netdev - Re: [PATCH bpf-next v9 05/11] bpf: support fsession for bpf_session

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Message-ID: <2687399.Lt9SDvczpP@7940hx>
Date: Wed, 14 Jan 2026 10:38:46 +0800
From: Menglong Dong <menglong.dong@...ux.dev>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>,
 Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Menglong Dong <menglong8.dong@...il.com>,
 Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 David Ahern <dsahern@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, jiang.biao@...ux.dev,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
 bpf <bpf@...r.kernel.org>, Network Development <netdev@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>
Subject:
 Re: [PATCH bpf-next v9 05/11] bpf: support fsession for bpf_session_cookie

On 2026/1/14 10:33 Alexei Starovoitov <alexei.starovoitov@...il.com> write:
> On Tue, Jan 13, 2026 at 5:24 PM Andrii Nakryiko
> <andrii.nakryiko@...il.com> wrote:
> >
> > On Sat, Jan 10, 2026 at 6:12 AM Menglong Dong <menglong8.dong@...il.com> wrote:
> > >
> > > Implement session cookie for fsession. In order to limit the stack usage,
> > > we make 4 as the maximum of the cookie count.
> >
> > This 4 is so random, tbh. Do we need to artificially limit it? Even if
> > all BPF_MAX_TRAMP_LINKS = 38 where using session cookies, it would be
> > 304 bytes. Not insignificant, but also not world-ending and IMO so
> > unlikely that I wouldn't add extra limits at all.
> 
> I forgot that we already have BPF_MAX_TRAMP_LINKS limit for the total
> number of progs. I guess extra 8 bytes per fsession prog isn't that bad.

Ah, so it's OK to not limit the session cookie. I'll remove such limitation
in the next version.

Thanks!
Menglong Dong

>