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([240d:1a:c0d:9f00:4f2f:926a:23dd:8588]) by smtp.gmail.com with ESMTPSA id l7-20020a170903120700b0016d692ff95esm3906400plh.133.2022.08.19.20.25.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Aug 2022 20:25:24 -0700 (PDT) From: Shigeru Yoshida To: mareklindner@neomailbox.ch, sw@simonwunderlich.de, a@unstable.cc, sven@narfation.org Subject: [PATCH] batman-adv: Fix hang up with small MTU hard-interface Date: Sat, 20 Aug 2022 12:25:16 +0900 Message-Id: <20220820032516.200446-1-syoshida@redhat.com> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com ARC-Seal: i=1; s=20121; d=open-mesh.org; t=1660965929; a=rsa-sha256; cv=none; b=q1ujplS9XuAtAYuqzmfp+FyispV8xi0ZOso0rFV7DeQx2U5OMq00VrK3pIeILXbpVBVNYA 2zvx+gcs0NoAAuwj80v/zMYtHDmSU4bYG1YN4YeaelNBw06/o0ToaNowW2p1Xw4DPeV0qB +dnxhqZ26/Et+3xC3wKU+Mcwv9zFdww= ARC-Authentication-Results: i=1; diktynna.open-mesh.org; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=dlEoL5Ul; spf=pass (diktynna.open-mesh.org: domain of syoshida@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=syoshida@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=open-mesh.org; s=20121; t=1660965929; 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:dkim-signature; bh=rCdaW8VW9KVhf4KlGQHWkOq32wI36GjplhXzdCZm9VA=; b=o380OeEbJV3l97mxC+TKEDSyDSH/5CDA1zmUgqeJecfbdX/DhKcEGv8G1aMkOAClMirzvI 6d9bPGqKjk1ZvjLqRLo8NgX3SUm9cQDalWaFWdIka0eHAouoNBGWkLcIraU8NlEwkmYC6L 57DDt0WQtkKpsy2lNH/R9Nvy1p4aJHs= X-MailFrom: syoshida@redhat.com X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-b.a.t.m.a.n.lists.open-mesh.org-0; header-match-b.a.t.m.a.n.lists.open-mesh.org-1 Message-ID-Hash: JZQWIB7UMUDBTYPAR4NYHPUJED6DFXPI X-Message-ID-Hash: JZQWIB7UMUDBTYPAR4NYHPUJED6DFXPI X-Mailman-Approved-At: Sat, 20 Aug 2022 06:55:06 +0200 CC: b.a.t.m.a.n@lists.open-mesh.org, linux-kernel@vger.kernel.org, Shigeru Yoshida X-Mailman-Version: 3.2.1 Precedence: list Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking List-Id: The list for a Better Approach To Mobile Ad-hoc Networking Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: The system hangs up when batman-adv soft-interface is created on hard-interface with small MTU. For example, the following commands create batman-adv soft-interface on dummy interface with zero MTU: # ip link add name dummy0 type dummy # ip link set mtu 0 dev dummy0 # ip link set up dev dummy0 # ip link add name bat0 type batadv # ip link set dev dummy0 master bat0 These commands cause the system hang up with the following messages: [ 90.578925][ T6689] batman_adv: bat0: Adding interface: dummy0 [ 90.580884][ T6689] batman_adv: bat0: The MTU of interface dummy0 is too small (0) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1560 would solve the problem. [ 90.586264][ T6689] batman_adv: bat0: Interface activated: dummy0 [ 90.590061][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320) [ 90.595517][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320) [ 90.598499][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320) This patch fixes this issue by returning error when enabling hard-interface with small MTU size. Signed-off-by: Shigeru Yoshida --- net/batman-adv/hard-interface.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index b8f8da7ee3de..dce5557800e9 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -700,6 +700,9 @@ int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface, int max_header_len = batadv_max_header_len(); int ret; + if (hard_iface->net_dev->mtu < ETH_MIN_MTU + max_header_len) + return -EINVAL; + if (hard_iface->if_status != BATADV_IF_NOT_IN_USE) goto out;