| /* $Id: evdns.c 6979 2006-08-04 18:31:13Z nickm $ */ |
| |
| /* The original version of this module was written by Adam Langley; for |
| * a history of modifications, check out the subversion logs. |
| * |
| * When editing this module, try to keep it re-mergeable by Adam. Don't |
| * reformat the whitespace, add Tor dependencies, or so on. |
| * |
| * TODO: |
| * - Support IPv6 and PTR records. |
| * - Replace all externally visible magic numbers with #defined constants. |
| * - Write doccumentation for APIs of all external functions. |
| */ |
| |
| /* Async DNS Library |
| * Adam Langley <agl@imperialviolet.org> |
| * http://www.imperialviolet.org/eventdns.html |
| * 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 <sys/types.h> |
| #ifdef HAVE_CONFIG_H |
| #include "config.h" |
| #endif |
| |
| #ifdef DNS_USE_FTIME_FOR_ID |
| #include <sys/timeb.h> |
| #endif |
| |
| #ifndef DNS_USE_CPU_CLOCK_FOR_ID |
| #ifndef DNS_USE_GETTIMEOFDAY_FOR_ID |
| #ifndef DNS_USE_OPENSSL_FOR_ID |
| #ifndef DNS_USE_FTIME_FOR_ID |
| #error Must configure at least one id generation method. |
| #error Please see the documentation. |
| #endif |
| #endif |
| #endif |
| #endif |
| |
| /* #define _POSIX_C_SOURCE 200507 */ |
| #ifndef _GNU_SOURCE |
| #define _GNU_SOURCE |
| #endif |
| |
| #ifdef DNS_USE_CPU_CLOCK_FOR_ID |
| #ifdef DNS_USE_OPENSSL_FOR_ID |
| #error Multiple id options selected |
| #endif |
| #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID |
| #error Multiple id options selected |
| #endif |
| #include <time.h> |
| #endif |
| |
| #ifdef DNS_USE_OPENSSL_FOR_ID |
| #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID |
| #error Multiple id options selected |
| #endif |
| #include <openssl/rand.h> |
| #endif |
| |
| #ifndef _FORTIFY_SOURCE |
| #define _FORTIFY_SOURCE 3 |
| #endif |
| |
| #include <string.h> |
| #include <fcntl.h> |
| #ifdef HAVE_SYS_TIME_H |
| #include <sys/time.h> |
| #endif |
| #ifdef HAVE_STDINT_H |
| #include <stdint.h> |
| #endif |
| #include <stdlib.h> |
| #include <string.h> |
| #include <errno.h> |
| #include <assert.h> |
| #ifdef HAVE_UNISTD_H |
| #include <unistd.h> |
| #endif |
| #include <limits.h> |
| #include <sys/stat.h> |
| #include <ctype.h> |
| #include <stdio.h> |
| #include <stdarg.h> |
| |
| #include "evdns.h" |
| #include "evutil.h" |
| #include "log.h" |
| #ifdef WIN32 |
| #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 HAVE_NETINET_IN6_H |
| #include <netinet/in6.h> |
| #endif |
| |
| #define EVDNS_LOG_DEBUG 0 |
| #define EVDNS_LOG_WARN 1 |
| |
| #ifndef HOST_NAME_MAX |
| #define HOST_NAME_MAX 255 |
| #endif |
| |
| #include <stdio.h> |
| |
| #undef MIN |
| #define MIN(a,b) ((a)<(b)?(a):(b)) |
| |
| #ifdef __USE_ISOC99B |
| /* libevent doesn't work without this */ |
| typedef ev_uint8_t u_char; |
| typedef unsigned int uint; |
| #endif |
| #include "event.h" |
| |
| #define u64 ev_uint64_t |
| #define u32 ev_uint32_t |
| #define u16 ev_uint16_t |
| #define u8 ev_uint8_t |
| |
| #ifdef WIN32 |
| #define open _open |
| #define read _read |
| #define close _close |
| #define strdup _strdup |
| #endif |
| |
| #define MAX_ADDRS 32 /* maximum number of addresses from a single packet */ |
| /* which we bother recording */ |
| |
| #define TYPE_A EVDNS_TYPE_A |
| #define TYPE_CNAME 5 |
| #define TYPE_PTR EVDNS_TYPE_PTR |
| #define TYPE_AAAA EVDNS_TYPE_AAAA |
| |
| #define CLASS_INET EVDNS_CLASS_INET |
| |
| #ifdef HAVE_SETFD |
| #define FD_CLOSEONEXEC(x) do { \ |
| if (fcntl(x, F_SETFD, 1) == -1) \ |
| event_warn("fcntl(%d, F_SETFD)", x); \ |
| } while (0) |
| #else |
| #define FD_CLOSEONEXEC(x) (void)0 |
| #endif |
| |
| struct request { |
| u8 *request; /* the dns packet data */ |
| unsigned int request_len; |
| int reissue_count; |
| int tx_count; /* the number of times that this packet has been sent */ |
| unsigned int request_type; /* TYPE_PTR or TYPE_A */ |
| void *user_pointer; /* the pointer given to us for this request */ |
| evdns_callback_type user_callback; |
| struct nameserver *ns; /* the server which we last sent it */ |
| |
| /* 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; |
| |
| /* these objects are kept in a circular list */ |
| struct request *next, *prev; |
| |
| struct event timeout_event; |
| |
| u16 trans_id; /* the transaction id */ |
| char request_appended; /* true if the request pointer is data which follows this struct */ |
| char transmit_me; /* needs to be transmitted */ |
| }; |
| |
| #ifndef HAVE_STRUCT_IN6_ADDR |
| struct in6_addr { |
| u8 s6_addr[16]; |
| }; |
| #endif |
| |
| struct reply { |
| unsigned int type; |
| unsigned int have_answer; |
| union { |
| struct { |
| u32 addrcount; |
| u32 addresses[MAX_ADDRS]; |
| } a; |
| struct { |
| u32 addrcount; |
| struct in6_addr addresses[MAX_ADDRS]; |
| } aaaa; |
| struct { |
| char name[HOST_NAME_MAX]; |
| } ptr; |
| } data; |
| }; |
| |
| struct nameserver { |
| int socket; /* a connected UDP socket */ |
| u32 address; |
| u16 port; |
| 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 */ |
| 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 */ |
| }; |
| |
| static struct request *req_head = NULL, *req_waiting_head = NULL; |
| static struct nameserver *server_head = NULL; |
| |
| /* Represents a local port where we're listening for DNS requests. Right now, */ |
| /* only UDP is supported. */ |
| struct evdns_server_port { |
| int 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; |
| }; |
| |
| /* 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 : 16; /* The RR type */ |
| u16 class : 16; /* 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 sockaddr_storage addr; /* Where to send the response */ |
| socklen_t addrlen; /* length of addr */ |
| |
| 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; |
| }; |
| |
| /* helper macro */ |
| #define OFFSET_OF(st, member) ((off_t) (((char*)&((st*)0)->member)-(char*)0)) |
| |
| /* 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) - OFFSET_OF(struct server_request, base)))) |
| |
| /* The number of good nameservers that we have */ |
| static int global_good_nameservers = 0; |
| |
| /* inflight requests are contained in the req_head list */ |
| /* and are actually going out across the network */ |
| static int global_requests_inflight = 0; |
| /* requests which aren't inflight are in the waiting list */ |
| /* and are counted here */ |
| static int global_requests_waiting = 0; |
| |
| static int global_max_requests_inflight = 64; |
| |
| static struct timeval global_timeout = {5, 0}; /* 5 seconds */ |
| static int global_max_reissues = 1; /* a reissue occurs when we get some errors from the server */ |
| static int global_max_retransmits = 3; /* 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 */ |
| static int global_max_nameserver_timeout = 3; |
| |
| /* These are the timeout values for nameservers. If we find a nameserver is down */ |
| /* we try to probe it at intervals as given below. Values are in seconds. */ |
| static const struct timeval global_nameserver_timeouts[] = {{10, 0}, {60, 0}, {300, 0}, {900, 0}, {3600, 0}}; |
| static const int global_nameserver_timeouts_length = sizeof(global_nameserver_timeouts)/sizeof(struct timeval); |
| |
| static struct nameserver *nameserver_pick(void); |
| static void evdns_request_insert(struct request *req, struct request **head); |
| static void nameserver_ready_callback(int fd, short events, void *arg); |
| static int evdns_transmit(void); |
| static int evdns_request_transmit(struct request *req); |
| static void nameserver_send_probe(struct nameserver *const ns); |
| static void search_request_finished(struct request *const); |
| static int search_try_next(struct request *const req); |
| static int search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg); |
| static void evdns_requests_pump_waiting_queue(void); |
| static u16 transaction_id_pick(void); |
| static struct request *request_new(int type, const char *name, int flags, evdns_callback_type callback, void *ptr); |
| 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(int fd, short events, void *arg); |
| |
| static int strtoint(const char *const str); |
| |
| #ifdef WIN32 |
| static int |
| last_error(int sock) |
| { |
| int optval, optvallen=sizeof(optval); |
| int err = WSAGetLastError(); |
| if (err == WSAEWOULDBLOCK && sock >= 0) { |
| if (getsockopt(sock, SOL_SOCKET, SO_ERROR, (void*)&optval, |
| &optvallen)) |
| return err; |
| if (optval) |
| return optval; |
| } |
| return err; |
| |
| } |
| static int |
| error_is_eagain(int err) |
| { |
| return err == EAGAIN || err == WSAEWOULDBLOCK; |
| } |
| static int |
| inet_aton(const char *c, struct in_addr *addr) |
| { |
| ev_uint32_t r; |
| if (strcmp(c, "255.255.255.255") == 0) { |
| addr->s_addr = 0xffffffffu; |
| } else { |
| r = inet_addr(c); |
| if (r == INADDR_NONE) |
| return 0; |
| addr->s_addr = r; |
| } |
| return 1; |
| } |
| #else |
| #define last_error(sock) (errno) |
| #define error_is_eagain(err) ((err) == EAGAIN) |
| #endif |
| #define CLOSE_SOCKET(s) EVUTIL_CLOSESOCKET(s) |
| |
| #define ISSPACE(c) isspace((int)(unsigned char)(c)) |
| #define ISDIGIT(c) isdigit((int)(unsigned char)(c)) |
| |
| static const char * |
| debug_ntoa(u32 address) |
| { |
| static char buf[32]; |
| u32 a = ntohl(address); |
| evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d", |
| (int)(u8)((a>>24)&0xff), |
| (int)(u8)((a>>16)&0xff), |
| (int)(u8)((a>>8 )&0xff), |
| (int)(u8)((a )&0xff)); |
| return buf; |
| } |
| |
| 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 warn, const char *fmt, ...) EVDNS_LOG_CHECK; |
| static void |
| _evdns_log(int warn, const char *fmt, ...) |
| { |
| va_list args; |
| static char buf[512]; |
| if (!evdns_log_fn) |
| return; |
| va_start(args,fmt); |
| evutil_vsnprintf(buf, sizeof(buf), fmt, args); |
| buf[sizeof(buf)-1] = '\0'; |
| evdns_log_fn(warn, buf); |
| va_end(args); |
| } |
| |
| #define log _evdns_log |
| |
| /* 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(u16 trans_id) { |
| struct request *req = req_head, *const started_at = req_head; |
| |
| 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(int fd, short events, void *arg) { |
| struct nameserver *const ns = (struct nameserver *) arg; |
| (void)fd; |
| (void)events; |
| |
| nameserver_send_probe(ns); |
| } |
| |
| /* 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) { |
| const struct timeval * timeout; |
| (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; |
| } |
| |
| timeout = |
| &global_nameserver_timeouts[MIN(ns->failed_times, |
| global_nameserver_timeouts_length - 1)]; |
| ns->failed_times++; |
| |
| if (evtimer_add(&ns->timeout_event, (struct timeval *) timeout) < 0) { |
| log(EVDNS_LOG_WARN, |
| "Error from libevent when adding timer event for %s", |
| debug_ntoa(ns->address)); |
| /* ???? Do more? */ |
| } |
| } |
| |
| /* 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) { |
| struct request *req, *started_at; |
| /* if this nameserver has already been marked as failed */ |
| /* then don't do anything */ |
| if (!ns->state) return; |
| |
| log(EVDNS_LOG_WARN, "Nameserver %s has failed: %s", |
| debug_ntoa(ns->address), msg); |
| global_good_nameservers--; |
| assert(global_good_nameservers >= 0); |
| if (global_good_nameservers == 0) { |
| log(EVDNS_LOG_WARN, "All nameservers have failed"); |
| } |
| |
| ns->state = 0; |
| ns->failed_times = 1; |
| |
| if (evtimer_add(&ns->timeout_event, (struct timeval *) &global_nameserver_timeouts[0]) < 0) { |
| log(EVDNS_LOG_WARN, |
| "Error from libevent when adding timer event for %s", |
| debug_ntoa(ns->address)); |
| /* ???? 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 (!global_good_nameservers) return; |
| |
| req = req_head; |
| started_at = req_head; |
| if (req) { |
| do { |
| if (req->tx_count == 0 && req->ns == ns) { |
| /* still waiting to go out, can be moved */ |
| /* to another server */ |
| req->ns = nameserver_pick(); |
| } |
| req = req->next; |
| } while (req != started_at); |
| } |
| } |
| |
| static void |
| nameserver_up(struct nameserver *const ns) { |
| if (ns->state) return; |
| log(EVDNS_LOG_WARN, "Nameserver %s is back up", |
| debug_ntoa(ns->address)); |
| evtimer_del(&ns->timeout_event); |
| ns->state = 1; |
| ns->failed_times = 0; |
| ns->timedout = 0; |
| 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. */ |
| static void |
| request_finished(struct request *const req, struct request **head) { |
| if (head) { |
| if (req->next == req) { |
| /* only item in the list */ |
| *head = NULL; |
| } else { |
| req->next->prev = req->prev; |
| req->prev->next = req->next; |
| if (*head == req) *head = req->next; |
| } |
| } |
| |
| log(EVDNS_LOG_DEBUG, "Removing timeout for request %lx", |
| (unsigned long) req); |
| evtimer_del(&req->timeout_event); |
| |
| search_request_finished(req); |
| global_requests_inflight--; |
| |
| if (!req->request_appended) { |
| /* need to free the request data on it's own */ |
| free(req->request); |
| } else { |
| /* the request data is appended onto the header */ |
| /* so everything gets free()ed when we: */ |
| } |
| |
| free(req); |
| |
| evdns_requests_pump_waiting_queue(); |
| } |
| |
| /* 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; |
| /* the last nameserver should have been marked as failing */ |
| /* by the caller of this function, therefore pick will try */ |
| /* not to return it */ |
| req->ns = nameserver_pick(); |
| 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. */ |
| static void |
| evdns_requests_pump_waiting_queue(void) { |
| while (global_requests_inflight < global_max_requests_inflight && |
| global_requests_waiting) { |
| struct request *req; |
| /* move a request from the waiting queue to the inflight queue */ |
| assert(req_waiting_head); |
| if (req_waiting_head->next == req_waiting_head) { |
| /* only one item in the queue */ |
| req = req_waiting_head; |
| req_waiting_head = NULL; |
| } else { |
| req = req_waiting_head; |
| req->next->prev = req->prev; |
| req->prev->next = req->next; |
| req_waiting_head = req->next; |
| } |
| |
| global_requests_waiting--; |
| global_requests_inflight++; |
| |
| req->ns = nameserver_pick(); |
| request_trans_id_set(req, transaction_id_pick()); |
| |
| evdns_request_insert(req, &req_head); |
| evdns_request_transmit(req); |
| evdns_transmit(); |
| } |
| } |
| |
| static void |
| reply_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) { |
| switch (req->request_type) { |
| case TYPE_A: |
| if (reply) |
| req->user_callback(DNS_ERR_NONE, DNS_IPv4_A, |
| reply->data.a.addrcount, ttl, |
| reply->data.a.addresses, |
| req->user_pointer); |
| else |
| req->user_callback(err, 0, 0, 0, NULL, req->user_pointer); |
| return; |
| case TYPE_PTR: |
| if (reply) { |
| char *name = reply->data.ptr.name; |
| req->user_callback(DNS_ERR_NONE, DNS_PTR, 1, ttl, |
| &name, req->user_pointer); |
| } else { |
| req->user_callback(err, 0, 0, 0, NULL, |
| req->user_pointer); |
| } |
| return; |
| case TYPE_AAAA: |
| if (reply) |
| req->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA, |
| reply->data.aaaa.addrcount, ttl, |
| reply->data.aaaa.addresses, |
| req->user_pointer); |
| else |
| req->user_callback(err, 0, 0, 0, NULL, req->user_pointer); |
| return; |
| } |
| assert(0); |
| } |
| |
| /* this processes a parsed reply packet */ |
| static void |
| reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) { |
| int error; |
| static const int error_codes[] = { |
| DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, |
| DNS_ERR_NOTIMPL, DNS_ERR_REFUSED |
| }; |
| |
| if (flags & 0x020f || !reply || !reply->have_answer) { |
| /* there was an error */ |
| if (flags & 0x0200) { |
| error = DNS_ERR_TRUNCATED; |
| } else { |
| u16 error_code = (flags & 0x000f) - 1; |
| if (error_code > 4) { |
| error = DNS_ERR_UNKNOWN; |
| } else { |
| error = error_codes[error_code]; |
| } |
| } |
| |
| switch(error) { |
| case DNS_ERR_NOTIMPL: |
| case DNS_ERR_REFUSED: |
| /* we regard these errors as marking a bad nameserver */ |
| if (req->reissue_count < global_max_reissues) { |
| char msg[64]; |
| evutil_snprintf(msg, sizeof(msg), |
| "Bad response %d (%s)", |
| error, evdns_err_to_string(error)); |
| nameserver_failed(req->ns, msg); |
| if (!request_reissue(req)) return; |
| } |
| break; |
| case DNS_ERR_SERVERFAILED: |
| /* rcode 2 (servfailed) sometimes means "we |
| * are broken" and sometimes (with some binds) |
| * means "that request was very confusing." |
| * Treat this as a timeout, not a failure. |
| */ |
| log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver %s; " |
| "will allow the request to time out.", |
| debug_ntoa(req->ns->address)); |
| break; |
| default: |
| /* we got a good reply from the nameserver */ |
| nameserver_up(req->ns); |
| } |
| |
| if (req->search_state && req->request_type != TYPE_PTR) { |
| /* if we have a list of domains to search in, |
| * try the next one */ |
| if (!search_try_next(req)) { |
| /* a new request was issued so this |
| * request is finished and */ |
| /* the user callback will be made when |
| * that request (or a */ |
| /* child of it) finishes. */ |
| request_finished(req, &req_head); |
| return; |
| } |
| } |
| |
| /* all else failed. Pass the failure up */ |
| reply_callback(req, 0, error, NULL); |
| request_finished(req, &req_head); |
| } else { |
| /* all ok, tell the user */ |
| reply_callback(req, ttl, 0, reply); |
| nameserver_up(req->ns); |
| request_finished(req, &req_head); |
| } |
| } |
| |
| static int |
| name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) { |
| int name_end = -1; |
| int j = *idx; |
| int ptr_count = 0; |
| #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while(0) |
| #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while(0) |
| #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while(0) |
| |
| char *cp = name_out; |
| const char *const end = name_out + name_out_len; |
| |
| /* Normally, names are a series of length prefixed strings terminated */ |
| /* with a length of 0 (the lengths are u8's < 63). */ |
| /* However, the length can start with a pair of 1 bits and that */ |
| /* means that the next 14 bits are a pointer within the current */ |
| /* packet. */ |
| |
| for(;;) { |
| u8 label_len; |
| if (j >= length) return -1; |
| GET8(label_len); |
| if (!label_len) break; |
| if (label_len & 0xc0) { |
| u8 ptr_low; |
| GET8(ptr_low); |
| if (name_end < 0) name_end = j; |
| j = (((int)label_len & 0x3f) << 8) + ptr_low; |
| /* Make sure that the target offset is in-bounds. */ |
| if (j < 0 || j >= length) return -1; |
| /* If we've jumped more times than there are characters in the |
| * message, we must have a loop. */ |
| if (++ptr_count > length) return -1; |
| continue; |
| } |
| if (label_len > 63) return -1; |
| if (cp != name_out) { |
| if (cp + 1 >= end) return -1; |
| *cp++ = '.'; |
| } |
| if (cp + label_len >= end) return -1; |
| memcpy(cp, packet + j, label_len); |
| cp += label_len; |
| j += label_len; |
| } |
| if (cp >= end) return -1; |
| *cp = '\0'; |
| if (name_end < 0) |
| *idx = j; |
| else |
| *idx = name_end; |
| return 0; |
| err: |
| return -1; |
| } |
| |
| /* parses a raw request from a nameserver */ |
| static int |
| reply_parse(u8 *packet, int length) { |
| int j = 0, k = 0; /* index into packet */ |
| u16 _t; /* used by the macros */ |
| u32 _t32; /* used by the macros */ |
| char tmp_name[256], cmp_name[256]; /* used by the macros */ |
| |
| u16 trans_id, questions, answers, authority, additional, datalength; |
| u16 flags = 0; |
| u32 ttl, ttl_r = 0xffffffff; |
| struct reply reply; |
| struct request *req = NULL; |
| unsigned int i; |
| |
| GET16(trans_id); |
| GET16(flags); |
| GET16(questions); |
| GET16(answers); |
| GET16(authority); |
| GET16(additional); |
| (void) authority; /* suppress "unused variable" warnings. */ |
| (void) additional; /* suppress "unused variable" warnings. */ |
| |
| req = request_find_from_trans_id(trans_id); |
| if (!req) return -1; |
| |
| memset(&reply, 0, sizeof(reply)); |
| |
| /* If it's not an answer, it doesn't correspond to any request. */ |
| if (!(flags & 0x8000)) return -1; /* must be an answer */ |
| if (flags & 0x020f) { |
| /* there was an error */ |
| goto err; |
| } |
| /* if (!answers) return; */ /* must have an answer of some form */ |
| |
| /* This macro skips a name in the DNS reply. */ |
| #define SKIP_NAME \ |
| do { tmp_name[0] = '\0'; \ |
| if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)\ |
| goto err; \ |
| } while(0) |
| #define TEST_NAME \ |
| do { tmp_name[0] = '\0'; \ |
| cmp_name[0] = '\0'; \ |
| k = j; \ |
| if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)\ |
| goto err; \ |
| if (name_parse(req->request, req->request_len, &k, cmp_name, sizeof(cmp_name))<0) \ |
| goto err; \ |
| if (memcmp(tmp_name, cmp_name, strlen (tmp_name)) != 0) \ |
| return (-1); /* we ignore mismatching names */ \ |
| } while(0) |
| |
| reply.type = req->request_type; |
| |
| /* skip over each question in the reply */ |
| for (i = 0; i < questions; ++i) { |
| /* the question looks like |
| * <label:name><u16:type><u16:class> |
| */ |
| TEST_NAME; |
| j += 4; |
| if (j > length) goto err; |
| } |
| |
| /* now we have the answer section which looks like |
| * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...> |
| */ |
| |
| for (i = 0; i < answers; ++i) { |
| u16 type, class; |
| |
| SKIP_NAME; |
| GET16(type); |
| GET16(class); |
| GET32(ttl); |
| GET16(datalength); |
| |
| if (type == TYPE_A && class == CLASS_INET) { |
| int addrcount, addrtocopy; |
| if (req->request_type != TYPE_A) { |
| j += datalength; continue; |
| } |
| if ((datalength & 3) != 0) /* not an even number of As. */ |
| goto err; |
| addrcount = datalength >> 2; |
| addrtocopy = MIN(MAX_ADDRS - reply.data.a.addrcount, (unsigned)addrcount); |
| |
| ttl_r = MIN(ttl_r, ttl); |
| /* we only bother with the first four addresses. */ |
| if (j + 4*addrtocopy > length) goto err; |
| memcpy(&reply.data.a.addresses[reply.data.a.addrcount], |
| packet + j, 4*addrtocopy); |
| j += 4*addrtocopy; |
| reply.data.a.addrcount += addrtocopy; |
| reply.have_answer = 1; |
| if (reply.data.a.addrcount == MAX_ADDRS) break; |
| } else if (type == TYPE_PTR && class == CLASS_INET) { |
| if (req->request_type != TYPE_PTR) { |
| j += datalength; continue; |
| } |
| if (name_parse(packet, length, &j, reply.data.ptr.name, |
| sizeof(reply.data.ptr.name))<0) |
| goto err; |
| ttl_r = MIN(ttl_r, ttl); |
| reply.have_answer = 1; |
| break; |
| } else if (type == TYPE_AAAA && class == CLASS_INET) { |
| int addrcount, addrtocopy; |
| if (req->request_type != TYPE_AAAA) { |
| j += datalength; continue; |
| } |
| if ((datalength & 15) != 0) /* not an even number of AAAAs. */ |
| goto err; |
| addrcount = datalength >> 4; /* each address is 16 bytes long */ |
| addrtocopy = MIN(MAX_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount); |
| ttl_r = MIN(ttl_r, ttl); |
| |
| /* we only bother with the first four addresses. */ |
| if (j + 16*addrtocopy > length) goto err; |
| memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount], |
| packet + j, 16*addrtocopy); |
| reply.data.aaaa.addrcount += addrtocopy; |
| j += 16*addrtocopy; |
| reply.have_answer = 1; |
| if (reply.data.aaaa.addrcount == MAX_ADDRS) break; |
| } else { |
| /* skip over any other type of resource */ |
| j += datalength; |
| } |
| } |
| |
| reply_handle(req, flags, ttl_r, &reply); |
| return 0; |
| err: |
| if (req) |
| reply_handle(req, flags, 0, NULL); |
| return -1; |
| } |
| |
| /* Parse a raw request (packet,length) sent to a nameserver port (port) from */ |
| /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */ |
| /* callback. */ |
| static int |
| request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, socklen_t addrlen) |
| { |
| int j = 0; /* index into packet */ |
| u16 _t; /* used by the macros */ |
| char tmp_name[256]; /* used by the macros */ |
| |
| int i; |
| u16 trans_id, flags, questions, answers, authority, additional; |
| struct server_request *server_req = NULL; |
| |
| /* Get the header fields */ |
| GET16(trans_id); |
| GET16(flags); |
| GET16(questions); |
| GET16(answers); |
| GET16(authority); |
| GET16(additional); |
| |
| if (flags & 0x8000) return -1; /* Must not be an answer. */ |
| flags &= 0x0110; /* Only RD and CD get preserved. */ |
| |
| server_req = malloc(sizeof(struct server_request)); |
| if (server_req == NULL) return -1; |
| memset(server_req, 0, sizeof(struct server_request)); |
| |
| server_req->trans_id = trans_id; |
| memcpy(&server_req->addr, addr, addrlen); |
| server_req->addrlen = addrlen; |
| |
| server_req->base.flags = flags; |
| server_req->base.nquestions = 0; |
| server_req->base.questions = malloc(sizeof(struct evdns_server_question *) * questions); |
| if (server_req->base.questions == NULL) |
| goto err; |
| |
| for (i = 0; i < questions; ++i) { |
| u16 type, class; |
| struct evdns_server_question *q; |
| int namelen; |
| if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0) |
| goto err; |
| GET16(type); |
| GET16(class); |
| namelen = strlen(tmp_name); |
| q = malloc(sizeof(struct evdns_server_question) + namelen); |
| if (!q) |
| goto err; |
| q->type = type; |
| q->dns_question_class = class; |
| memcpy(q->name, tmp_name, namelen+1); |
| server_req->base.questions[server_req->base.nquestions++] = q; |
| } |
| |
| /* Ignore answers, authority, and additional. */ |
| |
| server_req->port = port; |
| port->refcnt++; |
| |
| /* Only standard queries are supported. */ |
| if (flags & 0x7800) { |
| evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); |
| return -1; |
| } |
| |
| port->user_callback(&(server_req->base), port->user_data); |
| |
| return 0; |
| err: |
| if (server_req) { |
| if (server_req->base.questions) { |
| for (i = 0; i < server_req->base.nquestions; ++i) |
| free(server_req->base.questions[i]); |
| free(server_req->base.questions); |
| } |
| free(server_req); |
| } |
| return -1; |
| |
| #undef SKIP_NAME |
| #undef GET32 |
| #undef GET16 |
| #undef GET8 |
| } |
| |
| static u16 |
| default_transaction_id_fn(void) |
| { |
| u16 trans_id; |
| #ifdef DNS_USE_CPU_CLOCK_FOR_ID |
| struct timespec ts; |
| static int clkid = -1; |
| if (clkid == -1) { |
| clkid = CLOCK_REALTIME; |
| #ifdef CLOCK_MONOTONIC |
| if (clock_gettime(CLOCK_MONOTONIC, &ts) != -1) |
| clkid = CLOCK_MONOTONIC; |
| #endif |
| } |
| if (clock_gettime(clkid, &ts) == -1) |
| event_err(1, "clock_gettime"); |
| trans_id = ts.tv_nsec & 0xffff; |
| #endif |
| |
| #ifdef DNS_USE_FTIME_FOR_ID |
| struct _timeb tb; |
| _ftime(&tb); |
| trans_id = tb.millitm & 0xffff; |
| #endif |
| |
| #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID |
| struct timeval tv; |
| evutil_gettimeofday(&tv, NULL); |
| trans_id = tv.tv_usec & 0xffff; |
| #endif |
| |
| #ifdef DNS_USE_OPENSSL_FOR_ID |
| if (RAND_pseudo_bytes((u8 *) &trans_id, 2) == -1) { |
| /* in the case that the RAND call fails we back */ |
| /* down to using gettimeofday. */ |
| /* |
| struct timeval tv; |
| evutil_gettimeofday(&tv, NULL); |
| trans_id = tv.tv_usec & 0xffff; |
| */ |
| abort(); |
| } |
| #endif |
| return trans_id; |
| } |
| |
| static ev_uint16_t (*trans_id_function)(void) = default_transaction_id_fn; |
| |
| void |
| evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)) |
| { |
| if (fn) |
| trans_id_function = fn; |
| else |
| trans_id_function = default_transaction_id_fn; |
| } |
| |
| /* Try to choose a strong transaction id which isn't already in flight */ |
| static u16 |
| transaction_id_pick(void) { |
| for (;;) { |
| u16 trans_id = trans_id_function(); |
| |
| if (trans_id == 0xffff) continue; |
| |
| if (request_find_from_trans_id(trans_id) == NULL) |
| return trans_id; |
| } |
| } |
| |
| /* choose a namesever to use. This function will try to ignore */ |
| /* nameservers which we think are down and load balance across the rest */ |
| /* by updating the server_head global each time. */ |
| static struct nameserver * |
| nameserver_pick(void) { |
| struct nameserver *started_at = server_head, *picked; |
| if (!server_head) return NULL; |
| |
| /* if we don't have any good nameservers then there's no */ |
| /* point in trying to find one. */ |
| if (!global_good_nameservers) { |
| server_head = server_head->next; |
| return server_head; |
| } |
| |
| /* remember that nameservers are in a circular list */ |
| for (;;) { |
| if (server_head->state) { |
| /* we think this server is currently good */ |
| picked = server_head; |
| server_head = server_head->next; |
| return picked; |
| } |
| |
| server_head = server_head->next; |
| if (server_head == started_at) { |
| /* all the nameservers seem to be down */ |
| /* so we just return this one and hope for the */ |
| /* best */ |
| assert(global_good_nameservers == 0); |
| picked = server_head; |
| server_head = server_head->next; |
| return picked; |
| } |
| } |
| } |
| |
| static int |
| address_is_correct(struct nameserver *ns, struct sockaddr *sa, socklen_t slen) |
| { |
| struct sockaddr_in *sin = (struct sockaddr_in*) sa; |
| if (sa->sa_family != AF_INET || slen != sizeof(struct sockaddr_in)) |
| return 0; |
| if (sin->sin_addr.s_addr != ns->address) |
| return 0; |
| return 1; |
| } |
| |
| /* this is called when a namesever socket is ready for reading */ |
| static void |
| nameserver_read(struct nameserver *ns) { |
| u8 packet[1500]; |
| struct sockaddr_storage ss; |
| socklen_t addrlen = sizeof(ss); |
| |
| for (;;) { |
| const int r = recvfrom(ns->socket, packet, sizeof(packet), 0, |
| (struct sockaddr*)&ss, &addrlen); |
| if (r < 0) { |
| int err = last_error(ns->socket); |
| if (error_is_eagain(err)) return; |
| nameserver_failed(ns, strerror(err)); |
| return; |
| } |
| if (!address_is_correct(ns, (struct sockaddr*)&ss, addrlen)) { |
| log(EVDNS_LOG_WARN, "Address mismatch on received " |
| "DNS packet."); |
| return; |
| } |
| ns->timedout = 0; |
| reply_parse(packet, r); |
| } |
| } |
| |
| /* Read a packet from a DNS client on a server port s, parse it, and */ |
| /* act accordingly. */ |
| static void |
| server_port_read(struct evdns_server_port *s) { |
| u8 packet[1500]; |
| struct sockaddr_storage addr; |
| socklen_t addrlen; |
| int r; |
| |
| for (;;) { |
| addrlen = sizeof(struct sockaddr_storage); |
| r = recvfrom(s->socket, packet, sizeof(packet), 0, |
| (struct sockaddr*) &addr, &addrlen); |
| if (r < 0) { |
| int err = last_error(s->socket); |
| if (error_is_eagain(err)) return; |
| log(EVDNS_LOG_WARN, "Error %s (%d) while reading request.", |
| strerror(err), err); |
| return; |
| } |
| request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen); |
| } |
| } |
| |
| /* Try to write all pending replies on a given DNS server port. */ |
| static void |
| server_port_flush(struct evdns_server_port *port) |
| { |
| while (port->pending_replies) { |
| struct server_request *req = port->pending_replies; |
| int r = sendto(port->socket, req->response, req->response_len, 0, |
| (struct sockaddr*) &req->addr, req->addrlen); |
| if (r < 0) { |
| int err = last_error(port->socket); |
| if (error_is_eagain(err)) |
| return; |
| log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", strerror(err), err); |
| } |
| if (server_request_free(req)) { |
| /* we released the last reference to req->port. */ |
| return; |
| } |
| } |
| |
| /* We have no more pending requests; stop listening for 'writeable' events. */ |
| (void) event_del(&port->event); |
| event_set(&port->event, port->socket, EV_READ | EV_PERSIST, |
| server_port_ready_callback, port); |
| if (event_add(&port->event, NULL) < 0) { |
| log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server."); |
| /* ???? Do more? */ |
| } |
| } |
| |
| /* set if we are waiting for the ability to write to this server. */ |
| /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */ |
| /* we stop these events. */ |
| static void |
| nameserver_write_waiting(struct nameserver *ns, char waiting) { |
| if (ns->write_waiting == waiting) return; |
| |
| ns->write_waiting = waiting; |
| (void) event_del(&ns->event); |
| event_set(&ns->event, ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST, |
| nameserver_ready_callback, ns); |
| if (event_add(&ns->event, NULL) < 0) { |
| log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s", |
| debug_ntoa(ns->address)); |
| /* ???? Do more? */ |
| } |
| } |
| |
| /* a callback function. Called by libevent when the kernel says that */ |
| /* a nameserver socket is ready for writing or reading */ |
| static void |
| nameserver_ready_callback(int fd, short events, void *arg) { |
| struct nameserver *ns = (struct nameserver *) arg; |
| (void)fd; |
| |
| if (events & EV_WRITE) { |
| ns->choked = 0; |
| if (!evdns_transmit()) { |
| nameserver_write_waiting(ns, 0); |
| } |
| } |
| if (events & EV_READ) { |
| nameserver_read(ns); |
| } |
| } |
| |
| /* a callback function. Called by libevent when the kernel says that */ |
| /* a server socket is ready for writing or reading. */ |
| static void |
| server_port_ready_callback(int fd, short events, void *arg) { |
| struct evdns_server_port *port = (struct evdns_server_port *) arg; |
| (void) fd; |
| |
| if (events & EV_WRITE) { |
| port->choked = 0; |
| server_port_flush(port); |
| } |
| if (events & EV_READ) { |
| server_port_read(port); |
| } |
| } |
| |
| /* This is an inefficient representation; only use it via the dnslabel_table_* |
| * functions, so that is can be safely replaced with something smarter later. */ |
| #define MAX_LABELS 128 |
| /* Structures used to implement name compression */ |
| struct dnslabel_entry { char *v; off_t pos; }; |
| struct dnslabel_table { |
| int n_labels; /* number of current entries */ |
| /* map from name to position in message */ |
| struct dnslabel_entry labels[MAX_LABELS]; |
| }; |
| |
| /* Initialize dnslabel_table. */ |
| static void |
| dnslabel_table_init(struct dnslabel_table *table) |
| { |
| table->n_labels = 0; |
| } |
| |
| /* Free all storage held by table, but not the table itself. */ |
| static void |
| dnslabel_clear(struct dnslabel_table *table) |
| { |
| int i; |
| for (i = 0; i < table->n_labels; ++i) |
| free(table->labels[i].v); |
| table->n_labels = 0; |
| } |
| |
| /* return the position of the label in the current message, or -1 if the label */ |
| /* hasn't been used yet. */ |
| static int |
| dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label) |
| { |
| int i; |
| for (i = 0; i < table->n_labels; ++i) { |
| if (!strcmp(label, table->labels[i].v)) |
| return table->labels[i].pos; |
| } |
| return -1; |
| } |
| |
| /* remember that we've used the label at position pos */ |
| static int |
| dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos) |
| { |
| char *v; |
| int p; |
| if (table->n_labels == MAX_LABELS) |
| return (-1); |
| v = strdup(label); |
| if (v == NULL) |
| return (-1); |
| p = table->n_labels++; |
| table->labels[p].v = v; |
| table->labels[p].pos = pos; |
| |
| return (0); |
| } |
| |
| /* Converts a string to a length-prefixed set of DNS labels, starting */ |
| /* at buf[j]. name and buf must not overlap. name_len should be the length */ |
| /* of name. table is optional, and is used for compression. */ |
| /* */ |
| /* Input: abc.def */ |
| /* Output: <3>abc<3>def<0> */ |
| /* */ |
| /* Returns the first index after the encoded name, or negative on error. */ |
| /* -1 label was > 63 bytes */ |
| /* -2 name too long to fit in buffer. */ |
| /* */ |
| static off_t |
| dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j, |
| const char *name, const int name_len, |
| struct dnslabel_table *table) { |
| const char *end = name + name_len; |
| int ref = 0; |
| u16 _t; |
| |
| #define APPEND16(x) do { \ |
| if (j + 2 > (off_t)buf_len) \ |
| goto overflow; \ |
| _t = htons(x); \ |
| memcpy(buf + j, &_t, 2); \ |
| j += 2; \ |
| } while (0) |
| #define APPEND32(x) do { \ |
| if (j + 4 > (off_t)buf_len) \ |
| goto overflow; \ |
| _t32 = htonl(x); \ |
| memcpy(buf + j, &_t32, 4); \ |
| j += 4; \ |
| } while (0) |
| |
| if (name_len > 255) return -2; |
| |
| for (;;) { |
| const char *const start = name; |
| if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) { |
| APPEND16(ref | 0xc000); |
| return j; |
| } |
| name = strchr(name, '.'); |
| if (!name) { |
| const unsigned int label_len = end - start; |
| if (label_len > 63) return -1; |
| if ((size_t)(j+label_len+1) > buf_len) return -2; |
| if (table) dnslabel_table_add(table, start, j); |
| buf[j++] = label_len; |
| |
| memcpy(buf + j, start, end - start); |
| j += end - start; |
| break; |
| } else { |
| /* append length of the label. */ |
| const unsigned int label_len = name - start; |
| if (label_len > 63) return -1; |
| if ((size_t)(j+label_len+1) > buf_len) return -2; |
| if (table) dnslabel_table_add(table, start, j); |
| buf[j++] = label_len; |
| |
| memcpy(buf + j, start, name - start); |
| j += name - start; |
| /* hop over the '.' */ |
| name++; |
| } |
| } |
| |
| /* the labels must be terminated by a 0. */ |
| /* It's possible that the name ended in a . */ |
| /* in which case the zero is already there */ |
| if (!j || buf[j-1]) buf[j++] = 0; |
| return j; |
| overflow: |
| return (-2); |
| } |
| |
| /* Finds the length of a dns request for a DNS name of the given */ |
| /* length. The actual request may be smaller than the value returned */ |
| /* here */ |
| static int |
| evdns_request_len(const int name_len) { |
| return 96 + /* length of the DNS standard header */ |
| name_len + 2 + |
| 4; /* space for the resource type */ |
| } |
| |
| /* build a dns request packet into buf. buf should be at least as long */ |
| /* as evdns_request_len told you it should be. */ |
| /* */ |
| /* Returns the amount of space used. Negative on error. */ |
| static int |
| evdns_request_data_build(const char *const name, const int name_len, |
| const u16 trans_id, const u16 type, const u16 class, |
| u8 *const buf, size_t buf_len) { |
| off_t j = 0; /* current offset into buf */ |
| u16 _t; /* used by the macros */ |
| |
| APPEND16(trans_id); |
| APPEND16(0x0100); /* standard query, recusion needed */ |
| APPEND16(1); /* one question */ |
| APPEND16(0); /* no answers */ |
| APPEND16(0); /* no authority */ |
| APPEND16(0); /* no additional */ |
| |
| j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL); |
| if (j < 0) { |
| return (int)j; |
| } |
| |
| APPEND16(type); |
| APPEND16(class); |
| |
| return (int)j; |
| overflow: |
| return (-1); |
| } |
| |
| /* exported function */ |
| struct evdns_server_port * |
| evdns_add_server_port(int socket, int is_tcp, evdns_request_callback_fn_type cb, void *user_data) |
| { |
| struct evdns_server_port *port; |
| if (!(port = malloc(sizeof(struct evdns_server_port)))) |
| return NULL; |
| memset(port, 0, sizeof(struct evdns_server_port)); |
| |
| assert(!is_tcp); /* TCP sockets not yet implemented */ |
| port->socket = socket; |
| port->refcnt = 1; |
| port->choked = 0; |
| port->closing = 0; |
| port->user_callback = cb; |
| port->user_data = user_data; |
| port->pending_replies = NULL; |
| |
| event_set(&port->event, port->socket, EV_READ | EV_PERSIST, |
| server_port_ready_callback, port); |
| event_add(&port->event, NULL); /* check return. */ |
| return port; |
| } |
| |
| /* exported function */ |
| void |
| evdns_close_server_port(struct evdns_server_port *port) |
| { |
| if (--port->refcnt == 0) |
| server_port_free(port); |
| port->closing = 1; |
| } |
| |
| /* exported function */ |
| int |
| evdns_server_request_add_reply(struct evdns_server_request *_req, int section, const char *name, int type, int class, int ttl, int datalen, int is_name, const char *data) |
| { |
| struct server_request *req = TO_SERVER_REQUEST(_req); |
| struct server_reply_item **itemp, *item; |
| int *countp; |
| |
| if (req->response) /* have we already answered? */ |
| return (-1); |
| |
| switch (section) { |
| case EVDNS_ANSWER_SECTION: |
| itemp = &req->answer; |
| countp = &req->n_answer; |
| break; |
| case EVDNS_AUTHORITY_SECTION: |
| itemp = &req->authority; |
| countp = &req->n_authority; |
| break; |
| case EVDNS_ADDITIONAL_SECTION: |
| itemp = &req->additional; |
| countp = &req->n_additional; |
| break; |
| default: |
| return (-1); |
| } |
| while (*itemp) { |
| itemp = &((*itemp)->next); |
| } |
| item = malloc(sizeof(struct server_reply_item)); |
| if (!item) |
| return -1; |
| item->next = NULL; |
| if (!(item->name = strdup(name))) { |
| free(item); |
| return -1; |
| } |
| item->type = type; |
| item->dns_question_class = class; |
| item->ttl = ttl; |
| item->is_name = is_name != 0; |
| item->datalen = 0; |
| item->data = NULL; |
| if (data) { |
| if (item->is_name) { |
| if (!(item->data = strdup(data))) { |
| free(item->name); |
| free(item); |
| return -1; |
| } |
| item->datalen = (u16)-1; |
| } else { |
| if (!(item->data = malloc(datalen))) { |
| free(item->name); |
| free(item); |
| return -1; |
| } |
| item->datalen = datalen; |
| memcpy(item->data, data, datalen); |
| } |
| } |
| |
| *itemp = item; |
| ++(*countp); |
| return 0; |
| } |
| |
| /* exported function */ |
| int |
| evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, void *addrs, int ttl) |
| { |
| return evdns_server_request_add_reply( |
| req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET, |
| ttl, n*4, 0, addrs); |
| } |
| |
| /* exported function */ |
| int |
| evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, void *addrs, int ttl) |
| { |
| return evdns_server_request_add_reply( |
| req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET, |
| ttl, n*16, 0, addrs); |
| } |
| |
| /* exported function */ |
| int |
| evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl) |
| { |
| u32 a; |
| char buf[32]; |
| assert(in || inaddr_name); |
| assert(!(in && inaddr_name)); |
| if (in) { |
| a = ntohl(in->s_addr); |
| evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", |
| (int)(u8)((a )&0xff), |
| (int)(u8)((a>>8 )&0xff), |
| (int)(u8)((a>>16)&0xff), |
| (int)(u8)((a>>24)&0xff)); |
| inaddr_name = buf; |
| } |
| return evdns_server_request_add_reply( |
| req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET, |
| ttl, -1, 1, hostname); |
| } |
| |
| /* exported function */ |
| int |
| evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl) |
| { |
| return evdns_server_request_add_reply( |
| req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET, |
| ttl, -1, 1, cname); |
| } |
| |
| |
| static int |
| evdns_server_request_format_response(struct server_request *req, int err) |
| { |
| unsigned char buf[1500]; |
| size_t buf_len = sizeof(buf); |
| off_t j = 0, r; |
| u16 _t; |
| u32 _t32; |
| int i; |
| u16 flags; |
| struct dnslabel_table table; |
| |
| if (err < 0 || err > 15) return -1; |
| |
| /* Set response bit and error code; copy OPCODE and RD fields from |
| * question; copy RA and AA if set by caller. */ |
| flags = req->base.flags; |
| flags |= (0x8000 | err); |
| |
| dnslabel_table_init(&table); |
| APPEND16(req->trans_id); |
| APPEND16(flags); |
| APPEND16(req->base.nquestions); |
| APPEND16(req->n_answer); |
| APPEND16(req->n_authority); |
| APPEND16(req->n_additional); |
| |
| /* Add questions. */ |
| for (i=0; i < req->base.nquestions; ++i) { |
| const char *s = req->base.questions[i]->name; |
| j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table); |
| if (j < 0) { |
| dnslabel_clear(&table); |
| return (int) j; |
| } |
| APPEND16(req->base.questions[i]->type); |
| APPEND16(req->base.questions[i]->dns_question_class); |
| } |
| |
| /* Add answer, authority, and additional sections. */ |
| for (i=0; i<3; ++i) { |
| struct server_reply_item *item; |
| if (i==0) |
| item = req->answer; |
| else if (i==1) |
| item = req->authority; |
| else |
| item = req->additional; |
| while (item) { |
| r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table); |
| if (r < 0) |
| goto overflow; |
| j = r; |
| |
| APPEND16(item->type); |
| APPEND16(item->dns_question_class); |
| APPEND32(item->ttl); |
| if (item->is_name) { |
| off_t len_idx = j, name_start; |
| j += 2; |
| name_start = j; |
| r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table); |
| if (r < 0) |
| goto overflow; |
| j = r; |
| _t = htons( (short) (j-name_start) ); |
| memcpy(buf+len_idx, &_t, 2); |
| } else { |
| APPEND16(item->datalen); |
| if (j+item->datalen > (off_t)buf_len) |
| goto overflow; |
| memcpy(buf+j, item->data, item->datalen); |
| j += item->datalen; |
| } |
| item = item->next; |
| } |
| } |
| |
| if (j > 512) { |
| overflow: |
| j = 512; |
| buf[2] |= 0x02; /* set the truncated bit. */ |
| } |
| |
| req->response_len = j; |
| |
| if (!(req->response = malloc(req->response_len))) { |
| server_request_free_answers(req); |
| dnslabel_clear(&table); |
| return (-1); |
| } |
| memcpy(req->response, buf, req->response_len); |
| server_request_free_answers(req); |
| dnslabel_clear(&table); |
| return (0); |
| } |
| |
| /* exported function */ |
| int |
| evdns_server_request_respond(struct evdns_server_request *_req, int err) |
| { |
| struct server_request *req = TO_SERVER_REQUEST(_req); |
| struct evdns_server_port *port = req->port; |
| int r; |
| if (!req->response) { |
| if ((r = evdns_server_request_format_response(req, err))<0) |
| return r; |
| } |
| |
| r = sendto(port->socket, req->response, req->response_len, 0, |
| (struct sockaddr*) &req->addr, req->addrlen); |
| if (r<0) { |
| int sock_err = last_error(port->socket); |
| if (! error_is_eagain(sock_err)) |
| return -1; |
| |
| if (port->pending_replies) { |
| req->prev_pending = port->pending_replies->prev_pending; |
| req->next_pending = port->pending_replies; |
| req->prev_pending->next_pending = |
| req->next_pending->prev_pending = req; |
| } else { |
| req->prev_pending = req->next_pending = req; |
| port->pending_replies = req; |
| port->choked = 1; |
| |
| (void) event_del(&port->event); |
| event_set(&port->event, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port); |
| |
| if (event_add(&port->event, NULL) < 0) { |
| log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server"); |
| } |
| |
| } |
| |
| return 1; |
| } |
| if (server_request_free(req)) |
| return 0; |
| |
| if (port->pending_replies) |
| server_port_flush(port); |
| |
| return 0; |
| } |
| |
| /* Free all storage held by RRs in req. */ |
| static void |
| server_request_free_answers(struct server_request *req) |
| { |
| struct server_reply_item *victim, *next, **list; |
| int i; |
| for (i = 0; i < 3; ++i) { |
| if (i==0) |
| list = &req->answer; |
| else if (i==1) |
| list = &req->authority; |
| else |
| list = &req->additional; |
| |
| victim = *list; |
| while (victim) { |
| next = victim->next; |
| free(victim->name); |
| if (victim->data) |
| free(victim->data); |
| free(victim); |
| victim = next; |
| } |
| *list = NULL; |
| } |
| } |
| |
| /* Free all storage held by req, and remove links to it. */ |
| /* return true iff we just wound up freeing the server_port. */ |
| static int |
| server_request_free(struct server_request *req) |
| { |
| int i, rc=1; |
| if (req->base.questions) { |
| for (i = 0; i < req->base.nquestions; ++i) |
| free(req->base.questions[i]); |
| free(req->base.questions); |
| } |
| |
| if (req->port) { |
| if (req->port->pending_replies == req) { |
| if (req->next_pending) |
| req->port->pending_replies = req->next_pending; |
| else |
| req->port->pending_replies = NULL; |
| } |
| rc = --req->port->refcnt; |
| } |
| |
| if (req->response) { |
| free(req->response); |
| } |
| |
| server_request_free_answers(req); |
| |
| if (req->next_pending && req->next_pending != req) { |
| req->next_pending->prev_pending = req->prev_pending; |
| req->prev_pending->next_pending = req->next_pending; |
| } |
| |
| if (rc == 0) { |
| server_port_free(req->port); |
| free(req); |
| return (1); |
| } |
| free(req); |
| return (0); |
| } |
| |
| /* Free all storage held by an evdns_server_port. Only called when */ |
| static void |
| server_port_free(struct evdns_server_port *port) |
| { |
| assert(port); |
| assert(!port->refcnt); |
| assert(!port->pending_replies); |
| if (port->socket > 0) { |
| CLOSE_SOCKET(port->socket); |
| port->socket = -1; |
| } |
| (void) event_del(&port->event); |
| /* XXXX actually free the port? -NM */ |
| } |
| |
| /* exported function */ |
| int |
| evdns_server_request_drop(struct evdns_server_request *_req) |
| { |
| struct server_request *req = TO_SERVER_REQUEST(_req); |
| server_request_free(req); |
| return 0; |
| } |
| |
| /* exported function */ |
| int |
| evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len) |
| { |
| struct server_request *req = TO_SERVER_REQUEST(_req); |
| if (addr_len < (int)req->addrlen) |
| return -1; |
| memcpy(sa, &(req->addr), req->addrlen); |
| return req->addrlen; |
| } |
| |
| #undef APPEND16 |
| #undef APPEND32 |
| |
| /* this is a libevent callback function which is called when a request */ |
| /* has timed out. */ |
| static void |
| evdns_request_timeout_callback(int fd, short events, void *arg) { |
| struct request *const req = (struct request *) arg; |
| (void) fd; |
| (void) events; |
| |
| log(EVDNS_LOG_DEBUG, "Request %lx timed out", (unsigned long) arg); |
| |
| req->ns->timedout++; |
| if (req->ns->timedout > global_max_nameserver_timeout) { |
| req->ns->timedout = 0; |
| nameserver_failed(req->ns, "request timed out."); |
| } |
| |
| (void) evtimer_del(&req->timeout_event); |
| if (req->tx_count >= global_max_retransmits) { |
| /* this request has failed */ |
| reply_callback(req, 0, DNS_ERR_TIMEOUT, NULL); |
| request_finished(req, &req_head); |
| } else { |
| /* retransmit it */ |
| evdns_request_transmit(req); |
| } |
| } |
| |
| /* try to send a request to a given server. */ |
| /* */ |
| /* return: */ |
| /* 0 ok */ |
| /* 1 temporary failure */ |
| /* 2 other failure */ |
| static int |
| evdns_request_transmit_to(struct request *req, struct nameserver *server) { |
| struct sockaddr_in sin; |
| int r; |
| memset(&sin, 0, sizeof(sin)); |
| sin.sin_addr.s_addr = req->ns->address; |
| sin.sin_port = req->ns->port; |
| sin.sin_family = AF_INET; |
| |
| r = sendto(server->socket, req->request, req->request_len, 0, |
| (struct sockaddr*)&sin, sizeof(sin)); |
| if (r < 0) { |
| int err = last_error(server->socket); |
| if (error_is_eagain(err)) return 1; |
| nameserver_failed(req->ns, strerror(err)); |
| return 2; |
| } else if (r != (int)req->request_len) { |
| return 1; /* short write */ |
| } else { |
| return 0; |
| } |
| } |
| |
| /* try to send a request, updating the fields of the request */ |
| /* as needed */ |
| /* */ |
| /* return: */ |
| /* 0 ok */ |
| /* 1 failed */ |
| static int |
| evdns_request_transmit(struct request *req) { |
| int retcode = 0, r; |
| |
| /* if we fail to send this packet then this flag marks it */ |
| /* for evdns_transmit */ |
| req->transmit_me = 1; |
| if (req->trans_id == 0xffff) abort(); |
| |
| if (req->ns->choked) { |
| /* don't bother trying to write to a socket */ |
| /* which we have had EAGAIN from */ |
| return 1; |
| } |
| |
| r = evdns_request_transmit_to(req, req->ns); |
| switch (r) { |
| case 1: |
| /* temp failure */ |
| req->ns->choked = 1; |
| nameserver_write_waiting(req->ns, 1); |
| return 1; |
| case 2: |
| /* failed in some other way */ |
| retcode = 1; |
| /* fall through */ |
| default: |
| /* all ok */ |
| log(EVDNS_LOG_DEBUG, |
| "Setting timeout for request %lx", (unsigned long) req); |
| if (evtimer_add(&req->timeout_event, &global_timeout) < 0) { |
| log(EVDNS_LOG_WARN, |
| "Error from libevent when adding timer for request %lx", |
| (unsigned long) req); |
| /* ???? Do more? */ |
| } |
| req->tx_count++; |
| req->transmit_me = 0; |
| return retcode; |
| } |
| } |
| |
| static void |
| nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) { |
| struct nameserver *const ns = (struct nameserver *) arg; |
| (void) type; |
| (void) count; |
| (void) ttl; |
| (void) addresses; |
| |
| if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) { |
| /* this is a good reply */ |
| nameserver_up(ns); |
| } else nameserver_probe_failed(ns); |
| } |
| |
| static void |
| nameserver_send_probe(struct nameserver *const ns) { |
| struct request *req; |
| /* here we need to send a probe to a given nameserver */ |
| /* in the hope that it is up now. */ |
| |
| log(EVDNS_LOG_DEBUG, "Sending probe to %s", debug_ntoa(ns->address)); |
| |
| req = request_new(TYPE_A, "www.google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns); |
| if (!req) return; |
| /* we force this into the inflight queue no matter what */ |
| request_trans_id_set(req, transaction_id_pick()); |
| req->ns = ns; |
| request_submit(req); |
| } |
| |
| /* returns: */ |
| /* 0 didn't try to transmit anything */ |
| /* 1 tried to transmit something */ |
| static int |
| evdns_transmit(void) { |
| char did_try_to_transmit = 0; |
| |
| if (req_head) { |
| struct request *const started_at = req_head, *req = req_head; |
| /* first transmit all the requests which are currently waiting */ |
| do { |
| if (req->transmit_me) { |
| did_try_to_transmit = 1; |
| evdns_request_transmit(req); |
| } |
| |
| req = req->next; |
| } while (req != started_at); |
| } |
| |
| return did_try_to_transmit; |
| } |
| |
| /* exported function */ |
| int |
| evdns_count_nameservers(void) |
| { |
| const struct nameserver *server = server_head; |
| int n = 0; |
| if (!server) |
| return 0; |
| do { |
| ++n; |
| server = server->next; |
| } while (server != server_head); |
| return n; |
| } |
| |
| /* exported function */ |
| int |
| evdns_clear_nameservers_and_suspend(void) |
| { |
| struct nameserver *server = server_head, *started_at = server_head; |
| struct request *req = req_head, *req_started_at = req_head; |
| |
| if (!server) |
| return 0; |
| while (1) { |
| struct nameserver *next = server->next; |
| (void) event_del(&server->event); |
| if (evtimer_initialized(&server->timeout_event)) |
| (void) evtimer_del(&server->timeout_event); |
| if (server->socket >= 0) |
| CLOSE_SOCKET(server->socket); |
| free(server); |
| if (next == started_at) |
| break; |
| server = next; |
| } |
| server_head = NULL; |
| global_good_nameservers = 0; |
| |
| while (req) { |
| struct request *next = req->next; |
| req->tx_count = req->reissue_count = 0; |
| req->ns = NULL; |
| /* ???? What to do about searches? */ |
| (void) evtimer_del(&req->timeout_event); |
| req->trans_id = 0; |
| req->transmit_me = 0; |
| |
| global_requests_waiting++; |
| evdns_request_insert(req, &req_waiting_head); |
| /* We want to insert these suspended elements at the front of |
| * the waiting queue, since they were pending before any of |
| * the waiting entries were added. This is a circular list, |
| * so we can just shift the start back by one.*/ |
| req_waiting_head = req_waiting_head->prev; |
| |
| if (next == req_started_at) |
| break; |
| req = next; |
| } |
| req_head = NULL; |
| global_requests_inflight = 0; |
| |
| return 0; |
| } |
| |
| |
| /* exported function */ |
| int |
| evdns_resume(void) |
| { |
| evdns_requests_pump_waiting_queue(); |
| return 0; |
| } |
| |
| static int |
| _evdns_nameserver_add_impl(unsigned long int address, int port) { |
| /* first check to see if we already have this nameserver */ |
| |
| const struct nameserver *server = server_head, *const started_at = server_head; |
| struct nameserver *ns; |
| int err = 0; |
| if (server) { |
| do { |
| if (server->address == address) return 3; |
| server = server->next; |
| } while (server != started_at); |
| } |
| |
| ns = (struct nameserver *) malloc(sizeof(struct nameserver)); |
| if (!ns) return -1; |
| |
| memset(ns, 0, sizeof(struct nameserver)); |
| |
| evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns); |
| |
| ns->socket = socket(PF_INET, SOCK_DGRAM, 0); |
| if (ns->socket < 0) { err = 1; goto out1; } |
| FD_CLOSEONEXEC(ns->socket); |
| evutil_make_socket_nonblocking(ns->socket); |
| |
| ns->address = address; |
| ns->port = htons(port); |
| ns->state = 1; |
| event_set(&ns->event, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns); |
| if (event_add(&ns->event, NULL) < 0) { |
| err = 2; |
| goto out2; |
| } |
| |
| log(EVDNS_LOG_DEBUG, "Added nameserver %s", debug_ntoa(address)); |
| |
| /* insert this nameserver into the list of them */ |
| if (!server_head) { |
| ns->next = ns->prev = ns; |
| server_head = ns; |
| } else { |
| ns->next = server_head->next; |
| ns->prev = server_head; |
| server_head->next = ns; |
| if (server_head->prev == server_head) { |
| server_head->prev = ns; |
| } |
| } |
| |
| global_good_nameservers++; |
| |
| return 0; |
| |
| out2: |
| CLOSE_SOCKET(ns->socket); |
| out1: |
| free(ns); |
| log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", debug_ntoa(address), err); |
| return err; |
| } |
| |
| /* exported function */ |
| int |
| evdns_nameserver_add(unsigned long int address) { |
| return _evdns_nameserver_add_impl(address, 53); |
| } |
| |
| /* exported function */ |
| int |
| evdns_nameserver_ip_add(const char *ip_as_string) { |
| struct in_addr ina; |
| int port; |
| char buf[20]; |
| const char *cp; |
| cp = strchr(ip_as_string, ':'); |
| if (! cp) { |
| cp = ip_as_string; |
| port = 53; |
| } else { |
| port = strtoint(cp+1); |
| if (port < 0 || port > 65535) { |
| return 4; |
| } |
| if ((cp-ip_as_string) >= (int)sizeof(buf)) { |
| return 4; |
| } |
| memcpy(buf, ip_as_string, cp-ip_as_string); |
| buf[cp-ip_as_string] = '\0'; |
| cp = buf; |
| } |
| if (!inet_aton(cp, &ina)) { |
| return 4; |
| } |
| return _evdns_nameserver_add_impl(ina.s_addr, port); |
| } |
| |
| /* insert into the tail of the queue */ |
| static void |
| evdns_request_insert(struct request *req, struct request **head) { |
| if (!*head) { |
| *head = req; |
| req->next = req->prev = req; |
| return; |
| } |
| |
| req->prev = (*head)->prev; |
| req->prev->next = req; |
| req->next = *head; |
| (*head)->prev = req; |
| } |
| |
| static int |
| string_num_dots(const char *s) { |
| int count = 0; |
| while ((s = strchr(s, '.'))) { |
| s++; |
| count++; |
| } |
| return count; |
| } |
| |
| static struct request * |
| request_new(int type, const char *name, int flags, |
| evdns_callback_type callback, void *user_ptr) { |
| const char issuing_now = |
| (global_requests_inflight < global_max_requests_inflight) ? 1 : 0; |
| |
| const int name_len = strlen(name); |
| const int request_max_len = evdns_request_len(name_len); |
| const u16 trans_id = issuing_now ? transaction_id_pick() : 0xffff; |
| /* the request data is alloced in a single block with the header */ |
| struct request *const req = |
| (struct request *) malloc(sizeof(struct request) + request_max_len); |
| int rlen; |
| (void) flags; |
| |
| if (!req) return NULL; |
| memset(req, 0, sizeof(struct request)); |
| |
| evtimer_set(&req->timeout_event, evdns_request_timeout_callback, req); |
| |
| /* request data lives just after the header */ |
| req->request = ((u8 *) req) + sizeof(struct request); |
| /* denotes that the request data shouldn't be free()ed */ |
| req->request_appended = 1; |
| rlen = evdns_request_data_build(name, name_len, trans_id, |
| type, CLASS_INET, req->request, request_max_len); |
| if (rlen < 0) |
| goto err1; |
| req->request_len = rlen; |
| req->trans_id = trans_id; |
| req->tx_count = 0; |
| req->request_type = type; |
| req->user_pointer = user_ptr; |
| req->user_callback = callback; |
| req->ns = issuing_now ? nameserver_pick() : NULL; |
| req->next = req->prev = NULL; |
| |
| return req; |
| err1: |
| free(req); |
| return NULL; |
| } |
| |
| static void |
| request_submit(struct request *const req) { |
| if (req->ns) { |
| /* if it has a nameserver assigned then this is going */ |
| /* straight into the inflight queue */ |
| evdns_request_insert(req, &req_head); |
| global_requests_inflight++; |
| evdns_request_transmit(req); |
| } else { |
| evdns_request_insert(req, &req_waiting_head); |
| global_requests_waiting++; |
| } |
| } |
| |
| /* exported function */ |
| int evdns_resolve_ipv4(const char *name, int flags, |
| evdns_callback_type callback, void *ptr) { |
| log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); |
| if (flags & DNS_QUERY_NO_SEARCH) { |
| struct request *const req = |
| request_new(TYPE_A, name, flags, callback, ptr); |
| if (req == NULL) |
| return (1); |
| request_submit(req); |
| return (0); |
| } else { |
| return (search_request_new(TYPE_A, name, flags, callback, ptr)); |
| } |
| } |
| |
| /* exported function */ |
| int evdns_resolve_ipv6(const char *name, int flags, |
| evdns_callback_type callback, void *ptr) { |
| log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); |
| if (flags & DNS_QUERY_NO_SEARCH) { |
| struct request *const req = |
| request_new(TYPE_AAAA, name, flags, callback, ptr); |
| if (req == NULL) |
| return (1); |
| request_submit(req); |
| return (0); |
| } else { |
| return (search_request_new(TYPE_AAAA, name, flags, callback, ptr)); |
| } |
| } |
| |
| int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { |
| char buf[32]; |
| struct request *req; |
| u32 a; |
| assert(in); |
| a = ntohl(in->s_addr); |
| evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", |
| (int)(u8)((a )&0xff), |
| (int)(u8)((a>>8 )&0xff), |
| (int)(u8)((a>>16)&0xff), |
| (int)(u8)((a>>24)&0xff)); |
| log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); |
| req = request_new(TYPE_PTR, buf, flags, callback, ptr); |
| if (!req) return 1; |
| request_submit(req); |
| return 0; |
| } |
| |
| int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { |
| /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */ |
| char buf[73]; |
| char *cp; |
| struct request *req; |
| int i; |
| assert(in); |
| cp = buf; |
| for (i=15; i >= 0; --i) { |
| u8 byte = in->s6_addr[i]; |
| *cp++ = "0123456789abcdef"[byte & 0x0f]; |
| *cp++ = '.'; |
| *cp++ = "0123456789abcdef"[byte >> 4]; |
| *cp++ = '.'; |
| } |
| assert(cp + strlen("ip6.arpa") < buf+sizeof(buf)); |
| memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1); |
| log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); |
| req = request_new(TYPE_PTR, buf, flags, callback, ptr); |
| if (!req) return 1; |
| request_submit(req); |
| return 0; |
| } |
| |
| /*/////////////////////////////////////////////////////////////////// */ |
| /* Search support */ |
| /* */ |
| /* the libc resolver has support for searching a number of domains */ |
| /* to find a name. If nothing else then it takes the single domain */ |
| /* from the gethostname() call. */ |
| /* */ |
| /* It can also be configured via the domain and search options in a */ |
| /* resolv.conf. */ |
| /* */ |
| /* The ndots option controls how many dots it takes for the resolver */ |
| /* to decide that a name is non-local and so try a raw lookup first. */ |
| |
| struct search_domain { |
| int len; |
| struct search_domain *next; |
| /* the text string is appended to this structure */ |
| }; |
| |
| struct search_state { |
| int refcount; |
| int ndots; |
| int num_domains; |
| struct search_domain *head; |
| }; |
| |
| static struct search_state *global_search_state = NULL; |
| |
| static void |
| search_state_decref(struct search_state *const state) { |
| if (!state) return; |
| state->refcount--; |
| if (!state->refcount) { |
| struct search_domain *next, *dom; |
| for (dom = state->head; dom; dom = next) { |
| next = dom->next; |
| free(dom); |
| } |
| free(state); |
| } |
| } |
| |
| static struct search_state * |
| search_state_new(void) { |
| struct search_state *state = (struct search_state *) malloc(sizeof(struct search_state)); |
| if (!state) return NULL; |
| memset(state, 0, sizeof(struct search_state)); |
| state->refcount = 1; |
| state->ndots = 1; |
| |
| return state; |
| } |
| |
| static void |
| search_postfix_clear(void) { |
| search_state_decref(global_search_state); |
| |
| global_search_state = search_state_new(); |
| } |
| |
| /* exported function */ |
| void |
| evdns_search_clear(void) { |
| search_postfix_clear(); |
| } |
| |
| static void |
| search_postfix_add(const char *domain) { |
| int domain_len; |
| struct search_domain *sdomain; |
| while (domain[0] == '.') domain++; |
| domain_len = strlen(domain); |
| |
| if (!global_search_state) global_search_state = search_state_new(); |
| if (!global_search_state) return; |
| global_search_state->num_domains++; |
| |
| sdomain = (struct search_domain *) malloc(sizeof(struct search_domain) + domain_len); |
| if (!sdomain) return; |
| memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len); |
| sdomain->next = global_search_state->head; |
| sdomain->len = domain_len; |
| |
| global_search_state->head = sdomain; |
| } |
| |
| /* reverse the order of members in the postfix list. This is needed because, */ |
| /* when parsing resolv.conf we push elements in the wrong order */ |
| static void |
| search_reverse(void) { |
| struct search_domain *cur, *prev = NULL, *next; |
| cur = global_search_state->head; |
| while (cur) { |
| next = cur->next; |
| cur->next = prev; |
| prev = cur; |
| cur = next; |
| } |
| |
| global_search_state->head = prev; |
| } |
| |
| /* exported function */ |
| void |
| evdns_search_add(const char *domain) { |
| search_postfix_add(domain); |
| } |
| |
| /* exported function */ |
| void |
| evdns_search_ndots_set(const int ndots) { |
| if (!global_search_state) global_search_state = search_state_new(); |
| if (!global_search_state) return; |
| global_search_state->ndots = ndots; |
| } |
| |
| static void |
| search_set_from_hostname(void) { |
| char hostname[HOST_NAME_MAX + 1], *domainname; |
| |
| search_postfix_clear(); |
| if (gethostname(hostname, sizeof(hostname))) return; |
| domainname = strchr(hostname, '.'); |
| if (!domainname) return; |
| search_postfix_add(domainname); |
| } |
| |
| /* warning: returns malloced string */ |
| static char * |
| search_make_new(const struct search_state *const state, int n, const char *const base_name) { |
| const int base_len = strlen(base_name); |
| const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1; |
| struct search_domain *dom; |
| |
| for (dom = state->head; dom; dom = dom->next) { |
| if (!n--) { |
| /* this is the postfix we want */ |
| /* the actual postfix string is kept at the end of the structure */ |
| const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain); |
| const int postfix_len = dom->len; |
| char *const newname = (char *) malloc(base_len + need_to_append_dot + postfix_len + 1); |
| if (!newname) return NULL; |
| memcpy(newname, base_name, base_len); |
| if (need_to_append_dot) newname[base_len] = '.'; |
| memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len); |
| newname[base_len + need_to_append_dot + postfix_len] = 0; |
| return newname; |
| } |
| } |
| |
| /* we ran off the end of the list and still didn't find the requested string */ |
| abort(); |
| return NULL; /* unreachable; stops warnings in some compilers. */ |
| } |
| |
| static int |
| search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg) { |
| assert(type == TYPE_A || type == TYPE_AAAA); |
| if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) && |
| global_search_state && |
| global_search_state->num_domains) { |
| /* we have some domains to search */ |
| struct request *req; |
| if (string_num_dots(name) >= global_search_state->ndots) { |
| req = request_new(type, name, flags, user_callback, user_arg); |
| if (!req) return 1; |
| req->search_index = -1; |
| } else { |
| char *const new_name = search_make_new(global_search_state, 0, name); |
| if (!new_name) return 1; |
| req = request_new(type, new_name, flags, user_callback, user_arg); |
| free(new_name); |
| if (!req) return 1; |
| req->search_index = 0; |
| } |
| req->search_origname = strdup(name); |
| req->search_state = global_search_state; |
| req->search_flags = flags; |
| global_search_state->refcount++; |
| request_submit(req); |
| return 0; |
| } else { |
| struct request *const req = request_new(type, name, flags, user_callback, user_arg); |
| if (!req) return 1; |
| request_submit(req); |
| return 0; |
| } |
| } |
| |
| /* this is called when a request has failed to find a name. We need to check */ |
| /* if it is part of a search and, if so, try the next name in the list */ |
| /* returns: */ |
| /* 0 another request has been submitted */ |
| /* 1 no more requests needed */ |
| static int |
| search_try_next(struct request *const req) { |
| if (req->search_state) { |
| /* it is part of a search */ |
| char *new_name; |
| struct request *newreq; |
| req->search_index++; |
| if (req->search_index >= req->search_state->num_domains) { |
| /* no more postfixes to try, however we may need to try */ |
| /* this name without a postfix */ |
| if (string_num_dots(req->search_origname) < req->search_state->ndots) { |
| /* yep, we need to try it raw */ |
| newreq = request_new(req->request_type, req->search_origname, req->search_flags, req->user_callback, req->user_pointer); |
| log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", req->search_origname); |
| if (newreq) { |
| request_submit(newreq); |
| return 0; |
| } |
| } |
| return 1; |
| } |
| |
| new_name = search_make_new(req->search_state, req->search_index, req->search_origname); |
| if (!new_name) return 1; |
| log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, req->search_index); |
| newreq = request_new(req->request_type, new_name, req->search_flags, req->user_callback, req->user_pointer); |
| free(new_name); |
| if (!newreq) return 1; |
| newreq->search_origname = req->search_origname; |
| req->search_origname = NULL; |
| newreq->search_state = req->search_state; |
| newreq->search_flags = req->search_flags; |
| newreq->search_index = req->search_index; |
| newreq->search_state->refcount++; |
| request_submit(newreq); |
| return 0; |
| } |
| return 1; |
| } |
| |
| static void |
| search_request_finished(struct request *const req) { |
| if (req->search_state) { |
| search_state_decref(req->search_state); |
| req->search_state = NULL; |
| } |
| if (req->search_origname) { |
| free(req->search_origname); |
| req->search_origname = NULL; |
| } |
| } |
| |
| /*/////////////////////////////////////////////////////////////////// */ |
| /* Parsing resolv.conf files */ |
| |
| static void |
| evdns_resolv_set_defaults(int flags) { |
| /* if the file isn't found then we assume a local resolver */ |
| if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(); |
| if (flags & DNS_OPTION_NAMESERVERS) evdns_nameserver_ip_add("127.0.0.1"); |
| } |
| |
| #ifndef HAVE_STRTOK_R |
| static char * |
| strtok_r(char *s, const char *delim, char **state) { |
| return strtok(s, delim); |
| } |
| #endif |
| |
| /* helper version of atoi which returns -1 on error */ |
| static int |
| strtoint(const char *const str) { |
| char *endptr; |
| const int r = strtol(str, &endptr, 10); |
| if (*endptr) return -1; |
| return r; |
| } |
| |
| /* helper version of atoi that returns -1 on error and clips to bounds. */ |
| static int |
| strtoint_clipped(const char *const str, int min, int max) |
| { |
| int r = strtoint(str); |
| if (r == -1) |
| return r; |
| else if (r<min) |
| return min; |
| else if (r>max) |
| return max; |
| else |
| return r; |
| } |
| |
| /* exported function */ |
| int |
| evdns_set_option(const char *option, const char *val, int flags) |
| { |
| if (!strncmp(option, "ndots:", 6)) { |
| const int ndots = strtoint(val); |
| if (ndots == -1) return -1; |
| if (!(flags & DNS_OPTION_SEARCH)) return 0; |
| log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots); |
| if (!global_search_state) global_search_state = search_state_new(); |
| if (!global_search_state) return -1; |
| global_search_state->ndots = ndots; |
| } else if (!strncmp(option, "timeout:", 8)) { |
| const int timeout = strtoint(val); |
| if (timeout == -1) return -1; |
| if (!(flags & DNS_OPTION_MISC)) return 0; |
| log(EVDNS_LOG_DEBUG, "Setting timeout to %d", timeout); |
| global_timeout.tv_sec = timeout; |
| } else if (!strncmp(option, "max-timeouts:", 12)) { |
| const int maxtimeout = strtoint_clipped(val, 1, 255); |
| if (maxtimeout == -1) return -1; |
| if (!(flags & DNS_OPTION_MISC)) return 0; |
| log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d", |
| maxtimeout); |
| global_max_nameserver_timeout = maxtimeout; |
| } else if (!strncmp(option, "max-inflight:", 13)) { |
| const int maxinflight = strtoint_clipped(val, 1, 65000); |
| if (maxinflight == -1) return -1; |
| if (!(flags & DNS_OPTION_MISC)) return 0; |
| log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d", |
| maxinflight); |
| global_max_requests_inflight = maxinflight; |
| } else if (!strncmp(option, "attempts:", 9)) { |
| int retries = strtoint(val); |
| if (retries == -1) return -1; |
| if (retries > 255) retries = 255; |
| if (!(flags & DNS_OPTION_MISC)) return 0; |
| log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries); |
| global_max_retransmits = retries; |
| } |
| return 0; |
| } |
| |
| static void |
| resolv_conf_parse_line(char *const start, int flags) { |
| char *strtok_state; |
| static const char *const delims = " \t"; |
| #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) |
| |
| char *const first_token = strtok_r(start, delims, &strtok_state); |
| if (!first_token) return; |
| |
| if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) { |
| const char *const nameserver = NEXT_TOKEN; |
| struct in_addr ina; |
| |
| if (nameserver && inet_aton(nameserver, &ina)) { |
| /* address is valid */ |
| evdns_nameserver_add(ina.s_addr); |
| } |
| } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) { |
| const char *const domain = NEXT_TOKEN; |
| if (domain) { |
| search_postfix_clear(); |
| search_postfix_add(domain); |
| } |
| } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) { |
| const char *domain; |
| search_postfix_clear(); |
| |
| while ((domain = NEXT_TOKEN)) { |
| search_postfix_add(domain); |
| } |
| search_reverse(); |
| } else if (!strcmp(first_token, "options")) { |
| const char *option; |
| while ((option = NEXT_TOKEN)) { |
| const char *val = strchr(option, ':'); |
| evdns_set_option(option, val ? val+1 : "", flags); |
| } |
| } |
| #undef NEXT_TOKEN |
| } |
| |
| /* exported function */ |
| /* returns: */ |
| /* 0 no errors */ |
| /* 1 failed to open file */ |
| /* 2 failed to stat file */ |
| /* 3 file too large */ |
| /* 4 out of memory */ |
| /* 5 short read from file */ |
| int |
| evdns_resolv_conf_parse(int flags, const char *const filename) { |
| struct stat st; |
| int fd, n, r; |
| u8 *resolv; |
| char *start; |
| int err = 0; |
| |
| log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename); |
| |
| fd = open(filename, O_RDONLY); |
| if (fd < 0) { |
| evdns_resolv_set_defaults(flags); |
| return 1; |
| } |
| |
| if (fstat(fd, &st)) { err = 2; goto out1; } |
| if (!st.st_size) { |
| evdns_resolv_set_defaults(flags); |
| err = (flags & DNS_OPTION_NAMESERVERS) ? 6 : 0; |
| goto out1; |
| } |
| if (st.st_size > 65535) { err = 3; goto out1; } /* no resolv.conf should be any bigger */ |
| |
| resolv = (u8 *) malloc((size_t)st.st_size + 1); |
| if (!resolv) { err = 4; goto out1; } |
| |
| n = 0; |
| while ((r = read(fd, resolv+n, (size_t)st.st_size-n)) > 0) { |
| n += r; |
| if (n == st.st_size) |
| break; |
| assert(n < st.st_size); |
| } |
| if (r < 0) { err = 5; goto out2; } |
| resolv[n] = 0; /* we malloced an extra byte; this should be fine. */ |
| |
| start = (char *) resolv; |
| for (;;) { |
| char *const newline = strchr(start, '\n'); |
| if (!newline) { |
| resolv_conf_parse_line(start, flags); |
| break; |
| } else { |
| *newline = 0; |
| resolv_conf_parse_line(start, flags); |
| start = newline + 1; |
| } |
| } |
| |
| if (!server_head && (flags & DNS_OPTION_NAMESERVERS)) { |
| /* no nameservers were configured. */ |
| evdns_nameserver_ip_add("127.0.0.1"); |
| err = 6; |
| } |
| if (flags & DNS_OPTION_SEARCH && (!global_search_state || global_search_state->num_domains == 0)) { |
| search_set_from_hostname(); |
| } |
| |
| out2: |
| free(resolv); |
| out1: |
| close(fd); |
| return err; |
| } |
| |
| #ifdef WIN32 |
| /* Add multiple nameservers from a space-or-comma-separated list. */ |
| static int |
| evdns_nameserver_ip_add_line(const char *ips) { |
| const char *addr; |
| char *buf; |
| int r; |
| while (*ips) { |
| while (ISSPACE(*ips) || *ips == ',' || *ips == '\t') |
| ++ips; |
| addr = ips; |
| while (ISDIGIT(*ips) || *ips == '.' || *ips == ':') |
| ++ips; |
| buf = malloc(ips-addr+1); |
| if (!buf) return 4; |
| memcpy(buf, addr, ips-addr); |
| buf[ips-addr] = '\0'; |
| r = evdns_nameserver_ip_add(buf); |
| free(buf); |
| if (r) return r; |
| } |
| return 0; |
| } |
| |
| typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*); |
| |
| /* Use the windows GetNetworkParams interface in iphlpapi.dll to */ |
| /* figure out what our nameservers are. */ |
| static int |
| load_nameservers_with_getnetworkparams(void) |
| { |
| /* Based on MSDN examples and inspection of c-ares code. */ |
| FIXED_INFO *fixed; |
| HMODULE handle = 0; |
| ULONG size = sizeof(FIXED_INFO); |
| void *buf = NULL; |
| int status = 0, r, added_any; |
| IP_ADDR_STRING *ns; |
| GetNetworkParams_fn_t fn; |
| |
| if (!(handle = LoadLibraryA("iphlpapi.dll"))) { |
| log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll"); |
| status = -1; |
| goto done; |
| } |
| if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) { |
| log(EVDNS_LOG_WARN, "Could not get address of function."); |
| status = -1; |
| goto done; |
| } |
| |
| buf = malloc(size); |
| if (!buf) { status = 4; goto done; } |
| fixed = buf; |
| r = fn(fixed, &size); |
| if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) { |
| status = -1; |
| goto done; |
| } |
| if (r != ERROR_SUCCESS) { |
| free(buf); |
| buf = malloc(size); |
| if (!buf) { status = 4; goto done; } |
| fixed = buf; |
| r = fn(fixed, &size); |
| if (r != ERROR_SUCCESS) { |
| log(EVDNS_LOG_DEBUG, "fn() failed."); |
| status = -1; |
| goto done; |
| } |
| } |
| |
| assert(fixed); |
| added_any = 0; |
| ns = &(fixed->DnsServerList); |
| while (ns) { |
| r = evdns_nameserver_ip_add_line(ns->IpAddress.String); |
| if (r) { |
| log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d", |
| (ns->IpAddress.String),(int)GetLastError()); |
| status = r; |
| goto done; |
| } else { |
| log(EVDNS_LOG_DEBUG,"Succesfully added %s as nameserver",ns->IpAddress.String); |
| } |
| |
| added_any++; |
| ns = ns->Next; |
| } |
| |
| if (!added_any) { |
| log(EVDNS_LOG_DEBUG, "No nameservers added."); |
| status = -1; |
| } |
| |
| done: |
| if (buf) |
| free(buf); |
| if (handle) |
| FreeLibrary(handle); |
| return status; |
| } |
| |
| static int |
| config_nameserver_from_reg_key(HKEY key, const char *subkey) |
| { |
| char *buf; |
| DWORD bufsz = 0, type = 0; |
| int status = 0; |
| |
| if (RegQueryValueExA(key, subkey, 0, &type, NULL, &bufsz) |
| != ERROR_MORE_DATA) |
| return -1; |
| if (!(buf = malloc(bufsz))) |
| return -1; |
| |
| if (RegQueryValueExA |