nice to have: ICMP handling by router

[adferguson]

it would be nice if the router implemented some of the traditional ICMP messages for gateways and routers:

• ICMP destination unreachable
• ping requests to its own interfaces
• timestamp requests
• TTL expired (would require OpenFlow support for sure)

and others as discussed in http://tools.ietf.org/html/rfc1812, http://tools.ietf.org/html/rfc1122

Note: this issue is NOT about support for ICMP traffic in the NAT. it is about the router itself issuing ICMP messages.