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Message-ID: <20140603043047.GB22191@verge.net.au>
Date: Tue, 3 Jun 2014 13:30:47 +0900
From: Simon Horman <horms@...ge.net.au>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: Jesse Gross <jesse@...ira.com>, Thomas Graf <tgraf@...g.ch>,
David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
"dev@...nvswitch.org" <dev@...nvswitch.org>
Subject: Re: [PATCH v4 net-next] MPLS: Use mpls_features to activate software
MPLS GSO segmentation
Hi Eric,
On Mon, Jun 02, 2014 at 08:42:02PM -0700, Eric Dumazet wrote:
> Hi Simon
>
> On Tue, 2014-06-03 at 11:38 +0900, Simon Horman wrote:
> > +/* If MPLS offload request, verify we are testing hardware MPLS features
> > + * instead of standard features for the netdev.
> > + */
> > +#ifdef CONFIG_NET_MPLS_GSO
> > +static netdev_features_t net_mpls_features(struct sk_buff *skb,
> > + netdev_features_t features)
> > +{
> > + int tmp;
> > + __be16 type;
> > +
> > + type = skb_network_protocol(skb, &tmp);
> > + if (unlikely(type == cpu_to_be16(ETH_P_MPLS_UC) ||
> > + type == cpu_to_be16(ETH_P_MPLS_MC)))
>
> I believe net/core/dev.c prefers to use htons(ETH_P_MPLS_UC)
Thanks, I will fix that.
> (check netif_skb_features())
>
> > + features &= skb->dev->mpls_features;
> > +
> > + return features;
> > +}
> > +#else
> > +static netdev_features_t net_mpls_features(struct sk_buff *skb,
> > + netdev_features_t features)
> > +{
> > + return features;
> > +}
> > +#endif
> > +
> > static netdev_features_t harmonize_features(struct sk_buff *skb,
> > netdev_features_t features)
> > {
> > int tmp;
>
> _be16 type;
>
> type = skb_network_protocol(skb, &tmp);
>
> >
> > + features = net_mpls_features(skb, features);
>
> features = net_mpls_features(skb, features, type);
>
> > +
> > if (skb->ip_summed != CHECKSUM_NONE &&
> > !can_checksum_protocol(features, skb_network_protocol(skb, &tmp))) {
>
> !can_checksum_protocol(features, type)) {
>
> > features &= ~NETIF_F_ALL_CSUM;
Thanks, I'll switch things around as you suggest.
> I guess CONFIG_NET_MPLS_GSO will be set by all distros, right ?
That seems likely to me.
From: Simon Horman <horms@...ge.net.au>
MPLS: Use mpls_features to activate software MPLS GSO segmentation
If an MPLS packet requires segmentation then use mpls_features
to determine if the software implementation should be used.
As no driver advertises MPLS GSO segmentation this will always be
the case.
I had not noticed that this was necessary before as software MPLS GSO
segmentation was already being used in my test environment. I believe that
the reason for that is the skbs in question always had fragments and the
driver I used does not advertise NETIF_F_FRAGLIST (which seems to be the
case for most drivers). Thus software segmentation was activated by
skb_gso_ok().
This introduces the overhead of an extra call to skb_network_protocol()
in the case where where CONFIG_NET_MPLS_GSO is set and
skb->ip_summed == CHECKSUM_NONE.
Thanks to Jesse Gross for prompting me to investigate this.
Signed-off-by: Simon Horman <horms@...ge.net.au>
---
v4.2
* As suggested by Eric Dumazet
- Use htons() instead of cpu_to_be16()
- Refactor code to pass type to net_mpls_features.
v4.1
* Following fedback from Thomas Graff and Jesse Gross
- Use ethertype of packet to detect MPLS rather than
relying on mac_len indicating a gap between the end of L2
and the beginning of L3. That assumption seems to
be broken by the GRE GSO code.
- Move mpls_features handling into harmonize_features()
This allows an existing call in there to skb_network_protocol()
to be leveraged.
- Removed acks as the patch has now changed in a material way
v4
* As suggested by YAMAMOTO Takashi
- Correct typos in comment
* Added Ack from YAMAMOTO Takashi
v3
* As requested by David Miller
- Do not mark net_mpls_features as inline
- Correct alignment of parameters
v2
* Added Ack from Jesse Gross
* Removed duplicate 'Thus' from changelog
---
net/core/dev.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 0355ca5..7c063ac 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2498,13 +2498,42 @@ static int dev_gso_segment(struct sk_buff *skb, netdev_features_t features)
return 0;
}
+/* If MPLS offload request, verify we are testing hardware MPLS features
+ * instead of standard features for the netdev.
+ */
+#ifdef CONFIG_NET_MPLS_GSO
+static netdev_features_t net_mpls_features(struct sk_buff *skb,
+ netdev_features_t features,
+ __be16 type)
+{
+ int tmp;
+
+ if (unlikely(type == htons(ETH_P_MPLS_UC) ||
+ type == htons(ETH_P_MPLS_MC)))
+ features &= skb->dev->mpls_features;
+
+ return features;
+}
+#else
+static netdev_features_t net_mpls_features(struct sk_buff *skb,
+ netdev_features_t features,
+ __be16 type)
+{
+ return features;
+}
+#endif
+
static netdev_features_t harmonize_features(struct sk_buff *skb,
netdev_features_t features)
{
int tmp;
+ __be16 type;
+
+ type = skb_network_protocol(skb, &tmp);
+ features = net_mpls_features(skb, features, type);
if (skb->ip_summed != CHECKSUM_NONE &&
- !can_checksum_protocol(features, skb_network_protocol(skb, &tmp))) {
+ !can_checksum_protocol(features, type)) {
features &= ~NETIF_F_ALL_CSUM;
} else if (illegal_highdma(skb->dev, skb)) {
features &= ~NETIF_F_SG;
--
2.0.0.rc2
--
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