Re: [lwip-users] Connect [Bridge] two machines running lwip applications

[Saket Chawla]

Solved it and as a refrence to anyone who read this later

To enable a lwip stack access to/from other network over unix port

Here are the steps

sudo sysctl -w net.ipv4.ip_forward=1

sudo ifconfig eth0 0.0.0.0 promisc up

sudo brctl addbr br0

sudo ifconfig br0 <bridge IP suitable to network you wih to be on>

sudo brctl addif br0 eth0

Note : Remember bridging works only over ethernet not wirless interface

Contrib version : 1.4.0

Modifications to file contrib/ports/unix/netif/tapif.c

Function : low_level_init()

Near about Line# 137

/*  sprintf(buf, IFCONFIG_BIN IFCONFIG_ARGS,

           ip4_addr1(&(netif->gw)),

           ip4_addr2(&(netif->gw)),

           ip4_addr3(&(netif->gw)),

           ip4_addr4(&(netif->gw)));

*/

snprintf(buf,sizeof(buf),"ifconfig tap0 0.0.0.0 promisc up");

  LWIP_DEBUGF(TAPIF_DEBUG, ("tapif_init: system(\"%s\");\n", buf));

  system(buf);

snprintf(buf,sizeof(buf),"brctl addif br0 tap0");

  LWIP_DEBUGF(TAPIF_DEBUG, ("tapif_init: system(\"%s\");\n", buf));

  system(buf);

  sys_thread_new("tapif_thread", tapif_thread, netif, DEFAULT_THREAD_STACKSIZE, DEFAULT_THREAD_PRIO);

}

......................................................

This should make it work,

however it may some time to establish the path and return intial reply to ping 

and may even show "Destination Host Unreachable" for inital packet replies

If this take too much time or no connection at all then

After you run the simhost application

sudo arp -s <LWIP stack IP> <Tap0 MAC address>

Tap0 MAC address changes everytime you execute the application 

so if it suddenly stops working then please repeat the last step

Note :

LWIP stack IP : Host IP

Tap IP : Gateway IP

-- 

Thanks
Regards
Saket Chawla