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Another try at async DNS - getaddrinfo_a()
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The libevent's evdns seems not ready for serious use:

- proper random req id is available only in 2.0.x
- it does not use random source port for different reqs
- it does not check if req id conflicts with another one
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@markokr
markokr committed Sep 28, 2010
1 parent e414b2a commit b858a5e
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Showing 2 changed files with 195 additions and 59 deletions.
3 changes: 3 additions & 0 deletions configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,9 @@ AC_SEARCH_LIBS(gethostbyname, nsl)
AC_SEARCH_LIBS(hstrerror, resolv)
AC_CHECK_FUNCS(crypt lstat)

AC_SEARCH_LIBS(getaddrinfo_a, anl)
AC_CHECK_FUNCS(getaddrinfo_a)

dnl Find libevent
AC_USUAL_LIBEVENT(1)

Expand Down
251 changes: 192 additions & 59 deletions src/dnslookup.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,19 +19,36 @@
#include "bouncer.h"

/*
* getaddrinfo_a - glibc only
* libevent1 - returns TTL, ignores hosts file.
* libevent2 - does not return TTL, uses hosts file.
*/

/* do we have libevent2? */
#undef HAVE_GETADDRINFO_A

#ifdef HAVE_GETADDRINFO_A

/* getaddrinfo_a */
#include <netdb.h>
#include <signal.h>
#define NEED_GAI_RESULT

#else
#ifdef EV_ET
#define LIBEVENT2
#endif

#ifdef LIBEVENT2
/* libevent 2 */
#include <event2/dns.h>
#define LIBEVENT2
#define addrinfo evutil_addrinfo
#define freeaddrinfo evutil_freeaddrinfo
#define NEED_GAI_RESULT

#else

/* libevent 1 */
#include <evdns.h>

#endif
#endif


Expand Down Expand Up @@ -66,82 +83,121 @@ struct DNSContext {

static void deliver_info(struct DNSRequest *req);

#ifdef NEED_GAI_RESULT
struct addrinfo;
static void got_result_gai(int result, struct addrinfo *res, void *arg);
#endif

#ifdef LIBEVENT2

#ifdef HAVE_GETADDRINFO_A

/*
* ADNS with libevent2 <event2/dns.h>
* ADNS with glibc's getaddrinfo_a()
*/

static void got_result_gai(int result, struct evutil_addrinfo *res, void *arg)
{
struct DNSRequest *req = arg;
struct evutil_addrinfo *ai;
int count = 0;
int af = 0;
int adrlen;
uint8_t *dst;
struct GaiRequest {
struct List node;
struct DNSRequest *req;
struct gaicb gairq;
};

if (result != DNS_ERR_NONE) {
/* lookup failed */
log_warning("lookup failed: %s: result=%d", req->name, result);
goto failed;
}
struct GaiContext {
struct DNSContext *ctx;
struct List gairq_list;
struct event ev;
struct sigevent sev;
};

for (ai = res; ai; ai = ai->ai_next) {
/* pick single family for this address */
if (!af) {
if (ai->ai_family == AF_INET) {
af = ai->ai_family;
req->res_af = af;
adrlen = 4;
} else {
continue;
}
}
if (ai->ai_family != af)
static void dns_signal(int f, short ev, void *arg)
{
struct GaiContext *gctx = arg;
struct List *el, *tmp;
struct GaiRequest *rq;
int e;
list_for_each_safe(el, &gctx->gairq_list, tmp) {
rq = container_of(el, struct GaiRequest, node);
e = gai_error(&rq->gairq);
if (e == EAI_INPROGRESS)
continue;
count++;
}

/* did not found usable entry */
if (!af) {
log_warning("dns(%s): no usable address", req->name);
evutil_freeaddrinfo(res);
goto failed;
/* got one */
list_del(&rq->node);
rq->req->done = true;
got_result_gai(e, rq->gairq.ar_result, rq->req);
free(rq);
}
}

log_noise("dns(%s): got_result_gai: count=%d, adrlen=%d", req->name, count, adrlen);
static bool impl_init(struct DNSContext *ctx)
{
struct GaiContext *gctx = calloc(1, sizeof(*gctx));
if (!gctx)
return false;
list_init(&gctx->gairq_list);
gctx->ctx = ctx;

req->res_pos = 0;
req->done = true;
req->res_count = count;
req->res_list = malloc(adrlen * count);
if (!req->res_list) {
log_warning("req->res_list alloc failed");
goto failed;
}
req->res_ttl = get_cached_time() + cf_dns_max_ttl;
gctx->sev.sigev_notify = SIGEV_SIGNAL;
gctx->sev.sigev_signo = SIGALRM;

dst = req->res_list;
for (ai = res; ai; ai = ai->ai_next) {
struct sockaddr_in *in;
if (ai->ai_family != af)
continue;
in = (void*)ai->ai_addr;
log_noise("dns(%s) result: %s", req->name, inet_ntoa(in->sin_addr));
memcpy(dst, &in->sin_addr, adrlen);
dst += adrlen;
signal_set(&gctx->ev, SIGALRM, dns_signal, gctx);
if (signal_add(&gctx->ev, NULL) < 0) {
free(gctx);
return false;
}
ctx->edns = gctx;
return true;
}

deliver_info(req);
static void impl_launch_query(struct DNSRequest *req)
{
struct GaiContext *gctx = req->ctx->edns;
struct GaiRequest *grq = calloc(1, sizeof(*grq));
int res;
struct gaicb *cb;

grq = calloc(1, sizeof(*grq));
if (!grq)
goto failed2;

list_init(&grq->node);
grq->req = req;
grq->gairq.ar_name = req->name;
list_append(&gctx->gairq_list, &grq->node);

cb = &grq->gairq;
res = getaddrinfo_a(GAI_NOWAIT, &cb, 1, &gctx->sev);
if (res != 0)
goto failed;
return;

failed:
log_warning("dns: getaddrinfo_a(%s)=%d", req->name, res);
list_del(&grq->node);
free(grq);
failed2:
req->done = true;
req->res_af = 0;
req->res_list = NULL;
deliver_info(req);
}

static void impl_release(struct DNSContext *ctx)
{
struct GaiContext *gctx = ctx->edns;
if (gctx) {
signal_del(&gctx->ev);
free(gctx);
ctx->edns = NULL;
}
}

#else /* !HAVE_GETADDRINFO_A */

#ifdef LIBEVENT2

/*
* ADNS with libevent2 <event2/dns.h>
*/

static bool impl_init(struct DNSContext *ctx)
{
ctx->edns = evdns_base_new(NULL, 1);
Expand Down Expand Up @@ -233,6 +289,7 @@ static void impl_release(struct DNSContext *ctx)
evdns_shutdown(0);
}

#endif
#endif

/*
Expand Down Expand Up @@ -300,6 +357,8 @@ static void req_free(struct AANode *node, void *arg)
struct DNSContext *adns_create_context(void)
{
struct DNSContext *ctx = calloc(1, sizeof(*ctx));
if (!ctx)
return NULL;

aatree_init(&ctx->req_tree, req_cmp, req_free);
if (!impl_init(ctx)) {
Expand Down Expand Up @@ -370,4 +429,78 @@ void adns_resolve(struct DNSContext *ctx, const char *name, adns_callback_f cb_f
cb_func(cb_arg, 0, NULL);
}

#ifdef NEED_GAI_RESULT

/* struct addrinfo -> deliver_info() */
static void got_result_gai(int result, struct addrinfo *res, void *arg)
{
struct DNSRequest *req = arg;
struct addrinfo *ai;
int count = 0;
int af = 0;
int adrlen;
uint8_t *dst;

if (result != 0) {
/* lookup failed */
log_warning("lookup failed: %s: result=%d", req->name, result);
goto failed;
}

for (ai = res; ai; ai = ai->ai_next) {
/* pick single family for this address */
if (!af) {
if (ai->ai_family == AF_INET) {
af = ai->ai_family;
req->res_af = af;
adrlen = 4;
} else {
continue;
}
}
if (ai->ai_family != af)
continue;
count++;
}

/* did not found usable entry */
if (!af) {
log_warning("dns(%s): no usable address", req->name);
freeaddrinfo(res);
goto failed;
}

log_noise("dns(%s): got_result_gai: count=%d, adrlen=%d", req->name, count, adrlen);

req->res_pos = 0;
req->done = true;
req->res_count = count;
req->res_list = malloc(adrlen * count);
if (!req->res_list) {
log_warning("req->res_list alloc failed");
goto failed;
}
req->res_ttl = get_cached_time() + cf_dns_max_ttl;

dst = req->res_list;
for (ai = res; ai; ai = ai->ai_next) {
struct sockaddr_in *in;
if (ai->ai_family != af)
continue;
in = (void*)ai->ai_addr;
log_noise("dns(%s) result: %s", req->name, inet_ntoa(in->sin_addr));
memcpy(dst, &in->sin_addr, adrlen);
dst += adrlen;
}

deliver_info(req);
return;
failed:
req->done = true;
req->res_af = 0;
req->res_list = NULL;
deliver_info(req);
}

#endif

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