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 224F1EB64D9 for ; Mon, 26 Jun 2023 21:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230320AbjFZVX2 (ORCPT ); Mon, 26 Jun 2023 17:23:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229788AbjFZVXZ (ORCPT ); Mon, 26 Jun 2023 17:23:25 -0400 Received: from smtp-fw-2101.amazon.com (smtp-fw-2101.amazon.com [72.21.196.25]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E56C1C2; Mon, 26 Jun 2023 14:23:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1687814604; x=1719350604; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=AT/KPQKjSjG7XfGIa1PPJzx4QqnG/LdnhEF+Jfk66C8=; b=TE+AdBplSVc8mUvH0Ok/sqnE5lgn7mWtybROSF7802hIxl42Gk/tKRsW OkXJjpJZdHZJoQwnBl2kaTEkBivJxalof9blCYPT4wMmQz/qK1twx8VNg oGnqi2OLFVCPFPhCKHVmPo2TbAwmnH+97yQxKZ/mYxtBKM6rJFLDsi786 4=; X-IronPort-AV: E=Sophos;i="6.01,160,1684800000"; d="scan'208";a="336291050" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-pdx-2a-m6i4x-21d8d9f4.us-west-2.amazon.com) ([10.43.8.6]) by smtp-border-fw-2101.iad2.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jun 2023 21:23:19 +0000 Received: from EX19MTAUWB002.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan3.pdx.amazon.com [10.236.137.198]) by email-inbound-relay-pdx-2a-m6i4x-21d8d9f4.us-west-2.amazon.com (Postfix) with ESMTPS id 9FF0C8A669; Mon, 26 Jun 2023 21:23:17 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX19MTAUWB002.ant.amazon.com (10.250.64.231) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.26; Mon, 26 Jun 2023 21:23:17 +0000 Received: from 88665a182662.ant.amazon.com.com (10.187.170.15) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.30; Mon, 26 Jun 2023 21:23:12 +0000 From: Kuniyuki Iwashima To: CC: , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH bpf-next v3 6/7] bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign Date: Mon, 26 Jun 2023 14:23:03 -0700 Message-ID: <20230626212303.91671-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20230626210846.84206-1-kuniyu@amazon.com> References: <20230626210846.84206-1-kuniyu@amazon.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.187.170.15] X-ClientProxiedBy: EX19D039UWB003.ant.amazon.com (10.13.138.93) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kuniyuki Iwashima Date: Mon, 26 Jun 2023 14:08:46 -0700 > From: Lorenz Bauer > Date: Mon, 26 Jun 2023 16:09:03 +0100 > > Currently the bpf_sk_assign helper in tc BPF context refuses SO_REUSEPORT > > sockets. This means we can't use the helper to steer traffic to Envoy, > > which configures SO_REUSEPORT on its sockets. In turn, we're blocked > > from removing TPROXY from our setup. > > > > The reason that bpf_sk_assign refuses such sockets is that the > > bpf_sk_lookup helpers don't execute SK_REUSEPORT programs. Instead, > > one of the reuseport sockets is selected by hash. This could cause > > dispatch to the "wrong" socket: > > > > sk = bpf_sk_lookup_tcp(...) // select SO_REUSEPORT by hash > > bpf_sk_assign(skb, sk) // SK_REUSEPORT wasn't executed > > > > Fixing this isn't as simple as invoking SK_REUSEPORT from the lookup > > helpers unfortunately. In the tc context, L2 headers are at the start > > of the skb, while SK_REUSEPORT expects L3 headers instead. > > > > Instead, we execute the SK_REUSEPORT program when the assigned socket > > is pulled out of the skb, further up the stack. This creates some > > trickiness with regards to refcounting as bpf_sk_assign will put both > > refcounted and RCU freed sockets in skb->sk. reuseport sockets are RCU > > freed. We can infer that the sk_assigned socket is RCU freed if the > > reuseport lookup succeeds, but convincing yourself of this fact isn't > > straight forward. Therefore we defensively check refcounting on the > > sk_assign sock even though it's probably not required in practice. > > > > Fixes: 8e368dc72e86 ("bpf: Fix use of sk->sk_reuseport from sk_assign") > > Fixes: cf7fbe660f2d ("bpf: Add socket assign support") > > Co-developed-by: Daniel Borkmann > > Signed-off-by: Daniel Borkmann > > Signed-off-by: Lorenz Bauer > > Cc: Joe Stringer > > Link: https://lore.kernel.org/bpf/CACAyw98+qycmpQzKupquhkxbvWK4OFyDuuLMBNROnfWMZxUWeA@mail.gmail.com/ > > --- > > include/net/inet6_hashtables.h | 59 ++++++++++++++++++++++++++++++++++++++---- > > include/net/inet_hashtables.h | 52 +++++++++++++++++++++++++++++++++++-- > > include/net/sock.h | 7 +++-- > > include/uapi/linux/bpf.h | 3 --- > > net/core/filter.c | 2 -- > > net/ipv4/udp.c | 8 ++++-- > > net/ipv6/udp.c | 10 ++++--- > > tools/include/uapi/linux/bpf.h | 3 --- > > 8 files changed, 122 insertions(+), 22 deletions(-) > > > > diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h > > index 4d2a1a3c0be7..4d300af6ccb6 100644 > > --- a/include/net/inet6_hashtables.h > > +++ b/include/net/inet6_hashtables.h > > @@ -103,6 +103,49 @@ static inline struct sock *__inet6_lookup(struct net *net, > > daddr, hnum, dif, sdif); > > } > > > > +static inline > > +struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff, > > + const struct in6_addr *saddr, const __be16 sport, > > + const struct in6_addr *daddr, const __be16 dport, > > + bool *refcounted, inet6_ehashfn_t ehashfn) > > +{ > > + struct sock *sk, *reuse_sk; > > + bool prefetched; > > + > > + sk = skb_steal_sock(skb, refcounted, &prefetched); > > + if (!sk) > > + return NULL; > > + > > + if (!prefetched) > > + return sk; > > + > > + if (sk->sk_protocol == IPPROTO_TCP) { > > + if (sk->sk_state != TCP_LISTEN) > > + return sk; > > + } else if (sk->sk_protocol == IPPROTO_UDP) { > > + if (sk->sk_state != TCP_CLOSE) > > + return sk; > > + } else { > > + return sk; > > + } > > + > > + reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff, > > + saddr, sport, daddr, ntohs(dport), > > + ehashfn); > > + if (!reuse_sk || reuse_sk == sk) > > + return sk; > > + > > + /* We've chosen a new reuseport sock which is never refcounted. > > + * sk might be refcounted however, drop the reference if necessary. > > + */ > > + if (*refcounted) { > > + sock_put(sk); > > + *refcounted = false; > > + } > > As *refcounted should be false here (TCP_LISTEN and UDP sk have > SOCK_RCU_FREE and other sk does not reach here), I prefer adding > WARN_ON_ONCE() to catch a future bug: > > WARN_ON_ONCE(*refcounted); > sock_put(sk); Sorry, sock_put(sk) is not needed here.