
if (answer_is_wildcarded(answer_buf)) {
log_debug(LD_EXIT, "eventdns said that %s resolves to ISP-hijacked "
"address %s; treating as a failure.",
safe_str(escaped_address),
escaped_safe_str(answer_buf));
was_wildcarded = 1;
tor_addr_make_unspec(&addr);
result = DNS_ERR_NOTEXIST;
} else {
log_debug(LD_EXIT, "eventdns said that %s resolves to %s",
safe_str(escaped_address),
escaped_safe_str(answer_buf));
}
tor_free(escaped_address);
} else if (type == DNS_PTR && count) {
char *escaped_address;
hostname = ((char**)addresses)[0];
escaped_address = esc_for_log(string_address);
log_debug(LD_EXIT, "eventdns said that %s resolves to %s",
safe_str(escaped_address),
escaped_safe_str(hostname));
tor_free(escaped_address);
} else if (count) {
log_info(LD_EXIT, "eventdns returned only unrecognized answer types "
" for %s.",
escaped_safe_str(string_address));
} else {
log_info(LD_EXIT, "eventdns returned no addresses or error for %s.",
escaped_safe_str(string_address));
}
}
if (was_wildcarded) {
if (is_test_address(string_address)) {
/* Ick. We're getting redirected on known-good addresses. Our DNS
* server must really hate us. */
add_wildcarded_test_address(string_address);
}
}
if (orig_query_type && type && orig_query_type != type) {
log_warn(LD_BUG, "Weird; orig_query_type == %d but type == %d",
(int)orig_query_type, (int)type);
}
if (result != DNS_ERR_SHUTDOWN)
dns_found_answer(string_address, orig_query_type,
result, &addr, hostname, ttl);
tor_free(arg_);
}
/** Start a single DNS resolve for <b>address</b> (if <b>query_type</b> is
* DNS_IPv4_A or DNS_IPv6_AAAA) <b>ptr_address</b> (if <b>query_type</b> is
* DNS_PTR). Return 0 if we launched the request, -1 otherwise. */
static int
launch_one_resolve(const char *address, uint8_t query_type,
const tor_addr_t *ptr_address)
{
const int options = get_options()->ServerDNSSearchDomains ? 0
: DNS_QUERY_NO_SEARCH;
const size_t addr_len = strlen(address);
struct evdns_request *req = 0;
char *addr = tor_malloc(addr_len + 2);
addr[0] = (char) query_type;
memcpy(addr+1, address, addr_len + 1);
switch (query_type) {
case DNS_IPv4_A:
req = evdns_base_resolve_ipv4(the_evdns_base,
address, options, evdns_callback, addr);
break;
case DNS_IPv6_AAAA:
req = evdns_base_resolve_ipv6(the_evdns_base,
address, options, evdns_callback, addr);
++n_ipv6_requests_made;
break;
case DNS_PTR:
if (tor_addr_family(ptr_address) == AF_INET)
req = evdns_base_resolve_reverse(the_evdns_base,
tor_addr_to_in(ptr_address),
DNS_QUERY_NO_SEARCH,
evdns_callback, addr);
else if (tor_addr_family(ptr_address) == AF_INET6)
req = evdns_base_resolve_reverse_ipv6(the_evdns_base,
tor_addr_to_in6(ptr_address),
DNS_QUERY_NO_SEARCH,
evdns_callback, addr);
else
log_warn(LD_BUG, "Called with PTR query and unexpected address family");
break;
default:
log_warn(LD_BUG, "Called with unexpectd query type %d", (int)query_type);
break;
}
if (req) {
return 0;
} else {
tor_free(addr);
return -1;
}
}
/** For eventdns: start resolving as necessary to find the target for
* <b>exitconn</b>. Returns -1 on error, -2 on transient error,
* 0 on "resolve launched." */
MOCK_IMPL(STATIC int,
launch_resolve,(cached_resolve_t *resolve))
{
tor_addr_t a;
int r;
if (net_is_disabled())
return -1;
/* What? Nameservers not configured? Sounds like a bug. */
if (!nameservers_configured) {
log_warn(LD_EXIT, "(Harmless.) Nameservers not configured, but resolve "
"launched. Configuring.");
if (configure_nameservers(1) < 0) {
return -1;
}
}
r = tor_addr_parse_PTR_name(
&a, resolve->address, AF_UNSPEC, 0);
tor_assert(the_evdns_base);
if (r == 0) {
log_info(LD_EXIT, "Launching eventdns request for %s",
escaped_safe_str(resolve->address));
resolve->res_status_ipv4 = RES_STATUS_INFLIGHT;
if (get_options()->IPv6Exit)
resolve->res_status_ipv6 = RES_STATUS_INFLIGHT;
if (launch_one_resolve(resolve->address, DNS_IPv4_A, NULL) < 0) {
resolve->res_status_ipv4 = 0;
r = -1;
}
if (r==0 && get_options()->IPv6Exit) {
/* We ask for an IPv6 address for *everything*. */
if (launch_one_resolve(resolve->address, DNS_IPv6_AAAA, NULL) < 0) {
resolve->res_status_ipv6 = 0;
r = -1;
}
}
} else if (r == 1) {
r = 0;
log_info(LD_EXIT, "Launching eventdns reverse request for %s",
escaped_safe_str(resolve->address));
resolve->res_status_hostname = RES_STATUS_INFLIGHT;
if (launch_one_resolve(resolve->address, DNS_PTR, &a) < 0) {
resolve->res_status_hostname = 0;
r = -1;
}
} else if (r == -1) {
log_warn(LD_BUG, "Somehow a malformed in-addr.arpa address reached here.");
}
if (r < 0) {
log_fn(LOG_PROTOCOL_WARN, LD_EXIT, "eventdns rejected address %s.",
escaped_safe_str(resolve->address));
}
return r;
}
/** How many requests for bogus addresses have we launched so far? */
static int n_wildcard_requests = 0;
/** Map from dotted-quad IP address in response to an int holding how many
* times we've seen it for a randomly generated (hopefully bogus) address. It
* would be easier to use definitely-invalid addresses (as specified by
* RFC2606), but see comment in dns_launch_wildcard_checks(). */
static strmap_t *dns_wildcard_response_count = NULL;
/** If present, a list of dotted-quad IP addresses that we are pretty sure our
* nameserver wants to return in response to requests for nonexistent domains.
*/
static smartlist_t *dns_wildcard_list = NULL;
/** True iff we've logged about a single address getting wildcarded.
* Subsequent warnings will be less severe. */
static int dns_wildcard_one_notice_given = 0;
/** True iff we've warned that our DNS server is wildcarding too many failures.
*/
static int dns_wildcard_notice_given = 0;
/** List of supposedly good addresses that are getting wildcarded to the
* same addresses as nonexistent addresses. */
static smartlist_t *dns_wildcarded_test_address_list = NULL;
/** True iff we've warned about a test address getting wildcarded */
static int dns_wildcarded_test_address_notice_given = 0;
/** True iff all addresses seem to be getting wildcarded. */
static int dns_is_completely_invalid = 0;
/** Called when we see <b>id</b> (a dotted quad or IPv6 address) in response
* to a request for a hopefully bogus address. */
static void
wildcard_increment_answer(const char *id)
{
int *ip;
if (!dns_wildcard_response_count)
dns_wildcard_response_count = strmap_new();
ip = strmap_get(dns_wildcard_response_count, id); // may be null (0)
if (!ip) {
ip = tor_malloc_zero(sizeof(int));
strmap_set(dns_wildcard_response_count, id, ip);
}
++*ip;
if (*ip > 5 && n_wildcard_requests > 10) {
if (!dns_wildcard_list) dns_wildcard_list = smartlist_new();
if (!smartlist_contains_string(dns_wildcard_list, id)) {
tor_log(dns_wildcard_notice_given ? LOG_INFO : LOG_NOTICE, LD_EXIT,
"Your DNS provider has given \"%s\" as an answer for %d different "
"invalid addresses. Apparently they are hijacking DNS failures. "
"I'll try to correct for this by treating future occurrences of "
"\"%s\" as 'not found'.", id, *ip, id);
smartlist_add_strdup(dns_wildcard_list, id);
}
if (!dns_wildcard_notice_given)
control_event_server_status(LOG_NOTICE, "DNS_HIJACKED");
dns_wildcard_notice_given = 1;
}
}
/** Note that a single test address (one believed to be good) seems to be
* getting redirected to the same IP as failures are. */
static void
add_wildcarded_test_address(const char *address)
{
int n, n_test_addrs;
if (!dns_wildcarded_test_address_list)
dns_wildcarded_test_address_list = smartlist_new();
if (smartlist_contains_string_case(dns_wildcarded_test_address_list,
address))
return;
n_test_addrs = get_options()->ServerDNSTestAddresses ?
smartlist_len(get_options()->ServerDNSTestAddresses) : 0;
smartlist_add_strdup(dns_wildcarded_test_address_list, address);
n = smartlist_len(dns_wildcarded_test_address_list);
if (n > n_test_addrs/2) {
tor_log(dns_wildcarded_test_address_notice_given ? LOG_INFO : LOG_NOTICE,
LD_EXIT, "Your DNS provider tried to redirect \"%s\" to a junk "
"address. It has done this with %d test addresses so far. I'm "
"going to stop being an exit node for now, since our DNS seems so "
"broken.", address, n);
if (!dns_is_completely_invalid) {
dns_is_completely_invalid = 1;
mark_my_descriptor_dirty("dns hijacking confirmed");
}
if (!dns_wildcarded_test_address_notice_given)
control_event_server_status(LOG_WARN, "DNS_USELESS");
dns_wildcarded_test_address_notice_given = 1;
}
}
/** Callback function when we get an answer (possibly failing) for a request
* for a (hopefully) nonexistent domain. */
static void
evdns_wildcard_check_callback(int result, char type, int count, int ttl,
void *addresses, void *arg)
{
(void)ttl;
++n_wildcard_requests;
if (result == DNS_ERR_NONE && count) {
char *string_address = arg;
int i;
if (type == DNS_IPv4_A) {
const uint32_t *addrs = addresses;
for (i = 0; i < count; ++i) {
char answer_buf[INET_NTOA_BUF_LEN+1];
struct in_addr in;
in.s_addr = addrs[i];
tor_inet_ntoa(&in, answer_buf, sizeof(answer_buf));
wildcard_increment_answer(answer_buf);
}
} else if (type == DNS_IPv6_AAAA) {
const struct in6_addr *addrs = addresses;
for (i = 0; i < count; ++i) {
char answer_buf[TOR_ADDR_BUF_LEN+1];
tor_inet_ntop(AF_INET6, &addrs[i], answer_buf, sizeof(answer_buf));
wildcard_increment_answer(answer_buf);
}
}
tor_log(dns_wildcard_one_notice_given ? LOG_INFO : LOG_NOTICE, LD_EXIT,
"Your DNS provider gave an answer for \"%s\", which "
"is not supposed to exist. Apparently they are hijacking "
"DNS failures. Trying to correct for this. We've noticed %d "
"possibly bad address%s so far.",
string_address, strmap_size(dns_wildcard_response_count),
(strmap_size(dns_wildcard_response_count) == 1) ? "" : "es");
dns_wildcard_one_notice_given = 1;
}
tor_free(arg);
}
/** Launch a single request for a nonexistent hostname consisting of between
* <b>min_len</b> and <b>max_len</b> random (plausible) characters followed by
* <b>suffix</b> */
static void
launch_wildcard_check(int min_len, int max_len, int is_ipv6,
const char *suffix)
{
char *addr;
struct evdns_request *req;
addr = crypto_random_hostname(min_len, max_len, "", suffix);
log_info(LD_EXIT, "Testing whether our DNS server is hijacking nonexistent "
"domains with request for bogus hostname \"%s\"", addr);
tor_assert(the_evdns_base);
if (is_ipv6)
req = evdns_base_resolve_ipv6(
the_evdns_base,
/* This "addr" tells us which address to resolve */
addr,
DNS_QUERY_NO_SEARCH, evdns_wildcard_check_callback,
/* This "addr" is an argument to the callback*/ addr);
else
req = evdns_base_resolve_ipv4(
the_evdns_base,
/* This "addr" tells us which address to resolve */
addr,
DNS_QUERY_NO_SEARCH, evdns_wildcard_check_callback,
/* This "addr" is an argument to the callback*/ addr);
if (!req) {
/* There is no evdns request in progress; stop addr from getting leaked */
tor_free(addr);
}
}
/** Launch attempts to resolve a bunch of known-good addresses (configured in
* ServerDNSTestAddresses). [Callback for a libevent timer] */
static void
launch_test_addresses(evutil_socket_t fd, short event, void *args)
{
const or_options_t *options = get_options();
(void)fd;
(void)event;
(void)args;
if (net_is_disabled())
return;
log_info(LD_EXIT, "Launching checks to see whether our nameservers like to "
"hijack *everything*.");
/* This situation is worse than the failure-hijacking situation. When this
* happens, we're no good for DNS requests at all, and we shouldn't really
* be an exit server.*/
if (options->ServerDNSTestAddresses) {
tor_assert(the_evdns_base);
SMARTLIST_FOREACH_BEGIN(options->ServerDNSTestAddresses,
const char *, address) {
if (launch_one_resolve(address, DNS_IPv4_A, NULL) < 0) {
log_info(LD_EXIT, "eventdns rejected test address %s",
escaped_safe_str(address));
}
if (launch_one_resolve(address, DNS_IPv6_AAAA, NULL) < 0) {
log_info(LD_EXIT, "eventdns rejected test address %s",
escaped_safe_str(address));
}
} SMARTLIST_FOREACH_END(address);
}
}
#define N_WILDCARD_CHECKS 2
/** Launch DNS requests for a few nonexistent hostnames and a few well-known
* hostnames, and see if we can catch our nameserver trying to hijack them and
* map them to a stupid "I couldn't find ggoogle.com but maybe you'd like to
* buy these lovely encyclopedias" page. */
static void
dns_launch_wildcard_checks(void)
{
int i, ipv6;
log_info(LD_EXIT, "Launching checks to see whether our nameservers like "
"to hijack DNS failures.");
for (ipv6 = 0; ipv6 <= 1; ++ipv6) {
for (i = 0; i < N_WILDCARD_CHECKS; ++i) {
/* RFC2606 reserves these. Sadly, some DNS hijackers, in a silly
* attempt to 'comply' with rfc2606, refrain from giving A records for
* these. This is the standards-compliance equivalent of making sure
* that your crackhouse's elevator inspection certificate is up to date.
*/
launch_wildcard_check(2, 16, ipv6, ".invalid");
launch_wildcard_check(2, 16, ipv6, ".test");
/* These will break specs if there are ever any number of
* 8+-character top-level domains. */
launch_wildcard_check(8, 16, ipv6, "");
/* Try some random .com/org/net domains. This will work fine so long as
* not too many resolve to the same place. */
launch_wildcard_check(8, 16, ipv6, ".com");
launch_wildcard_check(8, 16, ipv6, ".org");
launch_wildcard_check(8, 16, ipv6, ".net");
}
}
}
/** If appropriate, start testing whether our DNS servers tend to lie to
* us. */
void
dns_launch_correctness_checks(void)
{
static struct event *launch_event = NULL;
struct timeval timeout;
if (!get_options()->ServerDNSDetectHijacking)
return;
dns_launch_wildcard_checks();
/* Wait a while before launching requests for test addresses, so we can
* get the results from checking for wildcarding. */
if (! launch_event)
launch_event = tor_evtimer_new(tor_libevent_get_base(),
launch_test_addresses, NULL);
timeout.tv_sec = 30;
timeout.tv_usec = 0;
if (evtimer_add(launch_event, &timeout)<0) {
log_warn(LD_BUG, "Couldn't add timer for checking for dns hijacking");
}
}
/** Return true iff our DNS servers lie to us too much to be trusted. */
int
dns_seems_to_be_broken(void)
{
return dns_is_completely_invalid;
}
/** Return true iff we think that IPv6 hostname lookup is broken */
int
dns_seems_to_be_broken_for_ipv6(void)
{
return dns_is_broken_for_ipv6;
}
/** Forget what we've previously learned about our DNS servers' correctness. */
void
dns_reset_correctness_checks(void)
{
strmap_free(dns_wildcard_response_count, tor_free_);
dns_wildcard_response_count = NULL;
n_wildcard_requests = 0;
n_ipv6_requests_made = n_ipv6_timeouts = 0;
if (dns_wildcard_list) {
SMARTLIST_FOREACH(dns_wildcard_list, char *, cp, tor_free(cp));
smartlist_clear(dns_wildcard_list);
}
if (dns_wildcarded_test_address_list) {
SMARTLIST_FOREACH(dns_wildcarded_test_address_list, char *, cp,
tor_free(cp));
smartlist_clear(dns_wildcarded_test_address_list);
}
dns_wildcard_one_notice_given = dns_wildcard_notice_given =
dns_wildcarded_test_address_notice_given = dns_is_completely_invalid =
dns_is_broken_for_ipv6 = 0;
}
/** Return true iff we have noticed that the dotted-quad <b>ip</b> has been
* returned in response to requests for nonexistent hostnames. */
static int
answer_is_wildcarded(const char *ip)
{
return dns_wildcard_list && smartlist_contains_string(dns_wildcard_list, ip);
}
/** Exit with an assertion if <b>resolve</b> is corrupt. */
static void
assert_resolve_ok(cached_resolve_t *resolve)
{
tor_assert(resolve);
tor_assert(resolve->magic == CACHED_RESOLVE_MAGIC);
tor_assert(strlen(resolve->address) < MAX_ADDRESSLEN);
tor_assert(tor_strisnonupper(resolve->address));
if (resolve->state != CACHE_STATE_PENDING) {
tor_assert(!resolve->pending_connections);
}
if (resolve->state == CACHE_STATE_PENDING ||
resolve->state == CACHE_STATE_DONE) {
#if 0
tor_assert(!resolve->ttl);
if (resolve->is_reverse)
tor_assert(!resolve->hostname);
else
tor_assert(!resolve->result_ipv4.addr_ipv4);
#endif /* 0 */
/*XXXXX ADD MORE */
}
}
/** Return the number of DNS cache entries as an int */
static int
dns_cache_entry_count(void)
{
return HT_SIZE(&cache_root);
}
/* Return the total size in bytes of the DNS cache. */
size_t
dns_cache_total_allocation(void)
{
return sizeof(struct cached_resolve_t) * dns_cache_entry_count() +
HT_MEM_USAGE(&cache_root);
}
/** Log memory information about our internal DNS cache at level 'severity'. */
void
dump_dns_mem_usage(int severity)
{
/* This should never be larger than INT_MAX. */
int hash_count = dns_cache_entry_count();
size_t hash_mem = dns_cache_total_allocation();
/* Print out the count and estimated size of our &cache_root. It undercounts
hostnames in cached reverse resolves.
*/
tor_log(severity, LD_MM, "Our DNS cache has %d entries.", hash_count);
tor_log(severity, LD_MM, "Our DNS cache size is approximately %u bytes.",
(unsigned)hash_mem);
}
/* Do a round of OOM cleanup on all DNS entries. Return the amount of removed
* bytes. It is possible that the returned value is lower than min_remove_bytes
* if the caches get emptied out so the caller should be aware of this. */
size_t
dns_cache_handle_oom(time_t now, size_t min_remove_bytes)
{
time_t time_inc = 0;
size_t total_bytes_removed = 0;
size_t current_size = dns_cache_total_allocation();
do {
/* If no DNS entries left, break loop. */
if (!dns_cache_entry_count())
break;
/* Get cutoff interval and remove entries. */
time_t cutoff = now + time_inc;
purge_expired_resolves(cutoff);
/* Update amount of bytes removed and array size. */
size_t bytes_removed = current_size - dns_cache_total_allocation();
current_size -= bytes_removed;
total_bytes_removed += bytes_removed;
time_inc += 3600; /* Increase time_inc by 1 hour. */
} while (total_bytes_removed < min_remove_bytes);
return total_bytes_removed;
}
#ifdef DEBUG_DNS_CACHE
/** Exit with an assertion if the DNS cache is corrupt. */
static void
assert_cache_ok_(void)
{
cached_resolve_t **resolve;
int bad_rep = HT_REP_IS_BAD_(cache_map, &cache_root);
if (bad_rep) {
log_err(LD_BUG, "Bad rep type %d on dns cache hash table", bad_rep);
tor_assert(!bad_rep);
}
HT_FOREACH(resolve, cache_map, &cache_root) {
assert_resolve_ok(*resolve);
tor_assert((*resolve)->state != CACHE_STATE_DONE);
}
if (!cached_resolve_pqueue)
return;
smartlist_pqueue_assert_ok(cached_resolve_pqueue,
compare_cached_resolves_by_expiry_,
offsetof(cached_resolve_t, minheap_idx));
SMARTLIST_FOREACH(cached_resolve_pqueue, cached_resolve_t *, res,
{
if (res->state == CACHE_STATE_DONE) {
cached_resolve_t *found = HT_FIND(cache_map, &cache_root, res);
tor_assert(!found || found != res);
} else {
cached_resolve_t *found = HT_FIND(cache_map, &cache_root, res);
tor_assert(found);
}
});
}
#endif /* defined(DEBUG_DNS_CACHE) */
cached_resolve_t *
dns_get_cache_entry(cached_resolve_t *query)
{
return HT_FIND(cache_map, &cache_root, query);
}
void
dns_insert_cache_entry(cached_resolve_t *new_entry)
{
HT_INSERT(cache_map, &cache_root, new_entry);
}
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