netdev - Re: [PATCH net-next] tcp: unalias tcp_skb_cb flags and ip

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <201109271228.44232.christoph.paasch@uclouvain.be>
Date:	Tue, 27 Sep 2011 12:28:44 +0300
From:	Christoph Paasch <christoph.paasch@...ouvain.be>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	hkchu@...gle.com, ilpo.jarvinen@...sinki.fi, jhs@...atatu.com
Subject: Re: [PATCH net-next] tcp: unalias tcp_skb_cb flags and ip_dsfield

Eric,

On Tuesday 27 September 2011 wrote Eric Dumazet:
> Le mardi 27 septembre 2011 à 11:38 +0300, Christoph Paasch a écrit :
> > On Tuesday 27 September 2011 wrote David Miller:
> > This two-byte hole, is it because "flags" and "sacked" are both __u8 and 
> > fields are aligned to 32-bit ?
> 
> Not exactly.
> 
> Reason for the hole is the following :
> 
> struct whatever {
>         u8   first;
>         u8   second;
>         u32  third;
> };
> 
> "third" field has an alignement requirement of 4 bytes on most arches.
> 
> Compiler inserts a 2 bytes hole before "third" to respect this
> requirement.
> 
> There is no hole between "first" and "second", since second has no
> alignment requirement.
> 
> sizeof(struct whatever) = 8


Ok, I understand.
Thanks for the info. I didn't knew this...

It's good news...
Maybe we win now a little bit of space in MultiPath TCP by rearranging our 
fields... :-)


Cheers,
Christoph


--
Christoph Paasch
PhD Student

IP Networking Lab --- http://inl.info.ucl.ac.be
MultiPath TCP in the Linux Kernel --- http://inl.info.ucl.ac.be/mptcp
Université Catholique de Louvain

www.rollerbulls.be
--
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html