Dynamically expand timeout when TCP connects

Wait ten seconds for a TCP connection to succeed or fail before moving
on.  During this wait time, other TCP connections will be serviced if
we already initiated them, but no new TCP connections will be created
and no UDP packets will be retransmitted.

[ghudson@mit.edu: minor adjustments; commit message]

ticket: 7604 (new)

diff --git a/src/lib/krb5/os/sendto_kdc.c b/src/lib/krb5/os/sendto_kdc.c
index 58e00671b1987bb9b8929a3b2ab73a6053492286..be9758e13b59c64d7f8aa3cba5aad15e47554664 100644 (file)
--- a/src/lib/krb5/os/sendto_kdc.c
+++ b/src/lib/krb5/os/sendto_kdc.c
@@ -109,6 +109,7 @@ struct conn_state {
     krb5_data callback_buffer;
     size_t server_index;
     struct conn_state *next;
+    time_ms endtime;
 };
 
 #undef DEBUG
@@ -1050,6 +1051,10 @@ service_tcp_fd(krb5_context context, struct conn_state *conn,
             goto kill_conn;
         }
         conn->state = WRITING;
+
+        if (get_curtime_ms(&conn->endtime) == 0)
+            conn->endtime += 10000;
+
         goto try_writing;
 
     case WRITING:
@@ -1195,6 +1200,22 @@ service_udp_fd(krb5_context context, struct conn_state *conn,
     return 1;
 }
 
+/* Return the maximum of endtime and the endtime fields of all currently active
+ * TCP connections. */
+static time_ms
+get_endtime(time_ms endtime, struct conn_state *conns)
+{
+    struct conn_state *state;
+
+    for (state = conns; state != NULL; state = state->next) {
+        if (state->addr.type == SOCK_STREAM &&
+            (state->state == READING || state->state == WRITING) &&
+            state->endtime > endtime)
+            endtime = state->endtime;
+    }
+    return endtime;
+}
+
 static krb5_boolean
 service_fds(krb5_context context, struct select_state *selstate,
             time_ms interval, struct conn_state *conns,
@@ -1215,7 +1236,8 @@ service_fds(krb5_context context, struct select_state *selstate,
 
     e = 0;
     while (selstate->nfds > 0) {
-        e = cm_select_or_poll(selstate, endtime, seltemp, &selret);
+        e = cm_select_or_poll(selstate, get_endtime(endtime, conns),
+                              seltemp, &selret);
         if (e == EINTR)
             continue;
         if (e != 0)
@@ -1282,6 +1304,10 @@ service_fds(krb5_context context, struct select_state *selstate,
  *
  * Note that if you try to reach two ports (e.g., both 88 and 750) on
  * one server, it counts as two.
+ *
+ * There is one exception to the above rules.  Whenever a TCP connection is
+ * established, we wait up to ten seconds for it to finish or fail before
+ * moving on.  This reduces network traffic significantly in a TCP environment.
  */
 
 krb5_error_code