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[Xen-users] Packet flow in Xen

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Packet flow in Xen
From: Siddharth Wagh <swagh@xxxxxxxxxxxxxxxx>
Date: Tue, 23 Nov 2010 08:55:27 -0500
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Hello all,

I am trying to understand the underlying mechanism behind how exactly the packet flows in a Xen virtualized system. There are some gaps in my knowledge that need to be filled.

Guest --> Internet:
1. Guest writes request on I/O ring buffers in hypervisor (using netfront.c)
2. Guest writes notification in grant tables in XenStore using event channels.
3. Dom-0 reads grant reference and locates/reads request from ring buffer (using netback.c)
4. Packet is bridged using Xenbr0 (created by network-bridge & vif-bridge to pass through peth0 (ebtables module).
5. There is interaction between real device driver in Dom-0 and NIC and packet is probably sent from ring buffers on the Internet using DMA.

I know there are lot of loopholes here, and I would really appreciate if someone could help me grasp the exact scenario, especially referring to scripts that carry out the process.

Thanks & Regards,
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