Add the notion of 'idling' a session when we get a response

A session is 'busy' when a request has been sent, and the
response not yet received.  As soon as the response is received,
the session re-enters the 'idle' state (and any associated read
timeouts can be cleared).

We also clear timeouts when a session enters connected state,
but only if we hadn't pre-queued the first request.

libtac/include/libtac.h

@@ -161,6 +161,7 @@ struct tac_session {
     uint32_t tac_session_id;
     bool tac_encryption;
     bool tac_multiplex;
+    bool tac_idle;			/* not exposed via API */
     uint8_t tac_priv_lvl;
     uint8_t tac_authen_method;
     uint8_t tac_authen_service;

libtac/lib/session.c

@@ -37,6 +37,7 @@ tac_session_alloc_extra(unsigned n)
     sess->tac_secret = NULL;
     sess->tac_session_id = magic();
     sess->tac_encryption = sess->tac_multiplex = false;
+    sess->tac_idle = true;
     sess->tac_priv_lvl = TAC_PLUS_PRIV_LVL_MIN;
     sess->tac_authen_service = TAC_PLUS_AUTHEN_SVC_PPP;
     sess->tac_authen_method = TAC_PLUS_AUTHEN_METH_TACACSPLUS;

libtac/lib/wrappers.c

@@ -144,8 +144,14 @@ static void eventcb(struct bufferevent *bev, short events, void *ptr)
     if (sess->oob_cb) {
         if (events & BEV_EVENT_CONNECTED) {
                 TACDEBUG(LOG_DEBUG, "session %p connected", sess);
-		/* change for setup timeout to read/write timeout values */
-		tac_session_reset_timeouts(sess, true);
+		/*
+		 * if we had enqueued a request before the connect
+		 * completed, then the idle flag would be false
+		 * and we would want to reset the timer; if we didn't
+		 * have a request on-the-wire, then the timeout gets
+		 * cleared once we're connected.
+		 */
+		tac_session_reset_timeouts(sess, !sess->tac_idle);
 		(sess->oob_cb)(sess, &sess->context, CONNECTED);
         }
         if (events & BEV_EVENT_ERROR) {
@@ -241,6 +247,9 @@ static void readcb(struct bufferevent *bev, void *ptr)
     /* turn off timeouts */
     tac_session_reset_timeouts(sess, false);
 
+    /* received response, so connection is idle again */
+    sess->tac_idle = true;
+
     tac_parse_pkt(sess, ctx, pkt, ((i > 0) ? i : 0));
 
     free(pkt);
@@ -328,6 +337,9 @@ tac_authen_send_ev(struct tac_session *sess,
     ret = bufferevent_write_buffer(sess->bufev, evbuf);
     evbuffer_free(evbuf);
 
+    /* we have a request on-the-wire */
+    sess->tac_idle = false;
+
     TACDEBUG(LOG_DEBUG, "session %p: write status=%d", sess, ret);
 
     return (ret == 0);
@@ -367,6 +379,9 @@ tac_author_send_ev(struct tac_session *sess,
     ret = bufferevent_write_buffer(sess->bufev, evbuf);
     evbuffer_free(evbuf);
 
+    /* we have a request on-the-wire */
+    sess->tac_idle = false;
+
     TACDEBUG(LOG_DEBUG, "session %p write status=%d", sess, ret);
 
     return (ret == 0);
@@ -406,6 +421,9 @@ tac_acct_send_ev(struct tac_session *sess,
     ret = bufferevent_write_buffer(sess->bufev, evbuf);
     evbuffer_free(evbuf);
 
+    /* we have a request on-the-wire */
+    sess->tac_idle = false;
+
     TACDEBUG(LOG_DEBUG, "session %p write status=%d", sess, ret);
 
     return (ret == 0);
@@ -442,6 +460,9 @@ tac_cont_send_ev(struct tac_session *sess, const char *pass) {
     ret = bufferevent_write_buffer(sess->bufev, evbuf);
     evbuffer_free(evbuf);
 
+    /* we have a request on-the-wire */
+    sess->tac_idle = false;
+
     TACDEBUG(LOG_DEBUG, "session %p write status=%d", sess, ret);
 
     return (ret == 0);