From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xie He Subject: [PATCH] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len Date: Sun, 26 Jul 2020 04:05:24 -0700 Message-ID: <20200726110524.151957-1-xie.he.0141@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=HiCRrQCxdIa5HIW679AjRc9wXiJ6/iMtc+VYMoge+3c=; b=WYkENyzYNLhggQIvWLddjbWxCjYrMSbzqNPQL1fj6YeDJ/9qPZxc5cQQwyNHLyZIM/ FGCZ9jLTyq9WFfYDRg0E8vaLl0le0BdIJ14LYb2+DbnaHJV1UoWAXTcURJqo7n8C837A UlP3Rcv2MkXCbkjYNkwvi0vKnYAorDTChREz40/kYkvpaF8rvEEABaWVdEhpYCzMCFCy Qml69TMC14lB3pyB9RatZMP5mMEyL+JY+t9GodCEblfEf8rNTk4bFCFJv0LFLnUHQuAO pxjVfCsKTX2lM8rooNJj53HGkb1EaDKuaM5ardkNToiC64I5vBjEzx8nWDftzGytEXfC vPbQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: "David S. Miller" , Jakub Kicinski , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-x25@vger.kernel.org Cc: Xie He In net/packet/af_packet.c, the function packet_snd first reserves a headroom of length (dev->hard_header_len + dev->needed_headroom). Then if the socket is a SOCK_DGRAM socket, it calls dev_hard_header, which calls dev->header_ops->create, to create the link layer header. If the socket is a SOCK_RAW socket, it "un-reserves" a headroom of length (dev->hard_header_len), and assumes the user to provide the appropriate link layer header. So according to the logic of af_packet.c, dev->hard_header_len should be the length of the header that would be created by dev->header_ops->create. However, this driver doesn't provide dev->header_ops, so logically dev->hard_header_len should be 0. So we should use dev->needed_headroom instead of dev->hard_header_len to request necessary headroom to be allocated. Signed-off-by: Xie He --- drivers/net/wan/lapbether.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c index b2868433718f..34cf6db89912 100644 --- a/drivers/net/wan/lapbether.c +++ b/drivers/net/wan/lapbether.c @@ -305,6 +305,7 @@ static void lapbeth_setup(struct net_device *dev) dev->netdev_ops = &lapbeth_netdev_ops; dev->needs_free_netdev = true; dev->type = ARPHRD_X25; + dev->hard_header_len = 0; dev->mtu = 1000; dev->addr_len = 0; } @@ -331,7 +332,8 @@ static int lapbeth_new_device(struct net_device *dev) * then this driver prepends a length field of 2 bytes, * then the underlying Ethernet device prepends its own header. */ - ndev->hard_header_len = -1 + 3 + 2 + dev->hard_header_len; + ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len + + dev->needed_headroom; lapbeth = netdev_priv(ndev); lapbeth->axdev = ndev; -- 2.25.1