Move to uint64 for procnet, deal with MaxConn

[fearful-symmetry]

So, in order to deal with the fact that TCP.MaxConn can be a -1, we originally stored ProcNet values in map[string]int64.

However, after talking with @urso and looking it over, chances are there's some uint64 sized values floating around in here. Looking at the kernel source, it appears that MaxConn is the only signed value in here, and it's stored in a unsigned long before being cast to an int in order to print.

I'm not entirely happy with this, but we're in a situation where we have one oddball value that we want to handle differently. This PR just requires the user that there's a value they need to print as an int or hex value in order to make it usable.

There's a few other solutions here:

Make a struct like this:

type SNMP struct {
	IP      map[string]uint64 `json:"ip" netstat:"Ip"`
	ICMP    map[string]uint64 `json:"icmp" netstat:"Icmp"`
	ICMPMsg map[string]uint64 `json:"icmp_msg" netstat:"IcmpMsg"`
	TCP     map[string]uint64 `json:"tcp" netstat:"Tcp"`
	UDP     map[string]uint64 `json:"udp" netstat:"Udp"`
	UDPLite map[string]uint64 `json:"udp_lite" netstat:"UdpLite"`
        TCPMaxConn int32 `json:"max_conn"`
}

Or like this:

type SNMP struct {
	IP      map[string]uint64 `json:"ip" netstat:"Ip"`
	ICMP    map[string]uint64 `json:"icmp" netstat:"Icmp"`
	ICMPMsg map[string]uint64 `json:"icmp_msg" netstat:"IcmpMsg"`
	TCP     SNMPTCP `json:"tcp" netstat:"Tcp"`
	UDP     map[string]uint64 `json:"udp" netstat:"Udp"`
	UDPLite map[string]uint64 `json:"udp_lite" netstat:"UdpLite"`
}

type SNMPTCP{
    MaxConn int32 
    Values map[string]uint64

}

[andrewkroh]

LGTM, but needs a CHANGELOG entry.

[urso]

I see it's also merged. Maybe worth to mention that this change fixes the parser returning error of the complete namespace if some octet counter has reached values > 2^63