misc/157700: tftpd in 8.2-RELEASE expects more data after EOF

[Barry Mishler]

>Number:         157700
>Category:       misc
>Synopsis:       tftpd in 8.2-RELEASE expects more data after EOF
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jun 08 08:20:13 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Barry Mishler
>Release:        8.2-RELEASE-p2
>Organization:
>Environment:
FreeBSD zn120.usace.army.mil 8.2-RELEASE-p2 FreeBSD 8.2-RELEASE-p2 #3: Fri Jun  3 09:13:34 JST 2011     root at zn120.usace.army.mil:/usr/obj/usr/src/sys/MYKERNEL  i386
>Description:
The new tftpd appears to want one more packet following the last (short) packet when receiving a file.  It waits 5 seconds before timing out and finishing up.  This causes a (5-second) delay in flushing the received file to the filesystem which makes other software think that the received file is empty.

At the very bottom of the tftp_receive function in tftp-transfer.c, the controlling 'while' loop continues as long as the received packet matches the expected segment size (n_data == segsize).  But after receiving a small (final) packet, the loop exits but still calls receive_packet one last time.  The comment implies that it's doing "late packet management".

>How-To-Repeat:
Copy a file from a tftp client and watch the file be empty for 5 seconds after the transfer completes.

I use an Expect script to copy Cisco configurations to a FreeBSD tftp server.  After that script finishes copying the file and logging off the device, I watch the size of the file...

./3750 3750-1 10.100.254.120 && for i in 1 2 3 4 5 6; do ls -l 3750-1.*; sleep 1; done

spawn cisco-login 3750-1
spawn ssh -l user 3750-1

3750-1>enable
Password:
3750-1#copy running-config tftp:
Address or name of remote host []? 10.100.254.120
Destination filename [3750-1-confg]? cfg/3750-1.running
!!
10482 bytes copied in 0.805 secs (13021 bytes/sec)
3750-1#copy startup-config tftp:
Address or name of remote host []? 10.100.254.120
Destination filename [3750-1-confg]? cfg/3750-1.startup
!!
10579 bytes copied in 0.059 secs (179305 bytes/sec)
3750-1#
Script Completed
-rwxrwxrwx  1 root  wheel  0 Jun  8 16:47 3750-1.running
-rwxrwxrwx  1 root  wheel  0 Jun  8 16:47 3750-1.startup
-rwxrwxrwx  1 root  wheel  0 Jun  8 16:47 3750-1.running
-rwxrwxrwx  1 root  wheel  0 Jun  8 16:47 3750-1.startup
-rwxrwxrwx  1 root  wheel  0 Jun  8 16:47 3750-1.running
-rwxrwxrwx  1 root  wheel  0 Jun  8 16:47 3750-1.startup
-rwxrwxrwx  1 root  wheel  0 Jun  8 16:47 3750-1.running
-rwxrwxrwx  1 root  wheel  0 Jun  8 16:47 3750-1.startup
-rwxrwxrwx  1 root  wheel  10482 Jun  8 16:47 3750-1.running
-rwxrwxrwx  1 root  wheel  10579 Jun  8 16:47 3750-1.startup
-rwxrwxrwx  1 root  wheel  10482 Jun  8 16:47 3750-1.running
-rwxrwxrwx  1 root  wheel  10579 Jun  8 16:47 3750-1.startup

>Fix:
Don't know exactly.  The code is so new and clean that I wouldn't presume to suggest my own patch that would just make a mess and cause problems elsewhere.


>Release-Note:
>Audit-Trail:
>Unformatted: