From patchwork Thu Mar 2 17:27:54 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Westphal X-Patchwork-Id: 13157691 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41E79C6FA8E for ; Thu, 2 Mar 2023 17:28:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230030AbjCBR2Q (ORCPT ); Thu, 2 Mar 2023 12:28:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38206 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230047AbjCBR2O (ORCPT ); Thu, 2 Mar 2023 12:28:14 -0500 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:237:300::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7DD25231F6; Thu, 2 Mar 2023 09:28:11 -0800 (PST) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1pXmiv-0002bd-PC; Thu, 02 Mar 2023 18:28:09 +0100 From: Florian Westphal To: bpf@vger.kernel.org Cc: , Florian Westphal Subject: [PATCH RFC v2 bpf-next 0/3] bpf: add netfilter program type Date: Thu, 2 Mar 2023 18:27:54 +0100 Message-Id: <20230302172757.9548-1-fw@strlen.de> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net X-Patchwork-State: RFC Add minimal support to hook bpf programs to netfilter hooks, e.g. PREROUTING or FORWARD. For this the most relevant parts for registering a netfilter hook via the in-kernel api are exposed to userspace via bpf_link. The new program type is 'tracing style' and assumes skb dynptrs are used rather than 'direct packet access'. With this its possible to build a small test program such as: #include "vmlinux.h" extern int bpf_dynptr_from_skb(struct __sk_buff *skb, __u64 flags, struct bpf_dynptr *ptr__uninit) __ksym; extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, uint32_t offset, void *buffer, uint32_t buffer__sz) __ksym; SEC("netfilter") int nf_test(struct bpf_nf_ctx *ctx) { struct nf_hook_state *state = ctx->state; struct sk_buff *skb = ctx->skb; const struct iphdr *iph, _iph; const struct tcphdr *th, _th; struct bpf_dynptr ptr; if (bpf_dynptr_from_skb(skb, 0, &ptr)) return NF_DROP; iph = bpf_dynptr_slice(&ptr, 0, &_iph, sizeof(_iph)); if (!iph) return NF_DROP; th = bpf_dynptr_slice(&ptr, iph->ihl << 2, &_th, sizeof(_th)); if (!th) return NF_DROP; bpf_printk("accept %x:%d->%x:%d, hook %d ifin %d\n", iph->saddr, bpf_ntohs(th->source), iph->daddr, bpf_ntohs(th->dest), state->hook, state->in->ifindex); return NF_ACCEPT; } (output can be observed via /sys/kernel/tracing/trace_pipe). At this point I think its fairly complete. Known problems are: - no test cases, I will look into this. Might take some time though because I might have to extend libbpf first. - nfnetlink_hook needs minor work so that it can dump the bpf program id. As-is, userspace could see that a bpf program is attached to e.g. forward and output, but it cannot tell which program. This is fairly simple and doesn't need changes on bpf side. I will work on these address those two next unless anyone spots a fundamental issue with this rfc set. Florian Westphal (3): bpf: add bpf_link support for BPF_NETFILTER programs libbpf: sync header file, add nf prog section name bpf: minimal support for programs hooked into netfilter framework include/linux/bpf_types.h | 4 + include/linux/netfilter.h | 1 + include/net/netfilter/nf_hook_bpf.h | 8 ++ include/uapi/linux/bpf.h | 12 ++ kernel/bpf/btf.c | 5 + kernel/bpf/syscall.c | 6 + kernel/bpf/verifier.c | 3 + net/netfilter/Kconfig | 3 + net/netfilter/Makefile | 1 + net/netfilter/nf_bpf_link.c | 192 ++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 12 ++ tools/lib/bpf/libbpf.c | 1 + 12 files changed, 248 insertions(+) create mode 100644 include/net/netfilter/nf_hook_bpf.h create mode 100644 net/netfilter/nf_bpf_link.c