[cups] duplex not working ("Transport endpoint is not connected")

[Martin Vogt]

Hello,

I try to use duplex printing from my workstations (RHEL7)
which access a 1.3.9 cups server (SLE11-SP4)

Basic printing works on RHEL7, but nothing more, for
example download the .ppd.

On RHEL7 (cups 1.6) I get the following error:

>vogt at pxe1[~]>lpoptions -p cpsg0a -l
>lpoptions: Unable to get PPD file for cpsG0a:
>Transport endpoint is not connected

With a cups 1.3 client this works:

>vogt at sle11[~]>lpoptions -p cpsg0a -l | wc -l
>53

If I look at the strace on the client, the problem
is that the client tries to accesses the printer in the printer
network directly.

Network setup:

10.x/client-net---<printserver:631>---192.x/printer-net

best regards,

Martin


PS: The (interesting) strace for the client:

Start connect to cups server:

socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 5
connect(5, {sa_family=AF_INET, sin_port=htons(631),
sin_addr=inet_addr("10.x.y.z")}, 16) = -1 EINPROGRESS
sendto(5, "POST /printers/cpsG0a HTTP/1.1..........")
recvfrom(5, "\1\1\0\0\0\0\0\3\1G\0\22attributes-charset

[client gets some more data]

socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 7
connect(7, {sa_family=AF_INET, sin_port=htons(631),
sin_addr=inet_addr("192.a.b.c")}, 16) = -1 EINPROGRESS (Operation now in
progress)
getpeername(7, 0x7fff30216980, [256])   = -1 ENOTCONN (Transport
endpoint is not connected)
close(7)
exit_group(0)