krb5 commit: Dynamically expand timeout when TCP connects

[Greg Hudson]

https://github.com/krb5/krb5/commit/f423c28a68e94e1aac2b40bb9902a017d2b0c83e
commit f423c28a68e94e1aac2b40bb9902a017d2b0c83e
Author: Nathaniel McCallum <npmccallum at redhat.com>
Date:   Tue Apr 9 13:32:20 2013 -0400

    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 at mit.edu: minor adjustments; commit message]
    
    ticket: 7604 (new)

 src/lib/krb5/os/sendto_kdc.c |   28 +++++++++++++++++++++++++++-
 1 files changed, 27 insertions(+), 1 deletions(-)

diff --git a/src/lib/krb5/os/sendto_kdc.c b/src/lib/krb5/os/sendto_kdc.c
index 58e0067..be9758e 100644
--- 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