From: Alexei Starovoitov <ast@plumgrid•com>
To: Daniel Borkmann <daniel@iogearbox•net>, davem@davemloft•net
Cc: netdev@vger•kernel.org
Subject: Re: [PATCH net-next] ebpf, filter: do not convert skb->protocol to host endianess during runtime
Date: Thu, 19 Mar 2015 11:50:57 -0700 [thread overview]
Message-ID: <550B1A91.6030502@plumgrid.com> (raw)
In-Reply-To: <daaebd74ce31bd9ef7509c7083ba03d67af008bd.1426789778.git.daniel@iogearbox.net>
On 3/19/15 11:38 AM, Daniel Borkmann wrote:
> Commit c24973957975 ("bpf: allow BPF programs access 'protocol' and 'vlan_tci'
> fields") has added support for accessing protocol, vlan_present and vlan_tci
> into the skb offset map.
>
> As referenced in the below discussion, accessing skb->protocol from an eBPF
> program should be converted without handling endianess.
>
> The reason for this is that an eBPF program could simply do a check more
> naturally, by f.e. testing skb->protocol == htons(ETH_P_IP), where the LLVM
> compiler resolves htons() against a constant automatically during compilation
> time, as opposed to an otherwise needed run time conversion.
>
> After all, the way of programming both from a user perspective differs quite
> a lot, i.e. bpf_asm ["ld proto"] versus a C subset/LLVM.
>
> Reference: https://patchwork.ozlabs.org/patch/450819/
> Signed-off-by: Daniel Borkmann <daniel@iogearbox•net>
> ---
> (Follow-up from our previous discussion)
sure. let's save few run-time cycles.
Acked-by: Alexei Starovoitov <ast@plumgrid•com>
next prev parent reply other threads:[~2015-03-19 18:50 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-19 18:38 [PATCH net-next] ebpf, filter: do not convert skb->protocol to host endianess during runtime Daniel Borkmann
2015-03-19 18:50 ` Alexei Starovoitov [this message]
2015-03-20 19:24 ` David Miller
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