linux-kernel - Re: [PATCH] net: Use nlmsg_unicast() instead of netlink

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Message-ID: <20210712164904.GA16733@salvia>
Date:   Mon, 12 Jul 2021 18:49:04 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Yajun Deng <yajun.deng@...ux.dev>
Cc:     davem@...emloft.net, yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        kuba@...nel.org, mathew.j.martineau@...ux.intel.com,
        matthieu.baerts@...sares.net, kadlec@...filter.org, fw@...len.de,
        vyasevich@...il.com, nhorman@...driver.com,
        marcelo.leitner@...il.com, johannes.berg@...el.com, ast@...nel.org,
        yhs@...com, 0x7f454c46@...il.com, aahringo@...hat.com,
        rdunlap@...radead.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, mptcp@...ts.linux.dev,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        linux-sctp@...r.kernel.org
Subject: Re: [PATCH] net: Use nlmsg_unicast() instead of netlink_unicast()

On Mon, Jul 12, 2021 at 08:53:01PM +0800, Yajun Deng wrote:
> diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c
> index 639c337c885b..aa3397eec330 100644
> --- a/net/netfilter/nft_compat.c
> +++ b/net/netfilter/nft_compat.c
> @@ -683,10 +683,8 @@ static int nfnl_compat_get_rcu(struct sk_buff *skb,
>  		goto out_put;
>  	}
>  
> -	ret = netlink_unicast(info->sk, skb2, NETLINK_CB(skb).portid,
> -			      MSG_DONTWAIT);
> -	if (ret > 0)
> -		ret = 0;
> +	ret = nlmsg_unicast(info->sk, skb2, NETLINK_CB(skb).portid);

netfilter needs nfnetlink_unicast to deal with EAGAIN, see e0241ae6ac59

So either:

a) use nfnetlink_unicast.
b) remove this chunk and I'll route a patch to fix this in the
   netfilter tree.

Pick one at your choice.

Thanks.

>  out_put:
>  	rcu_read_lock();
>  	module_put(THIS_MODULE);