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authorMartin Nagy <mnagy@redhat.com>2010-01-11 18:24:16 +0100
committerStephen Gallagher <sgallagh@redhat.com>2010-01-14 09:00:08 -0500
commit2d53bb82d617be1866762bf3b3c19fc31941b41c (patch)
tree6eb79fe395535b69aa80146549d883a7a1ad09c9 /server
parent815db657bea77807798aebd782cfa69eb73b3b38 (diff)
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Make periodic checks for DNS timeouts
Since we only call c-ares to process input on FD when there is an activity on them, c-ares never gets a chance to react to a timed-out request. This caused SSSD to hang. Fixes: #381
Diffstat (limited to 'server')
-rw-r--r--server/resolv/async_resolv.c83
1 files changed, 82 insertions, 1 deletions
diff --git a/server/resolv/async_resolv.c b/server/resolv/async_resolv.c
index 8455b575..5fd4084b 100644
--- a/server/resolv/async_resolv.c
+++ b/server/resolv/async_resolv.c
@@ -68,13 +68,18 @@ struct resolv_ctx {
struct resolv_ctx *next;
struct tevent_context *ev_ctx;
-
ares_channel channel;
+
/* List of file descriptors that are watched by tevent. */
struct fd_watch *fds;
/* Time in milliseconds before canceling a DNS request */
int timeout;
+
+ /* The timeout watcher periodically calls ares_process_fd() to check
+ * if our pending requests didn't timeout. */
+ int pending_requests;
+ struct tevent_timer *timeout_watcher;
};
struct resolv_ctx *context_list;
@@ -121,6 +126,73 @@ fd_input_available(struct tevent_context *ev, struct tevent_fd *fde,
ares_process_fd(watch->ctx->channel, watch->fd, watch->fd);
}
+static void
+check_fd_timeouts(struct tevent_context *ev, struct tevent_timer *te,
+ struct timeval current_time, void *private_data);
+
+static void
+add_timeout_timer(struct tevent_context *ev, struct resolv_ctx *ctx)
+{
+ struct timeval tv = { 0 };
+ struct timeval *tvp;
+
+ tvp = ares_timeout(ctx->channel, NULL, &tv);
+
+ if (tvp == NULL) {
+ tvp = &tv;
+ }
+
+ /* Enforce a minimum of 1 second. */
+ if (tvp->tv_sec < 1) {
+ tv = tevent_timeval_current_ofs(1, 0);
+ } else {
+ tv = tevent_timeval_current_ofs(tvp->tv_sec, tvp->tv_usec);
+ }
+
+ ctx->timeout_watcher = tevent_add_timer(ev, ctx, tv, check_fd_timeouts,
+ ctx);
+ if (ctx->timeout_watcher == NULL) {
+ DEBUG(1, ("Out of memory\n"));
+ }
+}
+
+static void
+check_fd_timeouts(struct tevent_context *ev, struct tevent_timer *te,
+ struct timeval current_time, void *private_data)
+{
+ struct resolv_ctx *ctx = private_data;
+
+ DEBUG(9, ("Checking for DNS timeouts\n"));
+ ares_process_fd(ctx->channel, ARES_SOCKET_BAD, ARES_SOCKET_BAD);
+ add_timeout_timer(ev, ctx);
+}
+
+static void
+schedule_timeout_watcher(struct tevent_context *ev, struct resolv_ctx *ctx)
+{
+ ctx->pending_requests++;
+ if (ctx->timeout_watcher) {
+ return;
+ }
+
+ DEBUG(9, ("Scheduling DNS timeout watcher\n"));
+ add_timeout_timer(ev, ctx);
+}
+
+static void
+unschedule_timeout_watcher(struct resolv_ctx *ctx)
+{
+ if (ctx->pending_requests <= 0) {
+ DEBUG(1, ("Pending DNS requests mismatch\n"));
+ return;
+ }
+
+ ctx->pending_requests--;
+ if (ctx->pending_requests == 0) {
+ DEBUG(9, ("Unscheduling DNS timeout watcher\n"));
+ talloc_zfree(ctx->timeout_watcher);
+ }
+}
static void fd_event_add(struct resolv_ctx *ctx, int s);
static void fd_event_write(struct resolv_ctx *ctx, int s);
@@ -423,6 +495,7 @@ resolv_gethostbyname_send(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
return NULL;
}
tevent_req_set_callback(subreq, ares_gethostbyname_wakeup, req);
+ schedule_timeout_watcher(ev, ctx);
return req;
}
@@ -440,6 +513,8 @@ resolv_gethostbyname_done(void *arg, int status, int timeouts, struct hostent *h
return;
}
+ unschedule_timeout_watcher(state->resolv_ctx);
+
if (hostent != NULL) {
state->hostent = resolv_copy_hostent(req, hostent);
if (state->hostent == NULL) {
@@ -621,6 +696,7 @@ resolv_getsrv_send(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
return NULL;
}
tevent_req_set_callback(subreq, ares_getsrv_wakeup, req);
+ schedule_timeout_watcher(ev, ctx);
return req;
}
@@ -640,6 +716,8 @@ resolv_getsrv_done(void *arg, int status, int timeouts, unsigned char *abuf, int
return;
}
+ unschedule_timeout_watcher(state->resolv_ctx);
+
state->status = status;
state->timeouts = timeouts;
@@ -821,6 +899,7 @@ resolv_gettxt_send(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
return NULL;
}
tevent_req_set_callback(subreq, ares_gettxt_wakeup, req);
+ schedule_timeout_watcher(ev, ctx);
return req;
}
@@ -840,6 +919,8 @@ resolv_gettxt_done(void *arg, int status, int timeouts, unsigned char *abuf, int
return;
}
+ unschedule_timeout_watcher(state->resolv_ctx);
+
state->status = status;
state->timeouts = timeouts;