From patchwork Tue Aug 24 17:30:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin KaFai Lau X-Patchwork-Id: 12455647 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF93BC4320A for ; Tue, 24 Aug 2021 17:32:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE692610E8 for ; Tue, 24 Aug 2021 17:32:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241461AbhHXRc7 (ORCPT ); Tue, 24 Aug 2021 13:32:59 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:54260 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239841AbhHXRa5 (ORCPT ); Tue, 24 Aug 2021 13:30:57 -0400 Received: from pps.filterd (m0109333.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 17OHU10O001203 for ; Tue, 24 Aug 2021 10:30:13 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=2/7YEoOaFLaNT1hOty6dyIlZiLaKsNSIpD0Ys8xvk1o=; b=kY8gzOCnKgS4E/ve4YawkL0mLOZw2tO3+VLBnH4YCjPtXMuWPpueH1ydeXM6O9+5q4aR cDX3SYZhbBmnvzbVlc4S1FcGn/pgMvUhJ2XGdJwLYjW3NZ3403ub0ZMDfhJdGVeOW09b oFp2fo4Z17fpwZGYdCe3MGPUrNUSwXpFRTY= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 3amfqt7t7n-5 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 24 Aug 2021 10:30:13 -0700 Received: from intmgw001.05.ash9.facebook.com (2620:10d:c085:208::11) by mail.thefacebook.com (2620:10d:c085:11d::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 24 Aug 2021 10:30:09 -0700 Received: by devbig005.ftw2.facebook.com (Postfix, from userid 6611) id 3FF0E2940D05; Tue, 24 Aug 2021 10:30:07 -0700 (PDT) From: Martin KaFai Lau To: CC: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , , Subject: [PATCH v2 bpf-next 1/4] bpf: tcp: Allow bpf-tcp-cc to call bpf_(get|set)sockopt Date: Tue, 24 Aug 2021 10:30:07 -0700 Message-ID: <20210824173007.3976921-1-kafai@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210824173000.3976470-1-kafai@fb.com> References: <20210824173000.3976470-1-kafai@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-FB-Source: Intern X-Proofpoint-GUID: p4wbFEH8SVQIK1PSVpUH0oRmRmKjb1Tj X-Proofpoint-ORIG-GUID: p4wbFEH8SVQIK1PSVpUH0oRmRmKjb1Tj X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-24_05:2021-08-24,2021-08-24 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 adultscore=0 phishscore=0 mlxlogscore=999 mlxscore=0 spamscore=0 impostorscore=0 suspectscore=0 clxscore=1015 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108240115 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net This patch allows the bpf-tcp-cc to call bpf_setsockopt. One use case is to allow a bpf-tcp-cc switching to another cc during init(). For example, when the tcp flow is not ecn ready, the bpf_dctcp can switch to another cc by calling setsockopt(TCP_CONGESTION). During setsockopt(TCP_CONGESTION), the new tcp-cc's init() will be called and this could cause a recursion but it is stopped by the current trampoline's logic (in the prog->active counter). While retiring a bpf-tcp-cc (e.g. in tcp_v[46]_destroy_sock()), the tcp stack calls bpf-tcp-cc's release(). To avoid the retiring bpf-tcp-cc making further changes to the sk, bpf_setsockopt is not available to the bpf-tcp-cc's release(). This will avoid release() making setsockopt() call that will potentially allocate new resources. Although the bpf-tcp-cc already has a more powerful way to read tcp_sock from the PTR_TO_BTF_ID, it is usually expected that bpf_getsockopt and bpf_setsockopt are available together. Thus, bpf_getsockopt() is also added to all tcp_congestion_ops except release(). When the old bpf-tcp-cc is calling setsockopt(TCP_CONGESTION) to switch to a new cc, the old bpf-tcp-cc will be released by bpf_struct_ops_put(). Thus, this patch also puts the bpf_struct_ops_map after a rcu grace period because the trampoline's image cannot be freed while the old bpf-tcp-cc is still running. bpf-tcp-cc can only access icsk_ca_priv as SCALAR. All kernel's tcp-cc is also accessing the icsk_ca_priv as SCALAR. The size of icsk_ca_priv has already been raised a few times to avoid extra kmalloc and memory referencing. The only exception is the kernel's tcp_cdg.c that stores a kmalloc()-ed pointer in icsk_ca_priv. To avoid the old bpf-tcp-cc accidentally overriding this tcp_cdg's pointer value stored in icsk_ca_priv after switching and without over-complicating the bpf's verifier for this one exception in tcp_cdg, this patch does not allow switching to tcp_cdg. If there is a need, bpf_tcp_cdg can be implemented and then use the bpf_sk_storage as the extended storage. bpf_sk_setsockopt proto has only been recently added and used in bpf-sockopt and bpf-iter-tcp, so impose the tcp_cdg limitation in the same proto instead of adding a new proto specifically for bpf-tcp-cc. Signed-off-by: Martin KaFai Lau --- kernel/bpf/bpf_struct_ops.c | 22 +++++++++++++++++++- net/core/filter.c | 6 ++++++ net/ipv4/bpf_tcp_ca.c | 41 ++++++++++++++++++++++++++++++++++--- 3 files changed, 65 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c index 70f6fd4fa305..d6731c32864e 100644 --- a/kernel/bpf/bpf_struct_ops.c +++ b/kernel/bpf/bpf_struct_ops.c @@ -28,6 +28,7 @@ struct bpf_struct_ops_value { struct bpf_struct_ops_map { struct bpf_map map; + struct rcu_head rcu; const struct bpf_struct_ops *st_ops; /* protect map_update */ struct mutex lock; @@ -622,6 +623,14 @@ bool bpf_struct_ops_get(const void *kdata) return refcount_inc_not_zero(&kvalue->refcnt); } +static void bpf_struct_ops_put_rcu(struct rcu_head *head) +{ + struct bpf_struct_ops_map *st_map; + + st_map = container_of(head, struct bpf_struct_ops_map, rcu); + bpf_map_put(&st_map->map); +} + void bpf_struct_ops_put(const void *kdata) { struct bpf_struct_ops_value *kvalue; @@ -632,6 +641,17 @@ void bpf_struct_ops_put(const void *kdata) st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue); - bpf_map_put(&st_map->map); + /* The struct_ops's function may switch to another struct_ops. + * + * For example, bpf_tcp_cc_x->init() may switch to + * another tcp_cc_y by calling + * setsockopt(TCP_CONGESTION, "tcp_cc_y"). + * During the switch, bpf_struct_ops_put(tcp_cc_x) is called + * and its map->refcnt may reach 0 which then free its + * trampoline image while tcp_cc_x is still running. + * + * Thus, a rcu grace period is needed here. + */ + call_rcu(&st_map->rcu, bpf_struct_ops_put_rcu); } } diff --git a/net/core/filter.c b/net/core/filter.c index 59b8f5050180..a863fd6d9b9b 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5039,6 +5039,12 @@ static int _bpf_getsockopt(struct sock *sk, int level, int optname, BPF_CALL_5(bpf_sk_setsockopt, struct sock *, sk, int, level, int, optname, char *, optval, int, optlen) { + if (level == SOL_TCP && optname == TCP_CONGESTION) { + if (optlen >= sizeof("cdg") - 1 && + !strncmp("cdg", optval, optlen)) + return -ENOTSUPP; + } + return _bpf_setsockopt(sk, level, optname, optval, optlen); } diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c index 9e41eff4a685..0dcee9df1326 100644 --- a/net/ipv4/bpf_tcp_ca.c +++ b/net/ipv4/bpf_tcp_ca.c @@ -10,6 +10,9 @@ #include #include +/* "extern" is to avoid sparse warning. It is only used in bpf_struct_ops.c. */ +extern struct bpf_struct_ops bpf_tcp_congestion_ops; + static u32 optional_ops[] = { offsetof(struct tcp_congestion_ops, init), offsetof(struct tcp_congestion_ops, release), @@ -163,6 +166,19 @@ static const struct bpf_func_proto bpf_tcp_send_ack_proto = { .arg2_type = ARG_ANYTHING, }; +static u32 prog_ops_moff(const struct bpf_prog *prog) +{ + const struct btf_member *m; + const struct btf_type *t; + u32 midx; + + midx = prog->expected_attach_type; + t = bpf_tcp_congestion_ops.type; + m = &btf_type_member(t)[midx]; + + return btf_member_bit_offset(t, m) / 8; +} + static const struct bpf_func_proto * bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) @@ -174,6 +190,28 @@ bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id, return &bpf_sk_storage_get_proto; case BPF_FUNC_sk_storage_delete: return &bpf_sk_storage_delete_proto; + case BPF_FUNC_setsockopt: + /* Does not allow release() to call setsockopt. + * release() is called when the current bpf-tcp-cc + * is retiring. It is not allowed to call + * setsockopt() to make further changes which + * may potentially allocate new resources. + */ + if (prog_ops_moff(prog) != + offsetof(struct tcp_congestion_ops, release)) + return &bpf_sk_setsockopt_proto; + return NULL; + case BPF_FUNC_getsockopt: + /* Since get/setsockopt is usually expected to + * be available together, disable getsockopt for + * release also to avoid usage surprise. + * The bpf-tcp-cc already has a more powerful way + * to read tcp_sock from the PTR_TO_BTF_ID. + */ + if (prog_ops_moff(prog) != + offsetof(struct tcp_congestion_ops, release)) + return &bpf_sk_getsockopt_proto; + return NULL; default: return bpf_base_func_proto(func_id); } @@ -286,9 +324,6 @@ static void bpf_tcp_ca_unreg(void *kdata) tcp_unregister_congestion_control(kdata); } -/* Avoid sparse warning. It is only used in bpf_struct_ops.c. */ -extern struct bpf_struct_ops bpf_tcp_congestion_ops; - struct bpf_struct_ops bpf_tcp_congestion_ops = { .verifier_ops = &bpf_tcp_ca_verifier_ops, .reg = bpf_tcp_ca_reg,