From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH V5 5/7] xen-netfront: reduce gso_max_size to account for max TCP header Date: Wed, 17 Apr 2013 14:51:42 +0100 Message-ID: <1366206702.25579.46.camel@zakaz.uk.xensource.com> References: <1366045581-31349-1-git-send-email-wei.liu2@citrix.com> <1366045581-31349-6-git-send-email-wei.liu2@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: "netdev@vger.kernel.org" , "xen-devel@lists.xen.org" , "annie.li@oracle.com" , "konrad.wilk@oracle.com" , "jbeulich@suse.com" , "wdauchy@gmail.com" , David Vrabel To: Wei Liu Return-path: Received: from smtp.eu.citrix.com ([46.33.159.39]:56179 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966116Ab3DQNvo (ORCPT ); Wed, 17 Apr 2013 09:51:44 -0400 In-Reply-To: <1366045581-31349-6-git-send-email-wei.liu2@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2013-04-15 at 18:06 +0100, Wei Liu wrote: > The maximum packet including header that can be handled by netfront / netback > wire format is 65535. Reduce gso_max_size accordingly. > > Drop skb and print warning when skb->len > 65535. This can 1) save the effort > to send malformed packet to netback, 2) help spotting misconfiguration of > netfront in the future. > > Signed-off-by: Wei Liu Acked-by: Ian Campbell (one commentlet is that you've used 65535 a few times (or left existing uses) but you've also just defined XEN_NETIF_MAX_TX_SIZE which would be a better thing to use) > --- > drivers/net/xen-netfront.c | 16 ++++++++++++++-- > include/xen/interface/io/netif.h | 1 + > 2 files changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c > index 1bb2e20..7c53d0c 100644 > --- a/drivers/net/xen-netfront.c > +++ b/drivers/net/xen-netfront.c > @@ -36,7 +36,7 @@ > #include > #include > #include > -#include > +#include > #include > #include > #include > @@ -547,6 +547,16 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev) > unsigned int len = skb_headlen(skb); > unsigned long flags; > > + /* If skb->len is too big for wire format, drop skb and alert > + * user about misconfiguration. > + */ > + if (unlikely(skb->len > XEN_NETIF_MAX_TX_SIZE)) { > + net_alert_ratelimited( > + "xennet: skb->len = %u, too big for wire format\n", > + skb->len); > + goto drop; > + } > + > slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) + > xennet_count_skb_frag_slots(skb); > if (unlikely(slots > MAX_SKB_FRAGS + 1)) { > @@ -1058,7 +1068,7 @@ err: > > static int xennet_change_mtu(struct net_device *dev, int mtu) > { > - int max = xennet_can_sg(dev) ? 65535 - ETH_HLEN : ETH_DATA_LEN; > + int max = xennet_can_sg(dev) ? 65535 - MAX_TCP_HEADER : ETH_DATA_LEN; > > if (mtu > max) > return -EINVAL; > @@ -1362,6 +1372,8 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev) > SET_ETHTOOL_OPS(netdev, &xennet_ethtool_ops); > SET_NETDEV_DEV(netdev, &dev->dev); > > + netif_set_gso_max_size(netdev, 65535 - MAX_TCP_HEADER); > + > np->netdev = netdev; > > netif_carrier_off(netdev); > diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h > index 9dfc120..58fadca 100644 > --- a/include/xen/interface/io/netif.h > +++ b/include/xen/interface/io/netif.h > @@ -47,6 +47,7 @@ > #define _XEN_NETTXF_extra_info (3) > #define XEN_NETTXF_extra_info (1U<<_XEN_NETTXF_extra_info) > > +#define XEN_NETIF_MAX_TX_SIZE 0xFFFF > struct xen_netif_tx_request { > grant_ref_t gref; /* Reference to buffer page */ > uint16_t offset; /* Offset within buffer page */