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Enough with “firewalls”

A mythical conversation on firewalls, and some observations

“Let’s put the firewall here, so it can protect the servers in this part of the network.”
“How would you define a firewall?”
“You know, the appliance that, well, protects servers and other machines from outside threats…”
“And how does it do this?”
“By filtering the traffic using some sort of stateful mechanism, and network address translation, and deep packet inspection, and blocking certain ports, and…”
“In other words, it’s a bunch of services on a single device?”
“Yes…”
“Then maybe we should think in terms of services instead of appliances.

I’ve never actually had this conversation, but I’ve had many similar ones across my times as a network engineer. I’ll admit, in fact, that it took a lot of conversations like this (with me on the receiving end) to grock the difference between a service and an appliance, and to see that my constant thinking in terms of appliances (or even devices) was actually hindering my ability to design networks. Let me give you two specific reasons you should think of security services, instead of security appliances.

First, When you disaggregate the “things a firewall Continue reading

snaproute Go BGP Code Dive (10): Moving to Established

In the last post on this topic, we traced how snaproute’s BGP code moved to the open state. At the end of that post, the speaker encodes an open message using packet, _ := bgpOpenMsg.Encode(), and then sends it. What we should be expecting next is for an open message from the new peer to be received and processed. Receiving this open message will be an event, so what we’re going to need to look for is someplace in the code that processes the receipt of an open message. All the way back in the fifth post of this series, we actually unraveled this chain, and found this is the call chain we’re looking for—

  • func (st *OpenSentState) processEvent()
  • st.fsm.StopConnectRetryTimer()
  • bgpMsg := data.(*packet.BGPMessage)
  • if st.fsm.ProcessOpenMessage(bgpMsg) {
    • st.fsm.sendKeepAliveMessage()
    • st.fsm.StartHoldTimer()
    • st.fsm.ChangeState(NewOpenConfirmState(st.fsm)) }

I don’t want to retrace all those steps here, but the call to func (st *OpenSentState) processEvent() (around line 444 in fsm.go) looks correct. The call in question must be a call to a function that processes an event while the peer is in the open state. This call seems to satisfy both Continue reading