From patchwork Fri Oct 30 16:50:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jesper Dangaard Brouer X-Patchwork-Id: 315972 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=-14.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS 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 000CBC56201 for ; Fri, 30 Oct 2020 16:51:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A597120756 for ; Fri, 30 Oct 2020 16:51:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PmRJ2QpZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727109AbgJ3QvC (ORCPT ); Fri, 30 Oct 2020 12:51:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:39898 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725808AbgJ3QvB (ORCPT ); Fri, 30 Oct 2020 12:51:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604076660; 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=EzMI+v2ILDpTyy8xf2G2Jpbn7b3vnXL/BR6ybaJuMdo=; b=PmRJ2QpZK640cjvInODblH+7U3zk5Nh+easoWAbfnkgCF6mLPTeYKM20StGwQrzY7V8KUG HMNLLAgpe5jFGaQfII/pRI0yu791iu1HZwRXnu9wiFhOEMHWxgja5Ki+v5/KX4OSr9AIZH w3GCmHYrxpfuXn2r/B1PiC/8XXOf/+k= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-556-rqwsCfzDOreIGSGrdL-K6A-1; Fri, 30 Oct 2020 12:50:55 -0400 X-MC-Unique: rqwsCfzDOreIGSGrdL-K6A-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 87710760C7; Fri, 30 Oct 2020 16:50:53 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.22]) by smtp.corp.redhat.com (Postfix) with ESMTP id 326AC5D99B; Fri, 30 Oct 2020 16:50:53 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id 42D9F30736C8B; Fri, 30 Oct 2020 17:50:52 +0100 (CET) Subject: [PATCH bpf-next V5 1/5] bpf: Remove MTU check in __bpf_skb_max_len From: Jesper Dangaard Brouer To: bpf@vger.kernel.org Cc: Jesper Dangaard Brouer , netdev@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , maze@google.com, lmb@cloudflare.com, shaun@tigera.io, Lorenzo Bianconi , marek@cloudflare.com, John Fastabend , Jakub Kicinski , eyal.birger@gmail.com Date: Fri, 30 Oct 2020 17:50:52 +0100 Message-ID: <160407665219.1525159.16849637089559475976.stgit@firesoul> In-Reply-To: <160407661383.1525159.12855559773280533146.stgit@firesoul> References: <160407661383.1525159.12855559773280533146.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Multiple BPF-helpers that can manipulate/increase the size of the SKB uses __bpf_skb_max_len() as the max-length. This function limit size against the current net_device MTU (skb->dev->mtu). When a BPF-prog grow the packet size, then it should not be limited to the MTU. The MTU is a transmit limitation, and software receiving this packet should be allowed to increase the size. Further more, current MTU check in __bpf_skb_max_len uses the MTU from ingress/current net_device, which in case of redirects uses the wrong net_device. Patch V4 keeps a sanity max limit of SKB_MAX_ALLOC (16KiB). The real limit is elsewhere in the system. Jesper's testing[1] showed it was not possible to exceed 8KiB when expanding the SKB size via BPF-helper. The limiting factor is the define KMALLOC_MAX_CACHE_SIZE which is 8192 for SLUB-allocator (CONFIG_SLUB) in-case PAGE_SIZE is 4096. This define is in-effect due to this being called from softirq context see code __gfp_pfmemalloc_flags() and __do_kmalloc_node(). Jakub's testing showed that frames above 16KiB can cause NICs to reset (but not crash). Keep this sanity limit at this level as memory layer can differ based on kernel config. [1] https://github.com/xdp-project/bpf-examples/tree/master/MTU-tests V3: replace __bpf_skb_max_len() with define and use IPv6 max MTU size. Signed-off-by: Jesper Dangaard Brouer --- net/core/filter.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 2ca5eecebacf..1ee97fdeea64 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3552,11 +3552,7 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff, return 0; } -static u32 __bpf_skb_max_len(const struct sk_buff *skb) -{ - return skb->dev ? skb->dev->mtu + skb->dev->hard_header_len : - SKB_MAX_ALLOC; -} +#define BPF_SKB_MAX_LEN SKB_MAX_ALLOC BPF_CALL_4(sk_skb_adjust_room, struct sk_buff *, skb, s32, len_diff, u32, mode, u64, flags) @@ -3605,7 +3601,7 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff, { u32 len_cur, len_diff_abs = abs(len_diff); u32 len_min = bpf_skb_net_base_len(skb); - u32 len_max = __bpf_skb_max_len(skb); + u32 len_max = BPF_SKB_MAX_LEN; __be16 proto = skb->protocol; bool shrink = len_diff < 0; u32 off; @@ -3688,7 +3684,7 @@ static int bpf_skb_trim_rcsum(struct sk_buff *skb, unsigned int new_len) static inline int __bpf_skb_change_tail(struct sk_buff *skb, u32 new_len, u64 flags) { - u32 max_len = __bpf_skb_max_len(skb); + u32 max_len = BPF_SKB_MAX_LEN; u32 min_len = __bpf_skb_min_len(skb); int ret; @@ -3764,7 +3760,7 @@ static const struct bpf_func_proto sk_skb_change_tail_proto = { static inline int __bpf_skb_change_head(struct sk_buff *skb, u32 head_room, u64 flags) { - u32 max_len = __bpf_skb_max_len(skb); + u32 max_len = BPF_SKB_MAX_LEN; u32 new_len = skb->len + head_room; int ret; From patchwork Fri Oct 30 16:50:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jesper Dangaard Brouer X-Patchwork-Id: 315971 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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED 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 B0539C4741F for ; Fri, 30 Oct 2020 16:51:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51A2E20727 for ; Fri, 30 Oct 2020 16:51:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Saf3o+m3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727286AbgJ3QvN (ORCPT ); Fri, 30 Oct 2020 12:51:13 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:59836 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726461AbgJ3QvL (ORCPT ); Fri, 30 Oct 2020 12:51:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604076669; 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=3r+pFgzaiYfSSD1NLAsVdGJ7DSzPuxegrYOI82nF42Y=; b=Saf3o+m33MQikboSGbXenm/VdyfxWWzaTIm4T8KSSL51rhdzGAb4Jvji7Py+PZ4FUaM9Ck x58Isu3Xdi+RRGCmjs7/ODmBTcsdASgot0I9N3TpVL4TEkX8MW4DxqltyrNU2JScmAOWN6 tlVsx4iNHpE36T5T8wj+SVh25ZWQ34M= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-230-HlmtBLh5N7SMes3xkivVPA-1; Fri, 30 Oct 2020 12:51:07 -0400 X-MC-Unique: HlmtBLh5N7SMes3xkivVPA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C6B121084D70; Fri, 30 Oct 2020 16:51:05 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.22]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6867B1000320; Fri, 30 Oct 2020 16:50:58 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id 5AA0D30736C8B; Fri, 30 Oct 2020 17:50:57 +0100 (CET) Subject: [PATCH bpf-next V5 2/5] bpf: bpf_fib_lookup return MTU value as output when looked up From: Jesper Dangaard Brouer To: bpf@vger.kernel.org Cc: Jesper Dangaard Brouer , netdev@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , maze@google.com, lmb@cloudflare.com, shaun@tigera.io, Lorenzo Bianconi , marek@cloudflare.com, John Fastabend , Jakub Kicinski , eyal.birger@gmail.com Date: Fri, 30 Oct 2020 17:50:57 +0100 Message-ID: <160407665728.1525159.18300199766779492971.stgit@firesoul> In-Reply-To: <160407661383.1525159.12855559773280533146.stgit@firesoul> References: <160407661383.1525159.12855559773280533146.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The BPF-helpers for FIB lookup (bpf_xdp_fib_lookup and bpf_skb_fib_lookup) can perform MTU check and return BPF_FIB_LKUP_RET_FRAG_NEEDED. The BPF-prog don't know the MTU value that caused this rejection. If the BPF-prog wants to implement PMTU (Path MTU Discovery) (rfc1191) it need to know this MTU value for the ICMP packet. Patch change lookup and result struct bpf_fib_lookup, to contain this MTU value as output via a union with 'tot_len' as this is the value used for the MTU lookup. V5: - Fixed uninit value spotted by Dan Carpenter. - Name struct output member mtu_result Reported-by: kernel test robot Reported-by: Dan Carpenter Signed-off-by: Jesper Dangaard Brouer Reviewed-by: David Ahern --- include/uapi/linux/bpf.h | 11 +++++++++-- net/core/filter.c | 22 +++++++++++++++------- tools/include/uapi/linux/bpf.h | 11 +++++++++-- 3 files changed, 33 insertions(+), 11 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index e6ceac3f7d62..01b2b17c645a 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2219,6 +2219,9 @@ union bpf_attr { * * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the * packet is not forwarded or needs assist from full stack * + * If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU + * was exceeded and result params->mtu contains the MTU. + * * long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags) * Description * Add an entry to, or update a sockhash *map* referencing sockets. @@ -4872,9 +4875,13 @@ struct bpf_fib_lookup { __be16 sport; __be16 dport; - /* total length of packet from network header - used for MTU check */ - __u16 tot_len; + union { /* used for MTU check */ + /* input to lookup */ + __u16 tot_len; /* total length of packet from network hdr */ + /* output: MTU value (if requested check_mtu) */ + __u16 mtu_result; + }; /* input: L3 device index for lookup * output: device index from FIB lookup */ diff --git a/net/core/filter.c b/net/core/filter.c index 1ee97fdeea64..edb543c477b6 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5265,12 +5265,14 @@ static const struct bpf_func_proto bpf_skb_get_xfrm_state_proto = { #if IS_ENABLED(CONFIG_INET) || IS_ENABLED(CONFIG_IPV6) static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params, const struct neighbour *neigh, - const struct net_device *dev) + const struct net_device *dev, u32 mtu) { memcpy(params->dmac, neigh->ha, ETH_ALEN); memcpy(params->smac, dev->dev_addr, ETH_ALEN); params->h_vlan_TCI = 0; params->h_vlan_proto = 0; + if (mtu) + params->mtu_result = mtu; /* union with tot_len */ return 0; } @@ -5286,8 +5288,8 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, struct net_device *dev; struct fib_result res; struct flowi4 fl4; + u32 mtu = 0; int err; - u32 mtu; dev = dev_get_by_index_rcu(net, params->ifindex); if (unlikely(!dev)) @@ -5354,8 +5356,10 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, if (check_mtu) { mtu = ip_mtu_from_fib_result(&res, params->ipv4_dst); - if (params->tot_len > mtu) + if (params->tot_len > mtu) { + params->mtu_result = mtu; /* union with tot_len */ return BPF_FIB_LKUP_RET_FRAG_NEEDED; + } } nhc = res.nhc; @@ -5389,7 +5393,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, if (!neigh) return BPF_FIB_LKUP_RET_NO_NEIGH; - return bpf_fib_set_fwd_params(params, neigh, dev); + return bpf_fib_set_fwd_params(params, neigh, dev, mtu); } #endif @@ -5406,7 +5410,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, struct flowi6 fl6; int strict = 0; int oif, err; - u32 mtu; + u32 mtu = 0; /* link local addresses are never forwarded */ if (rt6_need_strict(dst) || rt6_need_strict(src)) @@ -5481,8 +5485,10 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, if (check_mtu) { mtu = ipv6_stub->ip6_mtu_from_fib6(&res, dst, src); - if (params->tot_len > mtu) + if (params->tot_len > mtu) { + params->mtu_result = mtu; /* union with tot_len */ return BPF_FIB_LKUP_RET_FRAG_NEEDED; + } } if (res.nh->fib_nh_lws) @@ -5502,7 +5508,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, if (!neigh) return BPF_FIB_LKUP_RET_NO_NEIGH; - return bpf_fib_set_fwd_params(params, neigh, dev); + return bpf_fib_set_fwd_params(params, neigh, dev, mtu); } #endif @@ -5571,6 +5577,8 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb, dev = dev_get_by_index_rcu(net, params->ifindex); if (!is_skb_forwardable(dev, skb)) rc = BPF_FIB_LKUP_RET_FRAG_NEEDED; + + params->mtu_result = dev->mtu; /* union with tot_len */ } return rc; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index e6ceac3f7d62..01b2b17c645a 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -2219,6 +2219,9 @@ union bpf_attr { * * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the * packet is not forwarded or needs assist from full stack * + * If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU + * was exceeded and result params->mtu contains the MTU. + * * long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags) * Description * Add an entry to, or update a sockhash *map* referencing sockets. @@ -4872,9 +4875,13 @@ struct bpf_fib_lookup { __be16 sport; __be16 dport; - /* total length of packet from network header - used for MTU check */ - __u16 tot_len; + union { /* used for MTU check */ + /* input to lookup */ + __u16 tot_len; /* total length of packet from network hdr */ + /* output: MTU value (if requested check_mtu) */ + __u16 mtu_result; + }; /* input: L3 device index for lookup * output: device index from FIB lookup */ From patchwork Fri Oct 30 16:51:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jesper Dangaard Brouer X-Patchwork-Id: 315970 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=-9.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS autolearn=unavailable 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 CD662C4741F for ; Fri, 30 Oct 2020 16:51:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D17A2075E for ; Fri, 30 Oct 2020 16:51:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="CWbD7dQF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727312AbgJ3QvV (ORCPT ); Fri, 30 Oct 2020 12:51:21 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:39041 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727289AbgJ3QvU (ORCPT ); Fri, 30 Oct 2020 12:51:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604076678; 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=lUWxeT/l8C4pE90/Z0wnSWvne2OpdL0HrDJKXu4kZaw=; b=CWbD7dQFUR33N9LBkKBF3AKVAbzD8MJwFUlz9sxZYomRelAVoHxtWJxJDa7jJrepr2x3wE k8WLyRsP0SZYySXcNIQ4m/LYViqAil3WMgWvhhH7OJ7OFR+yDF9RtawRkurQPcxJrLjKKB +wk6kAG3SDLXSjhgdqzyvyqEIczQkQs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-442-QHelfDn5N46mzv3DezAwTA-1; Fri, 30 Oct 2020 12:51:14 -0400 X-MC-Unique: QHelfDn5N46mzv3DezAwTA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5E071101962A; Fri, 30 Oct 2020 16:51:12 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.22]) by smtp.corp.redhat.com (Postfix) with ESMTP id C19571A340; Fri, 30 Oct 2020 16:51:08 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id 8A5BE30736C8B; Fri, 30 Oct 2020 17:51:07 +0100 (CET) Subject: [PATCH bpf-next V5 4/5] bpf: drop MTU check when doing TC-BPF redirect to ingress From: Jesper Dangaard Brouer To: bpf@vger.kernel.org Cc: Jesper Dangaard Brouer , netdev@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , maze@google.com, lmb@cloudflare.com, shaun@tigera.io, Lorenzo Bianconi , marek@cloudflare.com, John Fastabend , Jakub Kicinski , eyal.birger@gmail.com Date: Fri, 30 Oct 2020 17:51:07 +0100 Message-ID: <160407666748.1525159.1515139110258948831.stgit@firesoul> In-Reply-To: <160407661383.1525159.12855559773280533146.stgit@firesoul> References: <160407661383.1525159.12855559773280533146.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The use-case for dropping the MTU check when TC-BPF does redirect to ingress, is described by Eyal Birger in email[0]. The summary is the ability to increase packet size (e.g. with IPv6 headers for NAT64) and ingress redirect packet and let normal netstack fragment packet as needed. [0] https://lore.kernel.org/netdev/CAHsH6Gug-hsLGHQ6N0wtixdOa85LDZ3HNRHVd0opR=19Qo4W4Q@mail.gmail.com/ V4: - Keep net_device "up" (IFF_UP) check. - Adjustment to handle bpf_redirect_peer() helper Signed-off-by: Jesper Dangaard Brouer --- include/linux/netdevice.h | 31 +++++++++++++++++++++++++++++-- net/core/dev.c | 19 ++----------------- net/core/filter.c | 14 +++++++++++--- 3 files changed, 42 insertions(+), 22 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 964b494b0e8d..bd02ddab8dfe 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3891,11 +3891,38 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb); bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb); +static __always_inline bool __is_skb_forwardable(const struct net_device *dev, + const struct sk_buff *skb, + const bool check_mtu) +{ + const u32 vlan_hdr_len = 4; /* VLAN_HLEN */ + unsigned int len; + + if (!(dev->flags & IFF_UP)) + return false; + + if (!check_mtu) + return true; + + len = dev->mtu + dev->hard_header_len + vlan_hdr_len; + if (skb->len <= len) + return true; + + /* if TSO is enabled, we don't care about the length as the packet + * could be forwarded without being segmented before + */ + if (skb_is_gso(skb)) + return true; + + return false; +} + static __always_inline int ____dev_forward_skb(struct net_device *dev, - struct sk_buff *skb) + struct sk_buff *skb, + const bool check_mtu) { if (skb_orphan_frags(skb, GFP_ATOMIC) || - unlikely(!is_skb_forwardable(dev, skb))) { + unlikely(!__is_skb_forwardable(dev, skb, check_mtu))) { atomic_long_inc(&dev->rx_dropped); kfree_skb(skb); return NET_RX_DROP; diff --git a/net/core/dev.c b/net/core/dev.c index 9499a414d67e..445ccf92c149 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2188,28 +2188,13 @@ static inline void net_timestamp_set(struct sk_buff *skb) bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb) { - unsigned int len; - - if (!(dev->flags & IFF_UP)) - return false; - - len = dev->mtu + dev->hard_header_len + VLAN_HLEN; - if (skb->len <= len) - return true; - - /* if TSO is enabled, we don't care about the length as the packet - * could be forwarded without being segmented before - */ - if (skb_is_gso(skb)) - return true; - - return false; + return __is_skb_forwardable(dev, skb, true); } EXPORT_SYMBOL_GPL(is_skb_forwardable); int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb) { - int ret = ____dev_forward_skb(dev, skb); + int ret = ____dev_forward_skb(dev, skb, true); if (likely(!ret)) { skb->protocol = eth_type_trans(skb, dev); diff --git a/net/core/filter.c b/net/core/filter.c index bd4a416bd9ad..71b78b8d443c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2083,13 +2083,21 @@ static const struct bpf_func_proto bpf_csum_level_proto = { static inline int __bpf_rx_skb(struct net_device *dev, struct sk_buff *skb) { - return dev_forward_skb(dev, skb); + int ret = ____dev_forward_skb(dev, skb, false); + + if (likely(!ret)) { + skb->protocol = eth_type_trans(skb, dev); + skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN); + ret = netif_rx(skb); + } + + return ret; } static inline int __bpf_rx_skb_no_mac(struct net_device *dev, struct sk_buff *skb) { - int ret = ____dev_forward_skb(dev, skb); + int ret = ____dev_forward_skb(dev, skb, false); if (likely(!ret)) { skb->dev = dev; @@ -2480,7 +2488,7 @@ int skb_do_redirect(struct sk_buff *skb) goto out_drop; dev = ops->ndo_get_peer_dev(dev); if (unlikely(!dev || - !is_skb_forwardable(dev, skb) || + !__is_skb_forwardable(dev, skb, false) || net_eq(net, dev_net(dev)))) goto out_drop; skb->dev = dev;