From JeffBreukelman@metronet.ca

I have written a script that uses Perl sockets to connect to a series of
routers. The script uses a SIGALRM function to close the connection if it
hasn't logged in or transmitted data after 30 seconds. The SIGALRM function
always works, but on occasion the socket() function causes a segmentation
fault on the next attempt to connect to a router. This always occurs after
the SIGALRM function closes the connection, but not every time. It seems to
occur most often if the connection that was closed had gotten stuck in an
infinite loop. However, I have seen it occur when the previous connection
was simply stuck waiting for input.

I am running Perl version 5.004_04 on Linux. The code for the SIGALRM
function is as follows;

sub SigALRMHandler{
  print "Got SIGALRM - closing socket.\n" if($Debug>=3);
  close(S) || print "Error closing socket\n";
  }

and the code where the error occurs is as follows;

while($#Routers>=0){
  $Current=shift(@​Routers);
  $RawIP=pack('C4',split(/\./,$Current));
  $Remote=pack($SockAddr,$AF_INET,$Port,$RawIP);
  alarm 30;
  print "Getting socket and connecting to $Current.\n" if($Debug>=2);
  print "$#Routers left in queue.\n" if($Debug>=2);
  shutdown(S, 2); # Close old sockets - might be causing
problems
  print "Getting socket.\n" if($Debug>=4);
  socket(S,$AF_INET,$SOCK_STREAM,$Proto) || die("Socket Error​: $!\n");
  print "Binding socket.\n" if($Debug>=4);
  bind(S,$Local) || die("Bind Error​: $!\n");
  print "Connecting to $Current.\n" if($Debug>=4);
  connect(S,$Remote) || do{
  push(@​CErr,$Current);
  push(@​NoConnect,$Current) if($!=/Interrupted/i);
  push(@​Refused,$Current) if($!=/refused/i);
  print "Connection refused to $Current.\n"
if($!=/refused/i);
  print "No connection to $Current.\n" if($!=/interrupted/i);
  next;
  };

When Perl crashes it always does so while running the socket() function
above.

Can you tell me what's going on here?

Jeff Breukelman.

"If you're going to do it, do it right. If you're not going to do it right,
don't do it." -me
Jeff Breukelman jeff@​ntgi.net
Sr Network Consultant Office​: (416)640-9426
NTG International Pager​: (416)608-5272

From The RT System itself

Signal handlers are documented to be unreliable.