On 04/10/2013 09:33 PM, Ian Campbell wrote:
> On Tue, 2013-03-26 at 06:19 +0000, Jason Wang wrote:
>> Currently, for the packets receives from netback, before doing header check,
>> kernel just reset the transport header in netif_receive_skb() which pretends
>> non
>> l4 header. This is suboptimal for precise packet length estimation
>> (introduced
>> in 1def9238: net_sched: more precise pkt_len computation) which needs
>> correct l4
>> header for gso packets.
>>
>> The patch just reuse the header probed by netback for partial checksum
>> packets
>> and tries to use skb_flow_dissect() for other cases, if both fail, just
>> pretend
>> no l4 header.
>>
>> Cc: Eric Dumazet <eduma...@google.com>
>> Cc: Ian Campbell <ian.campb...@citrix.com>
>> Signed-off-by: Jason Wang <jasow...@redhat.com>
>> ---
>> drivers/net/xen-netback/netback.c | 12 ++++++++++++
>> 1 files changed, 12 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/net/xen-netback/netback.c
>> b/drivers/net/xen-netback/netback.c
>> index aa28550..fc8faa7 100644
>> --- a/drivers/net/xen-netback/netback.c
>> +++ b/drivers/net/xen-netback/netback.c
>> @@ -39,6 +39,7 @@
>> #include <linux/udp.h>
>>
>> #include <net/tcp.h>
>> +#include <net/flow_keys.h>
>>
>> #include <xen/xen.h>
>> #include <xen/events.h>
>> @@ -1184,6 +1185,7 @@ static int checksum_setup(struct xenvif *vif, struct
>> sk_buff *skb)
>> if (th >= skb_tail_pointer(skb))
>> goto out;
>>
>> + skb_set_transport_header(skb, 4 * iph->ihl);
>> skb->csum_start = th - skb->head;
> Should the use of th here (and perhaps above) be replaced with
> skb_transport_header() too?
Yes, and furthermore looks like we can use skb_partial_csum_set() here,
will send a patch.
Thanks
>> switch (iph->protocol) {
>> case IPPROTO_TCP:
>> @@ -1495,6 +1497,7 @@ static void xen_netbk_tx_submit(struct xen_netbk
>> *netbk)
>>
>> skb->dev = vif->dev;
>> skb->protocol = eth_type_trans(skb, skb->dev);
>> + skb_reset_network_header(skb);
>>
>> if (checksum_setup(vif, skb)) {
>> netdev_dbg(vif->dev,
>> @@ -1503,6 +1506,15 @@ static void xen_netbk_tx_submit(struct xen_netbk
>> *netbk)
>> continue;
>> }
>>
>> + if (!skb_transport_header_was_set(skb)) {
>> + struct flow_keys keys;
>> +
>> + if (skb_flow_dissect(skb, &keys))
>> + skb_set_transport_header(skb, keys.thoff);
>> + else
>> + skb_reset_transport_header(skb);
>> + }
>> +
>> vif->dev->stats.rx_bytes += skb->len;
>> vif->dev->stats.rx_packets++;
>>
>
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