netdev - Re: [PATCH net-next 01/20] netlink: Pass extack to dump handlers

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Date:   Fri, 5 Oct 2018 19:41:05 +0200
From:   Christian Brauner <christian@...uner.io>
To:     David Ahern <dsahern@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jbenc@...hat.com,
        stephen@...workplumber.org, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH net-next 01/20] netlink: Pass extack to dump handlers

On Thu, Oct 04, 2018 at 02:33:36PM -0700, David Ahern wrote:
> From: David Ahern <dsahern@...il.com>
> 
> Declare extack in netlink_dump and pass to dump handlers via
> netlink_callback. Add any extack message after the dump_done_errno
> allowing error messages to be returned. This will be useful when
> strict checking is done on dump requests, returning why the dump
> fails EINVAL.
> 
> Signed-off-by: David Ahern <dsahern@...il.com>

Acked-by: Christian Brauner <christian@...uner.io>

> ---
>  include/linux/netlink.h  |  1 +
>  net/netlink/af_netlink.c | 12 +++++++++++-
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/netlink.h b/include/linux/netlink.h
> index 71f121b66ca8..88c8a2d83eb3 100644
> --- a/include/linux/netlink.h
> +++ b/include/linux/netlink.h
> @@ -176,6 +176,7 @@ struct netlink_callback {
>  	void			*data;
>  	/* the module that dump function belong to */
>  	struct module		*module;
> +	struct netlink_ext_ack	*extack;
>  	u16			family;
>  	u16			min_dump_alloc;
>  	unsigned int		prev_seq, seq;
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index e3a0538ec0be..7ac585f33a9e 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -2171,6 +2171,7 @@ EXPORT_SYMBOL(__nlmsg_put);
>  static int netlink_dump(struct sock *sk)
>  {
>  	struct netlink_sock *nlk = nlk_sk(sk);
> +	struct netlink_ext_ack extack = {};
>  	struct netlink_callback *cb;
>  	struct sk_buff *skb = NULL;
>  	struct nlmsghdr *nlh;
> @@ -2222,8 +2223,11 @@ static int netlink_dump(struct sock *sk)
>  	skb_reserve(skb, skb_tailroom(skb) - alloc_size);
>  	netlink_skb_set_owner_r(skb, sk);
>  
> -	if (nlk->dump_done_errno > 0)
> +	if (nlk->dump_done_errno > 0) {
> +		cb->extack = &extack;
>  		nlk->dump_done_errno = cb->dump(skb, cb);
> +		cb->extack = NULL;
> +	}
>  
>  	if (nlk->dump_done_errno > 0 ||
>  	    skb_tailroom(skb) < nlmsg_total_size(sizeof(nlk->dump_done_errno))) {
> @@ -2246,6 +2250,12 @@ static int netlink_dump(struct sock *sk)
>  	memcpy(nlmsg_data(nlh), &nlk->dump_done_errno,
>  	       sizeof(nlk->dump_done_errno));
>  
> +	if (extack._msg && nlk->flags & NETLINK_F_EXT_ACK) {
> +		nlh->nlmsg_flags |= NLM_F_ACK_TLVS;
> +		if (!nla_put_string(skb, NLMSGERR_ATTR_MSG, extack._msg))
> +			nlmsg_end(skb, nlh);
> +	}
> +
>  	if (sk_filter(sk, skb))
>  		kfree_skb(skb);
>  	else
> -- 
> 2.11.0
>