tcpdump mailing list archives
Re: vlan tagged packets and libpcap breakage
From: "David Laight" <David.Laight () ACULAB COM>
Date: Mon, 17 Dec 2012 09:50:17 -0000
I do agree that instead of a /proc entry, we should check for a kenrel version >= X where X is the upstream version that first started supporting all the features needed by libpcap for vlan filtering. This is not a compile time check but a run time one. Does anyone see any issues with this? Is there any long term implications of this, like if you backport patches to an older long term supported kernel? Are there other better ways to do this, like may be returning feature bits from an ioctl call? This is something we need to deal with on a continuous basis as we keep supporting newer AUX fields and libpcap and other user land code needs to make use of it. At the same time, they need to handle backward compatibility issues with older kernels.As Eric mentioned earlier, for now there seems not to be a reliable way to get to know which ops are present and which not. It's not really nice, but if you want to make use of those new (ANC*) features, probably checking kernel version might be the only way if I'm not missing something. Now net-next is closed, but if it reopens, I'll submit a version 2 of my patch where you've been CC'd to. If it gets in, then at least it's for sure that since kernel <xyz> this kind of feature test is present.
How are you going to tell whether a feature is present in a non-Linux kernel ? Testing kernel versions is somewhat suboptimal as support could be patched into a much older kernel (maybe not for this but ...) David _______________________________________________ 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 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)
- Re: vlan tagged packets and libpcap breakage Guy Harris (Dec 17)
- Re: vlan tagged packets and libpcap breakage Daniel Borkmann (Dec 17)
- Re: vlan tagged packets and libpcap breakage Ani Sinha (Dec 17)