From mboxrd@z Thu Jan 1 00:00:00 1970 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 8A15BC4321E for ; Fri, 2 Dec 2022 20:27:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233960AbiLBU1S (ORCPT ); Fri, 2 Dec 2022 15:27:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233637AbiLBU1P (ORCPT ); Fri, 2 Dec 2022 15:27:15 -0500 Received: from out-24.mta0.migadu.com (out-24.mta0.migadu.com [IPv6:2001:41d0:1004:224b::18]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B42EADF8F for ; Fri, 2 Dec 2022 12:27:13 -0800 (PST) Message-ID: <4cf2ecd4-2f21-848a-00df-4e4fd86667eb@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1670012831; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NUcEALuux82cTjstILvzqBke9w8vB4f799oxTJvNJ0Y=; b=rgsljsucGydqBrYw+l7rotjrX/oVrOk7tpEFaDxm9NO0nrNpXPgum9XLfUHhUKSsxsl22W WcsIMySL2O40G/zJZyozp1a+WQGByA4zzq+1unUQj9KktzMJ9PxRMKYbTmRcn9hsCM5Vgi uf4iisiXfmbCRLvGWo2NKm+jz7pVRZw= Date: Fri, 2 Dec 2022 12:27:01 -0800 MIME-Version: 1.0 Subject: Re: [PATCH bpf-next,v4 2/4] xfrm: interface: Add unstable helpers for setting/getting XFRM metadata from TC-BPF Content-Language: en-US To: Eyal Birger Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, steffen.klassert@secunet.com, herbert@gondor.apana.org.au, andrii@kernel.org, daniel@iogearbox.net, nicolas.dichtel@6wind.com, razor@blackwall.org, mykolal@fb.com, ast@kernel.org, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, liuhangbin@gmail.com, lixiaoyan@google.com References: <20221202095920.1659332-1-eyal.birger@gmail.com> <20221202095920.1659332-3-eyal.birger@gmail.com> <6d0e13eb-63e0-a777-2a27-7f2e02867a13@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 12/2/22 11:42 AM, Eyal Birger wrote: > Hi Martin, > > On Fri, Dec 2, 2022 at 9:08 PM Martin KaFai Lau wrote: >> >> On 12/2/22 1:59 AM, Eyal Birger wrote: >>> +__used noinline >>> +int bpf_skb_set_xfrm_info(struct __sk_buff *skb_ctx, >>> + const struct bpf_xfrm_info *from) >>> +{ >>> + struct sk_buff *skb = (struct sk_buff *)skb_ctx; >>> + struct metadata_dst *md_dst; >>> + struct xfrm_md_info *info; >>> + >>> + if (unlikely(skb_metadata_dst(skb))) >>> + return -EINVAL; >>> + >>> + md_dst = this_cpu_ptr(xfrm_md_dst); >>> + >>> + info = &md_dst->u.xfrm_info; >>> + >>> + info->if_id = from->if_id; >>> + info->link = from->link; >>> + skb_dst_force(skb); >>> + info->dst_orig = skb_dst(skb); >>> + >>> + dst_hold((struct dst_entry *)md_dst); >>> + skb_dst_set(skb, (struct dst_entry *)md_dst); >> >> >> I may be missed something obvious and this just came to my mind, >> >> What stops cleanup_xfrm_interface_bpf() being run while skb is still holding the >> md_dst? >> > Oh I think you're right. I missed this. > > In order to keep this implementation I suppose it means that the module would > not be allowed to be removed upon use of this kfunc. but this could be seen as > annoying from the configuration user experience. > > Alternatively the metadata dsts can be separately allocated from the kfunc, > which is probably the simplest approach to maintain, so I'll work on that > approach. If it means dst_alloc on every skb, it will not be cheap. Another option is to metadata_dst_alloc_percpu() once during the very first bpf_skb_set_xfrm_info() call and the xfrm_md_dst memory will never be freed. It is a tradeoff but likely the correct one. You can take a look at bpf_get_skb_set_tunnel_proto().