Geoff Collyer

Plan 9 and ex-Unix system programmer.

I was one of the first directors of the Plan 9 Foundation.

For a total of about 15 years, I was a Member of Technical Staff at Bell Labs in Murray Hill, NJ, where I worked on operating systems and messaging systems and protocols, among other things.

secrets of IPv6 prefix delegation on Comcast's business service

Mon Dec 20 23:51:41 PST 2021

A /56 is allocated to the cable modem, but only the first /59 (0) is routed initially. The next one (xx20::/59) may be allocated, perhaps to wifi. Each delegation establishes a route for a new /59 subnet. By requesting all possible delegations, one can force the whole /56 to be routed. But, more importantly, performing a release before renew avoids changing the SLA (/59 subnet) number(s):

release dhcpv6-pd interface eth1
renew   dhcpv6-pd interface eth1

The relevant fragment of configuration for Ubiquiti's Edgerouter, reformatted for brevity:

interfaces {
    ethernet eth0 { ... }
    ethernet eth1 {
        address 10.1.10.100/16
        address 2603:3024:90c:9e00::2/60
        /* omitted firewall, ipv6 stanzas */
        ip { enable-proxy-arp }
        dhcpv6-pd {
            pd 0 {
                interface eth0 {
                    host-address ::6
                    no-dns
                    prefix-id :1
                    service slaac
                }
                interface eth2 {
                    host-address ::2
                    no-dns
                    prefix-id :2
                    service slaac
                }
                prefix-length /59
            }
            pd 1 { prefix-length /59 }
            pd 2 { prefix-length /59 }
            pd 3 { prefix-length /59 }
            pd 4 { prefix-length /59 }
            pd 5 { prefix-length /59 }
            pd 6 { prefix-length /59 }
            pd 7 { prefix-length /59 }
            rapid-commit disable
        }
    }
}

Thanks for these articles: prefix notes, based on prefix exhaustion by John Burwell.

the sad state of cryptographic infrastructure

i hate git

I have used plenty of revision control systems and don't really like any of them (though I can use them), but I truly detest git, which I find unusable. It's slow, wasteful, bureaucratic, unpredictable, and over-complicated, which does make it a good match for Linux, for which it was written.

Worse is the mistaken belief that one can, in general, mix-and-match sets of changes to a program and get something useful and correct as a result, without human checking.

computing experience

ported Plan 9 to RISC-V systems, Xilinx Virtex 4 and 5 Power-PC-based evaluation boards, ARM-based systems including the Sheevaplug, Gumstix Overo and Trimslice, and MIPS-based systems including the Routerboard RB450G.
made the 9k kernel truly cope with 64 bits of address space.
wrote an NVMe driver for Plan 9.
maintained the original Plan 9 file server kernel (now upgraded to 64-bit sizes) and contribute to Plan 9 generally.
- merged the big-endian and little-endian MIPS compilers, assemblers and loaders.
- wrote the current (new) Plan 9 tar, which is cleaner and faster than the old one, and is POSIX-compliant (i.e., can cope with longer path names).
- modified the file server kernel to use 64-bit file sizes, offsets and block numbers internally, ported the CPU kernel's IDE code, thus enabling the use of DMA, RWM, etc., and ported the CPU kernel's Intel gigabit Ethernet driver.
- added greylisting and other anti-spam measures to smtpd.
- added multicasting (for IPv6) and shutdown entry points to drivers for all modern ethernet cards. updated the connection server to recognise icmpv6. fixed the kernel to recognise v6 addresses starting with ``20'' as global.
- ported dbm and mdbm libraries and made them use a consistent byte order on disk, rendering the databases portable across CPU architectures.
- arranged completely diskless booting of Plan 9 PCs using compact flash cards
- added device mirroring (think RAID 1) to the Plan 9 file server kernel. Combined with support for IDE disks, this enables use of inexpensive hardware to form a large Plan 9 file server.
- set up and ran the largest Plan 9 file server (with optical disc jukebox) inside Bell Labs other than the main Plan 9 development file server. Extended support for jukeboxes with optical disks of varying sizes. The smaller jukeboxes can now be had second-hand quite cheaply.
on the inferno distributed operating system, built a scalable message store that served a broken-out view of MIME messages, and designed and implemented rsmtp, an SMTP replacement. Got Inferno running on Mac OS X.
configuring IPv6 tunnelling networks
developed the operating system for the now-defunct AT&T HomeCenter™ set-top box, notably DSP communication, and the C library.
Unix device drivers (e.g. for Tektronix storage (display) tubes (for V6 Unix), Nuclear Medicine scintillation counters (for V6 Unix), terminal multiplexors, disks), bootstraps, and other kernel work (e.g. putting /tmp in memory).
reverse-engineering (``decompiling'') manual pages from nroff output to troff -man input: nam
invented the term const poisoning during development of the ANSI C standard
Unix system programming and running Unix systems (including 8th and 9th edition) for almost a decade at the University of Toronto, notably for the computing center, undergraduate computer science instruction, and the statistics department.
set up the original bell-labs.com servers during the ATT/Lucent split, notably DNS and mail servers on Plan 9 and internal and external web servers.

publications

assigning interrupt priorities in software via interrupt queueing, in Computing Systems, Spring 1996
evolution of operating systems: Research Unix in html and pdf (updated 23 Dec 1998 to more closely match the printed article in Microsystems in 1984). Also, a new, improved draft that fixes a number of errors we missed the first time around and adds real references, in html and pdf.
software reimplementation: the Unix shell. I am making available two modified shells, from Seventh and Ninth Edition Research UNIX. I've incorporated the memory management and directory reading changes from the paper, and some other modernisation (e.g., include files and 64-bit tweaks) into both shells. Both should run on POSIXy systems and have been used on Unix, OS X, the BSDs and Linux (among others) on 32- and 64-bit systems (and even 16-bit PDP-11s long ago) without trouble, including as my login shell. Among other features, they lack the GNU readline library, so what you type is what you get.
- The up-to-date V7 sh, updated most recently on 29 July 2017.
- The up-to-date V9 sh from the paper, updated most recently on 29 July 2017.
performance tuning and more software reimplementation: C news netnews software, Blue Gene Plan 9 caching: first cut, second cut
programming style: no ifdefs, can't happen (pdf)
automated game referees: othello

computing interests

Plan 9, the successor to Unix; a distributed system drawing on over 20 years of experience with Unix
- my own contributions of Plan 9 software
- an early outline of a proposed-but-rejected book about why Plan 9 matters. Pardon the formatting; it was converted to HTML mechanically.
Inferno's limbo and the follow-on go languages, which feature particularly helpful support for processes sharing address space. If POSIX pthreads give you the willies, these might be for you.
archiving and optical media, notably CD-R and BD-R (Bluray). Plan 9 has a convenient backup system using optical disks, discussed in its overview, file server and port papers. The venti block store is a worthy replacement when combined with fossil, the file server built on top of venti.
indexing. This is the distribution of my nov news overview database code. Nov is now incorporated into essentially all serious newsreaders.
software reimplementation: More Taste, Less Greed
strong cryptography as an aid to privacy and civil rights

UTF and Unicode examples

Geoff Collyer
geoff at collyer.net