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Diffstat (limited to 'evdns.c')
| -rw-r--r-- | evdns.c | 3117 |
1 files changed, 3117 insertions, 0 deletions
@@ -0,0 +1,3117 @@ +/* $Id: evdns.c,v 1.18 2007-11-06 17:20:42 root Exp $ */ + +/* 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 WIN32 +#ifndef EV_STANDALONE +#include "misc.h" +#endif +#endif + +/* #define NDEBUG */ + +#ifndef DNS_USE_CPU_CLOCK_FOR_ID +#ifndef DNS_USE_GETTIMEOFDAY_FOR_ID +#ifndef DNS_USE_OPENSSL_FOR_ID +#error Must configure at least one id generation method. +#error Please see the documentation. +#endif +#endif +#endif + +/* #define _POSIX_C_SOURCE 200507 */ +#define _GNU_SOURCE + +#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 + +#define _FORTIFY_SOURCE 3 + +#include <string.h> +#include <fcntl.h> +#include <sys/time.h> +#ifdef HAVE_STDINT_H +#include <stdint.h> +#endif +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <assert.h> +#include <unistd.h> +#include <limits.h> +#include <sys/stat.h> +#include <ctype.h> +#include <stdio.h> +#include <stdarg.h> + +#include "evdns.h" +#ifdef WIN32 +#include <windows.h> +#include <winsock2.h> +#include <iphlpapi.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 + +#ifdef WIN32 +typedef int socklen_t; +#endif + +#define EVDNS_LOG_DEBUG 0 +#define EVDNS_LOG_WARN 1 + +#ifndef HOST_NAME_MAX +#define HOST_NAME_MAX 255 +#endif + +#ifndef NDEBUG +#include <stdio.h> +#endif + +#undef MIN +#define MIN(a,b) ((a)<(b)?(a):(b)) + +#ifdef __USE_ISOC99B +/* libevent doesn't work without this */ +typedef uint8_t u_char; +typedef unsigned int uint; +#endif +#include <event.h> + +#define u64 uint64_t +#define u32 uint32_t +#define u16 uint16_t +#define u8 uint8_t + +#define MAX_ADDRS 4 /* 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 + +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; + 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 *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) +{ + 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; +} +#define CLOSE_SOCKET(x) closesocket(x) +#else +#define last_error(sock) (errno) +#define error_is_eagain(err) ((err) == EAGAIN) +#define CLOSE_SOCKET(x) close(x) +#endif + +#define ISSPACE(c) isspace((int)(unsigned char)(c)) +#define ISDIGIT(c) isdigit((int)(unsigned char)(c)) + +#ifndef NDEBUG +static const char * +debug_ntoa(u32 address) +{ + static char buf[32]; + u32 a = ntohl(address); + 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; +} +#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 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); +#ifdef WIN32 + _vsnprintf(buf, sizeof(buf), fmt, args); +#else + vsnprintf(buf, sizeof(buf), fmt, args); +#endif + 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++; + + evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns); + 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; + + evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns); + 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]; + 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; /* index into packet */ + u16 _t; /* used by the macros */ + u32 _t32; /* used by the macros */ + char tmp_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); + + 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> + */ + SKIP_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. */ + if (flags & 0x7800) return -1; /* only standard queries are supported */ + flags &= 0x0300; /* Only TC and RD 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->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++; + 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 +} + +/* Try to choose a strong transaction id which isn't already in flight */ +static u16 +transaction_id_pick(void) { + for (;;) { + const struct request *req = req_head, *started_at; +#ifdef DNS_USE_CPU_CLOCK_FOR_ID + struct timespec ts; + u16 trans_id; +#ifdef CLOCK_MONOTONIC + if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1) +#else + if (clock_gettime(CLOCK_REALTIME, &ts) == -1) +#endif + event_err(1, "clock_gettime"); + trans_id = ts.tv_nsec & 0xffff; +#endif + +#ifdef DNS_USE_GETTIMEOFDAY_FOR_ID + struct timeval tv; + u16 trans_id; + gettimeofday(&tv, NULL); + trans_id = tv.tv_usec & 0xffff; +#endif + +#ifdef DNS_USE_OPENSSL_FOR_ID + u16 trans_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; + gettimeofday(&tv, NULL); + trans_id = tv.tv_usec & 0xffff; */ + abort(); + } +#endif + + if (trans_id == 0xffff) continue; + /* now check to see if that id is already inflight */ + req = started_at = req_head; + if (req) { + do { + if (req->trans_id == trans_id) break; + req = req->next; + } while (req != started_at); + } + /* we didn't find it, so this is a good id */ + if (req == started_at) 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; + } + } +} + +/* this is called when a namesever socket is ready for reading */ +static void +nameserver_read(struct nameserver *ns) { + u8 packet[1500]; + + for (;;) { + const int r = recv(ns->socket, packet, sizeof(packet), 0); + if (r < 0) { + int err = last_error(ns->socket); + if (error_is_eagain(err)) return; + nameserver_failed(ns, strerror(err)); + 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->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); + 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_A, 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]->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->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( (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[3] |= 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 err = last_error(port->socket); + if (! error_is_eagain(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) { + const int r = send(server->socket, req->request, req->request_len, 0); + 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); + evtimer_set(&req->timeout_event, evdns_request_timeout_callback, 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); + (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; + struct sockaddr_in sin; + 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)); + + ns->socket = socket(PF_INET, SOCK_DGRAM, 0); + if (ns->socket < 0) { err = 1; goto out1; } +#ifdef WIN32 + { + u_long nonblocking = 1; + ioctlsocket(ns->socket, FIONBIO, &nonblocking); + } +#else + fcntl(ns->socket, F_SETFL, O_NONBLOCK); +#endif + sin.sin_addr.s_addr = address; + sin.sin_port = htons(port); + sin.sin_family = AF_INET; + if (connect(ns->socket, (struct sockaddr *) &sin, sizeof(sin)) != 0) { + err = 2; + goto out2; + } + + ns->address = address; + 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)); + + /* 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(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); + 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(struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { + char buf[96]; + 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 */ + struct request *const 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 (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 = LoadLibrary("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 (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz) + != ERROR_MORE_DATA) + return -1; + if (!(buf = malloc(bufsz))) + return -1; + + if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz) + == ERROR_SUCCESS && bufsz > 1) { + status = evdns_nameserver_ip_add_line(buf); + } + + free(buf); + return status; +} + +#define SERVICES_KEY "System\\CurrentControlSet\\Services\\" +#define WIN_NS_9X_KEY SERVICES_KEY "VxD\\MSTCP" +#define WIN_NS_NT_KEY SERVICES_KEY "Tcpip\\Parameters" + +static int +load_nameservers_from_registry(void) +{ + int found = 0; + int r; +#define TRY(k, name) \ + if (!found && config_nameserver_from_reg_key(k,name) == 0) { \ + log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \ + found = 1; \ + } else if (!found) { \ + log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \ + #k,#name); \ + } + + if (((int)GetVersion()) > 0) { /* NT */ + HKEY nt_key = 0, interfaces_key = 0; + + if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, + KEY_READ, &nt_key) != ERROR_SUCCESS) { + log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError()); + return -1; + } + r = RegOpenKeyEx(nt_key, "Interfaces", 0, + KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, + &interfaces_key); + if (r != ERROR_SUCCESS) { + log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError()); + return -1; + } + TRY(nt_key, "NameServer"); + TRY(nt_key, "DhcpNameServer"); + TRY(interfaces_key, "NameServer"); + TRY(interfaces_key, "DhcpNameServer"); + RegCloseKey(interfaces_key); + RegCloseKey(nt_key); + } else { + HKEY win_key = 0; + if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0, + KEY_READ, &win_key) != ERROR_SUCCESS) { + log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError()); + return -1; + } + TRY(win_key, "NameServer"); + RegCloseKey(win_key); + } + + if (found == 0) { + log(EVDNS_LOG_WARN,"Didn't find any nameservers."); + } + + return found ? 0 : -1; +#undef TRY +} + +int +evdns_config_windows_nameservers(void) +{ + if (load_nameservers_with_getnetworkparams() == 0) + return 0; + return load_nameservers_from_registry(); +} +#endif + +int +evdns_init(void) +{ + int res = 0; +#ifdef WIN32 + evdns_config_windows_nameservers(); +#else + res = evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf"); +#endif + + return (res); +} + +const char * +evdns_err_to_string(int err) +{ + switch (err) { + case DNS_ERR_NONE: return "no error"; + case DNS_ERR_FORMAT: return "misformatted query"; + case DNS_ERR_SERVERFAILED: return "server failed"; + case DNS_ERR_NOTEXIST: return "name does not exist"; + case DNS_ERR_NOTIMPL: return "query not implemented"; + case DNS_ERR_REFUSED: return "refused"; + + case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed"; + case DNS_ERR_UNKNOWN: return "unknown"; + case DNS_ERR_TIMEOUT: return "request timed out"; + case DNS_ERR_SHUTDOWN: return "dns subsystem shut down"; + default: return "[Unknown error code]"; + } +} + +void +evdns_shutdown(int fail_requests) +{ + struct nameserver *server, *server_next; + struct search_domain *dom, *dom_next; + + while (req_head) { + if (fail_requests) + reply_callback(req_head, 0, DNS_ERR_SHUTDOWN, NULL); + request_finished(req_head, &req_head); + } + while (req_waiting_head) { + if (fail_requests) + reply_callback(req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL); + request_finished(req_waiting_head, &req_waiting_head); + } + global_requests_inflight = global_requests_waiting = 0; + + for (server = server_head; server; server = server_next) { + server_next = server->next; + if (server->socket >= 0) + CLOSE_SOCKET(server->socket); + (void) event_del(&server->event); + if (server->state == 0) + (void) event_del(&server->timeout_event); + free(server); + if (server_next == server_head) + break; + } + server_head = NULL; + global_good_nameservers = 0; + + if (global_search_state) { + for (dom = global_search_state->head; dom; dom = dom_next) { + dom_next = dom->next; + free(dom); + } + free(global_search_state); + global_search_state = NULL; + } + evdns_log_fn = NULL; +} + +#ifdef EVDNS_MAIN +void +main_callback(int result, char type, int count, int ttl, + void *addrs, void *orig) { + char *n = (char*)orig; + int i; + for (i = 0; i < count; ++i) { + if (type == DNS_IPv4_A) { + printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i])); + } else if (type == DNS_PTR) { + printf("%s: %s\n", n, ((char**)addrs)[i]); + } + } + if (!count) { + printf("%s: No answer (%d)\n", n, result); + } + fflush(stdout); +} +void +evdns_server_callback(struct evdns_server_request *req, void *data) +{ + int i, r; + (void)data; + /* dummy; give 192.168.11.11 as an answer for all A questions, + * give foo.bar.example.com as an answer for all PTR questions. */ + for (i = 0; i < req->nquestions; ++i) { + u32 ans = htonl(0xc0a80b0bUL); + if (req->questions[i]->type == EVDNS_TYPE_A && + req->questions[i]->class == EVDNS_CLASS_INET) { + printf(" -- replying for %s (A)\n", req->questions[i]->name); + r = evdns_server_request_add_a_reply(req, req->questions[i]->name, + 1, &ans, 10); + if (r<0) + printf("eeep, didn't work.\n"); + } else if (req->questions[i]->type == EVDNS_TYPE_PTR && + req->questions[i]->class == EVDNS_CLASS_INET) { + printf(" -- replying for %s (PTR)\n", req->questions[i]->name); + r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name, + "foo.bar.example.com", 10); + } else { + printf(" -- skipping %s [%d %d]\n", req->questions[i]->name, + req->questions[i]->type, req->questions[i]->class); + } + } + + r = evdns_request_respond(req, 0); + if (r<0) + printf("eeek, couldn't send reply.\n"); +} + +void +logfn(int is_warn, const char *msg) { + (void) is_warn; + fprintf(stderr, "%s\n", msg); +} +int +main(int c, char **v) { + int idx; + int reverse = 0, verbose = 1, servertest = 0; + if (c<2) { + fprintf(stderr, "syntax: %s [-x] [-v] hostname\n", v[0]); + fprintf(stderr, "syntax: %s [-servertest]\n", v[0]); + return 1; + } + idx = 1; + while (idx < c && v[idx][0] == '-') { + if (!strcmp(v[idx], "-x")) + reverse = 1; + else if (!strcmp(v[idx], "-v")) + verbose = 1; + else if (!strcmp(v[idx], "-servertest")) + servertest = 1; + else + fprintf(stderr, "Unknown option %s\n", v[idx]); + ++idx; + } + event_init(); + if (verbose) + evdns_set_log_fn(logfn); + evdns_resolv_conf_parse(DNS_OPTION_NAMESERVERS, "/etc/resolv.conf"); + if (servertest) { + int sock; + struct sockaddr_in my_addr; + sock = socket(PF_INET, SOCK_DGRAM, 0); + fcntl(sock, F_SETFL, O_NONBLOCK); + my_addr.sin_family = AF_INET; + my_addr.sin_port = htons(10053); + my_addr.sin_addr.s_addr = INADDR_ANY; + if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) { + perror("bind"); + exit(1); + } + evdns_add_server_port(sock, 0, evdns_server_callback, NULL); + } + for (; idx < c; ++idx) { + if (reverse) { + struct in_addr addr; + if (!inet_aton(v[idx], &addr)) { + fprintf(stderr, "Skipping non-IP %s\n", v[idx]); + continue; + } + fprintf(stderr, "resolving %s...\n",v[idx]); + evdns_resolve_reverse(&addr, 0, main_callback, v[idx]); + } else { + fprintf(stderr, "resolving (fwd) %s...\n",v[idx]); + evdns_resolve_ipv4(v[idx], 0, main_callback, v[idx]); + } + } + fflush(stdout); + event_dispatch(); + return 0; +} +#endif |