Freeminded.org

PHP has always been a “messy” language. It’s API looks somewhat thrown together by several different people who do not seem to be aware of each other’s existence, but surely have the best intentions. Given these ‘tools’, it comes as little surprise that writing good PHP code used to be more of an art than science. If the language does not force consistency, then it requires a great deal from the developer.

Luckily, with PHP 7.0 and 7.1 came the awesome feature of type hinting:
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As a frequent user of the IEEEXplore database to search for literature concerning wireless networking, I often export a citation to BibTeX for use in my papers.

One of the things which has puzzled me for a long time, is why the BibTeX exporter adds a trailing comma after the last field.

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I’m using Thunderbird and Enigmail on Kubuntu, signing all my email and encrypting correspondence whenever possible. Lately (probably due to an update) the password-entry window does not appear. In stead, it complains immediately about:

openpgpg alert - error bad passphrase

I have set the preferences to remember my password for several minutes, so I figured there’s some problem there. I am not using gpg-agent, so EnigMail should fall back to the default.

Checking OpenPGP > Debugging Options > View Console shows what Enigmail is doing. I type my message (signing option checked) and click Send. The console shows:

gpg: gpg-agent is not available in this session
gpg: can't query passphrase in batch mode

Which makes sense, I am not using gpg-agent. Finally, it complains:

gpg; [stdin]: clearsign failed: bad passphrase

And gives up. Googling around I find similar problems, but no solution. Then I noted the following line in the console:

gpg: NOTE: old default options file '~/.gnupg/options' ignored

The ‘options’ file has been obsoleted, gnupg uses gpg.conf now. I checked, indeed the contents of ‘options’ are also present in gpg.conf. Moving ‘options’ away and restarting Thunderbird solved the problem.

Moreover, it also solved my password problem, I now get the password prompt and can happily sign my email.

Post-backoff was introduced into IEEE 802.11 to make sure that a station could not claim the channel by noting that the channel was idle after its own transmission, and then immediately transmit again. The idea is quite simple; transmission over -> pull a backoff from the contention window and count down (respecting the same rules w.r.t. carrier sense and inter-frame spacing etc.) and finally end up in the idle state. If a new packet was handed down by the network layer during post-backoff, the countdown would continue and result in a transmission. This behaviour is also implemented in MiXiM’s Mac80211 (and prior to that in the Mobility Framework). However, there’s a bug. Read the rest of this entry »

This post describes a bug in MiXiM’s Mac80211 which seems to be a fundamental error: when the MAC gets a packet from the Netw and the channel is busy, it schedules a senseChannelWhileIdle(currentIFS + remainingBackoff) after the ongoing transmission ends. Unfortunately, remainingBackoff is often 0 as post-backoff is likely to have completed. The result? Many synchronised collisions one IFS after the ongoing transmission. Read the rest of this entry »