[lwip-users] [lwip] lwip [linux]

[Sudha Padmaja Mudhavalapu]

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I tried to run the latest lwip-0.4.1 on a linux machine (2.4 kernel).To test 
lwip (unixsim), I found that there are two executables that I can use. 
Simrouter to run first a unix server. Then simnode the unix client.


                             Server        socket conn.     Client
|-----------|             |------------|                  |---------|
| Linux     | |-----------| Simrouter  |------------------| Simnode |           
| Stack     | |           |------------|                  |---------|
|-----------| |           |  |      |  |
              |           |--|      |--|                  192.168.1.2
              |      192.168.0.2    192.168.1.1
              |              
              |                  
              |192.168.0.1 
         |------|            
         | TapX |----------|------|
         |------|          | TapX |
                           |------|
       /dev/net/TapX       /dev/TapX ()
(tapX network side)        (tapX character side - simrouter gets packet from 
this side)
 linux/simrouter commn.

The "Linux connection" to the tap interface should have the IP address 
192.168.0.1.

Simrouter has two interfaces with ip addresses as 
192.168.0.2 which is the tap interface with gateway as 192.168.0.1 
192.168.1.1 which the server with gateway as 192.168.0.2.

The simnode is the client and has an ip address of 192.168.1.2

To my understanding, 
When a packet is received on the network side of the TapX, it is read by the 
Simrouter 
from the character side of the TapX.
If the packet is destined for the interfaces of the Simrouter, then the 
response is sent back through the network side of the TapX to the Linux side.
If the packet is destined for the Simnode then the Simrouter sends the packet 
to the Simnode.
The Simnode sends the response over the socket connection to the Simrouter which
inturn sends to the Linux side over the network side of the TapX.

I am running the Simhost and Simrouter of the same Linux machine.
When I say ping 192.168.0.1, I get the response back.
When I say ping 192.168.0.2, I do not see any response.Also tcpdump on TapX 
shows nothing.

As per my understanding when I say ping 192.168.0.2 it should reach the 
Simrouter over the character side of the TapX.
Any information in this regard would be helpful.

Doing an ifconfig on tap0 I get the following output
#ifconfig
tap0      Link encap:Ethernet  HWaddr 00:FF:C7:4C:2F:01
          inet addr:192.168.0.2  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100

Doing a route the output is as below
#route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.114.8.180    *               255.255.255.255 UH    0      0        0 eth0
10.114.8.0      *               255.255.255.0   U     0      0        0 eth0
192.168.0.0     *               255.255.255.0   U     0      0        0 tap0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
default         10.114.8.1      0.0.0.0         UG    0      0        0 eth0




       



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