Re: [pbs-devel] [PATCH proxmox{, -backup} 0/6] add user specific rate-limits

[Hannes Laimer <h.laimer@proxmox.com>]

On 11/7/25 08:33, Christian Ebner wrote:
> On 9/9/25 10:53 AM, Hannes Laimer wrote:
>> This adds support for specifying user specific rate-limits.
>> We add a user-tag to every rate-limited connection, with this present we
>> can limit the connection based on the authenticated user assiciated with
>> it.
>>
>> Authentication happens after accept, so we can't set this right when we
>> accept a connection. Currently we initialize the handle on accept, we
>> then give this handle to the rate_limiter callback function. And on
>> completed authentication we set the user using this handle.
>> I did consider using a Peer -> User map in the cache, and just adding
>> entries on auth, but there isn't really a good way to clean those
>> entries. And peers(so IP:port) may end up being reused, and that would
>> be a problem. With the current approach we don't have this problem.
>>
>> Currently rules with a user specified take priority over others. So:
>> user > IP only > neither, in case two rules match.
>>
>> If users and networks are specified, the rule only applies if both
>> match. So, Any of the specified user connect from any of the specified
>> network.
>>
>> And all of this ofc still only if the given timeframe matches.
>>
>> Note: this is only for users, you can't specify individual tokens. But I
>> don't think that is much of a problem, it is probably even better like
>> this.
>>
>> (I did look through BZ if there is an issue for this, I feel like there
>> should be, but did not find one)
> 
> Hi,
> thanks for the patches, this is a very useful feature I think.
> 
> I've planned to have a more in-depth look at this series today, but from 
> a first glance I see two possible issues which I think need to be 
> addressed:
> 

Thanks for taking a look!

> - The rate limiting happens on the RateLimitedStreams by token bucket 
> filtering, this however being agnostic to the traffic flowing above that 
> connection. And user authentication happens at request level. So while 
> probably not very problematic in general since there will be a dedicated 
> connection for different users, the same connection (TCP socket) could 
> be shared by multiple users, the connection is however tagged by the 
> first users after the first request being authenticated unless I'm 
> missing something. So a second user reusing the same TCP connection will 
> then get the limits of the first one?

Is that actually possible? I assumed new auth implies a new
connection(so the thing we tagged here). So a user could connect to the
PBS and not go through .accept() by the server?
Or do you mean after one connection is done a later one could end up
reusing the same port? In that case it would have to be accepted first
and go through auth again, no?

> - Tagging of the stream only happens *after* the first request being 
> processed and the response being generated. This however means that this 
> first request will never be limited, only subsequent requests are.

well, we can't before auth, we don't know who it is we're talking to,
no?

> - It would probably make sense to keep the stream part as generic as 
> possible, the stream should not be concerned about users. So maybe it 
> would make sense to allow to set generic `tags` on connections, and pass 
> this list of tags to the rate limiter callback, so it can determine the 
> lowest rate limits compatible with the given tags from the ruleset. This 
> would still apply the same limits to users reusing the same connection, 
> but in a more abstract fashion.

I did think about that, but I couldn't really come up with much of a
usecase. User is the only one I could think of that can't be done on
accept but has to be done after auth. But there may very well be some,
I just couldn't really think of any.

> 
> What do you think?



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