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From: "Pali Rohár" <pali@kernel.org>
To: Jakub Kicinski <kuba@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>,
	"David S. Miller" <davem@davemloft.net>,
	Guillaume Nault <gnault@redhat.com>,
	linux-ppp@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ppp: Add rtnl attribute IFLA_PPP_UNIT_ID for specifying ppp unit id
Date: Mon, 9 Aug 2021 21:31:09 +0200	[thread overview]
Message-ID: <20210809193109.mw6ritfdu27uhie7@pali> (raw)
In-Reply-To: <20210809122546.758e41de@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>

On Monday 09 August 2021 12:25:46 Jakub Kicinski wrote:
> On Sat,  7 Aug 2021 18:37:49 +0200 Pali Rohár wrote:
> > Currently there are two ways how to create a new ppp interface. Old method
> > via ioctl(PPPIOCNEWUNIT) and new method via rtnl RTM_NEWLINK/NLM_F_CREATE
> > which was introduced in v4.7 by commit 96d934c70db6 ("ppp: add rtnetlink
> > device creation support").
> > 
> > ...
> 
> Your 2 previous patches were fixes and went into net, this patch seems
> to be on top of them but is a feature, so should go to net-next. 

Yes

> But it doesn't apply to net-next given net was not merged into net-next.
> Please rebase on top of net-next or (preferably) wait until next week
> so that the trees can get merged and then you can repost without causing
> any conflicts.

Better to wait. I would like hear some comments / review on this patch
if this is the correct approach as it adds a new API/ABI for userspace.

> >  static const struct nla_policy ppp_nl_policy[IFLA_PPP_MAX + 1] = {
> >  	[IFLA_PPP_DEV_FD]	= { .type = NLA_S32 },
> > +	[IFLA_PPP_UNIT_ID]	= { .type = NLA_S32 },
> >  };
> 
> set .strict_start_type, please so new attrs get validated better
> 
> >  static int ppp_nl_validate(struct nlattr *tb[], struct nlattr *data[],
> > @@ -1274,6 +1277,15 @@ static int ppp_nl_validate(struct nlattr *tb[], struct nlattr *data[],
> >  
> >  	if (!data[IFLA_PPP_DEV_FD])
> >  		return -EINVAL;
> > +
> > +	/* Check for IFLA_PPP_UNIT_ID before IFLA_PPP_DEV_FD to allow userspace
> > +	 * detect if kernel supports IFLA_PPP_UNIT_ID or not by specifying
> > +	 * negative IFLA_PPP_DEV_FD. Previous kernel versions ignored
> > +	 * IFLA_PPP_UNIT_ID attribute.
> > +	 */
> > +	if (data[IFLA_PPP_UNIT_ID] && nla_get_s32(data[IFLA_PPP_UNIT_ID]) < -1)
> > +		return -EINVAL;
> 
> please use NLA_POLICY_MIN() instead, no need to open-code
> 
> >  	if (nla_get_s32(data[IFLA_PPP_DEV_FD]) < 0)
> >  		return -EBADF;

I will look at both issues... and I would like to know what is preferred
way to introduce new attributes in a way that userspace can detect if
kernel supports them or not.

  reply	other threads:[~2021-08-09 19:31 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-07 16:37 Pali Rohár
2021-08-09 19:25 ` Jakub Kicinski
2021-08-09 19:31   ` Pali Rohár [this message]
2021-08-10 15:39     ` Guillaume Nault
2021-08-10 16:04       ` Pali Rohár
2021-08-11 17:19         ` Guillaume Nault
2021-08-11 17:54           ` Pali Rohár
2021-08-12  9:19             ` Guillaume Nault
2021-08-12 14:09               ` Pali Rohár
2021-08-12 19:12                 ` Guillaume Nault
     [not found]       ` <BN0P223MB0327A247724B7AE211D2E84EA7F79@BN0P223MB0327.NAMP223.PROD.OUTLOOK.COM>
2021-08-10 17:16         ` Pali Rohár
2021-08-10 18:11           ` James Carlson
2021-08-11 17:38             ` Guillaume Nault
2021-08-11 18:04               ` Pali Rohár
2021-08-12  9:28                 ` Guillaume Nault
2021-08-12 13:48                   ` Pali Rohár
2021-08-12 18:26                     ` Guillaume Nault
2021-08-12 19:04                       ` Pali Rohár
2021-08-16 16:11                         ` Guillaume Nault
2021-08-16 16:23                           ` Pali Rohár
2021-08-17 16:05                             ` Guillaume Nault
2021-08-17 16:21                               ` Pali Rohár
2022-07-09 12:09                                 ` Pali Rohár
2022-07-12 17:34                                   ` Guillaume Nault

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