changesets:10878:6f9b44011132

dev: Extentions to etherlink to work for pd-gem5
This patch extends etherlink to enable accurate/deterministic simulation of

a cluster using pd-gem5
This patch adds 4 different operation modes to etherlink:
mode 0: default etherlink operation
mode 1 (no_delay): ehterlink instantly delivers incoming packets to peer
mode 2 (nic_connector): based on whether the packet is received from int0 or 

int1, etherlink adds a time stamp to packet or extract time-stamp from packet

respectively, then delivers it to peer.

We assume that int0 is always connected to NIC and int1 to ethertap.
mode 3 (sw_connector): etherlink adds link latency to packet time-stamp and

delivers it to peer instantly.