Re: [PATCH net v3 5/5] net: restrict message_cost and message_burst to non-negative values

[Hangbin Liu]

Hi Jiayuan,
On Sun, Nov 01, 2026 at 02:12:03PM +0800, Jiayuan Chen wrote:
> net.core.message_cost and net.core.message_burst feed the interval and
> burst of net_ratelimit_state, but neither rejects negative values:
> message_burst uses plain proc_dointvec, and message_cost uses
> proc_dointvec_jiffies, which happily stores -1 second as -HZ jiffies.
> 
> Since commit a940d145cc38 ("ratelimit: Warn if ->interval or ->burst are
> negative"), ___ratelimit() splats on such values, so the next
> net_ratelimit() caller warns, e.g. a martian source log:
> 
>   Negative interval (-250) or burst (10): Uninitialized ratelimit_state structure?
>   WARNING: lib/ratelimit.c:43 at ___ratelimit+0x56e/0x960, CPU#1: ping/3218
>   RIP: 0010:___ratelimit+0x578/0x960
>   Call Trace:
>    <IRQ>
>    net_ratelimit+0x1c/0x30
>    ip_handle_martian_source+0x1bb/0x340
>    ip_route_input_slow+0x1057/0x3650
>    ip_route_input_noref+0x104/0x260
>    arp_process+0x109b/0x2510
>    arp_rcv+0x381/0x460
>    __netif_receive_skb_one_core+0x173/0x1c0
>    __netif_receive_skb+0x21/0x150
>    process_backlog+0x37e/0x1200
>    __napi_poll.constprop.0+0xa5/0x5e0
>    net_rx_action+0x4c0/0xf70
>    handle_softirqs+0x204/0x9b0
>    __do_softirq+0x10/0x18
>    do_softirq.part.0+0x49/0xd0
>    </IRQ>
> 
> Negative values never meant anything here: 0 already expresses both
> "no limit" (interval) and "suppress everything" (burst).

Will this limit breaks the UAPI on old kernels that supports negative values?

As the comment in ___ratelimit() says:

        /*
         * Zero interval says never limit, otherwise, non-positive burst
         * says always limit.
         */

If all others agree to set the limit in this patch. I think the comment
and the WARN_ONCE() , and the admin-guide/sysctl/net.rst all need to be updated.

Thanks
Hangbin