What it means to support ECC RAM (especially for AMD Ryzen)
Ever since the AMD Ryzen series of CPUs was introduced, there'sbeen a lot of confusion about whether they supported ECC RAM andto what degree. One of the sources of confusion and imprecision isthere are a number of different possible meanings of 'supportingECC RAM'. So let's run down the hierarchy:
- The system will power up and run with ECC RAM modules installed.
- Single-bit errors will (always) be corrected.
- Corrected single-bit errors will be reported and logged, so you
Link: Citation Needed [on array indexing in programming languages]
Mike Hoye's Citation Needed isostensibly about the origins of zero-based array indexing inprogramming languages. But that's not really what it's about onceMike Hoye gets going; it's really about our field's attitude towardshistory, the consequences of that attitude, and the forces thatdrive it, including inaccessible papers. Even if you're indifferentto where zero-based array indexing comes from, that portion of thearticle is well worth reading and thinking about.
(I'
My new Linux machine for fall 2017 (planned)
My current home machine is about six years oldnow, and for a while I've been slowly planning a new PC.At this point my parts list is basically finalized and all thatremains is the hard part, which is ordering things and perhaps assembling them . Who knows if I'llget around to doing that this year (although with the Christmasrush approaching fast, I'd better do that soon if I want to geteverything before next year starts).
Because my office workstation is about as
Some early notes on WireGuard
WireGuard is a new(ish) secure IPtunnel system, currently only for Linux. Yesterday I wrote about why I've switched over to it ; today isfor some early notes on things about it that I've run into, especiallyin ways it's different from my previous IKE IPSec plus GRE setup.
For the most part, my WireGuard configuration is basically theirsimple example configuration, but with a single peer. The importantbit I had to get my head around is the AllowedIPs setting, which
How collections.defaultdict is good for your memory usage
There is a classical pattern in code that uses entries in dictionariesto accumulate data. In the simplest form, it looks like this:
e = dct.get(ky, None) if e is None: e = [] dct[ky] = e # now we work on e without # caring if it's new or old
There is an obvious variation of this that gets rid of the wholebureaucracy involving the if :
e = dct.setdefault(ky, [])# work on e
Why I've switched from GRE-over-IPSec to using WireGuard
I have a long standing IPSec IKE and point to point GRE tunnel that gives my home machine an inside IPaddress at work. This has worked reasonably well for years, but recently I discovered that its bandwidth hadcollapsed . Some subsequentstaring at network packet captures suggested that I was now seeingdropped or drastically delayed ACKs, and perhaps reordering andpacket drops in general. This smelled a lot like the kind of bugthat was not going to be fun to report and probably wasn't goingto get fixed any time
Illumos mountd caches netgroup lookups (relatively briefly)
Last time I covered how the Illumos NFS server caches filesystemaccess permissions . However, this is notthe only level of caching that's possibly going on in the overallNFS server ecosystem, because the Illumos NFS kernel ultimatelycalls up to mountd to find out about permissions and mountd canhave its own caching.
Specifically, mountd caches netgroup membership checks for 60seconds. Well, sort of. What it really caches is the result ofwhether a host is in a specific list of netgroups, not whether ornot
I think Certificate Transparency is better for the web than HTTP Key Pinning
Recently, the Chrome developers announced Intent to Deprecate andRemove: Public Key Pinning ( via ).The unkind way to describe HTTP Public Key Pinning is that it'sa great way to blow your foot off , or in oursituation have well-meaning people blow it off for us . The kind way to describe HPKP is that it'sintended to be a way to lessen the damage if a Certificate Authority(mis-)issues a certificate for your domain to someone else; in theright situation you
We've now seen malware in a tar archive
Our anti-spam system recently logged the following information aboutan incoming message:
1e92K6-0007yD-37 attachment application/octet-stream; MIME file ext: .tar; tar exts: .exe; email is in-dnsbl
rejected 1e92K6-0007yD-37 from 74.194.116.87/brand27@emediasol.com to: identified virus
The Illumos NFS server's caching of filesystem access permissions
Years ago I wrote The Solaris 10 NFS server's caching of filesystemaccess permissions . I was recently diggingin this area of the Illumos source code and discovered that therehave been a few changes, so here is a brief update. The backgroundis that that Illumos NFS server code, like basically all modernNFS servers , does not maintain a fulllist of what clients are authorized to access what filesystems.Instead it maintains a cache and upcalls to user level code wheneverit feels that the cache is insufficient information
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