[cups-devel] [UNKN] STR #4586: Under load CUPS loses client connections with "A TLS packet with unexpected length was received."

Alex Korobkin noreply at cups.org
Fri Feb 20 13:49:48 PST 2015


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[STR New]

This is reproducible on Ubuntu 12.04 x64 with CUPS 1.7.5 with a patch for
STR#4484, and Encryption set to Required. Tested with gnutls 2.12.14 and
2.12.23. 

How to reproduce:
1. Launch 500 commands "CUPS_SERVER=printserver lpstat -a" in parallel,
querying a single CUPS server. 
2. After successfully serving first few hundreds requests (about ~400),
CUPS begins to close every new connection with "A TLS packet with
unexpected length was received." message. 

Last successful client:
d [20/Feb/2015:21:19:57 +0000] [Client 15] con->uri="*", con->best=(nil)()
d [20/Feb/2015:21:19:57 +0000] [Client 15] Authorization=""
D [20/Feb/2015:21:19:57 +0000] [Client 15] No authentication data provided.
D [20/Feb/2015:21:19:57 +0000] [Client 15] Encrypting connection.
D [20/Feb/2015:21:19:57 +0000] Connection from 172.23.176.27 now encrypted.

next unsuccessul client:
d [20/Feb/2015:21:19:58 +0000] [Client 17] con->uri="*", con->best=(nil)()
d [20/Feb/2015:21:19:58 +0000] [Client 17] Authorization=""
D [20/Feb/2015:21:19:58 +0000] [Client 17] No authentication data provided.
D [20/Feb/2015:21:19:58 +0000] [Client 17] Encrypting connection.
E [20/Feb/2015:21:19:58 +0000] Unable to encrypt connection from
172.23.176.27 - A TLS packet with unexpected length was received.
D [20/Feb/2015:21:19:58 +0000] [Client 17] Closing connection.


If lpstat processes are killed, CUPS returns back to normal and starts
serving clients again. netstat stats are ok, no packets are dropped,
pruned, or discarded. tcpdump shows that packets are coming of the same
size, nothing unexpected. 

Attached is an debug2 error log with 10 seconds around the first rejected
packet (at 21:19:58).

Link: https://www.cups.org/str.php?L4586
Version: 1.7-current
Attachment: https://www.cups.org/strfiles.php/3456/error_log.211950
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