* Re: [PATCH] netlink: fix append of whole original message on negative ack.
[not found] <4900BFCF.2030707@gmail.com>
@ 2008-10-23 20:45 ` David Miller
2008-10-23 20:55 ` Evgeniy Polyakov
2008-10-23 21:02 ` Patrick McHardy
0 siblings, 2 replies; 3+ messages in thread
From: David Miller @ 2008-10-23 20:45 UTC (permalink / raw)
To: michellammertink; +Cc: linux-kernel, netdev
From: M Lammertink <michellammertink@gmail.com>
Date: Thu, 23 Oct 2008 20:17:51 +0200
You'll get a much better review of this if you send it to
the netdev mailing list, which is where all the networking
developers are subscribed. They don't read linux-kernel
Added to CC:
> From: Michel Lammertink <mlammertink <at> ti-wmc.nl>
> Signed-off-by: Michel Lammertink <mlammertink <at> ti-wmc.nl>
>
> Netlink can return an negative acknowledgement, which AFAICT should include an error code and the whole original message. This patch fixes the size argument given to the __nlmsg_put call. Without this patch only the original header was attached.
> ---
>
> 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);
> errmsg = nlmsg_data(rep);
> errmsg->error = err;
> memcpy(&errmsg->msg, nlh, err ? nlh->nlmsg_len : sizeof(*nlh));
> --
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] netlink: fix append of whole original message on negative ack.
2008-10-23 20:45 ` [PATCH] netlink: fix append of whole original message on negative ack David Miller
@ 2008-10-23 20:55 ` Evgeniy Polyakov
2008-10-23 21:02 ` Patrick McHardy
1 sibling, 0 replies; 3+ messages in thread
From: Evgeniy Polyakov @ 2008-10-23 20:55 UTC (permalink / raw)
To: David Miller; +Cc: michellammertink, linux-kernel, netdev
Hi.
On Thu, Oct 23, 2008 at 01:45:13PM -0700, David Miller (davem@davemloft.net) wrote:
> > Netlink can return an negative acknowledgement, which AFAICT should include an error code and the whole original message. This patch fixes the size argument given to the __nlmsg_put call. Without this patch only the original header was attached.
> > ---
> >
> > 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?
Having header (even seq/pid only) is enough to find a message
for that userspace which cares. Looks like your patch can break
existing applications which are used to work with header only,
even if that was a mistake? Although application is supposed to
check the length, it still can expect only a header. I have to
note, that I do not know any such application though.
--
Evgeniy Polyakov
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] netlink: fix append of whole original message on negative ack.
2008-10-23 20:45 ` [PATCH] netlink: fix append of whole original message on negative ack David Miller
2008-10-23 20:55 ` Evgeniy Polyakov
@ 2008-10-23 21:02 ` Patrick McHardy
1 sibling, 0 replies; 3+ messages in thread
From: Patrick McHardy @ 2008-10-23 21:02 UTC (permalink / raw)
To: David Miller; +Cc: michellammertink, linux-kernel, netdev
David Miller wrote:
> From: M Lammertink <michellammertink@gmail.com>
> 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.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2008-10-23 20:45 ` [PATCH] netlink: fix append of whole original message on negative ack David Miller
2008-10-23 20:55 ` Evgeniy Polyakov
2008-10-23 21:02 ` Patrick McHardy
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