Cannot find network scanner on multi-homed host

[phippo]

Debian stable, suld-driver2-1.00.06 and suld-driver2-common-1 from the bchemnet repo. The printer is at 192.168.1.5 and works from anywhere. One host with just eth0 and lo network interfaces finds the scanner, another host with eth0, wlan0 and lo interfaces fails to find it. Here's ifconfig from the multi-homed machine:

eth0      Link encap:Ethernet  HWaddr e0:cb:4e:e3:48:0c
          inet addr:192.168.1.4  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fd82:5862:16b6::1:4/64 Scope:Global
          inet6 addr: fe80::e2cb:4eff:fee3:480c/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:36262788 errors:0 dropped:0 overruns:0 frame:0
          TX packets:107082705 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4138015404 (3.8 GiB)  TX bytes:150690929058 (140.3 GiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:9321208 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9321208 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:16673579183 (15.5 GiB)  TX bytes:16673579183 (15.5 GiB)

wlan0     Link encap:Ethernet  HWaddr 1c:4b:d6:5a:52:22
          inet addr:192.168.0.4  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::1e4b:d6ff:fe5a:5222/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1789111 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2054127 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1272744281 (1.1 GiB)  TX bytes:1378639517 (1.2 GiB)


As you an see the eth0 is on the same subnet as the printer/scanner. Here's route in case I have stuffed up:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         skynet          0.0.0.0         UG    0      0        0 wlan0
192.168.0.0     *               255.255.255.0   U     0      0        0 wlan0
192.168.1.0     *               255.255.255.0   U     0      0        0 eth0
224.0.0.0       *               240.0.0.0       U     0      0        0 eth0

avahi-discover finds the scanner on both machines. I eve tried replacing /usr/lib/cups/backend/smfpnetdiscovery with a script that prints the output from the single-homed host but still no luck.

Is there an environment variable I can use to just tell libsane-smfp what to use?

[bchemnet]

As far as I know, there are not any environment variables that you can set.  The only thought I have would be to try setting the wireless network to a higher IP range than the wired (e.g., 192.168.2.x) - perhaps the issue is that libsane-smfp always uses the lowest?

Alternatively, try an older driver and see if it behaves better.

[phippo]

I think the problem is with my IPv6 routes. If I set the env variable SANE_DEFAULT_DEVICE to 'smfp:net;192.168.1.5' I can use xscanimage with no problems. I guess without the env variable it uses avahi and the scanner replies with an IPv6 address that my routing tables cannot handle.

[bchemnet]

Thanks for sharing the solution.  I will add this as a possible solution for network issues.