netdev - Re: [PATCH net-next 5/7] icmp: reflect tos through ip cookie rather than updating inet

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Message-ID: <67a55b76da19a_25109e294ee@willemb.c.googlers.com.notmuch>
Date: Thu, 06 Feb 2025 20:01:42 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 netdev@...r.kernel.org
Cc: davem@...emloft.net, 
 kuba@...nel.org, 
 edumazet@...gle.com, 
 pabeni@...hat.com, 
 Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next 5/7] icmp: reflect tos through ip cookie rather
 than updating inet_sk

Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@...gle.com>
> 
> Do not modify socket fields if it can be avoided.
> 
> The current code predates the introduction of ip cookies in commit
> aa6615814533 ("ipv4: processing ancillary IP_TOS or IP_TTL"). Now that
> cookies exist and support tos, update that field directly.
> 
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> 
> ---
> 
> Tested with ping -Q 32 127.0.0.1 and tcpdump
> 
> The existing logic works because inet->tos is read if ipc.tos (and
> with that cork->tos) is left unitialized:
> 
>   iph->tos = (cork->tos != -1) ? cork->tos : READ_ONCE(inet->tos);
> ---
>  net/ipv4/icmp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
> index 094084b61bff..9c5e052a7802 100644
> --- a/net/ipv4/icmp.c
> +++ b/net/ipv4/icmp.c
> @@ -429,7 +429,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
>  	icmp_param->data.icmph.checksum = 0;
>  
>  	ipcm_init(&ipc);
> -	inet->tos = ip_hdr(skb)->tos;
> +	ipc.tos = ip_hdr(skb)->tos;
>  	ipc.sockc.mark = mark;
>  	daddr = ipc.addr = ip_hdr(skb)->saddr;
>  	saddr = fib_compute_spec_dst(skb);

local variable inet is no longer used, needs to be removed.

Will fix in v2.