On Thu, Oct 04, 2018 at 02:33:36PM -0700, David Ahern wrote:
> From: David Ahern <dsah...@gmail.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 <dsah...@gmail.com>
Acked-by: Christian Brauner <christ...@brauner.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
>
