Fix bug in epoll_ctl() usage causing blocked connections (#41067)

diff --git a/CHANGES b/CHANGES
index 40972636deae6b6dd2d2a0f066d8cea71b84e6b3..c3b045b473650266bf33aa5f68af6206ec57b895 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,10 @@
+4262.  [bug]           Fixed a bug in epoll socket code that caused
+                       sockets to not be registered for ready
+                       notification in some cases, causing named to not
+                       read from or write to them, resulting in what
+                       appear to the user as blocked connections.
+                       [RT #41067]
+
 4261.  [maint]         H.ROOT-SERVERS.NET is 198.97.190.53 and 2001:500:1::53.
                        [RT #40556]
 

diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index ea009134c5ec4dfc8fc60a0bdc24bfd6d531c643..acdb73e234d1834669270a240f6db0d118c17711 100644 (file)
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -424,6 +424,9 @@ struct isc__socketmgr {
        /* Locked by fdlock. */
        isc__socket_t          **fds;
        int                     *fdstate;
+#if defined(USE_EPOLL)
+       uint32_t                *epoll_events;
+#endif
 #ifdef USE_DEVPOLL
        pollinfo_t              *fdpollinfo;
 #endif
@@ -915,15 +918,27 @@ watch_fd(isc__socketmgr_t *manager, int fd, int msg) {
        return (result);
 #elif defined(USE_EPOLL)
        struct epoll_event event;
+       uint32_t oldevents;
+       int ret;
+       int op;
 
+       oldevents = manager->epoll_events[fd];
        if (msg == SELECT_POKE_READ)
-               event.events = EPOLLIN;
+               manager->epoll_events[fd] |= EPOLLIN;
        else
-               event.events = EPOLLOUT;
+               manager->epoll_events[fd] |= EPOLLOUT;
+
+       event.events = manager->epoll_events[fd];
        memset(&event.data, 0, sizeof(event.data));
        event.data.fd = fd;
-       if (epoll_ctl(manager->epoll_fd, EPOLL_CTL_ADD, fd, &event) == -1 &&
-           errno != EEXIST) {
+
+       op = (oldevents == 0U) ? EPOLL_CTL_ADD : EPOLL_CTL_MOD;
+       ret = epoll_ctl(manager->epoll_fd, op, fd, &event);
+       if (ret == -1) {
+               if (errno == EEXIST)
+                       UNEXPECTED_ERROR(__FILE__, __LINE__,
+                                        "epoll_ctl(ADD/MOD) returned "
+                                        "EEXIST for fd %d", fd);
                result = isc__errno2result(errno);
        }
 
@@ -983,15 +998,21 @@ unwatch_fd(isc__socketmgr_t *manager, int fd, int msg) {
        return (result);
 #elif defined(USE_EPOLL)
        struct epoll_event event;
+       int ret;
+       int op;
 
        if (msg == SELECT_POKE_READ)
-               event.events = EPOLLIN;
+               manager->epoll_events[fd] &= ~(EPOLLIN);
        else
-               event.events = EPOLLOUT;
+               manager->epoll_events[fd] &= ~(EPOLLOUT);
+
+       event.events = manager->epoll_events[fd];
        memset(&event.data, 0, sizeof(event.data));
        event.data.fd = fd;
-       if (epoll_ctl(manager->epoll_fd, EPOLL_CTL_DEL, fd, &event) == -1 &&
-           errno != ENOENT) {
+
+       op = (event.events == 0U) ? EPOLL_CTL_DEL : EPOLL_CTL_MOD;
+       ret = epoll_ctl(manager->epoll_fd, op, fd, &event);
+       if (ret == -1 && errno != ENOENT) {
                char strbuf[ISC_STRERRORSIZE];
                isc__strerror(errno, strbuf, sizeof(strbuf));
                UNEXPECTED_ERROR(__FILE__, __LINE__,
@@ -2969,6 +2990,9 @@ socket_create(isc_socketmgr_t *manager0, int pf, isc_sockettype_t type,
        LOCK(&manager->fdlock[lockid]);
        manager->fds[sock->fd] = sock;
        manager->fdstate[sock->fd] = MANAGED;
+#if defined(USE_EPOLL)
+       manager->epoll_events[sock->fd] = 0;
+#endif
 #ifdef USE_DEVPOLL
        INSIST(sock->manager->fdpollinfo[sock->fd].want_read == 0 &&
               sock->manager->fdpollinfo[sock->fd].want_write == 0);
@@ -3045,6 +3069,9 @@ isc__socket_open(isc_socket_t *sock0) {
                LOCK(&sock->manager->fdlock[lockid]);
                sock->manager->fds[sock->fd] = sock;
                sock->manager->fdstate[sock->fd] = MANAGED;
+#if defined(USE_EPOLL)
+               sock->manager->epoll_events[sock->fd] = 0;
+#endif
 #ifdef USE_DEVPOLL
                INSIST(sock->manager->fdpollinfo[sock->fd].want_read == 0 &&
                       sock->manager->fdpollinfo[sock->fd].want_write == 0);
@@ -3105,6 +3132,9 @@ isc__socket_fdwatchcreate(isc_socketmgr_t *manager0, int fd, int flags,
        LOCK(&manager->fdlock[lockid]);
        manager->fds[sock->fd] = sock;
        manager->fdstate[sock->fd] = MANAGED;
+#if defined(USE_EPOLL)
+       manager->epoll_events[sock->fd] = 0;
+#endif
        UNLOCK(&manager->fdlock[lockid]);
 
        LOCK(&manager->lock);
@@ -3667,6 +3697,9 @@ internal_accept(isc_task_t *me, isc_event_t *ev) {
                LOCK(&manager->fdlock[lockid]);
                manager->fds[fd] = NEWCONNSOCK(dev);
                manager->fdstate[fd] = MANAGED;
+#if defined(USE_EPOLL)
+               manager->epoll_events[fd] = 0;
+#endif
                UNLOCK(&manager->fdlock[lockid]);
 
                LOCK(&manager->lock);
@@ -4616,6 +4649,15 @@ isc__socketmgr_create2(isc_mem_t *mctx, isc_socketmgr_t **managerp,
                result = ISC_R_NOMEMORY;
                goto free_manager;
        }
+#if defined(USE_EPOLL)
+       manager->epoll_events = isc_mem_get(mctx, (manager->maxsocks *
+                                                  sizeof(uint32_t)));
+       if (manager->epoll_events == NULL) {
+               result = ISC_R_NOMEMORY;
+               goto free_manager;
+       }
+       memset(manager->epoll_events, 0, manager->maxsocks * sizeof(uint32_t));
+#endif
        manager->stats = NULL;
 
        manager->common.methods = &socketmgrmethods;
@@ -4685,7 +4727,9 @@ isc__socketmgr_create2(isc_mem_t *mctx, isc_socketmgr_t **managerp,
        result = setup_watcher(mctx, manager);
        if (result != ISC_R_SUCCESS)
                goto cleanup;
+
        memset(manager->fdstate, 0, manager->maxsocks * sizeof(int));
+
 #ifdef USE_WATCHER_THREAD
        /*
         * Start up the select/poll thread.
@@ -4734,6 +4778,12 @@ free_manager:
                isc_mem_put(mctx, manager->fdlock,
                            FDLOCK_COUNT * sizeof(isc_mutex_t));
        }
+#if defined(USE_EPOLL)
+       if (manager->epoll_events != NULL) {
+               isc_mem_put(mctx, manager->epoll_events,
+                           manager->maxsocks * sizeof(uint32_t));
+       }
+#endif
        if (manager->fdstate != NULL) {
                isc_mem_put(mctx, manager->fdstate,
                            manager->maxsocks * sizeof(int));
@@ -4847,6 +4897,10 @@ isc__socketmgr_destroy(isc_socketmgr_t **managerp) {
                if (manager->fdstate[i] == CLOSE_PENDING) /* no need to lock */
                        (void)close(i);
 
+#if defined(USE_EPOLL)
+       isc_mem_put(manager->mctx, manager->epoll_events,
+                   manager->maxsocks * sizeof(uint32_t));
+#endif
        isc_mem_put(manager->mctx, manager->fds,
                    manager->maxsocks * sizeof(isc__socket_t *));
        isc_mem_put(manager->mctx, manager->fdstate,