[PATCH] traceroute: Fix hangs or delays in timeout

[James Raphael Tiovalen]

Currently, traceroute resets the timeout to 3 seconds within the same
probe when undesired ICMP traffic is received on the socket
continuously, which causes it to hang or delay in timeout.

This commit fixes this issue by setting the timeout to the remaining
time within the same probe while processing the undesired ICMP packet
instead of resetting the timeout to 3 seconds. The next probe is sent
either when it times out or when the desired ICMP message is received.

The fix can be verified by sending continuous ICMP traffic on the
traceroute socket. Traceroute should not hang and there should not be
any delays in the timeout.

Signed-off-by: James Raphael Tiovalen <jamestiotio@gmail.com>
---
 src/traceroute.c | 35 +++++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/src/traceroute.c b/src/traceroute.c
index e96f2307..f0e8c242 100644
--- a/src/traceroute.c
+++ b/src/traceroute.c
@@ -359,11 +359,18 @@ do_try (trace_t * trace, const int hop,
   fd_set readset;
   int ret, tries, readonly = 0;
   struct timeval now, time;
+  struct timeval start, end;
+  long sec_elapsed = 0;
+  long usec_elapsed = 0;
   double triptime = 0.0;
   uint32_t prev_addr = 0;
 
   printf (" %2d  ", hop);
 
+  memset (&time, 0, sizeof (time)); /* 64-bit issue. */
+  memset (&start, 0, sizeof (start)); /* 64-bit issue. */
+  memset (&end, 0, sizeof (end)); /* 64-bit issue. */
+
   for (tries = 0; tries < max_tries; tries++)
     {
       int save_errno;
@@ -372,18 +379,19 @@ do_try (trace_t * trace, const int hop,
       FD_ZERO (&readset);
       FD_SET (fd, &readset);
 
-      memset (&time, 0, sizeof (time));        /* 64-bit issue.  */
-      time.tv_sec = opt_wait;
-      time.tv_usec = 0;
-
       if (!readonly)
-       trace_write (trace);
+        {
+          time.tv_sec = opt_wait;
+          time.tv_usec = 0;
+          trace_write (trace);
+        }
 
       errno = 0;
       ret = select (fd + 1, &readset, NULL, NULL, &time);
       save_errno = errno;
 
       gettimeofday (&now, NULL);
+      gettimeofday (&start, NULL);
 
       now.tv_usec -= trace->tsent.tv_usec;
       now.tv_sec -= trace->tsent.tv_sec;
@@ -425,9 +433,20 @@ do_try (trace_t * trace, const int hop,
              if (rc < 0)
                {
                  /* FIXME: printf ("Some error ocurred\n"); */
-                 tries--;
-                 readonly = 1;
-                 continue;
+                 gettimeofday (&end, NULL);
+                 sec_elapsed = (end.tv_sec - start.tv_sec);
+                 usec_elapsed = (end.tv_usec - start.tv_usec);
+                 if (usec_elapsed < 0)
+                   usec_elapsed = 0;
+                 time.tv_sec -= sec_elapsed;
+                 time.tv_usec -= usec_elapsed;
+                 if (time.tv_sec >= 0 && time.tv_usec >= 0)
+                   {
+                     tries--;
+                     if (!readonly)
+                       readonly = 1;
+                     continue;
+                   }
                }
              else
                {
-- 
2.40.0