Subject: Re: [PATCH] netlink: fix append of whole original message on negative ack.

From: Patrick McHardy <[email-masked]>
Date: Thu, 23 Oct 2008 23:02:32 +0200

David Miller wrote:
> From: M Lammertink <[email-masked]>
> Date: Thu, 23 Oct 2008 20:17:51 +0200
>   
>> Can anyone explain to me why struct nlmsgerr contains an int error and the nlmsghdr struct. The comment in netlink_ack states that the whole message should be appended. Why not only include an int error in struct nlmsgerr and just append the original message?
>>
>> Comments appreciated.
>>
>> diff -uprN linux-2.6.27.3.orig/net/netlink/af_netlink.c linux-2.6.27.3/net/netlink/af_netlink.c
>> --- linux-2.6.27.3.orig/net/netlink/af_netlink.c	2008-10-23 18:01:54.000000000 +0200
>> +++ linux-2.6.27.3/net/netlink/af_netlink.c	2008-10-23 18:04:22.000000000 +0200
>> @@ -1656,7 +1656,7 @@ void netlink_ack(struct sk_buff *in_skb,
>>  	}
>>  
>>  	rep = __nlmsg_put(skb, NETLINK_CB(in_skb).pid, nlh->nlmsg_seq,
>> -			  NLMSG_ERROR, sizeof(struct nlmsgerr), 0);
>> +			  NLMSG_ERROR, payload, 0)

You can't include the full message since the resulting message
might exceed the 64k netlink limit.