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elemental-ircd/src/res.c

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/*
* A rewrite of Darren Reeds original res.c As there is nothing
* left of Darrens original code, this is now licensed by the hybrid group.
* (Well, some of the function names are the same, and bits of the structs..)
* You can use it where it is useful, free even. Buy us a beer and stuff.
*
* The authors takes no responsibility for any damage or loss
* of property which results from the use of this software.
*
*
* July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
* added callbacks and reference counting of returned hostents.
* --Bleep (Thomas Helvey <tomh@inxpress.net>)
*
* This was all needlessly complicated for irc. Simplified. No more hostent
* All we really care about is the IP -> hostname mappings. Thats all.
*
* Apr 28, 2003 --cryogen and Dianora
*
* DNS server flooding lessened, AAAA-or-A lookup removed, ip6.int support
* removed, various robustness fixes
*
* 2006 --jilles and nenolod
*/
#include "stdinc.h"
#include "ircd_defs.h"
#include "common.h"
#include "ircd.h"
#include "res.h"
#include "reslib.h"
#include "match.h"
#include "numeric.h"
#include "client.h" /* SNO_* */
#if (CHAR_BIT != 8)
#error this code needs to be able to address individual octets
#endif
static PF res_readreply;
#define MAXPACKET 1024 /* rfc sez 512 but we expand names so ... */
#define RES_MAXALIASES 35 /* maximum aliases allowed */
#define RES_MAXADDRS 35 /* maximum addresses allowed */
#define AR_TTL 600 /* TTL in seconds for dns cache entries */
/* RFC 1104/1105 wasn't very helpful about what these fields
* should be named, so for now, we'll just name them this way.
* we probably should look at what named calls them or something.
*/
#define TYPE_SIZE (size_t)2
#define CLASS_SIZE (size_t)2
#define TTL_SIZE (size_t)4
#define RDLENGTH_SIZE (size_t)2
#define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)
struct reslist {
rb_dlink_node node;
int id;
time_t ttl;
char type;
char queryname[IRCD_RES_HOSTLEN + 1]; /* name currently being queried */
char retries; /* retry counter */
char sends; /* number of sends (>1 means resent) */
time_t sentat;
time_t timeout;
unsigned int lastns; /* index of last server sent to */
struct rb_sockaddr_storage addr;
char *name;
struct DNSQuery *query; /* query callback for this request */
};
static rb_fde_t *res_fd;
static rb_dlink_list request_list = { NULL, NULL, 0 };
static int ns_timeout_count[IRCD_MAXNS];
static void rem_request(struct reslist *request);
static struct reslist *make_request(struct DNSQuery *query);
static void do_query_name(struct DNSQuery *query, const char *name, struct reslist *request, int);
static void do_query_number(struct DNSQuery *query, const struct rb_sockaddr_storage *,
struct reslist *request);
static void query_name(struct reslist *request);
static int send_res_msg(const char *buf, int len, int count);
static void resend_query(struct reslist *request);
static int check_question(struct reslist *request, HEADER * header, char *buf, char *eob);
static int proc_answer(struct reslist *request, HEADER * header, char *, char *);
static struct reslist *find_id(int id);
static struct DNSReply *make_dnsreply(struct reslist *request);
/*
* int
* res_ourserver(inp)
* looks up "inp" in irc_nsaddr_list[]
* returns:
* 0 : not found
* >0 : found
* author:
* paul vixie, 29may94
* revised for ircd, cryogen(stu) may03
*/
static int res_ourserver(const struct rb_sockaddr_storage *inp)
{
#ifdef RB_IPV6
const struct sockaddr_in6 *v6;
const struct sockaddr_in6 *v6in = (const struct sockaddr_in6 *)inp;
#endif
const struct sockaddr_in *v4;
const struct sockaddr_in *v4in = (const struct sockaddr_in *)inp;
int ns;
for (ns = 0; ns < irc_nscount; ns++) {
const struct rb_sockaddr_storage *srv = &irc_nsaddr_list[ns];
#ifdef RB_IPV6
v6 = (const struct sockaddr_in6 *)srv;
#endif
v4 = (const struct sockaddr_in *)srv;
/* could probably just memcmp(srv, inp, srv.ss_len) here
* but we'll air on the side of caution - stu
*/
switch (srv->ss_family) {
#ifdef RB_IPV6
case AF_INET6:
if (srv->ss_family == inp->ss_family)
if (v6->sin6_port == v6in->sin6_port)
if ((memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
sizeof(struct in6_addr)) == 0) ||
(memcmp(&v6->sin6_addr.s6_addr, &in6addr_any,
sizeof(struct in6_addr)) == 0)) {
ns_timeout_count[ns] = 0;
return 1;
}
break;
#endif
case AF_INET:
if (srv->ss_family == inp->ss_family)
if (v4->sin_port == v4in->sin_port)
if ((v4->sin_addr.s_addr == INADDR_ANY)
|| (v4->sin_addr.s_addr == v4in->sin_addr.s_addr)) {
ns_timeout_count[ns] = 0;
return 1;
}
break;
default:
break;
}
}
return 0;
}
/*
* timeout_query_list - Remove queries from the list which have been
* there too long without being resolved.
*/
static time_t timeout_query_list(time_t now)
{
rb_dlink_node *ptr;
rb_dlink_node *next_ptr;
struct reslist *request;
time_t next_time = 0;
time_t timeout = 0;
RB_DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head) {
request = ptr->data;
timeout = request->sentat + request->timeout;
if (now >= timeout) {
if (--request->retries <= 0) {
(*request->query->callback) (request->query->ptr, NULL);
rem_request(request);
continue;
} else {
ns_timeout_count[request->lastns]++;
request->sentat = now;
request->timeout += request->timeout;
resend_query(request);
}
}
if ((next_time == 0) || timeout < next_time) {
next_time = timeout;
}
}
return (next_time > now) ? next_time : (now + AR_TTL);
}
/*
* timeout_resolver - check request list
*/
static void timeout_resolver(void *notused)
{
timeout_query_list(rb_current_time());
}
static struct ev_entry *timeout_resolver_ev = NULL;
/*
* start_resolver - do everything we need to read the resolv.conf file
* and initialize the resolver file descriptor if needed
*/
static void start_resolver(void)
{
int i;
irc_res_init();
for (i = 0; i < irc_nscount; i++)
ns_timeout_count[i] = 0;
if (res_fd == NULL) {
if ((res_fd = rb_socket(irc_nsaddr_list[0].ss_family, SOCK_DGRAM, 0,
"UDP resolver socket")) == NULL)
return;
/* At the moment, the resolver FD data is global .. */
rb_setselect(res_fd, RB_SELECT_READ, res_readreply, NULL);
timeout_resolver_ev = rb_event_add("timeout_resolver", timeout_resolver, NULL, 1);
}
}
/*
* init_resolver - initialize resolver and resolver library
*/
void init_resolver(void)
{
#ifdef HAVE_SRAND48
srand48(rb_current_time());
#endif
start_resolver();
}
/*
* restart_resolver - reread resolv.conf, reopen socket
*/
void restart_resolver(void)
{
rb_close(res_fd);
res_fd = NULL;
rb_event_delete(timeout_resolver_ev); /* -ddosen */
start_resolver();
}
/*
* add_local_domain - Add the domain to hostname, if it is missing
* (as suggested by eps@TOASTER.SFSU.EDU)
*/
void add_local_domain(char *hname, size_t size)
{
/* try to fix up unqualified names */
if (strchr(hname, '.') == NULL) {
if (irc_domain[0]) {
size_t len = strlen(hname);
if ((strlen(irc_domain) + len + 2) < size) {
hname[len++] = '.';
strcpy(hname + len, irc_domain);
}
}
}
}
/*
* rem_request - remove a request from the list.
* This must also free any memory that has been allocated for
* temporary storage of DNS results.
*/
static void rem_request(struct reslist *request)
{
rb_dlinkDelete(&request->node, &request_list);
rb_free(request->name);
rb_free(request);
}
/*
* make_request - Create a DNS request record for the server.
*/
static struct reslist *make_request(struct DNSQuery *query)
{
struct reslist *request = rb_malloc(sizeof(struct reslist));
request->sentat = rb_current_time();
request->retries = 3;
request->timeout = 4; /* start at 4 and exponential inc. */
request->query = query;
rb_dlinkAdd(request, &request->node, &request_list);
return request;
}
/*
* delete_resolver_queries - cleanup outstanding queries
* for which there no longer exist clients or conf lines.
*/
void delete_resolver_queries(const struct DNSQuery *query)
{
rb_dlink_node *ptr;
rb_dlink_node *next_ptr;
struct reslist *request;
RB_DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head) {
if ((request = ptr->data) != NULL) {
if (query == request->query)
rem_request(request);
}
}
}
/*
* retryfreq - determine how many queries to wait before resending
* if there have been that many consecutive timeouts
*/
static int retryfreq(int timeouts)
{
switch (timeouts) {
case 1:
return 3;
case 2:
return 9;
case 3:
return 27;
case 4:
return 81;
default:
return 243;
}
}
/*
* send_res_msg - sends msg to a nameserver.
* This should reflect /etc/resolv.conf.
* Returns number of nameserver successfully sent to
* or -1 if no successful sends.
*/
static int send_res_msg(const char *msg, int len, int rcount)
{
int i;
int ns;
static int retrycnt;
retrycnt++;
/* First try a nameserver that seems to work.
* Every once in a while, try a possibly broken one to check
* if it is working again.
*/
for (i = 0; i < irc_nscount; i++) {
ns = (i + rcount - 1) % irc_nscount;
if (ns_timeout_count[ns] && retrycnt % retryfreq(ns_timeout_count[ns]))
continue;
if (sendto(rb_get_fd(res_fd), msg, len, 0,
(struct sockaddr *)&(irc_nsaddr_list[ns]),
GET_SS_LEN(&irc_nsaddr_list[ns])) == len)
return ns;
}
/* No known working nameservers, try some broken one. */
for (i = 0; i < irc_nscount; i++) {
ns = (i + rcount - 1) % irc_nscount;
if (!ns_timeout_count[ns])
continue;
if (sendto(rb_get_fd(res_fd), msg, len, 0,
(struct sockaddr *)&(irc_nsaddr_list[ns]),
GET_SS_LEN(&irc_nsaddr_list[ns])) == len)
return ns;
}
return -1;
}
/*
* find_id - find a dns request id (id is determined by dn_mkquery)
*/
static struct reslist *find_id(int id)
{
rb_dlink_node *ptr;
struct reslist *request;
RB_DLINK_FOREACH(ptr, request_list.head) {
request = ptr->data;
if (request->id == id)
return (request);
}
return (NULL);
}
/*
* gethost_byname_type - get host address from name
*
*/
void gethost_byname_type(const char *name, struct DNSQuery *query, int type)
{
assert(name != 0);
do_query_name(query, name, NULL, type);
}
/*
* gethost_byaddr - get host name from address
*/
void gethost_byaddr(const struct rb_sockaddr_storage *addr, struct DNSQuery *query)
{
do_query_number(query, addr, NULL);
}
/*
* do_query_name - nameserver lookup name
*/
static void do_query_name(struct DNSQuery *query, const char *name, struct reslist *request,
int type)
{
char host_name[IRCD_RES_HOSTLEN + 1];
rb_strlcpy(host_name, name, IRCD_RES_HOSTLEN + 1);
add_local_domain(host_name, IRCD_RES_HOSTLEN);
if (request == NULL) {
request = make_request(query);
request->name = (char *)rb_malloc(strlen(host_name) + 1);
strcpy(request->name, host_name);
}
rb_strlcpy(request->queryname, host_name, sizeof(request->queryname));
request->type = type;
query_name(request);
}
/*
* do_query_number - Use this to do reverse IP# lookups.
*/
static void do_query_number(struct DNSQuery *query, const struct rb_sockaddr_storage *addr,
struct reslist *request)
{
const unsigned char *cp;
if (request == NULL) {
request = make_request(query);
memcpy(&request->addr, addr, sizeof(struct rb_sockaddr_storage));
request->name = (char *)rb_malloc(IRCD_RES_HOSTLEN + 1);
}
if (addr->ss_family == AF_INET) {
const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr;
cp = (const unsigned char *)&v4->sin_addr.s_addr;
sprintf(request->queryname, "%u.%u.%u.%u.in-addr.arpa", (unsigned int)(cp[3]),
(unsigned int)(cp[2]), (unsigned int)(cp[1]), (unsigned int)(cp[0]));
}
#ifdef RB_IPV6
else if (addr->ss_family == AF_INET6) {
const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr;
cp = (const unsigned char *)&v6->sin6_addr.s6_addr;
(void)sprintf(request->queryname, "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa",
(unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
(unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
(unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
(unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
(unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
(unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
(unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
(unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
(unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
(unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
(unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
(unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
(unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
(unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
(unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
(unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
}
#endif
request->type = T_PTR;
query_name(request);
}
/*
* query_name - generate a query based on class, type and name.
*/
static void query_name(struct reslist *request)
{
char buf[MAXPACKET];
int request_len = 0;
int ns;
memset(buf, 0, sizeof(buf));
if ((request_len =
irc_res_mkquery(request->queryname, C_IN, request->type, (unsigned char *)buf, sizeof(buf))) > 0) {
HEADER *header = (HEADER *) buf;
#ifndef HAVE_LRAND48
int k = 0;
struct timeval tv;
#endif
/*
* generate an unique id
* NOTE: we don't have to worry about converting this to and from
* network byte order, the nameserver does not interpret this value
* and returns it unchanged
*/
#ifdef HAVE_LRAND48
do {
header->id = (header->id + lrand48()) & 0xffff;
} while (find_id(header->id));
#else
gettimeofday(&tv, NULL);
do {
header->id = (header->id + k + tv.tv_usec) & 0xffff;
k++;
} while (find_id(header->id));
#endif /* HAVE_LRAND48 */
request->id = header->id;
++request->sends;
ns = send_res_msg(buf, request_len, request->sends);
if (ns != -1)
request->lastns = ns;
}
}
static void resend_query(struct reslist *request)
{
switch (request->type) {
case T_PTR:
do_query_number(NULL, &request->addr, request);
break;
case T_A:
#ifdef RB_IPV6
case T_AAAA:
#endif
do_query_name(NULL, request->name, request, request->type);
break;
default:
break;
}
}
/*
* check_question - check if the reply really belongs to the
* name we queried (to guard against late replies from previous
* queries with the same id).
*/
static int check_question(struct reslist *request, HEADER * header, char *buf, char *eob)
{
char hostbuf[IRCD_RES_HOSTLEN + 1]; /* working buffer */
unsigned char *current; /* current position in buf */
int n; /* temp count */
current = (unsigned char *)buf + sizeof(HEADER);
if (header->qdcount != 1)
return 0;
n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf,
sizeof(hostbuf));
if (n <= 0)
return 0;
if (strcasecmp(hostbuf, request->queryname))
return 0;
return 1;
}
/*
* proc_answer - process name server reply
*/
static int proc_answer(struct reslist *request, HEADER * header, char *buf, char *eob)
{
char hostbuf[IRCD_RES_HOSTLEN + 100]; /* working buffer */
unsigned char *current; /* current position in buf */
int query_class; /* answer class */
int type; /* answer type */
int n; /* temp count */
int rd_length;
struct sockaddr_in *v4; /* conversion */
#ifdef RB_IPV6
struct sockaddr_in6 *v6;
#endif
current = (unsigned char *)buf + sizeof(HEADER);
for (; header->qdcount > 0; --header->qdcount) {
if ((n = irc_dn_skipname(current, (unsigned char *)eob)) < 0)
return 0;
current += (size_t) n + QFIXEDSZ;
}
/*
* process each answer sent to us blech.
*/
while (header->ancount > 0 && (char *)current < eob) {
header->ancount--;
n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf,
sizeof(hostbuf));
if (n < 0) {
/*
* broken message
*/
return (0);
} else if (n == 0) {
/*
* no more answers left
*/
return (0);
}
hostbuf[IRCD_RES_HOSTLEN] = '\0';
/* With Address arithmetic you have to be very anal
* this code was not working on alpha due to that
* (spotted by rodder/jailbird/dianora)
*/
current += (size_t) n;
if (!(((char *)current + ANSWER_FIXED_SIZE) < eob))
break;
type = irc_ns_get16(current);
current += TYPE_SIZE;
query_class = irc_ns_get16(current);
current += CLASS_SIZE;
request->ttl = irc_ns_get32(current);
current += TTL_SIZE;
rd_length = irc_ns_get16(current);
current += RDLENGTH_SIZE;
/*
* Wait to set request->type until we verify this structure
*/
switch (type) {
case T_A:
if (request->type != T_A)
return (0);
/*
* check for invalid rd_length or too many addresses
*/
if (rd_length != sizeof(struct in_addr))
return (0);
v4 = (struct sockaddr_in *)&request->addr;
SET_SS_LEN(&request->addr, sizeof(struct sockaddr_in));
v4->sin_family = AF_INET;
memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
return (1);
break;
#ifdef RB_IPV6
case T_AAAA:
if (request->type != T_AAAA)
return (0);
if (rd_length != sizeof(struct in6_addr))
return (0);
SET_SS_LEN(&request->addr, sizeof(struct sockaddr_in6));
v6 = (struct sockaddr_in6 *)&request->addr;
v6->sin6_family = AF_INET6;
memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
return (1);
break;
#endif
case T_PTR:
if (request->type != T_PTR)
return (0);
n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current,
hostbuf, sizeof(hostbuf));
if (n < 0)
return (0); /* broken message */
else if (n == 0)
return (0); /* no more answers left */
rb_strlcpy(request->name, hostbuf, IRCD_RES_HOSTLEN + 1);
return (1);
break;
case T_CNAME:
/* real answer will follow */
current += rd_length;
break;
default:
/* XXX I'd rather just throw away the entire bogus thing
* but its possible its just a broken nameserver with still
* valid answers. But lets do some rudimentary logging for now...
*/
ilog(L_MAIN, "irc_res.c bogus type %d", type);
break;
}
}
return (1);
}
/*
* res_read_single_reply - read a dns reply from the nameserver and process it.
* Return value: 1 if a packet was read, 0 otherwise
*/
static int res_read_single_reply(rb_fde_t *F, void *data)
{
char buf[sizeof(HEADER) + MAXPACKET]
/* Sparc and alpha need 16bit-alignment for accessing header->id
* (which is uint16_t). Because of the header = (HEADER*) buf;
* lateron, this is neeeded. --FaUl
*/
#if defined(__sparc__) || defined(__alpha__)
__attribute__ ((aligned(16)))
#endif
;
HEADER *header;
struct reslist *request = NULL;
struct DNSReply *reply = NULL;
int rc;
int answer_count;
socklen_t len = sizeof(struct rb_sockaddr_storage);
struct rb_sockaddr_storage lsin;
rc = recvfrom(rb_get_fd(F), buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len);
/* No packet */
if (rc == 0 || rc == -1)
return 0;
/* Too small */
if (rc <= (int)(sizeof(HEADER)))
return 1;
/*
* convert DNS reply reader from Network byte order to CPU byte order.
*/
header = (HEADER *) buf;
header->ancount = ntohs(header->ancount);
header->qdcount = ntohs(header->qdcount);
header->nscount = ntohs(header->nscount);
header->arcount = ntohs(header->arcount);
/*
* response for an id which we have already received an answer for
* just ignore this response.
*/
if (0 == (request = find_id(header->id)))
return 1;
/*
* check against possibly fake replies
*/
if (!res_ourserver(&lsin))
return 1;
if (!check_question(request, header, buf, buf + rc))
return 1;
if ((header->rcode != NO_ERRORS) || (header->ancount == 0)) {
if (NXDOMAIN == header->rcode) {
(*request->query->callback) (request->query->ptr, NULL);
rem_request(request);
} else {
/*
* If a bad error was returned, we stop here and dont send
* send any more (no retries granted).
*/
(*request->query->callback) (request->query->ptr, NULL);
rem_request(request);
}
return 1;
}
/*
* If this fails there was an error decoding the received packet,
* give up. -- jilles
*/
answer_count = proc_answer(request, header, buf, buf + rc);
if (answer_count) {
if (request->type == T_PTR) {
if (request->name == NULL) {
/*
* got a PTR response with no name, something bogus is happening
* don't bother trying again, the client address doesn't resolve
*/
(*request->query->callback) (request->query->ptr, reply);
rem_request(request);
return 1;
}
/*
* Lookup the 'authoritative' name that we were given for the
* ip#.
*
*/
#ifdef RB_IPV6
if (request->addr.ss_family == AF_INET6)
gethost_byname_type(request->name, request->query, T_AAAA);
else
#endif
gethost_byname_type(request->name, request->query, T_A);
rem_request(request);
} else {
/*
* got a name and address response, client resolved
*/
reply = make_dnsreply(request);
(*request->query->callback) (request->query->ptr, reply);
rb_free(reply);
rem_request(request);
}
} else {
/* couldn't decode, give up -- jilles */
(*request->query->callback) (request->query->ptr, NULL);
rem_request(request);
}
return 1;
}
static void res_readreply(rb_fde_t *F, void *data)
{
while (res_read_single_reply(F, data))
;
rb_setselect(F, RB_SELECT_READ, res_readreply, NULL);
}
static struct DNSReply *make_dnsreply(struct reslist *request)
{
struct DNSReply *cp;
s_assert(request != 0);
cp = (struct DNSReply *)rb_malloc(sizeof(struct DNSReply));
cp->h_name = request->name;
memcpy(&cp->addr, &request->addr, sizeof(cp->addr));
return (cp);
}
void report_dns_servers(struct Client *source_p)
{
int i;
char ipaddr[128];
for (i = 0; i < irc_nscount; i++) {
if (!rb_inet_ntop_sock((struct sockaddr *)&(irc_nsaddr_list[i]),
ipaddr, sizeof ipaddr))
rb_strlcpy(ipaddr, "?", sizeof ipaddr);
sendto_one_numeric(source_p, RPL_STATSDEBUG,
"A %s %d", ipaddr, ns_timeout_count[i]);
}
}
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