netdev - Re: [PATCH net-next 0/8] Add complementary BPF conditional jump instructions

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Mon, 31 Dec 2012 19:29:02 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	dborkman@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/8] Add complementary BPF conditional jump
 instructions

On Mon, 2012-12-31 at 14:37 -0800, David Miller wrote:

> Whilst I agree that adding NE jumps adds great value and closes a
> serious gap, the rest can be synthesized by simply swapping the
> arguments and using a comparison that does already exist.
> 
> Why isn't that sufficient?

I am afraid none of these patches is needed at all.

Swapping the jt/jf is plainly enough for the user land compiler.

libcap seems to do it already

# tcpdump -i lo 'len!=0 && ip6' -d
(000) ld       #pktlen
(001) jeq      #0x0             jt 5	jf 2
(002) ldh      [12]
(003) jeq      #0x86dd          jt 4	jf 5
(004) ret      #96
(005) ret      #0
# tcpdump -i lo 'len==0 && ip6' -d
(000) ld       #pktlen
(001) jeq      #0x0             jt 2	jf 5
(002) ldh      [12]
(003) jeq      #0x86dd          jt 4	jf 5
(004) ret      #96
(005) ret      #0


--
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