inpcb: merge two versions of in6_pcbconnect() into one

[glebius]

Summary

No functional change.

[markj]

sys/netinet6/in6_pcb.c

491

We have the INP_INHASHLIST flag. That flag will be set if and only if rehash is true, so do we really need rehash at all?

[glebius]

sys/netinet6/in6_pcb.c

491

Right now protocols (TCP & UDP) know if the inpcb is in the hash or not and tell the inpcb layer either "please add to hash" or please "move inside the hash". This makes INP_INHASHLIST a debug flag and at least for some time I want to keep it like that. Maybe later when all this code get easier to read & maintain we can shortcut these checks.

[markj]

sys/netinet6/in6_pcb.c

491

I'd argue that checking INP_INHASHLIST would make the code easier to read and maintain. :)
In particular, it's hard to remember what all of these boolean flags do when staring at a call like in_pcbconnect(..., true);.

[glebius]

I agree that it makes hard to remember. I started a patch to remove the parameter, but then backed up. I think it is important to not allow protocols to move inpcb in a hash unintentionally. At least at this stage of code cleanup.