netdev - Re: [PATCH net-next v3 03/15] quic: provide common utilities and data structures

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Message-ID: <2152c576-68ce-4bc4-9658-bb1e8ccce423@redhat.com>
Date: Thu, 25 Sep 2025 17:50:07 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Xin Long <lucien.xin@...il.com>
Cc: network dev <netdev@...r.kernel.org>, quic@...ts.linux.dev,
 davem@...emloft.net, kuba@...nel.org, Eric Dumazet <edumazet@...gle.com>,
 Simon Horman <horms@...nel.org>, Stefan Metzmacher <metze@...ba.org>,
 Moritz Buhl <mbuhl@...nbsd.org>, Tyler Fanelli <tfanelli@...hat.com>,
 Pengtao He <hepengtao@...omi.com>, linux-cifs@...r.kernel.org,
 Steve French <smfrench@...il.com>, Namjae Jeon <linkinjeon@...nel.org>,
 Paulo Alcantara <pc@...guebit.com>, Tom Talpey <tom@...pey.com>,
 kernel-tls-handshake@...ts.linux.dev, Chuck Lever <chuck.lever@...cle.com>,
 Jeff Layton <jlayton@...nel.org>, Benjamin Coddington <bcodding@...hat.com>,
 Steve Dickson <steved@...hat.com>, Hannes Reinecke <hare@...e.de>,
 Alexander Aring <aahringo@...hat.com>, David Howells <dhowells@...hat.com>,
 Matthieu Baerts <matttbe@...nel.org>, John Ericson <mail@...nericson.me>,
 Cong Wang <xiyou.wangcong@...il.com>, "D . Wythe"
 <alibuda@...ux.alibaba.com>, Jason Baron <jbaron@...mai.com>,
 illiliti <illiliti@...tonmail.com>, Sabrina Dubroca <sd@...asysnail.net>,
 Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
 Daniel Stenberg <daniel@...x.se>,
 Andy Gospodarek <andrew.gospodarek@...adcom.com>
Subject: Re: [PATCH net-next v3 03/15] quic: provide common utilities and data
 structures

On 9/23/25 6:06 PM, Xin Long wrote:
> On Tue, Sep 23, 2025 at 7:21 AM Paolo Abeni <pabeni@...hat.com> wrote:
>> On 9/19/25 12:34 AM, Xin Long wrote:
>>> +static int quic_uhash_table_init(struct quic_uhash_table *ht, u32 max_size, int order)
>>> +{
>>> +     int i, max_order, size;
>>> +
>>> +     /* Same sizing logic as in quic_shash_table_init(). */
>>> +     max_order = get_order(max_size * sizeof(struct quic_uhash_head));
>>> +     order = min(order, max_order);
>>> +     do {
>>> +             ht->hash = (struct quic_uhash_head *)
>>> +                     __get_free_pages(GFP_KERNEL | __GFP_NOWARN, order);
>>> +     } while (!ht->hash && --order > 0);
>>
>> You can avoid a little complexity, and see more consistent behaviour,
>> using plain vmalloc() or alloc_large_system_hash() with no fallback.
>>
> I wanted to use alloc_large_system_hash(), but the memory allocated
> by it is usually NOT meant to be freed at runtime. I don't see a free_
> function to do it either.
> 
> If QUIC works as a kernel module, what should I do with this memory
> in module_exit()?

Right, I did not think about such case. I suggest using a plain
vmalloc() without the loop than.

>>> +/* rfc9000#section-a.3: DecodePacketNumber()
>>> + *
>>> + * Reconstructs the full packet number from a truncated one.
>>> + */
>>> +s64 quic_get_num(s64 max_pkt_num, s64 pkt_num, u32 n)
>>> +{
>>> +     s64 expected = max_pkt_num + 1;
>>> +     s64 win = BIT_ULL(n * 8);
>>> +     s64 hwin = win / 2;
>>> +     s64 mask = win - 1;
>>> +     s64 cand;
>>> +
>>> +     cand = (expected & ~mask) | pkt_num;
>>> +     if (cand <= expected - hwin && cand < (1ULL << 62) - win)
>>> +             return cand + win;
>>> +     if (cand > expected + hwin && cand >= win)
>>> +             return cand - win;
>>> +     return cand;
>>
>> The above is a bit obscure to me; replacing magic nubers (62) with macro
>> could help. Some more comments also would do.
>>
> The code is exactly from the commented doc:
> /* rfc9000#section-a.3: DecodePacketNumber()
> 
> See:
> https://datatracker.ietf.org/doc/html/rfc9000#section-a.3
> 
> I will bring some comments from there.

You can quote or make a synopsis of the RFC where it makes sense. In any
case, please try to reduce magic numbers usage.

Thanks,

Paolo