From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99F4D1D54F for ; Mon, 2 Oct 2023 18:49:42 +0000 (UTC) Received: from mail-lj1-x22a.google.com (mail-lj1-x22a.google.com [IPv6:2a00:1450:4864:20::22a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C2469B; Mon, 2 Oct 2023 11:49:39 -0700 (PDT) Received: by mail-lj1-x22a.google.com with SMTP id 38308e7fff4ca-2bfea381255so581751fa.3; Mon, 02 Oct 2023 11:49:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1696272578; x=1696877378; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=QArjfUTTcgJwwXB2cHAnDmcQypRbqPPM7kA043mYYzA=; b=Y1/N4ixQxacvshz2OvOUeh5iTSNIMmzW6fz938wKqu/3SKX54FuSXkYB1dPE6spDot w8O5KHTT0PMnKxMKXJNsq0dZCrfiDO0tybQKmV2GTmUE2op+GjXrt0BBUHMCCwFGEmCm Z1pvQ8H+xQ9j/+qFq94swx4oAG3QJbxllBFP3v3K1BtiDiIwhdwCtomlpveuursCcjN7 wmtqapB0UCug3SEbxy4nMBNfwUKBOIOsvJqqGWML19gqWGM7kuZxK0Men9PuPD8xwkBq iGt+c4dUj3URFEtwJfGU0JUKnWcruwbJ0PpQnSwFBLSN5gZOCI4/KQLghXzy7KE3QBlW tUWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696272578; x=1696877378; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=QArjfUTTcgJwwXB2cHAnDmcQypRbqPPM7kA043mYYzA=; b=urpi3N2YdXOe/oR+TQTkqPj4LNouOBg6G1VvQLQvr/3HKpspFf2P19QyeDJPLO2IZ8 6xulmlfso+YppN5M6mKQZDMX3M3GUb0so/gclPZqzqDQ1sOM4oNvnubjwoeSnx3myOYb 4zmH9STm9+OV37U0uwI7mi/7nbaAIYVMHkPlBBa0T+ip/TQ/Xtwfj7Jlgvz6uEWZ2cNS GN8nO8AKRCff7flu6pSp6L5PrYuVDIKrfyOb7GD6fybo+iS9FXyHLzkdjh8n9dewM9wH mVf8biIxPG/riR9TFr/G/QtEVB35w6p5oLnnnTY2XgbJ/62tpEmJ+jS+JksQNemewCPL ClRg== X-Gm-Message-State: AOJu0Yw9C06BOK2h4BErxNt+r0VOIsh3ndZjwUxs0dPtqT51LpbTilu8 BCzhj1VaA7V0wPzDRAjWL+A= X-Google-Smtp-Source: AGHT+IH3M+qevVH7Kr9KnZ3kt9CcZO9iV+yGM+179shLGbvDskmG59LydCDjwjajO6Hvh17XAOJKvQ== X-Received: by 2002:a05:6512:2813:b0:4fb:caed:95c3 with SMTP id cf19-20020a056512281300b004fbcaed95c3mr12030931lfb.53.1696272577665; Mon, 02 Oct 2023 11:49:37 -0700 (PDT) Received: from pc.localnet (c-7e17235c.012-196-6c6b701.bbcust.telenor.se. [92.35.23.126]) by smtp.gmail.com with ESMTPSA id f21-20020a19ae15000000b00500d1f67be9sm4820914lfc.43.2023.10.02.11.49.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Oct 2023 11:49:37 -0700 (PDT) From: Henrik =?ISO-8859-1?Q?Lindstr=F6m?= To: Florian Westphal Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: macvtap performs IP defragmentation, causing MTU problems for virtual machines Date: Mon, 02 Oct 2023 20:49:36 +0200 Message-ID: <2197902.NgBsaNRSFp@pc> In-Reply-To: <20231002092010.GA30843@breakpoint.cc> References: <20231002092010.GA30843@breakpoint.cc> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Spam-Status: No, score=-1.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Had to change "return 0" to "return vif" but other than that your changes seem to work, even with macvlan defragmentation removed. I tested it by sending 8K fragmented multicast packets, with 5 macvlans on the receiving side. I consistently received 6 copies of the packet (1 from the real interface and 1 per macvlan). While doing this i had my VM running with a macvtap, and it was receiving fragmented packets as expected. Here are the changes i was testing with, first time sending a diff over mail so hope it works :-) diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c index 02bd201bc7e5..5f638433cef9 100644 --- a/drivers/net/macvlan.c +++ b/drivers/net/macvlan.c @@ -462,10 +462,6 @@ static rx_handler_result_t macvlan_handle_frame(struct sk_buff **pskb) if (is_multicast_ether_addr(eth->h_dest)) { unsigned int hash; - skb = ip_check_defrag(dev_net(skb->dev), skb, IP_DEFRAG_MACVLAN); - if (!skb) - return RX_HANDLER_CONSUMED; - *pskb = skb; eth = eth_hdr(skb); if (macvlan_forward_source(skb, port, eth->h_source)) { kfree_skb(skb); diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index a4941f53b523..30b822dfa222 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -479,11 +479,29 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb, return err; } +static int ip_defrag_vif(const struct sk_buff *skb, const struct net_device *dev) +{ + int vif = l3mdev_master_ifindex_rcu(dev); + + if (vif) + return vif; + + /* some folks insist that receiving a fragmented mcast dgram on n devices shall + * result in n defragmented packets. + */ + if (skb->pkt_type == PACKET_BROADCAST || skb->pkt_type == PACKET_MULTICAST) { + if (dev) + vif = dev->ifindex; + } + + return vif; +} + /* Process an incoming IP datagram fragment. */ int ip_defrag(struct net *net, struct sk_buff *skb, u32 user) { struct net_device *dev = skb->dev ? : skb_dst(skb)->dev; - int vif = l3mdev_master_ifindex_rcu(dev); + int vif = ip_defrag_vif(skb, dev); struct ipq *qp; __IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);