LKML Archive on
help / color / mirror / Atom feed
From: Rocco Yue <>
To: David Ahern <>
Cc: "David S . Miller" <>,
	Hideaki YOSHIFUJI <>,
	David Ahern <>,
	Jakub Kicinski <>,
	Matthias Brugger <>,
	<>, <>,
	<>, <>,
	<>, <>,
	Rocco Yue <>
Subject: Re: [PATCH net-next v4] ipv6: add IFLA_INET6_RA_MTU to expose mtu value in the RA message
Date: Sat, 21 Aug 2021 14:10:30 +0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, 2021-08-17 at 09:05 -0600, David Ahern wrote:
On 8/17/21 1:26 AM, Rocco Yue wrote:
>> @@ -1496,6 +1490,11 @@ static void ndisc_router_discovery(struct sk_buff *skb)
>>  		memcpy(&n, ((u8 *)(ndopts.nd_opts_mtu+1))+2, sizeof(mtu));
>>  		mtu = ntohl(n);
>> +		if (in6_dev->ra_mtu != mtu) {
>> +			in6_dev->ra_mtu = mtu;
>> +			send_ifinfo_notify = true;
>> +		}
>> +
>>  		if (mtu < IPV6_MIN_MTU || mtu > skb->dev->mtu) {
>>  			ND_PRINTK(2, warn, "RA: invalid mtu: %d\n", mtu);
>>  		} else if (in6_dev->cnf.mtu6 != mtu) {
> If an RA no longer carries an MTU or if accept_ra_mtu is reset, then
> in6_dev->ra_mtu should be reset to 0 right?
> rest of the change looks good to me.

Hi David,

Thanks for your review.

In this patch, if an RA no longer carries an MTU or if accept_ra_mtu is reset,
in6_dev->ra_mtu will not be reset to 0, its value will remain the previous
accept_ra_mtu=1 and the value of the mtu carried in the RA msg. This behavior
is same with mtu6. This should be reasonable, it would show that the device
had indeed received the ra_mtu before set accept_ra_mtu to 0 or an RA no longer
carries an mtu value. I am willing to listen to your suggestions and make
changes if needed, maybe it needs to add a new separate proc handler for

In addition, at your prompt, I find that this patch maybe have a defect for
some types of virtual devices, that is, when the state of the virtual device
updates the value of ra_mtu during the UP period, when its state is set to
DOWN, ra_mtu is not reset to 0, so that its ra_mtu value remains the previous
value after the interface is re-UP. I think I need to fix it.


  reply	other threads:[~2021-08-21  6:12 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-17  7:26 Rocco Yue
2021-08-17 15:05 ` David Ahern
2021-08-21  6:10   ` Rocco Yue [this message]
2021-08-23  3:01     ` David Ahern

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [PATCH net-next v4] ipv6: add IFLA_INET6_RA_MTU to expose mtu value in the RA message' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).