Daniel Borkmann 3769229931 net: filter: let bpf_tell_extensions return SKF_AD_MAX ... Michal Sekletar added in commit ea02f9411d ("net: introduce SO_BPF_EXTENSIONS") a facility where user space can enquire the BPF ancillary instruction set, which is imho a step into the right direction for letting user space high-level to BPF optimizers make an informed decision for possibly using these extensions. The original rationale was to return through a getsockopt(2) a bitfield of which instructions are supported and which are not, as of right now, we just return 0 to indicate a base support for SKF_AD_PROTOCOL up to SKF_AD_PAY_OFFSET. Limitations of this approach are that this API which we need to maintain for a long time can only support a maximum of 32 extensions, and needs to be additionally maintained/updated when each new extension that comes in. I thought about this a bit more and what we can do here to overcome this is to just return SKF_AD_MAX. Since we never remove any extension since we cannot break user space and always linearly increase SKF_AD_MAX on each newly added extension, user space can make a decision on what extensions are supported in the whole set of extensions and which aren't, by just checking which of them from the whole set have an offset < SKF_AD_MAX of the underlying kernel. Since SKF_AD_MAX must be updated each time we add new ones, we don't need to introduce an additional enum and got maintenance for free. At some point in time when SO_BPF_EXTENSIONS becomes ubiquitous for most kernels, then an application can simply make use of this and easily be run on newer or older underlying kernels without needing to be recompiled, of course. Since that is for 3.14, it's not too late to do this change. Cc: Michal Sekletar <msekleta@redhat.com> Cc: Eric Dumazet <edumazet@google.com> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Acked-by: Michal Sekletar <msekleta@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2014-01-21 18:57:43 -08:00
..
acpi	Merge branches 'acpi-pci-pm' and 'acpi-pci-hotplug'	2013-12-31 22:03:37 +01:00
asm-generic	Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2014-01-06 17:37:45 -05:00
clocksource
crypto	crypto: scatterwalk - Use sg_chain_ptr on chain entries	2013-12-09 19:58:52 +08:00
drm	drm/radeon: 0x9649 is SUMO2 not SUMO	2013-12-23 10:03:41 -05:00
dt-bindings	For the 3.13 merge window we have a couple of new drivers for the AMS	2013-11-15 16:37:40 -08:00
keys
kvm
linux	net: filter: let bpf_tell_extensions return SKF_AD_MAX	2014-01-21 18:57:43 -08:00
math-emu
media	[media] videobuf2: Add support for file access mode flags for DMABUF exporting	2013-12-09 14:50:50 -02:00
memory
misc
net	sctp: remove macros sctp_bh_[un]lock_sock	2014-01-21 18:41:36 -08:00
pcmcia
ras
rdma	IB/core: const'ify inbuf in struct ib_udata	2013-12-16 10:38:28 -08:00
rxrpc
scsi	[SCSI] Disable WRITE SAME for RAID and virtual host adapter drivers	2013-11-29 08:48:39 +04:00
sound	ALSA: memalloc.h - fix wrong truncation of dma_addr_t	2013-12-10 15:30:46 +01:00
target	target/file: Update hw_max_sectors based on current block_size	2013-12-19 00:18:54 -08:00
trace	net: Add trace events for all receive entry points, exposing more skb fields	2014-01-14 14:46:02 -08:00
uapi	ipv6: add a flag to get the flow label used remotly	2014-01-19 17:12:31 -08:00
video	fbdev changes for 3.13	2013-11-14 14:44:20 +09:00
xen	Bug-fixes:	2013-12-20 09:34:54 -08:00
Kbuild