Not being able to setup a gdbserver connection over a bridged tap interface

prashast.srivastava · 05-03-2017, 10:12 PM

Hi so I am trying to remotely debug a binary running in QEMU by running a gdbserver on the emulated guest and then trying to connect to it from the host. I had setup a host-only network using a bridge and a tap interface as given below and even though I am able to ping the guest from the host and vice-versa I am still not able to get gdb to connect remotely to the gdbserver on the guest:

My bridge is setup on the host as given below:

Code:

 brctl addbr br0
 ip addr add 192.168.179.1/24 broadcast 192.168.179.255 dev br0
 ip link set br0 up

To which I then create a tap interface and add to the bridge:

Code:

ip tuntap add dev tap0 mode tap
ip link set tap0 up promisc on
brctl addif br0 tap0

I was then using dnsmasq to get the VM's eth0 be assigned a IP address using the given command.

Code:

dnsmasq --interface=br0 --bind-interfaces --dhcp-range=192.168.179.10,192.168.179.254

I was wondering as to what could be the issue as to why I am not able to connect remotely to the gdbserver even though I am able to ping the guest successfully. Is there a forwarding rule that I need to add or can anyone tell me as to how should I approach this problem? I chose this thread because I feel it's a networking issue and probably there is a routing issue that I need to take care of.

nini09 · 05-05-2017, 03:06 PM

What's Linux distribution on Host and what's VM om guest?

prashast.srivastava · 05-05-2017, 03:24 PM

Host is Ubuntu 16.04 and guest is a Debian squeeze mipsel 32-bit image which I was emulating using QEMU.

nini09 · 05-08-2017, 02:35 PM

You run GDB target on guest machine and GDB debug client on host machine, don't you?
If so, it might have problem. GDB doesn't request network only. It request CPU too. You might have to use two machine to do your debugging.