From: David Miller <davem@davemloft.net>
To: vkuznets@redhat.com
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
ptalbert@redhat.com, boris.ostrovsky@oracle.com,
david.vrabel@citrix.com, jgross@suse.com,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH net-next RESEND] xen-netfront: avoid packet loss when ethernet header crosses page boundary
Date: Sun, 18 Sep 2016 22:26:07 -0400 (EDT) [thread overview]
Message-ID: <20160918.222607.1930094684278444086.davem@davemloft.net> (raw)
In-Reply-To: <1474023554-24520-1-git-send-email-vkuznets@redhat.com>
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: Fri, 16 Sep 2016 12:59:14 +0200
> @@ -595,6 +596,19 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
> offset = offset_in_page(skb->data);
> len = skb_headlen(skb);
>
> + /* The first req should be at least ETH_HLEN size or the packet will be
> + * dropped by netback.
> + */
> + if (unlikely(PAGE_SIZE - offset < ETH_HLEN)) {
> + nskb = skb_copy(skb, GFP_ATOMIC);
> + if (!nskb)
> + goto drop;
> + dev_kfree_skb_any(skb);
> + skb = nskb;
> + page = virt_to_page(skb->data);
> + offset = offset_in_page(skb->data);
> + }
> +
> spin_lock_irqsave(&queue->tx_lock, flags);
I think you also have to recalculate 'len' in this case too, as
skb_headlen() will definitely be different for nskb.
In fact, I can't see how this code can work properly without that fix.
next prev parent reply other threads:[~2016-09-19 2:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-16 10:59 [PATCH net-next RESEND] xen-netfront: avoid packet loss when ethernet header crosses page boundary Vitaly Kuznetsov
2016-09-19 2:26 ` David Miller
2016-09-19 2:26 ` David Miller [this message]
2016-09-19 10:22 ` Vitaly Kuznetsov
2016-09-19 10:23 ` David Vrabel
2016-09-19 10:36 ` Vitaly Kuznetsov
2016-09-19 10:36 ` Vitaly Kuznetsov
2016-09-19 10:23 ` David Vrabel
2016-09-19 10:22 ` Vitaly Kuznetsov
-- strict thread matches above, loose matches on Subject: below --
2016-09-16 10:59 Vitaly Kuznetsov
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