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netfilter: meta: add PRANDOM support

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Can be used to randomly match packets e.g. for statistic traffic sampling.

See commit 3ad0040573
("bpf: split state from prandom_u32() and consolidate {c, e}BPF prngs")
for more info why this doesn't use prandom_u32 directly.

Unlike bpf nft_meta can be built as a module, so add an EXPORT_SYMBOL
for prandom_seed_full_state too.

Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2016-02-16 17:24:08 +01:00 committed by Pablo Neira Ayuso
parent f12d33f4d8
commit b07edbe1cf
3 changed files with 14 additions and 0 deletions
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2
include/uapi/linux/netfilter/nf_tables.h
View file

@ -681,6 +681,7 @@ enum nft_exthdr_attributes {
* @NFT_META_IIFGROUP: packet input interface group
* @NFT_META_OIFGROUP: packet output interface group
* @NFT_META_CGROUP: socket control group (skb->sk->sk_classid)
* @NFT_META_PRANDOM: a 32bit pseudo-random number
*/
enum nft_meta_keys {
NFT_META_LEN,
@ -707,6 +708,7 @@ enum nft_meta_keys {
NFT_META_IIFGROUP,
NFT_META_OIFGROUP,
NFT_META_CGROUP,
NFT_META_PRANDOM,
};
/**

1
lib/random32.c
View file

@ -255,6 +255,7 @@ void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
prandom_warmup(state);
}
}
EXPORT_SYMBOL(prandom_seed_full_state);
/*
* Generate better values after random number generator

11
net/netfilter/nft_meta.c
View file

@ -28,6 +28,8 @@
#include <uapi/linux/netfilter_bridge.h> /* NF_BR_PRE_ROUTING */
static DEFINE_PER_CPU(struct rnd_state, nft_prandom_state);
void nft_meta_get_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
@ -181,6 +183,11 @@ void nft_meta_get_eval(const struct nft_expr *expr,
*dest = sock_cgroup_classid(&sk->sk_cgrp_data);
break;
#endif
case NFT_META_PRANDOM: {
struct rnd_state *state = this_cpu_ptr(&nft_prandom_state);
*dest = prandom_u32_state(state);
break;
}
default:
WARN_ON(1);
goto err;
@ -277,6 +284,10 @@ int nft_meta_get_init(const struct nft_ctx *ctx,
case NFT_META_OIFNAME:
len = IFNAMSIZ;
break;
case NFT_META_PRANDOM:
prandom_init_once(&nft_prandom_state);
len = sizeof(u32);
break;
default:
return -EOPNOTSUPP;
}