From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: [PATCH v4 net-next 5/5] net: filter: split 'struct sk_filter' into socket and bpf parts Date: Fri, 1 Aug 2014 21:03:41 +0200 Message-ID: <20140801190341.GA28642@salvia> References: <1406777656-27755-1-git-send-email-ast@plumgrid.com> <1406777656-27755-6-git-send-email-ast@plumgrid.com> <20140731194059.GA8681@salvia> <20140801160612.GA4679@salvia> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , Daniel Borkmann , Willem de Bruijn , Kees Cook , Network Development , LKML , netfilter-devel To: Alexei Starovoitov Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org On Fri, Aug 01, 2014 at 09:50:31AM -0700, Alexei Starovoitov wrote: > On Fri, Aug 1, 2014 at 9:06 AM, Pablo Neira Ayuso wrote: > > On Thu, Jul 31, 2014 at 02:02:19PM -0700, Alexei Starovoitov wrote: > >> On Thu, Jul 31, 2014 at 12:40 PM, Pablo Neira Ayuso wrote: > >> > On Wed, Jul 30, 2014 at 08:34:16PM -0700, Alexei Starovoitov wrote: > >> >> clean up names related to socket filtering and bpf in the following way: > >> >> - everything that deals with sockets keeps 'sk_*' prefix > >> >> - everything that is pure BPF is changed to 'bpf_*' prefix > >> >> > >> >> split 'struct sk_filter' into > >> >> struct sk_filter { > >> >> atomic_t refcnt; > >> >> struct rcu_head rcu; > >> >> struct bpf_prog *prog; > >> >> }; > >> > > >> > I think you can use 'struct bpf_prog prog' instead so the entire > >> > sk_filter remains in the same memory blob (as it is before this > >> > patch). > >> > > >> > You can add an inline function to retrieve the bpg prog from the > >> > filter: > >> > > >> > static inline struct bpf_prog *sk_filter_bpf(struct sk_filter *) > >> > > >> > and use it whenever possible to fetch the bpf program. I'm suggesting > >> > this because we can use the zero array size in the socket filtering > >> > abstraction later on, if the function above is used, this just needs > >> > one line in that function to be updated to fetch the program from the > >> > placeholder. > >> > >> correct. It would speed up SK_RUN_FILTER macro a little and I've > >> considered it, but decided to go with the pointer for two reasons: > >> 1.In sk_attach_filter() the bpf_prog is allocated, then reallocated > >> as part of bpf_prepare_filter(). My patch #1 cleans up that part to > >> avoid 'struct sock *' dependency, so all bpf_* functions work > >> purely with bpf_prog... If bpf_prog is embedded inside sk_filter, > >> bpf_prepare_filter would need to have a callback to reallocate > >> the container struct and pass this callback through the chain > >> of calls, which is ugly > > > > I think you can allocate the sk_filter once you get the final bpf > > program, then you can memcpy() it. This adds some extra overhead in > > the sk_attach_filter(), but that path is executed from user context > > and it's also a rare operation (only once to attach the filter). It's > > still not going to be a beauty, but IMO it's worth to focus on getting > > that little speed up in the packet path at the cost of adding some > > overhead on the socket attach path. > > memcpy of 'bpf_prog' is not just 'not a beauty', it won't work, since > bpf_prog is freed via work_queue due to JIT. See bpf_jit_free() [...] I see, in this patch you renamed sk_filter to bpf_prog in bpf_jit_free() so no access to sk_filter anymore and alignment needs a closer look. OK... let's stick to the struct bpf_prog pointer.