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Date: Fri, 20 Mar 2015 11:27:18 +0100 From: Michal Sekletar <msekleta@...hat.com> To: Alexei Starovoitov <ast@...mgrid.com> Cc: netdev@...r.kernel.org, Jiri Pirko <jpirko@...hat.com>, Ralf Baechle <ralf@...ux-mips.org>, Russell King <linux@....linux.org.uk>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Martin Schwidefsky <schwidefsky@...ibm.com>, "David S. Miller" <davem@...emloft.net> Subject: Re: [PATCH net-next v2] filter: introduce SKF_AD_VLAN_TPID BPF extension On Thu, Mar 19, 2015 at 09:08:35AM -0700, Alexei Starovoitov wrote: > On 3/19/15 4:10 AM, Michal Sekletar wrote: > >If vlan offloading takes place then vlan header is removed from frame > >and its contents, both vlan_tci and vlan_proto, is available to userspace via > >TPACKET interface. However, only vlan_tci can be used in BPF filters. > > > >This commit introduces new BPF extension. It makes possible to load value of > >vlan_proto (vlan TPID) to register A. > > Agree with the idea, though we need to decide whether to do ntohs on > vlan_proto or not. Since right now your patch makes it consistent > on different architectures. > > For arch where extended BPF jit is available the following: > > + case SKF_AD_OFF + SKF_AD_VLAN_TPID: > ... > > + /* A = ntohs(A) [emitting a nop or swap16] */ > > + *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16); > > will make sure that it's doing ntohs, > whereas arm JIT is doing normal 16-bit load. > ppc can be both big and little, so PPC_LHZ_OFFS is incorrect. > > Since it's a new field, I think it makes sense not to do ntohs at all. > Let bpf programs do htons(PROTO_CONSTANT), since it can be done at > compile time instead of run-time. Doing htons is not needed for vlan_tci thus I wanted to avoid surprise for users. But of course I'll do whatever you think is the best. Also in v3 I will leave out all the jit bits. Once non-jit bits are merged then I will be sending separate patches for the rest. Hope that makes sense, Michal > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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