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XA2 with 3.0.3 consumes more energy when using different APN setting

asked 2019-05-23 20:35:53 +0300

Pliocen gravatar image

updated 2019-05-28 16:06:01 +0300

Maus gravatar image

My cellular network (Orange) usually employs RFC1918 addresses for the internet clients. For a monthly fee, they offer using a different APN (named "vpn", the product's name is Orange VPN) which makes use of a dynamic IP address range from a pool of public addresses.

I noticed that my XA2 Plus with SFOS 3.0.3 (Hossa) consumes more electricity if I switch to the Orange VPN internet access point than with the default APN - the battery discharges faster. Has anyone noticed similar phone behavior?

Standard APN: after a night in standby mode (4G, without Android support) the battery indicates 95%. With optional APN ("vpn") enabled, the battery shows 80% under otherwise similar operating conditions.

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more dns traffic?

tortoisedoc ( 2019-05-25 18:41:30 +0300 )edit

I had a hard time understanding this question. I hope I made sense of it all while re-structuring and partially re-writing the question.

I see you limited your connection to 4G, presumably in both tests. Then I have absolutely no idea why this should happen. Perhaps you get some tips to do RIL debugging here on TJC.

Maus ( 2019-05-28 16:11:50 +0300 )edit

Thank you, you're right, now the question is clear.

Pliocen ( 2019-05-28 18:45:12 +0300 )edit

And answered it is, thanks to @DrYak!

Maus ( 2019-05-28 22:36:35 +0300 )edit

1 Answer

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answered 2019-05-28 19:27:37 +0300

DrYak gravatar image

Note that if you have a public address, your device is reachable from the internet.

From personal experience (public IP addresses are commonly used in nearly all the university I've worked in. ETH is the first time that they're not wide open to the internet), your device is almost guaranteed to get hammered by port scans / brute force password guessing/etc. All this incoming internet traffic from the internet is going to put your 4G cell modem on work and eat battery faster. (as an anecdote there was so much hammering going on at my uni a decade and a half ago that the CPU load caused occasional stutter on the music player running on my crappy laptop).

(If I'm not mistaken - but I might be wrong the default behaviour of the built-in firewall is to open SSH on all interface, so you could observe the login failures when using the command journalctl (as root, devel-su) and searching for sshd.)

From there, two steps :

  • To be on the safe side (though I'm not sure if the port is open for 4G links), consider disabling password logins for SSH and use only SSH-keys.

  • Try to check if your Orange service provider can provide their own firewall service (at the ISP level) and thus block any traffic you don't want before it even reaches you over 4G. (Note that this might be an extra paying "business" options, not necessarily available on your "Orange VPN" plan).

    Remember to leave open the ports for the service you intend to run with you public address. (Out of curiosity, why are you needing public addresses on your smartphone's 4G ?)

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Perhaps to make cloud services work properly which they don't in mixed IPv4/6 environments.

Kopekenscheich ( 2019-05-29 05:52:32 +0300 )edit

Honestly? Out of curiosity, I used vpn in BB Z30 before and it seemed to me that the network connection works faster and more stable, so I tried in XA2 with SFOS

Pliocen ( 2019-05-30 10:23:40 +0300 )edit

@Pliocen : I would say that BB Z30 runs Blackberry OS and has no service listening by default. You'd still have the port scans going on (packet getting dropped), but at least no brute-forcing attempts of SSH (or other services) thus no SSH connection set-up + handshake + crypto-SSL/TLS-handshake + failed login + connection teardown.

Though now Xperia XA2 also has CPU core with hardware AES, so I might be wrong and the SSH hammering would NOT then be the source of battery loss.

A buggy Sailfish implementation of whatever layer Orange provides on top (is there an actual VPN ?) could be another alternative source of battery loss.

Last but not least, BlackBerry OS could be offloading some processing to the cell modem (e.g.: packet filtering ?) and thus doesn't wake up the main CPU cores for every single incoming packet from every portscan on the internet.

Normally, recent (-ish) linux kernels like the XA2's kernel 4.4 are able to correctly deal with big.LITTLE core arrangement and schedule task to appropriate cores (unlike, say X's kernel 3.10) and should be using the low-power cores when processing packet while idle, so at least that should not be a source of battery loss.

Anyway the most likely idea is that with a public IP you're exposing your phone to more internet traffic and that extra traffic might somehow have a larger impact on Sailfish OS than on BlackBerry OS.

DrYak ( 2019-05-31 12:00:14 +0300 )edit
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Asked: 2019-05-23 20:35:53 +0300

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Last updated: May 28 '19