[PATCH 2/6] xen-netfront: reduce gso_max_size to account for ethernet header
From: Wei Liu <hidden>
Date: 2013-03-25 11:09:04
Subsystem:
networking drivers, the rest, xen hypervisor interface · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Juergen Gross, Stefano Stabellini
The maximum packet including ethernet 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 <redacted> --- drivers/net/xen-netfront.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 5527663..3ae9dc1 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c@@ -547,6 +547,18 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev) unsigned int len = skb_headlen(skb); unsigned long flags; + /* Wire format of xen_netif_tx_request only supports skb->len + * < 64K, because size field in xen_netif_tx_request is + * uint16_t. If skb->len is too big, drop it and alert user about + * misconfiguration. + */ + if (unlikely(skb->len >= (uint16_t)(~0))) { + 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)) {
@@ -1362,6 +1374,8 @@ 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 - ETH_HLEN); + np->netdev = netdev; netif_carrier_off(netdev);
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1.7.10.4