From: Ani Sinha <ani@aristanetworks.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org,
Francesco Ruggeri <fruggeri@aristanetworks.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
tcpdump-workers@lists.tcpdump.org,
Michael Richardson <mcr@sandelman.ca>
Subject: Re: vlan tagged packets and libpcap breakage
Date: Tue, 11 Dec 2012 16:46:05 -0800 [thread overview]
Message-ID: <CAOxq_8PRGWh86oqvxqvPEqmW1TN+0ztNzhczbTqfHKeOinozzQ@mail.gmail.com> (raw)
In-Reply-To: <1355267060.27891.139.camel@edumazet-glaptop>
On Tue, Dec 11, 2012 at 3:04 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Tue, 2012-12-11 at 14:36 -0800, Ani Sinha 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)
>
> This patch is wrong.
yes I generated this patch wrong.
>
> Check lines 546, 547, 548 where we do the check for unknown instructions
>
> code = codes[code];
> if (!code)
> return -EINVAL;
yepph it's OK here.
>
> If you want to test ANCILLARY possible values, its already too late, as
> old kernels wont use any patch anyway.
yepph, I was looking at possible ancilliary values. Basically this
case statement :
#define ANCILLARY(CODE) case SKF_AD_OFF + SKF_AD_##CODE: \
code = BPF_S_ANC_##CODE; \
break
switch (ftest->k) {
ANCILLARY(PROTOCOL);
ANCILLARY(PKTTYPE);
ANCILLARY(IFINDEX);
ANCILLARY(NLATTR);
ANCILLARY(NLATTR_NEST);
ANCILLARY(MARK);
ANCILLARY(QUEUE);
ANCILLARY(HATYPE);
ANCILLARY(RXHASH);
ANCILLARY(CPU);
ANCILLARY(ALU_XOR_X);
ANCILLARY(VLAN_TAG);
ANCILLARY(VLAN_TAG_PRESENT);
}
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next prev parent reply other threads:[~2012-12-12 0:46 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 [this message]
2012-12-12 0:50 ` Ani Sinha
2012-12-11 23:12 ` Stephen Hemminger
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