From: Stephen Hemminger <shemminger@vyatta.com>
To: ani@aristanetworks.com
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Michael Richardson <mcr@sandelman.ca>,
netdev@vger.kernel.org, tcpdump-workers@lists.tcpdump.org,
Francesco Ruggeri <fruggeri@aristanetworks.com>
Subject: Re: [tcpdump-workers] vlan tagged packets and libpcap breakage
Date: Tue, 11 Dec 2012 15:12:31 -0800 [thread overview]
Message-ID: <20121211151231.0272015b@nehalam.linuxnetplumber.net> (raw)
In-Reply-To: <alpine.OSX.2.00.1212111432430.78903@animac.local>
On Tue, 11 Dec 2012 14:36:33 -0800 (PST)
Ani Sinha <ani@aristanetworks.com> wrote:
> >
> > It is possible to test for the presence of support of the new vlan bpf
> > extensions by attempting to load a filter that uses them. As only valid
> > filters can be loaded, old kernels that do not support filtering of vlan
> > tags will fail to load the a test filter with uses them.
>
> Unfortunately I do not see this. The sk_chk_filter() does not have a
> default in the case statement and the check will not detect an unknown
> instruction. It will fail when the filter is run and as far as I can see,
> the packet will be dropped. Something like this might help?
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index c23543c..96338aa 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -548,6 +548,8 @@ int sk_chk_filter(struct sock_filter *filter, unsigned int flen)
> return -EINVAL;
> /* Some instructions need special checks */
> switch (code) {
> + /* for unknown instruction, return EINVAL */
> + default : return -EINVAL;
> case BPF_S_ALU_DIV_K:
> /* check for division by zero */
> if (ftest->k == 0)
Did you test this? I think it will blow up for some existing instructions
like BPF_S_ALU_XOR_X or any of the other non-special instructions.
Also it is not formatted correctly for the kernel programming style.
ERROR: space prohibited before that ':' (ctx:WxW)
#86: FILE: net/core/filter.c:552:
+ default : return -EINVAL;
^
prev parent reply other threads:[~2012-12-11 23:18 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAOxq_8Nd8VP3MaNBfUt9v82nmGDpxZz5_5QMdsruET1tjwuQPw@mail.gmail.com>
[not found] ` <3246.1351717319@obiwan.sandelman.ca>
2012-10-31 21:50 ` [tcpdump-workers] vlan tagged packets and libpcap breakage Ani Sinha
2012-10-31 22:20 ` Guy Harris
2012-10-31 22:35 ` Ani Sinha
2012-11-01 0:50 ` [tcpdump-workers] " Guy Harris
2012-11-01 1:22 ` Ani Sinha
2012-12-06 21:20 ` Ani Sinha
2012-11-02 16:13 ` Bill Fenner
2012-11-13 22:41 ` Ani Sinha
2012-11-13 22:42 ` [tcpdump-workers] " Ani Sinha
2012-11-14 18:58 ` Michael Richardson
2012-10-31 22:42 ` [tcpdump-workers] " Michael Richardson
2012-12-12 21:53 ` Ani Sinha
2012-12-12 22:16 ` Ani Sinha
2012-12-13 8:35 ` [tcpdump-workers] " Daniel Borkmann
2012-12-13 17:34 ` Ani Sinha
2012-12-13 21:49 ` Daniel Borkmann
2012-12-13 22:07 ` Ani Sinha
2012-12-17 9:50 ` David Laight
2012-12-17 10:35 ` Guy Harris
2012-12-17 11:08 ` Daniel Borkmann
2012-12-17 19:49 ` [tcpdump-workers] " Ani Sinha
2012-11-16 6:51 ` Eric W. Biederman
2012-11-17 22:14 ` Michael Richardson
2012-11-17 23:16 ` Daniel Borkmann
2012-11-17 23:37 ` Eric W. Biederman
2012-11-17 23:33 ` Eric W. Biederman
2012-12-06 21:22 ` Ani Sinha
2012-12-06 22:19 ` Eric W. Biederman
2012-12-06 22:40 ` Ani Sinha
2012-12-07 0:55 ` Ani Sinha
2012-12-07 1:03 ` [tcpdump-workers] " Eric W. Biederman
2012-12-07 1:28 ` Ani Sinha
2012-12-07 1:31 ` Ani Sinha
2012-12-07 1:41 ` Eric W. Biederman
2012-12-07 1:59 ` Michael Richardson
2012-12-11 0:11 ` [tcpdump-workers] " Ani Sinha
2012-12-11 22:36 ` Ani Sinha
2012-12-11 23:04 ` Eric Dumazet
2012-12-12 0:46 ` Ani Sinha
2012-12-12 0:50 ` [tcpdump-workers] " Ani Sinha
2012-12-11 23:12 ` Stephen Hemminger [this message]
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