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evdns.c
5712 lines (5061 loc) · 156 KB
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evdns.c
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/* Copyright 2006-2007 Niels Provos
* Copyright 2007-2012 Nick Mathewson and Niels Provos
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/* Based on software by Adam Langly. Adam's original message:
*
* Async DNS Library
* Adam Langley <agl@imperialviolet.org>
* Public Domain code
*
* This software is Public Domain. To view a copy of the public domain dedication,
* visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
* Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
*
* I ask and expect, but do not require, that all derivative works contain an
* attribution similar to:
* Parts developed by Adam Langley <agl@imperialviolet.org>
*
* You may wish to replace the word "Parts" with something else depending on
* the amount of original code.
*
* (Derivative works does not include programs which link against, run or include
* the source verbatim in their source distributions)
*
* Version: 0.1b
*/
#include "event2/event-config.h"
#include "evconfig-private.h"
#include <sys/types.h>
#ifndef _FORTIFY_SOURCE
#define _FORTIFY_SOURCE 3
#endif
#include <string.h>
#include <fcntl.h>
#ifdef EVENT__HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef EVENT__HAVE_STDINT_H
#include <stdint.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#ifdef EVENT__HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <limits.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdarg.h>
#ifdef _WIN32
#include <winsock2.h>
#include <winerror.h>
#include <ws2tcpip.h>
#ifndef _WIN32_IE
#define _WIN32_IE 0x400
#endif
#include <shlobj.h>
#endif
#include "event2/buffer.h"
#include "event2/bufferevent.h"
#include "event2/dns.h"
#include "event2/dns_struct.h"
#include "event2/dns_compat.h"
#include "event2/util.h"
#include "event2/event.h"
#include "event2/event_struct.h"
#include "event2/listener.h"
#include "event2/thread.h"
#include "defer-internal.h"
#include "log-internal.h"
#include "mm-internal.h"
#include "strlcpy-internal.h"
#include "ipv6-internal.h"
#include "util-internal.h"
#include "evthread-internal.h"
#ifdef _WIN32
#include <ctype.h>
#include <winsock2.h>
#include <windows.h>
#include <iphlpapi.h>
#include <io.h>
#else
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#endif
#ifdef EVENT__HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif
#define EVDNS_LOG_DEBUG EVENT_LOG_DEBUG
#define EVDNS_LOG_WARN EVENT_LOG_WARN
#define EVDNS_LOG_MSG EVENT_LOG_MSG
#ifndef EVDNS_NAME_MAX
#define EVDNS_NAME_MAX 255
#endif
#include <stdio.h>
#undef MIN
#undef MAX
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define ASSERT_VALID_REQUEST(req) \
EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req))
#define u64 ev_uint64_t
#define u32 ev_uint32_t
#define u16 ev_uint16_t
#define u8 ev_uint8_t
/* maximum number of addresses from a single packet */
/* that we bother recording */
#define MAX_V4_ADDRS 32
#define MAX_V6_ADDRS 32
/* Maximum allowable size of a DNS message over UDP without EDNS.*/
#define DNS_MAX_UDP_SIZE 512
/* Maximum allowable size of a DNS message over UDP with EDNS.*/
#define EDNS_MAX_UDP_SIZE 65535
#define EDNS_ENABLED(base) \
(((base)->global_max_udp_size) > DNS_MAX_UDP_SIZE)
#define TYPE_A EVDNS_TYPE_A
#define TYPE_CNAME 5
#define TYPE_PTR EVDNS_TYPE_PTR
#define TYPE_SOA EVDNS_TYPE_SOA
#define TYPE_AAAA EVDNS_TYPE_AAAA
#define TYPE_OPT 41
#define CLASS_INET EVDNS_CLASS_INET
/* Timeout in seconds for idle TCP connections that server keeps alive. */
#define SERVER_IDLE_CONN_TIMEOUT 10
/* Timeout in seconds for idle TCP connections that client keeps alive. */
#define CLIENT_IDLE_CONN_TIMEOUT 5
/* Default maximum number of simultaneous TCP client connections that DNS server can hold. */
#define MAX_CLIENT_CONNECTIONS 10
struct reply {
unsigned int type;
unsigned int have_answer : 1;
u32 rr_count;
union {
u32 *a;
struct in6_addr *aaaa;
char *ptr_name;
void *raw;
} data;
char *cname;
};
/* Persistent handle. We keep this separate from 'struct request' since we
* need some object to last for as long as an evdns_request is outstanding so
* that it can be canceled, whereas a search request can lead to multiple
* 'struct request' instances being created over its lifetime. */
struct evdns_request {
struct request *current_req;
struct evdns_base *base;
int pending_cb; /* Waiting for its callback to be invoked; not
* owned by event base any more. */
/* data used when fulfilling the callback */
struct event_callback deferred;
evdns_callback_type user_callback;
void *user_pointer;
u8 request_type;
u8 have_reply;
u32 ttl;
u32 err;
struct reply reply;
/* elements used by the searching code */
int search_index;
struct search_state *search_state;
char *search_origname; /* needs to be free()ed */
int search_flags;
u16 tcp_flags;
};
struct request {
u8 *request; /* the dns packet data */
u16 request_size; /* size of memory block stored in request field */
u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */
unsigned int request_len;
int reissue_count;
int tx_count; /* the number of times that this packet has been sent */
struct nameserver *ns; /* the server which we last sent it */
/* these objects are kept in a circular list */
/* XXX We could turn this into a CIRCLEQ. */
struct request *next, *prev;
struct event timeout_event;
u16 trans_id; /* the transaction id */
unsigned request_appended :1; /* true if the request pointer is data which follows this struct */
unsigned transmit_me :1; /* needs to be transmitted */
unsigned need_cname :1; /* make a separate callback for CNAME */
/* XXXX This is a horrible hack. */
char **put_cname_in_ptr; /* store the cname here if we get one. */
struct evdns_base *base;
struct evdns_request *handle;
};
enum tcp_state {
TS_DISCONNECTED,
TS_CONNECTING,
TS_CONNECTED
};
struct tcp_connection {
struct bufferevent *bev;
enum tcp_state state;
u16 awaiting_packet_size;
};
struct evdns_server_port;
struct client_tcp_connection {
LIST_ENTRY(client_tcp_connection) next;
struct tcp_connection connection;
struct evdns_server_port *port;
};
struct nameserver {
evutil_socket_t socket; /* a connected UDP socket */
struct tcp_connection *connection; /* intended for TCP support */
struct sockaddr_storage address;
ev_socklen_t addrlen;
int failed_times; /* number of times which we have given this server a chance */
int timedout; /* number of times in a row a request has timed out */
struct event event;
/* these objects are kept in a circular list */
struct nameserver *next, *prev;
struct event timeout_event; /* used to keep the timeout for */
/* when we next probe this server. */
/* Valid if state == 0 */
/* Outstanding probe request for this nameserver, if any */
struct evdns_request *probe_request;
char state; /* zero if we think that this server is down */
char choked; /* true if we have an EAGAIN from this server's socket */
char write_waiting; /* true if we are waiting for EV_WRITE events */
struct evdns_base *base;
/* Number of currently inflight requests: used
* to track when we should add/del the event. */
int requests_inflight;
};
/* Represents a local port where we're listening for DNS requests. */
struct evdns_server_port {
evutil_socket_t socket; /* socket we use to read queries and write replies. */
int refcnt; /* reference count. */
char choked; /* Are we currently blocked from writing? */
char closing; /* Are we trying to close this port, pending writes? */
evdns_request_callback_fn_type user_callback; /* Fn to handle requests */
void *user_data; /* Opaque pointer passed to user_callback */
struct event event; /* Read/write event */
/* circular list of replies that we want to write. */
struct server_request *pending_replies;
struct event_base *event_base;
/* Structures for tcp support */
struct evconnlistener *listener;
LIST_HEAD(client_list, client_tcp_connection) client_connections;
unsigned client_connections_count;
unsigned max_client_connections;
struct timeval tcp_idle_timeout;
#ifndef EVENT__DISABLE_THREAD_SUPPORT
void *lock;
#endif
};
/* Represents part of a reply being built. (That is, a single RR.) */
struct server_reply_item {
struct server_reply_item *next; /* next item in sequence. */
char *name; /* name part of the RR */
u16 type; /* The RR type */
u16 class; /* The RR class (usually CLASS_INET) */
u32 ttl; /* The RR TTL */
char is_name; /* True iff data is a label */
u16 datalen; /* Length of data; -1 if data is a label */
void *data; /* The contents of the RR */
};
/* Represents a request that we've received as a DNS server, and holds */
/* the components of the reply as we're constructing it. */
struct server_request {
/* Pointers to the next and previous entries on the list of replies */
/* that we're waiting to write. Only set if we have tried to respond */
/* and gotten EAGAIN. */
struct server_request *next_pending;
struct server_request *prev_pending;
u16 trans_id; /* Transaction id. */
struct evdns_server_port *port; /* Which port received this request on? */
struct client_tcp_connection *client; /* Equal to NULL in case of UDP connection. */
struct sockaddr_storage addr; /* Where to send the response in case of UDP. Equal to NULL in case of TCP connection.*/
ev_socklen_t addrlen; /* length of addr */
u16 max_udp_reply_size; /* Maximum size of udp reply that client can handle. */
int n_answer; /* how many answer RRs have been set? */
int n_authority; /* how many authority RRs have been set? */
int n_additional; /* how many additional RRs have been set? */
struct server_reply_item *answer; /* linked list of answer RRs */
struct server_reply_item *authority; /* linked list of authority RRs */
struct server_reply_item *additional; /* linked list of additional RRs */
/* Constructed response. Only set once we're ready to send a reply. */
/* Once this is set, the RR fields are cleared, and no more should be set. */
char *response;
size_t response_len;
/* Caller-visible fields: flags, questions. */
struct evdns_server_request base;
};
struct evdns_base {
/* An array of n_req_heads circular lists for inflight requests.
* Each inflight request req is in req_heads[req->trans_id % n_req_heads].
*/
struct request **req_heads;
/* A circular list of requests that we're waiting to send, but haven't
* sent yet because there are too many requests inflight */
struct request *req_waiting_head;
/* A circular list of nameservers. */
struct nameserver *server_head;
int n_req_heads;
struct event_base *event_base;
/* The number of good nameservers that we have */
int global_good_nameservers;
/* inflight requests are contained in the req_head list */
/* and are actually going out across the network */
int global_requests_inflight;
/* requests which aren't inflight are in the waiting list */
/* and are counted here */
int global_requests_waiting;
int global_max_requests_inflight;
struct timeval global_timeout; /* 5 seconds by default */
int global_max_reissues; /* a reissue occurs when we get some errors from the server */
int global_max_retransmits; /* number of times we'll retransmit a request which timed out */
/* number of timeouts in a row before we consider this server to be down */
int global_max_nameserver_timeout;
/* true iff we will use the 0x20 hack to prevent poisoning attacks. */
int global_randomize_case;
/* Maximum size of a UDP DNS packet. */
u16 global_max_udp_size;
/* The first time that a nameserver fails, how long do we wait before
* probing to see if it has returned? */
struct timeval global_nameserver_probe_initial_timeout;
/* Combination of DNS_QUERY_USEVC, DNS_QUERY_IGNTC flags
* to control requests via TCP. */
u16 global_tcp_flags;
/* Idle timeout for outgoing TCP connections. */
struct timeval global_tcp_idle_timeout;
/** Port to bind to for outgoing DNS packets. */
struct sockaddr_storage global_outgoing_address;
/** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */
ev_socklen_t global_outgoing_addrlen;
struct timeval global_getaddrinfo_allow_skew;
int so_rcvbuf;
int so_sndbuf;
int getaddrinfo_ipv4_timeouts;
int getaddrinfo_ipv6_timeouts;
int getaddrinfo_ipv4_answered;
int getaddrinfo_ipv6_answered;
struct search_state *global_search_state;
TAILQ_HEAD(hosts_list, hosts_entry) hostsdb;
#ifndef EVENT__DISABLE_THREAD_SUPPORT
void *lock;
#endif
int disable_when_inactive;
/* Maximum timeout between two probe packets
* will change `global_nameserver_probe_initial_timeout`
* when this value is smaller */
int ns_max_probe_timeout;
/* Backoff factor of probe timeout */
int ns_timeout_backoff_factor;
};
struct hosts_entry {
TAILQ_ENTRY(hosts_entry) next;
union {
struct sockaddr sa;
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} addr;
int addrlen;
char hostname[1];
};
static struct evdns_base *current_base = NULL;
struct evdns_base *
evdns_get_global_base(void)
{
return current_base;
}
/* Given a pointer to an evdns_server_request, get the corresponding */
/* server_request. */
#define TO_SERVER_REQUEST(base_ptr) \
((struct server_request*) \
(((char*)(base_ptr) - evutil_offsetof(struct server_request, base))))
#define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads])
static struct nameserver *nameserver_pick(struct evdns_base *base);
static void evdns_request_insert(struct request *req, struct request **head);
static void evdns_request_remove(struct request *req, struct request **head);
static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg);
static int evdns_transmit(struct evdns_base *base);
static int evdns_request_transmit(struct request *req);
static void nameserver_send_probe(struct nameserver *const ns);
static void search_request_finished(struct evdns_request *const);
static int search_try_next(struct evdns_request *const req);
static struct request *search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags);
static void evdns_requests_pump_waiting_queue(struct evdns_base *base);
static u16 transaction_id_pick(struct evdns_base *base);
static struct request *request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags);
static struct request *request_clone(struct evdns_base *base, struct request* current);
static void request_submit(struct request *const req);
static int server_request_free(struct server_request *req);
static void server_request_free_answers(struct server_request *req);
static void server_port_free(struct evdns_server_port *port);
static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg);
static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename);
static int evdns_base_set_option_impl(struct evdns_base *base,
const char *option, const char *val, int flags);
static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests);
static void evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg);
static int evdns_server_request_format_response(struct server_request *req, int err);
static void incoming_conn_cb(struct evconnlistener *listener, evutil_socket_t fd,
struct sockaddr *address, int socklen, void *arg);
static int strtoint(const char *const str);
#ifdef EVENT__DISABLE_THREAD_SUPPORT
#define EVDNS_LOCK(base) EVUTIL_NIL_STMT_
#define EVDNS_UNLOCK(base) EVUTIL_NIL_STMT_
#define ASSERT_LOCKED(base) EVUTIL_NIL_STMT_
#else
#define EVDNS_LOCK(base) \
EVLOCK_LOCK((base)->lock, 0)
#define EVDNS_UNLOCK(base) \
EVLOCK_UNLOCK((base)->lock, 0)
#define ASSERT_LOCKED(base) \
EVLOCK_ASSERT_LOCKED((base)->lock)
#endif
static evdns_debug_log_fn_type evdns_log_fn = NULL;
void
evdns_set_log_fn(evdns_debug_log_fn_type fn)
{
evdns_log_fn = fn;
}
#ifdef __GNUC__
#define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3)))
#else
#define EVDNS_LOG_CHECK
#endif
static void evdns_log_(int severity, const char *fmt, ...) EVDNS_LOG_CHECK;
static void
evdns_log_(int severity, const char *fmt, ...)
{
va_list args;
va_start(args,fmt);
if (evdns_log_fn) {
char buf[512];
int is_warn = (severity == EVDNS_LOG_WARN);
evutil_vsnprintf(buf, sizeof(buf), fmt, args);
evdns_log_fn(is_warn, buf);
} else {
event_logv_(severity, NULL, fmt, args);
}
va_end(args);
}
#define log evdns_log_
/* Initialize tcp_connection structure. */
static void
init_tcp_connection(struct tcp_connection *conn, struct bufferevent *bev)
{
memset(conn, 0, sizeof(*conn));
conn->state = TS_DISCONNECTED;
conn->bev = bev;
conn->awaiting_packet_size = 0;
}
/* Disconnect tcp connection. */
static void
evdns_tcp_disconnect(struct tcp_connection *conn)
{
if (!conn)
return;
conn->state = TS_DISCONNECTED;
conn->awaiting_packet_size = 0;
if (conn->bev) {
bufferevent_free(conn->bev);
conn->bev = NULL;
}
}
/* Add new tcp client to the list of TCP clients in the TCP DNS server. */
static struct client_tcp_connection*
evdns_add_tcp_client(struct evdns_server_port *port, struct bufferevent *bev)
{
struct client_tcp_connection *client;
EVUTIL_ASSERT(port && bev);
if (port->max_client_connections == port->client_connections_count)
goto error;
client = mm_calloc(1, sizeof(*client));
if (!client)
goto error;
init_tcp_connection(&client->connection, bev);
client->port = port;
LIST_INSERT_HEAD(&port->client_connections, client, next);
++port->client_connections_count;
/* we need to hold evdns_server_port as long as one connection at least stays alive */
++port->refcnt;
return client;
error:
return NULL;
}
/* Remove tcp client and free all associated data from the TCP DNS server. */
static int
evdns_remove_tcp_client(struct evdns_server_port *port, struct client_tcp_connection *client)
{
if (!port || !client)
goto error;
evdns_tcp_disconnect(&client->connection);
LIST_REMOVE(client, next);
mm_free(client);
--port->client_connections_count;
--port->refcnt;
return 0;
error:
return -1;
}
/* Remove all tcp clients and free all associated data from the TCP DNS server. */
static void
evdns_remove_all_tcp_clients(struct evdns_server_port *port)
{
struct client_tcp_connection *client;
while ((client = LIST_FIRST(&port->client_connections))) {
evdns_remove_tcp_client(port, client);
}
}
/* Create new tcp connection structure for DNS client. */
static struct tcp_connection *
new_tcp_connection(struct bufferevent *bev)
{
struct tcp_connection *conn;
if (!bev)
return NULL;
conn = mm_calloc(1, sizeof(*conn));
if (!conn)
return NULL;
init_tcp_connection(conn, bev);
return conn;
}
/* Disconnect and free all associated data for the tcp connection in DNS client. */
static void
disconnect_and_free_connection(struct tcp_connection *conn)
{
if (!conn)
return;
evdns_tcp_disconnect(conn);
mm_free(conn);
}
/* This walks the list of inflight requests to find the */
/* one with a matching transaction id. Returns NULL on */
/* failure */
static struct request *
request_find_from_trans_id(struct evdns_base *base, u16 trans_id) {
struct request *req = REQ_HEAD(base, trans_id);
struct request *const started_at = req;
ASSERT_LOCKED(base);
if (req) {
do {
if (req->trans_id == trans_id) return req;
req = req->next;
} while (req != started_at);
}
return NULL;
}
/* a libevent callback function which is called when a nameserver */
/* has gone down and we want to test if it has came back to life yet */
static void
nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) {
struct nameserver *const ns = (struct nameserver *) arg;
(void)fd;
(void)events;
EVDNS_LOCK(ns->base);
nameserver_send_probe(ns);
EVDNS_UNLOCK(ns->base);
}
/* a libevent callback which is called when a nameserver probe (to see if */
/* it has come back to life) times out. We increment the count of failed_times */
/* and wait longer to send the next probe packet. */
static void
nameserver_probe_failed(struct nameserver *const ns) {
struct timeval timeout;
int i;
ASSERT_LOCKED(ns->base);
(void) evtimer_del(&ns->timeout_event);
if (ns->state == 1) {
/* This can happen if the nameserver acts in a way which makes us mark */
/* it as bad and then starts sending good replies. */
return;
}
memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout,
sizeof(struct timeval));
for (i = ns->failed_times; i > 0 && timeout.tv_sec < ns->base->ns_max_probe_timeout; --i) {
timeout.tv_sec *= ns->base->ns_timeout_backoff_factor;
timeout.tv_usec *= ns->base->ns_timeout_backoff_factor;
if (timeout.tv_usec > 1000000) {
timeout.tv_sec += timeout.tv_usec / 1000000;
timeout.tv_usec %= 1000000;
}
}
if (timeout.tv_sec > ns->base->ns_max_probe_timeout) {
timeout.tv_sec = ns->base->ns_max_probe_timeout;
timeout.tv_usec = 0;
}
ns->failed_times++;
if (evtimer_add(&ns->timeout_event, &timeout) < 0) {
char addrbuf[128];
log(EVDNS_LOG_WARN,
"Error from libevent when adding timer event for %s",
evutil_format_sockaddr_port_(
(struct sockaddr *)&ns->address,
addrbuf, sizeof(addrbuf)));
}
}
static void
request_swap_ns(struct request *req, struct nameserver *ns) {
if (ns && req->ns != ns) {
EVUTIL_ASSERT(req->ns->requests_inflight > 0);
req->ns->requests_inflight--;
ns->requests_inflight++;
req->ns = ns;
}
}
/* called when a nameserver has been deemed to have failed. For example, too */
/* many packets have timed out etc */
static void
nameserver_failed(struct nameserver *const ns, const char *msg, int err) {
struct request *req, *started_at;
struct evdns_base *base = ns->base;
int i;
char addrbuf[128];
ASSERT_LOCKED(base);
/* if this nameserver has already been marked as failed */
/* then don't do anything */
if (!ns->state) return;
log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s",
evutil_format_sockaddr_port_(
(struct sockaddr *)&ns->address,
addrbuf, sizeof(addrbuf)),
msg);
base->global_good_nameservers--;
EVUTIL_ASSERT(base->global_good_nameservers >= 0);
if (base->global_good_nameservers == 0) {
log(EVDNS_LOG_MSG, "All nameservers have failed");
}
ns->state = 0;
ns->failed_times = 1;
if (ns->connection) {
disconnect_and_free_connection(ns->connection);
ns->connection = NULL;
} else if (err == ENOTCONN) {
/* XXX: If recvfrom results in ENOTCONN, the socket remains readable
* which triggers another recvfrom. The observed behavior is 100% CPU use.
* This occurs on iOS (kqueue) after the process has been backgrounded
* for a long time (~300 seconds) and then resumed.
* All sockets, TCP and UDP, seem to get ENOTCONN and must be closed.
* https://github.com/libevent/libevent/issues/265 */
const struct sockaddr *address = (const struct sockaddr *)&ns->address;
evutil_closesocket(ns->socket);
ns->socket = evutil_socket_(address->sa_family,
SOCK_DGRAM | EVUTIL_SOCK_NONBLOCK | EVUTIL_SOCK_CLOEXEC, 0);
if (base->global_outgoing_addrlen &&
!evutil_sockaddr_is_loopback_(address)) {
if (bind(ns->socket,
(struct sockaddr *)&base->global_outgoing_address,
base->global_outgoing_addrlen) < 0) {
log(EVDNS_LOG_WARN, "Couldn't bind to outgoing address");
}
}
event_del(&ns->event);
event_assign(&ns->event, ns->base->event_base, ns->socket,
EV_READ | (ns->write_waiting ? EV_WRITE : 0) | EV_PERSIST,
nameserver_ready_callback, ns);
if (!base->disable_when_inactive && event_add(&ns->event, NULL) < 0) {
log(EVDNS_LOG_WARN, "Couldn't add %s event",
ns->write_waiting ? "rw": "read");
}
}
if (evtimer_add(&ns->timeout_event,
&base->global_nameserver_probe_initial_timeout) < 0) {
log(EVDNS_LOG_WARN,
"Error from libevent when adding timer event for %s",
evutil_format_sockaddr_port_(
(struct sockaddr *)&ns->address,
addrbuf, sizeof(addrbuf)));
/* ???? Do more? */
}
/* walk the list of inflight requests to see if any can be reassigned to */
/* a different server. Requests in the waiting queue don't have a */
/* nameserver assigned yet */
/* if we don't have *any* good nameservers then there's no point */
/* trying to reassign requests to one */
if (!base->global_good_nameservers) return;
for (i = 0; i < base->n_req_heads; ++i) {
req = started_at = base->req_heads[i];
if (req) {
do {
if (req->tx_count == 0 && req->ns == ns) {
/* still waiting to go out, can be moved */
/* to another server */
request_swap_ns(req, nameserver_pick(base));
}
req = req->next;
} while (req != started_at);
}
}
}
static void
nameserver_up(struct nameserver *const ns)
{
char addrbuf[128];
ASSERT_LOCKED(ns->base);
if (ns->state) return;
log(EVDNS_LOG_MSG, "Nameserver %s is back up",
evutil_format_sockaddr_port_(
(struct sockaddr *)&ns->address,
addrbuf, sizeof(addrbuf)));
evtimer_del(&ns->timeout_event);
if (ns->probe_request) {
evdns_cancel_request(ns->base, ns->probe_request);
ns->probe_request = NULL;
}
ns->state = 1;
ns->failed_times = 0;
ns->timedout = 0;
ns->base->global_good_nameservers++;
}
static void
request_trans_id_set(struct request *const req, const u16 trans_id) {
req->trans_id = trans_id;
*((u16 *) req->request) = htons(trans_id);
}
/* Called to remove a request from a list and dealloc it. */
/* head is a pointer to the head of the list it should be */
/* removed from or NULL if the request isn't in a list. */
/* when free_handle is one, free the handle as well. */
static void
request_finished(struct request *const req, struct request **head, int free_handle) {
struct evdns_base *base = req->base;
int was_inflight = (head != &base->req_waiting_head);
EVDNS_LOCK(base);
ASSERT_VALID_REQUEST(req);
if (head)
evdns_request_remove(req, head);
log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", (void *)req);
if (was_inflight) {
evtimer_del(&req->timeout_event);
base->global_requests_inflight--;
req->ns->requests_inflight--;
} else {
base->global_requests_waiting--;
}
/* it was initialized during request_new / evtimer_assign */
event_debug_unassign(&req->timeout_event);
if (req->ns &&
req->ns->requests_inflight == 0 &&
req->base->disable_when_inactive) {
event_del(&req->ns->event);
evtimer_del(&req->ns->timeout_event);
}
if (!req->request_appended) {
/* need to free the request data on it's own */
mm_free(req->request);
} else {
/* the request data is appended onto the header */
/* so everything gets free()ed when we: */
}
if (req->handle) {
EVUTIL_ASSERT(req->handle->current_req == req);
if (free_handle) {
search_request_finished(req->handle);
req->handle->current_req = NULL;
if (! req->handle->pending_cb) {
/* If we're planning to run the callback,
* don't free the handle until later. */
mm_free(req->handle);
}
req->handle = NULL; /* If we have a bug, let's crash
* early */
} else {
req->handle->current_req = NULL;
}
}
mm_free(req);
evdns_requests_pump_waiting_queue(base);
EVDNS_UNLOCK(base);
}
/* This is called when a server returns a funny error code. */
/* We try the request again with another server. */
/* */
/* return: */
/* 0 ok */
/* 1 failed/reissue is pointless */
static int
request_reissue(struct request *req) {
const struct nameserver *const last_ns = req->ns;
ASSERT_LOCKED(req->base);
ASSERT_VALID_REQUEST(req);
/* the last nameserver should have been marked as failing */
/* by the caller of this function, therefore pick will try */
/* not to return it */
request_swap_ns(req, nameserver_pick(req->base));
if (req->ns == last_ns) {
/* ... but pick did return it */
/* not a lot of point in trying again with the */
/* same server */
return 1;
}
req->reissue_count++;
req->tx_count = 0;
req->transmit_me = 1;
return 0;
}
/* this function looks for space on the inflight queue and promotes */
/* requests from the waiting queue if it can. */
/* */
/* TODO: */
/* add return code, see at nameserver_pick() and other functions. */
static void
evdns_requests_pump_waiting_queue(struct evdns_base *base) {
ASSERT_LOCKED(base);
while (base->global_requests_inflight < base->global_max_requests_inflight &&
base->global_requests_waiting) {
struct request *req;
EVUTIL_ASSERT(base->req_waiting_head);
req = base->req_waiting_head;
req->ns = nameserver_pick(base);
if (!req->ns)
return;
/* move a request from the waiting queue to the inflight queue */
req->ns->requests_inflight++;
evdns_request_remove(req, &base->req_waiting_head);
base->global_requests_waiting--;
base->global_requests_inflight++;
request_trans_id_set(req, transaction_id_pick(base));
evdns_request_insert(req, &REQ_HEAD(base, req->trans_id));
evdns_request_transmit(req);
evdns_transmit(base);
}
}
static void
reply_run_callback(struct event_callback *d, void *user_pointer)
{
struct evdns_request *handle =
EVUTIL_UPCAST(d, struct evdns_request, deferred);
switch (handle->request_type) {
case TYPE_A:
if (handle->have_reply) {
handle->user_callback(DNS_ERR_NONE, DNS_IPv4_A,
handle->reply.rr_count, handle->ttl,
handle->reply.data.a,
user_pointer);
if (handle->reply.cname)
handle->user_callback(DNS_ERR_NONE, DNS_CNAME, 1,
handle->ttl, handle->reply.cname, user_pointer);
} else
handle->user_callback(handle->err, 0, 0, handle->ttl, NULL, user_pointer);
break;
case TYPE_PTR:
if (handle->have_reply) {