netdev - Re: [PATCHv2 net-next 1/6] sctp: add sctp_info dump api for sctp

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Message-ID: <570A4EE3.9090302@mojatatu.com>
Date:	Sun, 10 Apr 2016 09:02:27 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Xin Long <lucien.xin@...il.com>,
	network dev <netdev@...r.kernel.org>,
	linux-sctp@...r.kernel.org,
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
	Vlad Yasevich <vyasevich@...il.com>, daniel@...earbox.net,
	davem@...emloft.net
Subject: Re: [PATCHv2 net-next 1/6] sctp: add sctp_info dump api for sctp_diag

On 16-04-09 01:21 PM, Eric Dumazet wrote:


> Well, once a hole is there, nothing we can do really, because of
> compatibility with old kernels / old binaries.
>
>
> But when a _new_ structure is defined, this is the time where we can ask
> for doing sensible things ;)
>

This one is fixable. sizeof() already includes the accounting of
the pad. something like:

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index fe95446..52542eb 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -158,6 +158,7 @@ struct tcp_info {
         __u8    tcpi_options;
         __u8    tcpi_snd_wscale : 4, tcpi_rcv_wscale : 4;

+       __u8    pad;    /*reuse this space if you need 8bits for something*/
         __u32   tcpi_rto;
         __u32   tcpi_ato;
         __u32   tcpi_snd_mss;

cheers,
jamal