tcpdump mailing list archives
Re: vlan tagged packets and libpcap breakage
From: Eric Dumazet <eric.dumazet () gmail com>
Date: Tue, 11 Dec 2012 15:04:20 -0800
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. Check lines 546, 547, 548 where we do the check for unknown instructions code = codes[code]; if (!code) return -EINVAL; If you want to test ANCILLARY possible values, its already too late, as old kernels wont use any patch anyway. _______________________________________________ tcpdump-workers mailing list tcpdump-workers () lists tcpdump org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
Current thread:
- Re: vlan tagged packets and libpcap breakage, (continued)
- Re: vlan tagged packets and libpcap breakage Eric W. Biederman (Dec 06)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 06)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 06)
- Re: vlan tagged packets and libpcap breakage Eric W. Biederman (Dec 06)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 06)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 06)
- Re: vlan tagged packets and libpcap breakage Eric W. Biederman (Dec 06)
- Re: vlan tagged packets and libpcap breakage Michael Richardson (Dec 06)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 10)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 11)
- Re: vlan tagged packets and libpcap breakage Eric Dumazet (Dec 13)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 11)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 11)
- Re: vlan tagged packets and libpcap breakage Stephen Hemminger (Dec 13)
- Message not available
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 12)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 12)
- Re: vlan tagged packets and libpcap breakage Daniel Borkmann (Dec 13)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 13)
- Re: vlan tagged packets and libpcap breakage Daniel Borkmann (Dec 13)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 13)
- Re: vlan tagged packets and libpcap breakage David Laight (Dec 17)