Too many package level constants/variables?

[irfabid]

In my opinion, layers package is too polluted with exported constants/variables. Would it be a good idea to have separate package for each layer?
Perhaps all commonly used layers in a single package (layers), and all uncommon layers in their own packages? (e.g. layers/lldp package).

This can have an additional advantage of shorter identifier names because then we can drop prefix. For example, layers.LLDPChassisIDSubType will become lldp.ChassisIDSubType.

This would be breaking change however.

Any thoughts?

[gconnell]

Yep :P

Doing this while preserving backwards-compatibility will be very hard, but given that go has type aliases should now actually be possible. If, for example, we moved the IP/TCP/UDP/ICMP stuff into layers/tcpip, or even layers/tcpip/icmp4 we'd probably do something like:

type TCP = tcpip.TCP

and

const ICMPv4CodeNet = icmp4.CodeNet

So: layers would still have references to all the types, but if folks wanted just core tcpip they could pull in just that instead. It'd be pretty darn tedious work, but if you want to, go for it!

Backwards compatibility is the name of the game, though. I'll push back on any change that could break existing code.

[vtolstov]

Does it possible if i'm interest only on ip and dhcp layers iport only needed layers and skip decoding intermediate layers?
For example after ip next is udp, but we don't decode it and skip to udp payload?

[gconnell]

No, since you don't know the size of the intermediate layer without decoding it. Some layers have constant size, but many do not.

[vtolstov]

@gconnell but if layer have size in header, why not parse it first and skip the rest decoding?

[gconnell]

That actually is currently possible, by overriding the layer decoder. The short version is that you write your own decoder of UDP that just reads/skips the right size, then you say:

gopacket.OverrideLayerType(LayerTypeUDP, mySkippingUDPDecoder)