Re: [clisp-list] errors from socket-status

[<don...@is...>]

Sam Steingold writes:
 > > I also have code for doing it from lisp if you have rawsock.
 > > Let me know if you want to go down that path.
 > yes, please.
 > I want the code that would let me debug this without an external
 > telnet. i.e., clisp should open the connection, kill it, and send a
 > reset.
I'm trying to make this as simple as possible, but you'll see it's 
really not there.  I actually spent way too much time on this trying
to figure out what I was doing wrong before I discovered that it
behaved as I expected over the net but not for communication within
one machine (localhost).  I still don't understand why that is, but
I suggest you do the testing on two different machines as described
below.  It could be related to the OS version, in this case both
machines are FC4:
Linux don-eve.dyndns.org 2.6.17-1.2142_FC4 #1 Tue Jul 11 22:41:14 EDT
2006 i686 i686 i386 GNU/Linux

BTW, as part of my search I started to suspect the checksum routines
and I did find a few small problems with them.  More on that later...

Anyhow, here's my demo:

The code I'm sending uses rawsock, so of course you need a clisp built
with rawsock.  And you have to be root to use it.
On the server machine (where you'll be adding gdb to what I do):
 run lisp
 [1]> (setf ss (socket:socket-server 1234 :interface "64.27.16.100")) 

64.27.16.100 => ip address of your server, not 127.0.0.1
Same substitution applies below.

 #<SOCKET-SERVER 64.27.16.100:1234> 
 [2]> (setf str (socket:socket-accept ss)) 

on the client machine as root
 run clisp with rawsock
 (load "reset.lisp") ;; provided below
 (waitforpkt '(64 27 16 100) 1234)

This is likely to print some *'s to show you that it sees packets
other than what it's waiting for.

Now in another process on the same client machine

 $ telnet 64.27.16.100 1234 
 Trying 64.27.16.100... 
 Connected to 64.27.16.100 (64.27.16.100). 
 Escape character is '^]'. 


This should cause the other two lisp processes that are waiting for
relevant packets to return.

server:
 [3]>

client:
 ... *****
 T
 [2]>
now you can send the reset from the client lisp process:
 [2]> (reset)

and now on the server I get this
 [3]> (socket:socket-status str) 
 
 [../src/stream.d:6143]  
 *** - UNIX error 104 (ECONNRESET): Connection reset by peer 
 The following restarts are available: 
 ABORT          :R1      Abort main loop 
 Break 1 [4]> 

By the way, at this point you can now return to the telnet and
simply type enter to get this:
 
 Connection closed by foreign host. 
   
==== reset.lisp
(defvar default-socket (rawsock:socket :inet :packet #+ignore :all #x300)) 
(unless (> default-socket 0) (error "socket failed - running as root?")) 
(defvar default-buffer 
  (make-array 1518 :element-type '(unsigned-byte 8) :fill-pointer 100)) 
(defvar default-device  
  (rawsock:make-sockaddr :packet 
                         (make-array 14 :element-type '(unsigned-byte 8)))) 
(defun waitforpkt(serverip serverport &key (show 100)) 
  (loop for i from 0 with len do  
    (setf (fill-pointer default-buffer) 1518) 
    (setf len (rawsock:recvfrom default-socket default-buffer default-device)) 
    (when (= 0 (mod i show))(princ "*")) 
    (when (and (>= len 52) 
               (= (aref default-buffer 12) 8) ;; ip 
               (= (aref default-buffer 13) 0) 
               (= (aref default-buffer 14) 69) ;; ipv4, len 5 
               (= (aref default-buffer 23) 6) ;; tcp 
               (loop for j from 0 as a in serverip always 
                 (= a (aref default-buffer (+ j 30)))) ;; correct ip addr 
               (= serverport 
                  (+ (aref default-buffer 37) 
                     (* 256 (aref default-buffer 36)))) 
               (= 16 (aref default-buffer 47))) 
      (return t)))) 
(defun reset() 
  ;; change flags to from ack to rst+ack 
  (setf (aref default-buffer 47) 20) 
  (setf (aref default-buffer 46) 80) ;tcp header length = 5 words 
  ;; set buffer length 
  (setf (fill-pointer default-buffer) 54) ;; 60 ?? 
  (setf (aref default-buffer 17) 40) 
  (rawsock:tcpcsum default-buffer)  ;; not returning right answer? 
  (setf ipc (rawsock:ipcsum default-buffer)) ;; returns bytes reversed? 
  (rawsock:sendto default-socket default-buffer default-device)) 
 
#| 
(waitforpkt '(64 27 16 100) 1234) 
(reset) 
|#