| Message ID | 1366683556-4956-2-git-send-email-horms@verge.net.au |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On Mon, 22 Apr 2013, Simon Horman wrote: > "net: Add support for hardware-offloaded encapsulation" introduced > the encapsulation field of struct skb, which when set provides hints > that GSO should handle an skb that encapsulates a packet. > > This patch adds an encapsulation_features field which provides > a hint to dev dev_hard_start_xmit() that harware-offload encapsulation > features should be used. Previously this hint was provided by the > encapsulation field. > > The other uses of the encapsulation field are left unchanged. > > The two in-tree locations that set the encapsulation have been updated to > also set encapsulation_field. > > The motivation for this is to provide support segmentation of GSO MPLS skbs. > This may be necessary when a non-MPLS GSO skb is turned into an MPLS GSO > skb by Open vSwtich and its MPLS push action. > > In this case it harware-offload encapsulation features should be used, > actually to be more exact software segmentation should be selected, but > other hints provided by the encapsulation field are not applicable. > > Cc: Joseph Gasparakis <joseph.gasparakis@intel.com> > Cc: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com> > Cc: Alexander Duyck <alexander.h.duyck@intel.com> > Signed-off-by: Simon Horman <horms@verge.net.au> > --- > include/linux/skbuff.h | 9 ++++++++- > net/core/dev.c | 2 +- > net/core/skbuff.c | 1 + > net/ipv4/gre.c | 1 + > net/ipv4/ipip.c | 1 + > 5 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 2e0ced1..d9ec1de 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -494,7 +494,14 @@ struct sk_buff { > * headers if needed > */ > __u8 encapsulation:1; > - /* 7/9 bit hole (depending on ndisc_nodetype presence) */ > + /* Encapsulation protocol and NIC drivers should use > + * this flag to indicate to each other if the skb contains > + * encapsulated packet and GSO should use encapsulation features > + * instead of standard features for the netdev. This is typically > + * a subset of cases where skb->encapsulation is set. > + */ > + __u8 encapsulation_features:1; > + /* 6/8 bit hole (depending on ndisc_nodetype presence) */ > kmemcheck_bitfield_end(flags2); > > #ifdef CONFIG_NET_DMA > diff --git a/net/core/dev.c b/net/core/dev.c > index 9e26b8d..53236c5 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -2498,7 +2498,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev, > * hardware encapsulation features instead of standard > * features for the netdev > */ > - if (skb->encapsulation) > + if (skb->encapsulation_features) > features &= dev->hw_enc_features; > > if (netif_needs_gso(skb, features)) { > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 898cf5c..f23d136 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -708,6 +708,7 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old) > new->l4_rxhash = old->l4_rxhash; > new->no_fcs = old->no_fcs; > new->encapsulation = old->encapsulation; > + new->encapsulation_features = old->encapsulation_features; > #ifdef CONFIG_XFRM > new->sp = secpath_get(old->sp); > #endif > diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c > index 0ae998b..8420f29 100644 > --- a/net/ipv4/gre.c > +++ b/net/ipv4/gre.c > @@ -157,6 +157,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb, > } > > skb->encapsulation = 0; > + skb->encapsulation_features = 0; > > if (unlikely(!pskb_may_pull(skb, ghl))) > goto out; > diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c > index 77bfcce..a6db3c0 100644 > --- a/net/ipv4/ipip.c > +++ b/net/ipv4/ipip.c > @@ -220,6 +220,7 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) > if (likely(!skb->encapsulation)) { > skb_reset_inner_headers(skb); > skb->encapsulation = 1; > + skb->encapsulation_features = 1; > } > > ip_tunnel_xmit(skb, dev, tiph); > Any particular reason to introduce skb->encapsulation_features instead of using the existing skb->encapsulation? Also I don't see it used in your second patch either. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > > > On Mon, 22 Apr 2013, Simon Horman wrote: > > > "net: Add support for hardware-offloaded encapsulation" introduced > > the encapsulation field of struct skb, which when set provides hints > > that GSO should handle an skb that encapsulates a packet. > > > > This patch adds an encapsulation_features field which provides > > a hint to dev dev_hard_start_xmit() that harware-offload encapsulation > > features should be used. Previously this hint was provided by the > > encapsulation field. > > > > The other uses of the encapsulation field are left unchanged. > > > > The two in-tree locations that set the encapsulation have been updated to > > also set encapsulation_field. > > > > The motivation for this is to provide support segmentation of GSO MPLS skbs. > > This may be necessary when a non-MPLS GSO skb is turned into an MPLS GSO > > skb by Open vSwtich and its MPLS push action. > > > > In this case it harware-offload encapsulation features should be used, > > actually to be more exact software segmentation should be selected, but > > other hints provided by the encapsulation field are not applicable. > > > > Cc: Joseph Gasparakis <joseph.gasparakis@intel.com> > > Cc: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com> > > Cc: Alexander Duyck <alexander.h.duyck@intel.com> > > Signed-off-by: Simon Horman <horms@verge.net.au> > > --- > > include/linux/skbuff.h | 9 ++++++++- > > net/core/dev.c | 2 +- > > net/core/skbuff.c | 1 + > > net/ipv4/gre.c | 1 + > > net/ipv4/ipip.c | 1 + > > 5 files changed, 12 insertions(+), 2 deletions(-) > > > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > > index 2e0ced1..d9ec1de 100644 > > --- a/include/linux/skbuff.h > > +++ b/include/linux/skbuff.h > > @@ -494,7 +494,14 @@ struct sk_buff { > > * headers if needed > > */ > > __u8 encapsulation:1; > > - /* 7/9 bit hole (depending on ndisc_nodetype presence) */ > > + /* Encapsulation protocol and NIC drivers should use > > + * this flag to indicate to each other if the skb contains > > + * encapsulated packet and GSO should use encapsulation features > > + * instead of standard features for the netdev. This is typically > > + * a subset of cases where skb->encapsulation is set. > > + */ > > + __u8 encapsulation_features:1; > > + /* 6/8 bit hole (depending on ndisc_nodetype presence) */ > > kmemcheck_bitfield_end(flags2); > > > > #ifdef CONFIG_NET_DMA > > diff --git a/net/core/dev.c b/net/core/dev.c > > index 9e26b8d..53236c5 100644 > > --- a/net/core/dev.c > > +++ b/net/core/dev.c > > @@ -2498,7 +2498,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev, > > * hardware encapsulation features instead of standard > > * features for the netdev > > */ > > - if (skb->encapsulation) > > + if (skb->encapsulation_features) > > features &= dev->hw_enc_features; > > > > if (netif_needs_gso(skb, features)) { > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > > index 898cf5c..f23d136 100644 > > --- a/net/core/skbuff.c > > +++ b/net/core/skbuff.c > > @@ -708,6 +708,7 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old) > > new->l4_rxhash = old->l4_rxhash; > > new->no_fcs = old->no_fcs; > > new->encapsulation = old->encapsulation; > > + new->encapsulation_features = old->encapsulation_features; > > #ifdef CONFIG_XFRM > > new->sp = secpath_get(old->sp); > > #endif > > diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c > > index 0ae998b..8420f29 100644 > > --- a/net/ipv4/gre.c > > +++ b/net/ipv4/gre.c > > @@ -157,6 +157,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb, > > } > > > > skb->encapsulation = 0; > > + skb->encapsulation_features = 0; > > > > if (unlikely(!pskb_may_pull(skb, ghl))) > > goto out; > > diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c > > index 77bfcce..a6db3c0 100644 > > --- a/net/ipv4/ipip.c > > +++ b/net/ipv4/ipip.c > > @@ -220,6 +220,7 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) > > if (likely(!skb->encapsulation)) { > > skb_reset_inner_headers(skb); > > skb->encapsulation = 1; > > + skb->encapsulation_features = 1; > > } > > > > ip_tunnel_xmit(skb, dev, tiph); > > > > Any particular reason to introduce skb->encapsulation_features instead of > using the existing skb->encapsulation? Also I don't see it used in your > second patch either. My reasoning is that skb->encapsulation seems to alter the behaviour of many different locations and I'm not sure that any of them, other than the one in dev_hard_start_xmit() make sense for MPLS. For example the following in inet_gso_segment() tunnel = !!skb->encapsulation; ... do { ... if (!tunnel && proto == IPPROTO_UDP) { iph->id = htons(id); iph->frag_off = htons(offset >> 3); if (skb->next != NULL) iph->frag_off |= htons(IP_MF); offset += (skb->len - skb->mac_len - iph->ihl * 4); } else { iph->id = htons(id++); } ... On reflection I need to examine the relevant code-paths more closely, but I believe the !tunnel portion of the above code is intended to help effect GSO segmentation UDP tunnelling protocols and is not relevant to MPLS. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Apr 25, 2013 at 04:36:44PM +0900, Simon Horman wrote: > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > > > > > > On Mon, 22 Apr 2013, Simon Horman wrote: > > > > > "net: Add support for hardware-offloaded encapsulation" introduced > > > the encapsulation field of struct skb, which when set provides hints > > > that GSO should handle an skb that encapsulates a packet. > > > > > > This patch adds an encapsulation_features field which provides > > > a hint to dev dev_hard_start_xmit() that harware-offload encapsulation > > > features should be used. Previously this hint was provided by the > > > encapsulation field. > > > > > > The other uses of the encapsulation field are left unchanged. > > > > > > The two in-tree locations that set the encapsulation have been updated to > > > also set encapsulation_field. > > > > > > The motivation for this is to provide support segmentation of GSO MPLS skbs. > > > This may be necessary when a non-MPLS GSO skb is turned into an MPLS GSO > > > skb by Open vSwtich and its MPLS push action. > > > > > > In this case it harware-offload encapsulation features should be used, > > > actually to be more exact software segmentation should be selected, but > > > other hints provided by the encapsulation field are not applicable. > > > > > > Cc: Joseph Gasparakis <joseph.gasparakis@intel.com> > > > Cc: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com> > > > Cc: Alexander Duyck <alexander.h.duyck@intel.com> > > > Signed-off-by: Simon Horman <horms@verge.net.au> > > > --- > > > include/linux/skbuff.h | 9 ++++++++- > > > net/core/dev.c | 2 +- > > > net/core/skbuff.c | 1 + > > > net/ipv4/gre.c | 1 + > > > net/ipv4/ipip.c | 1 + > > > 5 files changed, 12 insertions(+), 2 deletions(-) > > > > > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > > > index 2e0ced1..d9ec1de 100644 > > > --- a/include/linux/skbuff.h > > > +++ b/include/linux/skbuff.h > > > @@ -494,7 +494,14 @@ struct sk_buff { > > > * headers if needed > > > */ > > > __u8 encapsulation:1; > > > - /* 7/9 bit hole (depending on ndisc_nodetype presence) */ > > > + /* Encapsulation protocol and NIC drivers should use > > > + * this flag to indicate to each other if the skb contains > > > + * encapsulated packet and GSO should use encapsulation features > > > + * instead of standard features for the netdev. This is typically > > > + * a subset of cases where skb->encapsulation is set. > > > + */ > > > + __u8 encapsulation_features:1; > > > + /* 6/8 bit hole (depending on ndisc_nodetype presence) */ > > > kmemcheck_bitfield_end(flags2); > > > > > > #ifdef CONFIG_NET_DMA > > > diff --git a/net/core/dev.c b/net/core/dev.c > > > index 9e26b8d..53236c5 100644 > > > --- a/net/core/dev.c > > > +++ b/net/core/dev.c > > > @@ -2498,7 +2498,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev, > > > * hardware encapsulation features instead of standard > > > * features for the netdev > > > */ > > > - if (skb->encapsulation) > > > + if (skb->encapsulation_features) > > > features &= dev->hw_enc_features; > > > > > > if (netif_needs_gso(skb, features)) { > > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > > > index 898cf5c..f23d136 100644 > > > --- a/net/core/skbuff.c > > > +++ b/net/core/skbuff.c > > > @@ -708,6 +708,7 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old) > > > new->l4_rxhash = old->l4_rxhash; > > > new->no_fcs = old->no_fcs; > > > new->encapsulation = old->encapsulation; > > > + new->encapsulation_features = old->encapsulation_features; > > > #ifdef CONFIG_XFRM > > > new->sp = secpath_get(old->sp); > > > #endif > > > diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c > > > index 0ae998b..8420f29 100644 > > > --- a/net/ipv4/gre.c > > > +++ b/net/ipv4/gre.c > > > @@ -157,6 +157,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb, > > > } > > > > > > skb->encapsulation = 0; > > > + skb->encapsulation_features = 0; > > > > > > if (unlikely(!pskb_may_pull(skb, ghl))) > > > goto out; > > > diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c > > > index 77bfcce..a6db3c0 100644 > > > --- a/net/ipv4/ipip.c > > > +++ b/net/ipv4/ipip.c > > > @@ -220,6 +220,7 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) > > > if (likely(!skb->encapsulation)) { > > > skb_reset_inner_headers(skb); > > > skb->encapsulation = 1; > > > + skb->encapsulation_features = 1; > > > } > > > > > > ip_tunnel_xmit(skb, dev, tiph); > > > > > > > Any particular reason to introduce skb->encapsulation_features instead of > > using the existing skb->encapsulation? Also I don't see it used in your > > second patch either. > > My reasoning is that skb->encapsulation seems to alter the behaviour of > many different locations and I'm not sure that any of them, other than the > one in dev_hard_start_xmit() make sense for MPLS. > > For example the following in inet_gso_segment() > > tunnel = !!skb->encapsulation; > ... > do { > ... > if (!tunnel && proto == IPPROTO_UDP) { > iph->id = htons(id); > iph->frag_off = htons(offset >> 3); > if (skb->next != NULL) > iph->frag_off |= htons(IP_MF); > offset += (skb->len - skb->mac_len - iph->ihl * 4); > } else { > iph->id = htons(id++); > } > ... > > On reflection I need to examine the relevant code-paths more closely, but I > believe the !tunnel portion of the above code is intended to help effect > GSO segmentation UDP tunnelling protocols and is not relevant to MPLS. I forgot to mention in my previous email that this change is used in the patch "[PATCH v2.26] datapath: Add basic MPLS support to kernel". -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: >> Any particular reason to introduce skb->encapsulation_features instead of >> using the existing skb->encapsulation? Also I don't see it used in your >> second patch either. > > My reasoning is that skb->encapsulation seems to alter the behaviour of > many different locations and I'm not sure that any of them, other than the > one in dev_hard_start_xmit() make sense for MPLS. The problem is the meaning of skb->encapsulation isn't really defined clearly and I'm certain that the current implementation is not going to work in the future. Depending on your perspective, vlans, MPLS, tunnels, etc. can all be considered forms of encapsulation but clearly there are many NICs that have different capabilities across those. I believe the intention here was really to describe L3 tunnels as encapsulation, in which case MPLS really shouldn't be using this mechanism at all. Now there is some overlap, especially today since most currently shipping silicon wasn't designed to support tunnels and so is using some form of offset based offloads. In that case, all forms of encapsulation are pretty similar. However, in the future that won't be the case as support for specific protocols is implemented for higher performance and richer support. When that happens, not only will MPLS and tunnels have different capabilities but various forms tunnels might as well. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: > On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: > > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > >> Any particular reason to introduce skb->encapsulation_features instead of > >> using the existing skb->encapsulation? Also I don't see it used in your > >> second patch either. > > > > My reasoning is that skb->encapsulation seems to alter the behaviour of > > many different locations and I'm not sure that any of them, other than the > > one in dev_hard_start_xmit() make sense for MPLS. > > The problem is the meaning of skb->encapsulation isn't really defined > clearly and I'm certain that the current implementation is not going > to work in the future. Depending on your perspective, vlans, MPLS, > tunnels, etc. can all be considered forms of encapsulation but clearly > there are many NICs that have different capabilities across those. I > believe the intention here was really to describe L3 tunnels as > encapsulation, in which case MPLS really shouldn't be using this > mechanism at all. > > Now there is some overlap, especially today since most currently > shipping silicon wasn't designed to support tunnels and so is using > some form of offset based offloads. In that case, all forms of > encapsulation are pretty similar. However, in the future that won't be > the case as support for specific protocols is implemented for higher > performance and richer support. When that happens, not only will MPLS > and tunnels have different capabilities but various forms tunnels > might as well. Wouldn't be possible to describe those differences using, dev->hw_enc_features? I assumed that was its purpose. The intention of my patch was allow MPLS to utilise dev->hw_enc_features without any of the other implications of skb->encapsulation. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: >> >> Any particular reason to introduce skb->encapsulation_features instead of >> >> using the existing skb->encapsulation? Also I don't see it used in your >> >> second patch either. >> > >> > My reasoning is that skb->encapsulation seems to alter the behaviour of >> > many different locations and I'm not sure that any of them, other than the >> > one in dev_hard_start_xmit() make sense for MPLS. >> >> The problem is the meaning of skb->encapsulation isn't really defined >> clearly and I'm certain that the current implementation is not going >> to work in the future. Depending on your perspective, vlans, MPLS, >> tunnels, etc. can all be considered forms of encapsulation but clearly >> there are many NICs that have different capabilities across those. I >> believe the intention here was really to describe L3 tunnels as >> encapsulation, in which case MPLS really shouldn't be using this >> mechanism at all. >> >> Now there is some overlap, especially today since most currently >> shipping silicon wasn't designed to support tunnels and so is using >> some form of offset based offloads. In that case, all forms of >> encapsulation are pretty similar. However, in the future that won't be >> the case as support for specific protocols is implemented for higher >> performance and richer support. When that happens, not only will MPLS >> and tunnels have different capabilities but various forms tunnels >> might as well. > > Wouldn't be possible to describe those differences using, > dev->hw_enc_features? I assumed that was its purpose. If there truly are differences between the offload capabilities of MPLS and L3 tunnels then no, it's not possible, because it's a single field. It's certainly not a valid assumption that a NIC that can do TSO over GRE can also do it over MPLS. However, it's unlikely that there are truly significant differences between various encapsulation formats on a per-feature basis. I think what we need to do is separate out the ability to understand the headers from the capabilities so you have two fields: header (none, VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, etc.) rather than the product of each. Otherwise, we end up with a ton of different combinations. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: > On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: > > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: > >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: > >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > >> >> Any particular reason to introduce skb->encapsulation_features instead of > >> >> using the existing skb->encapsulation? Also I don't see it used in your > >> >> second patch either. > >> > > >> > My reasoning is that skb->encapsulation seems to alter the behaviour of > >> > many different locations and I'm not sure that any of them, other than the > >> > one in dev_hard_start_xmit() make sense for MPLS. > >> > >> The problem is the meaning of skb->encapsulation isn't really defined > >> clearly and I'm certain that the current implementation is not going > >> to work in the future. Depending on your perspective, vlans, MPLS, > >> tunnels, etc. can all be considered forms of encapsulation but clearly > >> there are many NICs that have different capabilities across those. I > >> believe the intention here was really to describe L3 tunnels as > >> encapsulation, in which case MPLS really shouldn't be using this > >> mechanism at all. > >> > >> Now there is some overlap, especially today since most currently > >> shipping silicon wasn't designed to support tunnels and so is using > >> some form of offset based offloads. In that case, all forms of > >> encapsulation are pretty similar. However, in the future that won't be > >> the case as support for specific protocols is implemented for higher > >> performance and richer support. When that happens, not only will MPLS > >> and tunnels have different capabilities but various forms tunnels > >> might as well. > > > > Wouldn't be possible to describe those differences using, > > dev->hw_enc_features? I assumed that was its purpose. > > If there truly are differences between the offload capabilities of > MPLS and L3 tunnels then no, it's not possible, because it's a single > field. It's certainly not a valid assumption that a NIC that can do > TSO over GRE can also do it over MPLS. > > However, it's unlikely that there are truly significant differences > between various encapsulation formats on a per-feature basis. I think > what we need to do is separate out the ability to understand the > headers from the capabilities so you have two fields: header (none, > VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, > etc.) rather than the product of each. Otherwise, we end up with a ton > of different combinations. I'm not quite sure that I follow. Is your idea to replace skb->encapsulation (a single bit) with a field that corresponds to the outer-most (encapsulation) header in use and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? If so, I believe that would solve the problem I was trying to address with this patch. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, May 1, 2013 at 12:50 AM, Simon Horman <horms@verge.net.au> wrote: > On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: >> On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: >> > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: >> >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: >> >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: >> >> >> Any particular reason to introduce skb->encapsulation_features instead of >> >> >> using the existing skb->encapsulation? Also I don't see it used in your >> >> >> second patch either. >> >> > >> >> > My reasoning is that skb->encapsulation seems to alter the behaviour of >> >> > many different locations and I'm not sure that any of them, other than the >> >> > one in dev_hard_start_xmit() make sense for MPLS. >> >> >> >> The problem is the meaning of skb->encapsulation isn't really defined >> >> clearly and I'm certain that the current implementation is not going >> >> to work in the future. Depending on your perspective, vlans, MPLS, >> >> tunnels, etc. can all be considered forms of encapsulation but clearly >> >> there are many NICs that have different capabilities across those. I >> >> believe the intention here was really to describe L3 tunnels as >> >> encapsulation, in which case MPLS really shouldn't be using this >> >> mechanism at all. >> >> >> >> Now there is some overlap, especially today since most currently >> >> shipping silicon wasn't designed to support tunnels and so is using >> >> some form of offset based offloads. In that case, all forms of >> >> encapsulation are pretty similar. However, in the future that won't be >> >> the case as support for specific protocols is implemented for higher >> >> performance and richer support. When that happens, not only will MPLS >> >> and tunnels have different capabilities but various forms tunnels >> >> might as well. >> > >> > Wouldn't be possible to describe those differences using, >> > dev->hw_enc_features? I assumed that was its purpose. >> >> If there truly are differences between the offload capabilities of >> MPLS and L3 tunnels then no, it's not possible, because it's a single >> field. It's certainly not a valid assumption that a NIC that can do >> TSO over GRE can also do it over MPLS. >> >> However, it's unlikely that there are truly significant differences >> between various encapsulation formats on a per-feature basis. I think >> what we need to do is separate out the ability to understand the >> headers from the capabilities so you have two fields: header (none, >> VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, >> etc.) rather than the product of each. Otherwise, we end up with a ton >> of different combinations. > > I'm not quite sure that I follow. > > Is your idea to replace skb->encapsulation (a single bit) with > a field that corresponds to the outer-most (encapsulation) header in use > and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? No, I'm talking about netdev features. You can already tell the encapsulation type of a packet by looking at the EtherType. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, May 01, 2013 at 11:16:40AM -0700, Jesse Gross wrote: > On Wed, May 1, 2013 at 12:50 AM, Simon Horman <horms@verge.net.au> wrote: > > On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: > >> On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: > >> > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: > >> >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: > >> >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > >> >> >> Any particular reason to introduce skb->encapsulation_features instead of > >> >> >> using the existing skb->encapsulation? Also I don't see it used in your > >> >> >> second patch either. > >> >> > > >> >> > My reasoning is that skb->encapsulation seems to alter the behaviour of > >> >> > many different locations and I'm not sure that any of them, other than the > >> >> > one in dev_hard_start_xmit() make sense for MPLS. > >> >> > >> >> The problem is the meaning of skb->encapsulation isn't really defined > >> >> clearly and I'm certain that the current implementation is not going > >> >> to work in the future. Depending on your perspective, vlans, MPLS, > >> >> tunnels, etc. can all be considered forms of encapsulation but clearly > >> >> there are many NICs that have different capabilities across those. I > >> >> believe the intention here was really to describe L3 tunnels as > >> >> encapsulation, in which case MPLS really shouldn't be using this > >> >> mechanism at all. > >> >> > >> >> Now there is some overlap, especially today since most currently > >> >> shipping silicon wasn't designed to support tunnels and so is using > >> >> some form of offset based offloads. In that case, all forms of > >> >> encapsulation are pretty similar. However, in the future that won't be > >> >> the case as support for specific protocols is implemented for higher > >> >> performance and richer support. When that happens, not only will MPLS > >> >> and tunnels have different capabilities but various forms tunnels > >> >> might as well. > >> > > >> > Wouldn't be possible to describe those differences using, > >> > dev->hw_enc_features? I assumed that was its purpose. > >> > >> If there truly are differences between the offload capabilities of > >> MPLS and L3 tunnels then no, it's not possible, because it's a single > >> field. It's certainly not a valid assumption that a NIC that can do > >> TSO over GRE can also do it over MPLS. > >> > >> However, it's unlikely that there are truly significant differences > >> between various encapsulation formats on a per-feature basis. I think > >> what we need to do is separate out the ability to understand the > >> headers from the capabilities so you have two fields: header (none, > >> VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, > >> etc.) rather than the product of each. Otherwise, we end up with a ton > >> of different combinations. > > > > I'm not quite sure that I follow. > > > > Is your idea to replace skb->encapsulation (a single bit) with > > a field that corresponds to the outer-most (encapsulation) header in use > > and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? > > No, I'm talking about netdev features. You can already tell the > encapsulation type of a packet by looking at the EtherType. Now I am completely confused about what are the two fields that you refer to in your previous email. In regards to looking ath the ethernet type: One of the tricky parts of MPLS is that the packet itself does not contain the ethernet type or any other way of knowing the type of the inner-packet. Information that is needed for GSO. My proposal to get around this is to leave skb->protocol as the original, in the case we are interested in non-MPLS, ethernet type. The MPLS ethertype is in in the packet itself, however checking that seems expensive. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, May 1, 2013 at 3:57 PM, Simon Horman <horms@verge.net.au> wrote: > On Wed, May 01, 2013 at 11:16:40AM -0700, Jesse Gross wrote: >> On Wed, May 1, 2013 at 12:50 AM, Simon Horman <horms@verge.net.au> wrote: >> > On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: >> >> On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: >> >> > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: >> >> >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: >> >> >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: >> >> >> >> Any particular reason to introduce skb->encapsulation_features instead of >> >> >> >> using the existing skb->encapsulation? Also I don't see it used in your >> >> >> >> second patch either. >> >> >> > >> >> >> > My reasoning is that skb->encapsulation seems to alter the behaviour of >> >> >> > many different locations and I'm not sure that any of them, other than the >> >> >> > one in dev_hard_start_xmit() make sense for MPLS. >> >> >> >> >> >> The problem is the meaning of skb->encapsulation isn't really defined >> >> >> clearly and I'm certain that the current implementation is not going >> >> >> to work in the future. Depending on your perspective, vlans, MPLS, >> >> >> tunnels, etc. can all be considered forms of encapsulation but clearly >> >> >> there are many NICs that have different capabilities across those. I >> >> >> believe the intention here was really to describe L3 tunnels as >> >> >> encapsulation, in which case MPLS really shouldn't be using this >> >> >> mechanism at all. >> >> >> >> >> >> Now there is some overlap, especially today since most currently >> >> >> shipping silicon wasn't designed to support tunnels and so is using >> >> >> some form of offset based offloads. In that case, all forms of >> >> >> encapsulation are pretty similar. However, in the future that won't be >> >> >> the case as support for specific protocols is implemented for higher >> >> >> performance and richer support. When that happens, not only will MPLS >> >> >> and tunnels have different capabilities but various forms tunnels >> >> >> might as well. >> >> > >> >> > Wouldn't be possible to describe those differences using, >> >> > dev->hw_enc_features? I assumed that was its purpose. >> >> >> >> If there truly are differences between the offload capabilities of >> >> MPLS and L3 tunnels then no, it's not possible, because it's a single >> >> field. It's certainly not a valid assumption that a NIC that can do >> >> TSO over GRE can also do it over MPLS. >> >> >> >> However, it's unlikely that there are truly significant differences >> >> between various encapsulation formats on a per-feature basis. I think >> >> what we need to do is separate out the ability to understand the >> >> headers from the capabilities so you have two fields: header (none, >> >> VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, >> >> etc.) rather than the product of each. Otherwise, we end up with a ton >> >> of different combinations. >> > >> > I'm not quite sure that I follow. >> > >> > Is your idea to replace skb->encapsulation (a single bit) with >> > a field that corresponds to the outer-most (encapsulation) header in use >> > and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? >> >> No, I'm talking about netdev features. You can already tell the >> encapsulation type of a packet by looking at the EtherType. > > Now I am completely confused about what are the two fields that you > refer to in your previous email. I have always been referring to the netdev features for various protocol types. This is because considering MPLS as a form of encapsulation for the purpose of offloads buckets too many protocols into the same set and NICs will have varying features for those. Trying to avoid this by having a bit for offloadable encapsulations is just going to be very confusing and not very future proof. > In regards to looking ath the ethernet type: > > One of the tricky parts of MPLS is that the packet itself does not contain > the ethernet type or any other way of knowing the type of the inner-packet. > Information that is needed for GSO. I'm aware of that. However, you were referring to the type of encapsulation. It is easy to determine that a packet is MPLS. > My proposal to get around this is to leave skb->protocol as the > original, in the case we are interested in non-MPLS, ethernet type. At the very least, this is not consistent with how it is currently handled (for example, with VLANs) and seems difficult to do properly. However, I have not seen any further analysis since the last time that we discussed this. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, May 01, 2013 at 09:53:42PM -0700, Jesse Gross wrote: > On Wed, May 1, 2013 at 3:57 PM, Simon Horman <horms@verge.net.au> wrote: > > On Wed, May 01, 2013 at 11:16:40AM -0700, Jesse Gross wrote: > >> On Wed, May 1, 2013 at 12:50 AM, Simon Horman <horms@verge.net.au> wrote: > >> > On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: > >> >> On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: > >> >> > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: > >> >> >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: > >> >> >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > >> >> >> >> Any particular reason to introduce skb->encapsulation_features instead of > >> >> >> >> using the existing skb->encapsulation? Also I don't see it used in your > >> >> >> >> second patch either. > >> >> >> > > >> >> >> > My reasoning is that skb->encapsulation seems to alter the behaviour of > >> >> >> > many different locations and I'm not sure that any of them, other than the > >> >> >> > one in dev_hard_start_xmit() make sense for MPLS. > >> >> >> > >> >> >> The problem is the meaning of skb->encapsulation isn't really defined > >> >> >> clearly and I'm certain that the current implementation is not going > >> >> >> to work in the future. Depending on your perspective, vlans, MPLS, > >> >> >> tunnels, etc. can all be considered forms of encapsulation but clearly > >> >> >> there are many NICs that have different capabilities across those. I > >> >> >> believe the intention here was really to describe L3 tunnels as > >> >> >> encapsulation, in which case MPLS really shouldn't be using this > >> >> >> mechanism at all. > >> >> >> > >> >> >> Now there is some overlap, especially today since most currently > >> >> >> shipping silicon wasn't designed to support tunnels and so is using > >> >> >> some form of offset based offloads. In that case, all forms of > >> >> >> encapsulation are pretty similar. However, in the future that won't be > >> >> >> the case as support for specific protocols is implemented for higher > >> >> >> performance and richer support. When that happens, not only will MPLS > >> >> >> and tunnels have different capabilities but various forms tunnels > >> >> >> might as well. > >> >> > > >> >> > Wouldn't be possible to describe those differences using, > >> >> > dev->hw_enc_features? I assumed that was its purpose. > >> >> > >> >> If there truly are differences between the offload capabilities of > >> >> MPLS and L3 tunnels then no, it's not possible, because it's a single > >> >> field. It's certainly not a valid assumption that a NIC that can do > >> >> TSO over GRE can also do it over MPLS. > >> >> > >> >> However, it's unlikely that there are truly significant differences > >> >> between various encapsulation formats on a per-feature basis. I think > >> >> what we need to do is separate out the ability to understand the > >> >> headers from the capabilities so you have two fields: header (none, > >> >> VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, > >> >> etc.) rather than the product of each. Otherwise, we end up with a ton > >> >> of different combinations. > >> > > >> > I'm not quite sure that I follow. > >> > > >> > Is your idea to replace skb->encapsulation (a single bit) with > >> > a field that corresponds to the outer-most (encapsulation) header in use > >> > and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? > >> > >> No, I'm talking about netdev features. You can already tell the > >> encapsulation type of a packet by looking at the EtherType. > > > > Now I am completely confused about what are the two fields that you > > refer to in your previous email. > > I have always been referring to the netdev features for various > protocol types. This is because considering MPLS as a form of > encapsulation for the purpose of offloads buckets too many protocols > into the same set and NICs will have varying features for those. > Trying to avoid this by having a bit for offloadable encapsulations is > just going to be very confusing and not very future proof. > > > In regards to looking ath the ethernet type: > > > > One of the tricky parts of MPLS is that the packet itself does not contain > > the ethernet type or any other way of knowing the type of the inner-packet. > > Information that is needed for GSO. > > I'm aware of that. However, you were referring to the type of > encapsulation. It is easy to determine that a packet is MPLS. > > > My proposal to get around this is to leave skb->protocol as the > > original, in the case we are interested in non-MPLS, ethernet type. > > At the very least, this is not consistent with how it is currently > handled (for example, with VLANs) and seems difficult to do properly. > However, I have not seen any further analysis since the last time that > we discussed this. Unfortunately my efforts to solicit feedback from others regarding that have not been successful. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, May 02, 2013 at 02:31:44PM +0900, Simon Horman wrote: > On Wed, May 01, 2013 at 09:53:42PM -0700, Jesse Gross wrote: > > On Wed, May 1, 2013 at 3:57 PM, Simon Horman <horms@verge.net.au> wrote: > > > On Wed, May 01, 2013 at 11:16:40AM -0700, Jesse Gross wrote: > > >> On Wed, May 1, 2013 at 12:50 AM, Simon Horman <horms@verge.net.au> wrote: > > >> > On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: > > >> >> On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: > > >> >> > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: > > >> >> >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: > > >> >> >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > > >> >> >> >> Any particular reason to introduce skb->encapsulation_features instead of > > >> >> >> >> using the existing skb->encapsulation? Also I don't see it used in your > > >> >> >> >> second patch either. > > >> >> >> > > > >> >> >> > My reasoning is that skb->encapsulation seems to alter the behaviour of > > >> >> >> > many different locations and I'm not sure that any of them, other than the > > >> >> >> > one in dev_hard_start_xmit() make sense for MPLS. > > >> >> >> > > >> >> >> The problem is the meaning of skb->encapsulation isn't really defined > > >> >> >> clearly and I'm certain that the current implementation is not going > > >> >> >> to work in the future. Depending on your perspective, vlans, MPLS, > > >> >> >> tunnels, etc. can all be considered forms of encapsulation but clearly > > >> >> >> there are many NICs that have different capabilities across those. I > > >> >> >> believe the intention here was really to describe L3 tunnels as > > >> >> >> encapsulation, in which case MPLS really shouldn't be using this > > >> >> >> mechanism at all. > > >> >> >> > > >> >> >> Now there is some overlap, especially today since most currently > > >> >> >> shipping silicon wasn't designed to support tunnels and so is using > > >> >> >> some form of offset based offloads. In that case, all forms of > > >> >> >> encapsulation are pretty similar. However, in the future that won't be > > >> >> >> the case as support for specific protocols is implemented for higher > > >> >> >> performance and richer support. When that happens, not only will MPLS > > >> >> >> and tunnels have different capabilities but various forms tunnels > > >> >> >> might as well. > > >> >> > > > >> >> > Wouldn't be possible to describe those differences using, > > >> >> > dev->hw_enc_features? I assumed that was its purpose. > > >> >> > > >> >> If there truly are differences between the offload capabilities of > > >> >> MPLS and L3 tunnels then no, it's not possible, because it's a single > > >> >> field. It's certainly not a valid assumption that a NIC that can do > > >> >> TSO over GRE can also do it over MPLS. > > >> >> > > >> >> However, it's unlikely that there are truly significant differences > > >> >> between various encapsulation formats on a per-feature basis. I think > > >> >> what we need to do is separate out the ability to understand the > > >> >> headers from the capabilities so you have two fields: header (none, > > >> >> VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, > > >> >> etc.) rather than the product of each. Otherwise, we end up with a ton > > >> >> of different combinations. > > >> > > > >> > I'm not quite sure that I follow. > > >> > > > >> > Is your idea to replace skb->encapsulation (a single bit) with > > >> > a field that corresponds to the outer-most (encapsulation) header in use > > >> > and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? > > >> > > >> No, I'm talking about netdev features. You can already tell the > > >> encapsulation type of a packet by looking at the EtherType. > > > > > > Now I am completely confused about what are the two fields that you > > > refer to in your previous email. > > > > I have always been referring to the netdev features for various > > protocol types. This is because considering MPLS as a form of > > encapsulation for the purpose of offloads buckets too many protocols > > into the same set and NICs will have varying features for those. > > Trying to avoid this by having a bit for offloadable encapsulations is > > just going to be very confusing and not very future proof. I understand your point regarding a magic bit for encapsulation not being particularly future-proof. I agree that it is reasonable to expect that a NIC may support an offload for one of the growing list of supported encapsulation protocols and not another. However, as tedious as this may be, I am rather confused about what your proposal above is. > > > In regards to looking ath the ethernet type: > > > > > > One of the tricky parts of MPLS is that the packet itself does not contain > > > the ethernet type or any other way of knowing the type of the inner-packet. > > > Information that is needed for GSO. > > > > I'm aware of that. However, you were referring to the type of > > encapsulation. It is easy to determine that a packet is MPLS. > > > > > My proposal to get around this is to leave skb->protocol as the > > > original, in the case we are interested in non-MPLS, ethernet type. > > > > At the very least, this is not consistent with how it is currently > > handled (for example, with VLANs) and seems difficult to do properly. > > However, I have not seen any further analysis since the last time that > > we discussed this. > > Unfortunately my efforts to solicit feedback from others regarding > that have not been successful. An idea I have for the treatment of skb->protocol and friends is to add skb->inner_protocol. It could be set to the inner protocol, if known, for protocols such as MPLS which don't include that information in the packet. It would allow skb->protocol to be set to the MPLS ethernet type corresponding to the ethernet type of the packet. From here I see two options: 1. Offloads could be registered for MPLS unicast and multicast. And the registered MPLS GSO segmentation call-back could set and restore skb->protocol before and after calling skb_mac_gso_segment(). The MPLS GSO segmentation callback could also calculate features to pass to skb_mac_gso_segment() by some means. 2. Teach skb_network_protocol() about skb->inner_protocol. And most likely teach netif_skb_features() about skb->protocol == ETH_P_MPLS*. I'm not entirely sure how to avoid overhead for non-MPLS packets using this approach. I believe the above could be achieved without using skb->encapsulation in newly added code. Your features proposal above not withstanding, in the current scheme of things, it would seem that it would be appropriate to add SKB_GSO_GRE - currently not supported by any hardware - and set skb_shinfo(skb)->gso_type = SKB_GSO_GRE in the datapath. I think this should be sufficient to trigger a call to skb_mac_gso_segment() in dev_hard_start_xmit(). -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, May 1, 2013 at 10:31 PM, Simon Horman <horms@verge.net.au> wrote: > On Wed, May 01, 2013 at 09:53:42PM -0700, Jesse Gross wrote: >> On Wed, May 1, 2013 at 3:57 PM, Simon Horman <horms@verge.net.au> wrote: >> > On Wed, May 01, 2013 at 11:16:40AM -0700, Jesse Gross wrote: >> >> On Wed, May 1, 2013 at 12:50 AM, Simon Horman <horms@verge.net.au> wrote: >> >> > On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: >> >> >> On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: >> >> >> > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: >> >> >> >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: >> >> >> >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: >> >> >> >> >> Any particular reason to introduce skb->encapsulation_features instead of >> >> >> >> >> using the existing skb->encapsulation? Also I don't see it used in your >> >> >> >> >> second patch either. >> >> >> >> > >> >> >> >> > My reasoning is that skb->encapsulation seems to alter the behaviour of >> >> >> >> > many different locations and I'm not sure that any of them, other than the >> >> >> >> > one in dev_hard_start_xmit() make sense for MPLS. >> >> >> >> >> >> >> >> The problem is the meaning of skb->encapsulation isn't really defined >> >> >> >> clearly and I'm certain that the current implementation is not going >> >> >> >> to work in the future. Depending on your perspective, vlans, MPLS, >> >> >> >> tunnels, etc. can all be considered forms of encapsulation but clearly >> >> >> >> there are many NICs that have different capabilities across those. I >> >> >> >> believe the intention here was really to describe L3 tunnels as >> >> >> >> encapsulation, in which case MPLS really shouldn't be using this >> >> >> >> mechanism at all. >> >> >> >> >> >> >> >> Now there is some overlap, especially today since most currently >> >> >> >> shipping silicon wasn't designed to support tunnels and so is using >> >> >> >> some form of offset based offloads. In that case, all forms of >> >> >> >> encapsulation are pretty similar. However, in the future that won't be >> >> >> >> the case as support for specific protocols is implemented for higher >> >> >> >> performance and richer support. When that happens, not only will MPLS >> >> >> >> and tunnels have different capabilities but various forms tunnels >> >> >> >> might as well. >> >> >> > >> >> >> > Wouldn't be possible to describe those differences using, >> >> >> > dev->hw_enc_features? I assumed that was its purpose. >> >> >> >> >> >> If there truly are differences between the offload capabilities of >> >> >> MPLS and L3 tunnels then no, it's not possible, because it's a single >> >> >> field. It's certainly not a valid assumption that a NIC that can do >> >> >> TSO over GRE can also do it over MPLS. >> >> >> >> >> >> However, it's unlikely that there are truly significant differences >> >> >> between various encapsulation formats on a per-feature basis. I think >> >> >> what we need to do is separate out the ability to understand the >> >> >> headers from the capabilities so you have two fields: header (none, >> >> >> VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, >> >> >> etc.) rather than the product of each. Otherwise, we end up with a ton >> >> >> of different combinations. >> >> > >> >> > I'm not quite sure that I follow. >> >> > >> >> > Is your idea to replace skb->encapsulation (a single bit) with >> >> > a field that corresponds to the outer-most (encapsulation) header in use >> >> > and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? >> >> >> >> No, I'm talking about netdev features. You can already tell the >> >> encapsulation type of a packet by looking at the EtherType. >> > >> > Now I am completely confused about what are the two fields that you >> > refer to in your previous email. >> >> I have always been referring to the netdev features for various >> protocol types. This is because considering MPLS as a form of >> encapsulation for the purpose of offloads buckets too many protocols >> into the same set and NICs will have varying features for those. >> Trying to avoid this by having a bit for offloadable encapsulations is >> just going to be very confusing and not very future proof. >> >> > In regards to looking ath the ethernet type: >> > >> > One of the tricky parts of MPLS is that the packet itself does not contain >> > the ethernet type or any other way of knowing the type of the inner-packet. >> > Information that is needed for GSO. >> >> I'm aware of that. However, you were referring to the type of >> encapsulation. It is easy to determine that a packet is MPLS. >> >> > My proposal to get around this is to leave skb->protocol as the >> > original, in the case we are interested in non-MPLS, ethernet type. >> >> At the very least, this is not consistent with how it is currently >> handled (for example, with VLANs) and seems difficult to do properly. >> However, I have not seen any further analysis since the last time that >> we discussed this. > > Unfortunately my efforts to solicit feedback from others regarding > that have not been successful. Give me a break, Simon. These are your patches and therefore it is your responsibility to do the analysis. This has come up over and over again and I'm not happy about it. Rather than trying to respond to me as quickly as possible, you need to slow down, take a step back, and think about the correct direction. Given that some of these patches have revision numbers in the 20s you have nothing to complain about as far as receiving help. In order to assist you in this, I'm going to drop all of your pending patches from my queue and not respond to anything further from you until the merge window is open again. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, May 02, 2013 at 09:53:25AM -0700, Jesse Gross wrote: > On Wed, May 1, 2013 at 10:31 PM, Simon Horman <horms@verge.net.au> wrote: > > On Wed, May 01, 2013 at 09:53:42PM -0700, Jesse Gross wrote: > >> On Wed, May 1, 2013 at 3:57 PM, Simon Horman <horms@verge.net.au> wrote: > >> > On Wed, May 01, 2013 at 11:16:40AM -0700, Jesse Gross wrote: > >> >> On Wed, May 1, 2013 at 12:50 AM, Simon Horman <horms@verge.net.au> wrote: > >> >> > On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: > >> >> >> On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <horms@verge.net.au> wrote: > >> >> >> > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: > >> >> >> >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <horms@verge.net.au> wrote: > >> >> >> >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > >> >> >> >> >> Any particular reason to introduce skb->encapsulation_features instead of > >> >> >> >> >> using the existing skb->encapsulation? Also I don't see it used in your > >> >> >> >> >> second patch either. > >> >> >> >> > > >> >> >> >> > My reasoning is that skb->encapsulation seems to alter the behaviour of > >> >> >> >> > many different locations and I'm not sure that any of them, other than the > >> >> >> >> > one in dev_hard_start_xmit() make sense for MPLS. > >> >> >> >> > >> >> >> >> The problem is the meaning of skb->encapsulation isn't really defined > >> >> >> >> clearly and I'm certain that the current implementation is not going > >> >> >> >> to work in the future. Depending on your perspective, vlans, MPLS, > >> >> >> >> tunnels, etc. can all be considered forms of encapsulation but clearly > >> >> >> >> there are many NICs that have different capabilities across those. I > >> >> >> >> believe the intention here was really to describe L3 tunnels as > >> >> >> >> encapsulation, in which case MPLS really shouldn't be using this > >> >> >> >> mechanism at all. > >> >> >> >> > >> >> >> >> Now there is some overlap, especially today since most currently > >> >> >> >> shipping silicon wasn't designed to support tunnels and so is using > >> >> >> >> some form of offset based offloads. In that case, all forms of > >> >> >> >> encapsulation are pretty similar. However, in the future that won't be > >> >> >> >> the case as support for specific protocols is implemented for higher > >> >> >> >> performance and richer support. When that happens, not only will MPLS > >> >> >> >> and tunnels have different capabilities but various forms tunnels > >> >> >> >> might as well. > >> >> >> > > >> >> >> > Wouldn't be possible to describe those differences using, > >> >> >> > dev->hw_enc_features? I assumed that was its purpose. > >> >> >> > >> >> >> If there truly are differences between the offload capabilities of > >> >> >> MPLS and L3 tunnels then no, it's not possible, because it's a single > >> >> >> field. It's certainly not a valid assumption that a NIC that can do > >> >> >> TSO over GRE can also do it over MPLS. > >> >> >> > >> >> >> However, it's unlikely that there are truly significant differences > >> >> >> between various encapsulation formats on a per-feature basis. I think > >> >> >> what we need to do is separate out the ability to understand the > >> >> >> headers from the capabilities so you have two fields: header (none, > >> >> >> VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, > >> >> >> etc.) rather than the product of each. Otherwise, we end up with a ton > >> >> >> of different combinations. > >> >> > > >> >> > I'm not quite sure that I follow. > >> >> > > >> >> > Is your idea to replace skb->encapsulation (a single bit) with > >> >> > a field that corresponds to the outer-most (encapsulation) header in use > >> >> > and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? > >> >> > >> >> No, I'm talking about netdev features. You can already tell the > >> >> encapsulation type of a packet by looking at the EtherType. > >> > > >> > Now I am completely confused about what are the two fields that you > >> > refer to in your previous email. > >> > >> I have always been referring to the netdev features for various > >> protocol types. This is because considering MPLS as a form of > >> encapsulation for the purpose of offloads buckets too many protocols > >> into the same set and NICs will have varying features for those. > >> Trying to avoid this by having a bit for offloadable encapsulations is > >> just going to be very confusing and not very future proof. > >> > >> > In regards to looking ath the ethernet type: > >> > > >> > One of the tricky parts of MPLS is that the packet itself does not contain > >> > the ethernet type or any other way of knowing the type of the inner-packet. > >> > Information that is needed for GSO. > >> > >> I'm aware of that. However, you were referring to the type of > >> encapsulation. It is easy to determine that a packet is MPLS. > >> > >> > My proposal to get around this is to leave skb->protocol as the > >> > original, in the case we are interested in non-MPLS, ethernet type. > >> > >> At the very least, this is not consistent with how it is currently > >> handled (for example, with VLANs) and seems difficult to do properly. > >> However, I have not seen any further analysis since the last time that > >> we discussed this. > > > > Unfortunately my efforts to solicit feedback from others regarding > > that have not been successful. > > Give me a break, Simon. These are your patches and therefore it is > your responsibility to do the analysis. This has come up over and over > again and I'm not happy about it. > > Rather than trying to respond to me as quickly as possible, you need > to slow down, take a step back, and think about the correct direction. > Given that some of these patches have revision numbers in the 20s you > have nothing to complain about as far as receiving help. > > In order to assist you in this, I'm going to drop all of your pending > patches from my queue and not respond to anything further from you > until the merge window is open again. I apologise, the comment I made above was unnecessary. I accept your criticism in regards to responding to quickly. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 2e0ced1..d9ec1de 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -494,7 +494,14 @@ struct sk_buff { * headers if needed */ __u8 encapsulation:1; - /* 7/9 bit hole (depending on ndisc_nodetype presence) */ + /* Encapsulation protocol and NIC drivers should use + * this flag to indicate to each other if the skb contains + * encapsulated packet and GSO should use encapsulation features + * instead of standard features for the netdev. This is typically + * a subset of cases where skb->encapsulation is set. + */ + __u8 encapsulation_features:1; + /* 6/8 bit hole (depending on ndisc_nodetype presence) */ kmemcheck_bitfield_end(flags2); #ifdef CONFIG_NET_DMA diff --git a/net/core/dev.c b/net/core/dev.c index 9e26b8d..53236c5 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2498,7 +2498,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev, * hardware encapsulation features instead of standard * features for the netdev */ - if (skb->encapsulation) + if (skb->encapsulation_features) features &= dev->hw_enc_features; if (netif_needs_gso(skb, features)) { diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 898cf5c..f23d136 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -708,6 +708,7 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old) new->l4_rxhash = old->l4_rxhash; new->no_fcs = old->no_fcs; new->encapsulation = old->encapsulation; + new->encapsulation_features = old->encapsulation_features; #ifdef CONFIG_XFRM new->sp = secpath_get(old->sp); #endif diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c index 0ae998b..8420f29 100644 --- a/net/ipv4/gre.c +++ b/net/ipv4/gre.c @@ -157,6 +157,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb, } skb->encapsulation = 0; + skb->encapsulation_features = 0; if (unlikely(!pskb_may_pull(skb, ghl))) goto out; diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c index 77bfcce..a6db3c0 100644 --- a/net/ipv4/ipip.c +++ b/net/ipv4/ipip.c @@ -220,6 +220,7 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) if (likely(!skb->encapsulation)) { skb_reset_inner_headers(skb); skb->encapsulation = 1; + skb->encapsulation_features = 1; } ip_tunnel_xmit(skb, dev, tiph);
"net: Add support for hardware-offloaded encapsulation" introduced the encapsulation field of struct skb, which when set provides hints that GSO should handle an skb that encapsulates a packet. This patch adds an encapsulation_features field which provides a hint to dev dev_hard_start_xmit() that harware-offload encapsulation features should be used. Previously this hint was provided by the encapsulation field. The other uses of the encapsulation field are left unchanged. The two in-tree locations that set the encapsulation have been updated to also set encapsulation_field. The motivation for this is to provide support segmentation of GSO MPLS skbs. This may be necessary when a non-MPLS GSO skb is turned into an MPLS GSO skb by Open vSwtich and its MPLS push action. In this case it harware-offload encapsulation features should be used, actually to be more exact software segmentation should be selected, but other hints provided by the encapsulation field are not applicable. Cc: Joseph Gasparakis <joseph.gasparakis@intel.com> Cc: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com> Cc: Alexander Duyck <alexander.h.duyck@intel.com> Signed-off-by: Simon Horman <horms@verge.net.au> --- include/linux/skbuff.h | 9 ++++++++- net/core/dev.c | 2 +- net/core/skbuff.c | 1 + net/ipv4/gre.c | 1 + net/ipv4/ipip.c | 1 + 5 files changed, 12 insertions(+), 2 deletions(-)