Linux steam client seems to be downloading slow when IPv6 is enabled

[em4n3m]

Hi,

I'm currently on a 1 GBps fibre optics network and I can easily reach download speeds of ~100 MiB/s.
If I keep IPv6 enabled the steam client downloads at abysmal speeds (300 KiB/s), whilst if I disable IPv6:

sysctl -w net.ipv6.conf.all.disable_ipv6=1
sysctl -w net.ipv6.conf.default.disable_ipv6=1

my download speeds are optimal.

I think there's some issue with the steam client that when IPv6 is enabled it somehow doesn't work properly and slows down.

I've tested my IPv4 vs IPv6 speed and all is good: http://ipv6-test.com/speedtest/

Is there a way for the Steam client to use only IPv4?
I'm running version 1552545139 on Ubuntu 18.04 with Kernel HWE (4.18.0-16-generic).

Thanks!

[MadMat]

I have the same problem and your workaround works for me, too. Thank you. Might be a problem introduced with the last update:

Re-enabled IPv6 content downloads with automatic fallback to IPv4

There is already a bug report for the issue: https://github.com/ValveSoftware/steam-for-linux/issues/6126

[SeriousCCIE]

Out of curiosity, have you tried streaming between hosts? I am wondering if this would impact local subnet streaming performance speeds.

People on wifi doing steam link streaming might experience something horrendous if this affects them.

[em4n3m]

SeriousCCIE の投稿を引用：

Out of curiosity, have you tried streaming between hosts? I am wondering if this would impact local subnet streaming performance speeds.

People on wifi doing steam link streaming might experience something horrendous if this affects them.

I'm connected using the ethernet wire, to both my hub and externally (you can't get true 1 Gbps on wifi...).

[SeriousCCIE]

Oh I didn't mean to suggest you were on wifi for your internet downloads, I meant to ask if local network performance suffered the same way. It'd be a test within steam, since copying files won't quite test a steam issue. That's why I was wondering if streaming may be affected by this on systems with ipv6 enabled and unexpectedly talking.

The bug and the posted logs don't cover that scenario, so... wasn't sure if you've seen that as a problem, too. (The logs don't even seem to make reference to IPV6.)

[em4n3m]

SeriousCCIE の投稿を引用：

Oh I didn't mean to suggest you were on wifi for your internet downloads...

No worries, mate.
I also run speed tests (both IPv4 and IPv6) whilst Steam was (poorly) downloading - those went flawless, whilst Steam was struggling like a horse on the Alps.

[Marlock]

did you try switching download servers on steam properties?

steam was streaming screenshots, gameplay videos and such very slowly on the store pages (but only on steam app, not via browsers) and I fixed the issue (at least for now) by changing from the geographically closest server to the second closest.

ipv6 might perform better on some servers/routings than others

[MadMat]

I tried a few different download locations (in Europe), but this didn't make much difference.

[em4n3m]

MadMat の投稿を引用：

I tried a few different download locations (in Europe), but this didn't make much difference.

Same here. Issue with the client I believe...

[Zyro]

I also guess it's a client problem, but you could give installing dnsmasq a try.

[em4n3m]

Zyro の投稿を引用：

I also guess it's a client problem, but you could give installing dnsmasq a try.

Thanks - Could you remind me why dnsmasq would help? What's the rationale behind?

[Zyro]

em4n3m の投稿を引用：

Thanks - Could you remind me why dnsmasq would help? What's the rationale behind?

I wouldn't know why it would help especially for IP6, so it's a wild shot, but generally, it caches and resolves DNS queries locally, and the Steam Linux client is infamous for making way too many DNS resolve calls, which can dramatically slow down downloads.
(*edit* If it doesn't help the specific problem, it should be good for any network access including browsing the webs in any case.)

[em4n3m]

Zyro の投稿を引用：

em4n3m の投稿を引用：

Thanks - Could you remind me why dnsmasq would help? What's the rationale behind?

I wouldn't know why it would help especially for IP6, so it's a wild shot, but generally, it caches and resolves DNS queries locally, and the Steam Linux client is infamous for making way too many DNS resolve calls, which can dramatically slow down downloads.
(*edit* If it doesn't help the specific problem, it should be good for any network access including browsing the webs in any case.)

That's my point, mate. Feels like a bit of a long-shot without any rationale?
A bit like "my head hurts" then "try not to move your leg"? Not sure the correlation is there.

Of course, if we find such correlation it may be very relevant...

[Zyro]

em4n3m の投稿を引用：

That's my point, mate. Feels like a bit of a long-shot without any rationale?
A bit like "my head hurts" then "try not to move your leg"? Not sure the correlation is there.

Of course, if we find such correlation it may be very relevant...

It's more like "It's not highly likely to fix your problem, but it is highly likely to not only not hurt your system, but improve it." Say like "my head hurts" - "do eat some fruits". ;) And as it doesn't take any configuration, it's done in less time than we've used to write these four posts. So... try it if you like.

[SeriousCCIE]

In somewhat relatable news, i have multiple DNS servers running in my home, and Steam sometimes ignores them and attempts to tunnel a connection to their own name servers and then comes back with ipv6 names that my servers couldn't possibly provide the client because none of my servers run ipv6 nor respond to requests for such naming.

Disabling ipv6 on the host in question will prevent any manner of ipv6 name resolution, given the lack of administrative control otherwise. Steam will otherwise even try to connect to to the IPV6 addresses resolved even if there is no... anything ipv6 on the network, except for the host its on with the self-assigned IPV6 address and no available gateway, etc.

It seems determined to blindly trust that ipv6 will work and goes out of its way to fail sometimes.

Disabling ipv6 also has the benefit of reducing the latency/timeouts while it hopelessly waits to connect. It otherwise seems to prefer ipv6 as its primary means to communicate and then fails back to ipv4 if things time out.

Maybe one day they'll introduce an option in the client to accept administrative differences.

[Aoi Blue]

They should test both IPv4 and IPv6 some ISPs still have slow IPv6 connections compared to IPv4. Slow IPv6 should be treated as fallback.