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Date: Tue, 15 Apr 2014 18:44:29 +0200 From: Daniel Borkmann <dborkman@...hat.com> To: Chema Gonzalez <chema@...gle.com> CC: David Miller <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org, ast@...mgrid.com Subject: Re: [PATCH] filter: added BPF random opcode On 04/15/2014 06:30 PM, Chema Gonzalez wrote: > On Tue, Apr 15, 2014 at 12:24 AM, Daniel Borkmann <dborkman@...hat.com> wrote: >> Hi Chema, >> >> [cc'ing Alexei as well] >> >> note, net-next is still closed, so you might need to resend this later >> on again when it opens up. > I will. Thanks! Great, thanks. >> On 04/15/2014 01:02 AM, Chema Gonzalez wrote: >>> diff --git a/tools/net/bpf_exp.l b/tools/net/bpf_exp.l >>> index bf7be77..804256f 100644 >>> --- a/tools/net/bpf_exp.l >>> +++ b/tools/net/bpf_exp.l >>> @@ -92,6 +92,7 @@ extern void yyerror(const char *str); >>> "#"?("cpu") { return K_CPU; } >>> "#"?("vlan_tci") { return K_VLANT; } >>> "#"?("vlan_pr") { return K_VLANP; } >>> +"#"?("random") { return K_RAND; } >> >> >> Thanks for also updating bpf_asm ! :) > bpf_asm was key in ensuring this worked. In fact, we should modify the > Makefile so that it relies on the local filter.h before the > /usr/include/ one (my Ubuntu Precise /usr/include/linux/filter.h does > not define BPF_MOD, BPF_XOR, SKF_AD_VLAN_TAG, SKF_AD_VLAN_TAG_PRESENT, > or SKF_AD_PAY_OFFSET). Good point, feel free to send a patch. :) >> I think using just "rnd" is cleaner here. > I think using always random (in fact I may s/K_RAND/K_RANDOM/g) allows > easier grepping. I know it's just nitpicking, but I'd be happier if that would either be rnd or rand in bpf_asm. >>> diff --git a/tools/net/icmp_random.bpf b/tools/net/icmp_random.bpf >>> new file mode 100644 >>> index 0000000..b9adcbf >>> --- /dev/null >>> +++ b/tools/net/icmp_random.bpf >>> @@ -0,0 +1,12 @@ >>> +# icmp random packet sampling, 1 in 4 >>> +ldh [12] >>> +jne #0x800, drop >>> +ldb [23] >>> +jneq #1, drop >>> +# get a random uint32 number >>> +ld random >>> +mod #4 >>> +jneq #1, drop >>> +ret #-1 >>> +drop: ret #0 >>> + >>> >> >> This example should rather go into Documentation/networking/filter.txt's >> example section, rather than tools/net/ . > I'll add it there. Ok, thanks. > Now, I'd like to add a new directory for BPF programs (tools/net/bpf/ > ?). It allows playing with bpf_asm. For 'playing', I'd rather be happy to add that to the documentation file in Documentation/networking/filter.txt where we have other examples, or alternatively, if there is really no other way around, a new folder inside of Documentation/networking/ . -- 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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