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Date:	Tue, 17 Jun 2014 22:20:48 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	Jesse Gross <jesse@...ira.com>, dev@...nvswitch.org,
	netdev@...r.kernel.org
Cc:	Ravi K <rkerur@...il.com>, Joe Stringer <joe@...d.net.nz>,
	Thomas Graf <tgraf@...g.ch>
Subject: Re: [PATCH v2.60] datapath: Add basic MPLS support to kernel

Hi Jesse,

I think this is getting pretty close.
Is there anything I can do to help edge it over the line?

On Fri, Jun 06, 2014 at 07:28:51PM +0900, Simon Horman wrote:
> Allow datapath to recognize and extract MPLS labels into flow keys
> and execute actions which push, pop, and set labels on packets.
> 
> Based heavily on work by Leo Alterman, Ravi K, Isaku Yamahata and Joe Stringer.
> 
> Cc: Ravi K <rkerur@...il.com>
> Cc: Leo Alterman <lalterman@...ira.com>
> Cc: Isaku Yamahata <yamahata@...inux.co.jp>
> Cc: Joe Stringer <joe@...d.net.nz>
> Signed-off-by: Simon Horman <horms@...ge.net.au>
> 
> ---
> v2.60
> * Add missing break statement in do_execute_actions().
>   Previously there was a fall-through from OVS_ACTION_ATTR_HASH
>   to OVS_ACTION_ATTR_PUSH_MPLS which is incorrect.
>   (Thanks to a private tip-off.)
> 
> v2.59
> * Increase coverage of compatibility code from v3.11 to v3.16.
>   Although MPLS GSO segmentation support was added in v3.11 it did not
>   use mpls_features to enable it. It turns out that due to the features
>   (n.b. not mpls_features) set by the drivers for most NICs (including the
>   one in my test environment) that it was activated anyway. But to be safe
>   increase compatibility coverage.
>   N.B.: The mpls_features has been queued up for v3.16 as
>         "MPLS: Use mpls_features to activate software MPLS GSO segmentation"
> * As suggested by Jesse Gross
>   - Prohibit pop MPLS actions in the presence of VLANS.
>     This addresses the following:
>     "* Difference between push and pop underneath vlan tags.
>      * Pop with multiple vlan tags
>      * Differences with varying EtherTypes used for vlans"
> 
> v2.58
> * Make ovs_gso_cb small enough to fit in skb->cb
> * As suggested by Jesse Gross
>   - Do not free skb on error in push_mpls.
>     Instead let the caller's regular error handling do so.
>   - Remove handling of impossible error case for too-short skb
>     in pop_mpls()
>   - Call ovs_skb_set_inner_protocol() in push_mpls()
>     This is to support GSO segmentation.
>     This mysteriously went missing in v2.54.
>   - Only call ovs_skb_init_inner_protocol if recirc is false
>     to avoid inner_protocol being clobbered on recirculation.
>   - Reject MPLS push on VLAN packets by inspecting TCI during
>     flow verification
>   - dev_supports_vlan_tx should return true for
>     kernel versions >= 2.6.37 rather than < 2.6.37.
>   - Update rpl_skb_gso_segment() to allow for MPLS inside VLANs
> * Update __skb_network_protocol() to allow for MPLS inside VLANs
> * Detect MPLS in the presence of VLAN tags in rpl_dev_queue_xmit()
> 
> v2.57
> * The sample action has been changed such that its nested actions no
>   longer have side affects. Accordingly remove the complex logic to verify
>   multiple possible ethtype changes resulting from MPLS actions inside the
>   nested actions of a sample action. Instead provide much simpler logic
>   that tracks changes to the single possible ethtype a packet may have.
> 
>   By my calculations this reduces the size of the patch by about 25%.
> 
> v2.56
> * Update whitelist of ethtypes where mpls_push may be used to include
>   the MPLS ethtypes. The whitelist is now:
>   - ETH_P_IP (0x0800)
>   - ETH_P_ARP (0x0806)
>   - ETH_P_RARP (0x0835)
>   - ETH_P_IPV6 (0x86DD)
>   - ETH_P_MPLS_UC (0x8847)
>   - ETH_P_MPLS_MC (0x8847)
> * Rebase for
>   - 6d328fa23ddf5c75
>     ("ofproto: Honour Table Mod settings for  table-miss handling")
>   - 708fb4c50aa5547f
>     ("datapath: Compact sw_flow_key.")
>   - 0962036c0ec3db8a
>     ("recirculation: Adjust ovs_key_attr ABI")
> 
> v2.55
> * Use a whitelist of ethtypes where mpls_push may be used
>   rather than a blacklist of ethtypes where mpls_push may not be used.
>   This is a more restrictive and more conservative approach that guarantees
>   that the tag order is known and defined.
>   The new whitelist is:
>   - ETH_P_IP (0x0800)
>   - ETH_P_ARP (0x0806)
>   - ETH_P_RARP (0x0835)
>   - ETH_P_IPV6 (0x86DD)
>   The old blacklist was:
>   - ETH_P_8021Q (0x8100)
>   - ETH_P_8021AD (0x88A8)
>   - ETH_P_QINQ1 (0x0x9100)
>   - ETH_P_QINQ2 (0x0x9200)
>   - ETH_P_QINQ3 (0x0x9300)
> * Rebase for
>   29c71cfa0c137abd ("datapath: Add support for Linux 3.12")
>   982a47eceac1be71 ("datapath: Use ether_addr_copy")
> 
> v2.54
> * Do not allow push MPLS in the presence of VLANs
> * Remove support for push MPLS in the presence of VLANs from actions.c
> 
> v2.53
> * Push MPLS labels after VLAN tags
>   - This is consistent with OF1.2 and plans for OF1.3.4, and OF1.5+.
>     It is inconsistent with OF1.4, which appears to be an aberration
> 
> v2.52
> * Do not guard __skb_network_protocol with KERNEL_VERSION(3.11.0)
>   It was not guarded before this patch and should not be guarded
>   afterwards as it is currently needed regardless of the kernel version
> 
> v2.50 - v2.51
> * No change
> 
> v2.49
> * Remove MPLS items from OPENFLOW-1.1+. They should now be complete.
> 
> v2.47
> * Rebase for HAVE_RHEL_OVS_HOOK and OVS_KEY_ATTR_TCP_FLAGS
> 
> v2.43 - v2.46
> * No change
> 
> v2.42
> * Rebase for:
>   + 0585f7a ("datapath: Simplify mega-flow APIs.")
>   + a097c0b ("datapath: Restructure datapath.c and flow.c")
> * As suggested by Jesse Gross
>   + Take into account that push_mpls() will have freed the skb on error
>   + Remove dubious !eth_p_mpls(skb->protocol) condition from push_mpls
>     The !eth_p_mpls(skb->protocol) condition on setting inner_protocol
>     has no effect. Its motivation was to ensure that inner_protocol was
>     only set the first time that mpls_push occured. However this is already
>     ensured by the !ovs_skb_get_inner_protocol(skb) condition.
>   + Return -EINVAL instead of -ENOMEM from pop_mpls() if the skb is too short
>   + Do not add @inner_protocol to kernel doc for struct ovs_skb_cb.
>     The patch no longer adds an inner_protocol member to struct ovs_skb_cb
>   + Do not add and set otherwise unsued inner_protocol variable in
>     rpl_dev_queue_xmit()
> * As suggested by Pravin Shelar
>   + Implement compatibility code in existing rpl_skb_gso_segment
>     rather than introducing to use rpl___skb_gso_segment
> 
> v2.41
> * No change
> 
> v2.40
> * Rebase for:
>   + New dev_queue_xmit compat code
>   + Updated put_vlan()
> * As suggested by Jesse Gross
>   + Remove bogus mac_len update from push_mpls()
>   + Slightly simplify push_mpls() by using eth_hdr()
>   + Remove dubious condition !eth_p_mpls(inner_protocol) on
>     an skb being considered to be MPLS in netdev_send()
>   + Only use compatibility code for MPLS GSO segmentation on kernels
>     older than 3.11
>   + Revamp setting of inner_protocol
>     1. Do not unconditionally set inner_protocol to the value of
>        skb->protocol in ovs_execute_actions().
>     2. Initialise inner_protocol it to zero only if compatibility code is in
>        use. In the case where compatibility code is not in use it will either
>        be zero due since the allocation of the skb or some other value set
>        by some other user.
>     3. Conditionally set the inner_protocol in push_mpls() to the value of
>        skb->protocol when entering push_mpls(). The condition is that
>        inner_protocol is zero and the value of skb->protocol is not an MPLS
>        ethernet type.
>     - This new scheme:
>       + Pushes logic to set inner_protocol closer to the case where it is
> 	needed.
>       + Avoids over-writing values set by other users.
> * As suggested by Pravin Shelar
>   + Only set and restore skb->protocol in rpl___skb_gso_segment() in the
>     case of MPLS
>   + Add inner_protocol field to struct ovs_gso_cb instead of ovs_skb_cb.
>     This moves compatibility code closer to where it is used
>     and creates fewer differences with mainline.
> * Update comment on mac_len updates in datapath/actions.c
> * Remove HAVE_INNER_PROCOTOL and instead just check
>   against kernel version 3.11 directly.
>   HAVE_INNER_PROCOTOL is a hang-over from work done prior
>   to the merge of inner_protocol into the kernel.
> * Remove dubious condition !eth_p_mpls(inner_protocol) on
>   using inner_protocol as the type in rpl_skb_network_protocol()
> * Do not update type of features in rpl_dev_queue_xmit.
>   Though arguably correct this is not an inherent part of
>   the changes made by this patch.
> * Use skb_cow_head() in push_mpls()
>   + Call skb_cow_head(skb, MPLS_HLEN) instead of
>     make_writable(skb, skb->mac_len) to ensure that there is enough head
>     room to push an MPLS LSE regardless of whether the skb is cloned or not.
>   + This is consistent with the behaviour of rpl__vlan_put_tag().
>   + This is a fix for crashes reported when performing mpls_push
>     with headroom less than 4. This problem was introduced in v3.36.
> * Skip popping in mpls_pop if the skb is too short to contain an MPLS LSE
> 
> v2.39
> * Rebase for removal of vlan, checksum and skb->mark compat code
> 
> v2.38
> * Rebase for SCTP support
> * Refactor validate_tp_port() to iterate over eth_types rather
>   than open-coding the loop. With the addition of SCTP this logic
>   is now used three times.
> 
> v2.37
> * Rebase
> 
> v2.36
> * Do not add set_ethertype() to datapath/actions.c.
>   As this patch has evolved this function had devolved into
>   to sets of functionality wrapped into a single function with
>   only one line of common code. Refactor things to simply
>   open-code setting the ether type in the two locations where
>   set_ethertype() was previously used. The aim here is to improve
>   readability.
> 
> * Update setting skb->protocol after mpls push and pop.
>   - In the case of push_mpls it should be set unconditionally
>     as in v2.35 the behaviour of this function to always push
>     an MPLS LSE before any VLAN tags.
>   - In the case of mpls_pop eth_p_mpls(skb->protocol) is a better
>     test than skb->protocol != htons(ETH_P_8021Q) as it will give the
>     correct behaviour in the presence of other VLAN ethernet types,
>     for example 0x88a8 which is used by 802.1ad. Moreover, it seems
>     correct to update the ethernet type if it was previously set
>     according to the top-most MPLS LSE.
> 
> * Deaccelerate VLANs when pushing MPLS tags the
>   - Since v2.35 MPLS push will insert an MPLS LSE before any VLAN tags.
>     This means that if an accelerated tag is present it should be
>     deaccelerated to ensure it ends up in the correct position.
> 
> * Update skb->mac_len in push_mpls() so that it will be correct
>   when used by a subsequent call to pop_mpls().
> 
>   As things stand I do not believe this is strictly necessary as
>   ovs-vswitchd will not send a pop MPLS action after a push MPLS action.
>   However, I have added this in order to code more defensively as I believe
>   that if such a sequence did occur it would be rather unobvious why
>   it didn't work.
> 
> * Do not add skb_cow_head() call in push_mpls().
>   It is unnecessary as there is a make_writable() call.
>   This change was also made in v2.30 but some how the
>   code regressed between then and v2.35.
> 
> v2.35
> * Rebase
> * Move MPLS constants to mpls.h
> * Push MPLS tags after ethernet, before VLAN tags
>   - This is consistent with the OpenFlow 1.3 specification
>   - Compatibility with OpenFlow 1.2 and earlier versions
>     may be provided by ovs-vswitchd.
> * Correct GSO behaviour in the presence of MPLS but absence of VLANs
> 
> v2.34
> * Rebase for megaflow changes
> 
> v2.33
> * Ensure that inner_protocol is always set to to the current
>   skb->protocol value in ovs_execute_actions(). This ensures
>   it is set to the correct value in the absence of a push_mpls action.
>   Also remove setting of inner_protocol in push_mpls() as
>   it duplicates the code now in ovs_execute_actions().
> * Call __skb_gso_segment() instead of skb_gso_segment() from
>   rpl___skb_gso_segment() in the case that HAVE___SKB_GSO_SEGMENT is set.
>   This was a typo.
> 
> v2.32
> * As suggested by Jesse Gross
>   - Use int instead of size_t in validate_and_copy_actions__().
>   - Fix crazy edit mess in pop_mpls() action comment
>   - Move eth_p_mpls() into mpls.h
>   - Refactor skb_gso_segment MPLS handling into rpl_skb_gso_segment
>     Address Jesse's comments regarding this code:
>     "Can we push this completely into the skb_gso_segment() compatibility
>      code? It's both nicer and may make the interactions with the vlan code
>      less confusing."
>   - Move GSO compatibility code into linux/compat/gso.*
>   - Set skb->protocol on mpls_push and mpls_pop in the presence
>     of an offloaded VLAN.
> 
> v2.31
> * As suggested by Jesse Gross
>   - There is no need to make mac_header_end inline as it is not in a header file
>   - Remove dubious if (*skb_ethertype == ethertype) optimisation from
>     set_ethertype
>   - Only set skb->protocol in push_mpls() or pop_mpls() for non-VLAN packets
>   - Use MAX_ETH_TYPES instead of SAMPLE_ACTION_DEPTH for array size
>     of types in struct eth_types. This corrects a typo/thinko.
>   - Correct eth type tracking logic such that start isn't advanced
>     when entering a sample action, ensuring that all possibly types
>     are checked when verifying nested actions.
> * Define HAVE_INNER_PROTOCOL based on kernel version.
>   inner_protocol has been merged into net-next and should appear in
>   v3.11 so there is no longer a need for a acinclude.m4 test to check for it.
> * Add MPLS GSO compatibility code.
>   This is for use on kernels that do not have MPLS GSO support.
>   Thanks to Joe Stringer for his work on this.
> 
> v2.30
> * As suggested by Jesse Gross
>   - Use skb_cow_head in push_mpls to ensure there is sufficient headroom for
>     skb_push
>   - Call make_writable with skb->mac_len instead of skb->mac_len + MPLS_HLEN
>     in push_mpls as only the first skb->mac_len bytes of existing packet data
>     are modified.
>   - Rename skb_mac_header_end as mac_header_end, this seems
>     to be a more appropriate name for a local function.
>   - Remove OVS_CSUM_COMPLETE code from set_ethertype().
>     Inside OVS the ethernet header is not covered by OVS_CSUM_COMPLETE.
>   - Use __skb_pull() instead of skb_pull() in pop_mpls()
>   - Decrement and decrement skb->mac_len when poping and pushing VLAN tags.
>     Previously mac_len was reset, but this would result in forgetting
>     the MPLS label stack.
>   - Remove spurious comment from before do_execute_actions().
>   - Move OVS_KEY_ATTR_MPLS attribute to its final, upstreamable, location.
>   - Correct ethertype check for OVS_ACTION_ATTR_POP_MPLS case in
>     validate_and_copy_actions() to check for MPLS ethertypes rather than
>     ETH_P_IP.
>   - Rewrite tracking of eth types used to verify actions in the presence
>     of sample actions. There is a large comment above struct eth_types
>     describing the new implementation.
> 
> v2.29
> * Break include/ and lib/ portions of the patch out into a
>   separate patch "datapath: Add basic MPLS support to kernel"
> * Update for new MPLS GSO scheme
>   - skb->protocol is set to the new ethertype of the packet
>     on MPLS push and pop
>   - When pushing the first MPLS LSE onto a previously non-MPLS
>     packet set skb->inner_protocol to the original ethertype.
>   - skb->inner_protocol may be used by the network stack
>     for GSO of the inner-packet.
> * Drop const from ethertype parameter of set_ethertype.
>   This appears to be a legacy of this parameter being a pointer.
> * Pass the ethertype patrameter of pop_mpls as a value rather
>   than a pointer.
> 
> v2.28
> * Kernel Datapath changes as suggested by Jarno Rajahalme
>   + Correct the logic introduced in v2.27 to set the network_header
>     to after the MPLS label stack in the case of an MPLS packet.
>     - Increment stack_len offset so that label stacks of depth greater
>       than two do not cause an infinite loop.
>     - Correct offset passed to check_header to include skb->mac len
> 
> v2.27
> * Kernel Datapath changes as suggested by Jarno Rajahalme and Jesse Gross:
>   + Previously the mac_len and network_header of an skb corresponded
>     to the end of the L2 header.  To support GSO, just before transmission,
>     do_output, with the results as follows:
> 
>     Input: non-MPLS skb: Output: network header and mac_len correspond
>                          to the beginning of the L3 headers
>     Input: MPLS:         Output: network header and mac_len correspond to the
>                          end of the L2 headers.
> 
>     This is somewhat confusing.
> 
>   + The new scheme is as follows:
>     - The mac_len always corresponds to the end of the L2 header.
>     - The network header always corresponds to the beginning of the
>       L3 header.
> 
>   + Note that in the case of MPLS output the end of the L2 headers and the
>   beginning of the L3 headers will differ.
> 
> * Remove unused declaration of skb_cb_mpls_stack()
> 
> v2.26
> * Rebase on master
> * Kernel Datapath changes as suggested by Jarno Rajahalme
>   - Use skb_network_header() instead of skb_mac_header() to locate
>     the ethertype to set in set_ethertype() as the latter will
>     be wrong in the presence of VLAN tags. This resolves
>     a regression introduced in v2.24.
>   - Enhance comment in do_output()
>   - do_execute_actions(): Do not alter mpls_stack_depth if
>     a MPLS push or pop action fail. This is achieved by altering
>     mpls_stack_depth at the end of push_mpls() and pop_mpls().
> 
> v2.25
> * Rebase on master
> * Pass big-endian value as the last argument of eth_types_set() in
>   validate_and_copy_actions__()
> * Use revised GSO support as provided by the patch series
>   "[PATCH 0/2] Small Modifications to GSO to allow segmentation of MPLS"
>   - Set skb->mac_len to the length of the l2 header + MPLS stack length
>   - Update skb->network_header accordingly
>   - Set skb->encapsulated_features
> 
> v2.24
> * Use skb_mac_header() in set_ethertype()
> * Set skb->encapsulation in set_ethertype() to support MPLS GSO.
>   Also add a note about the other requirements for MPLS GSO.
>   MPLS GSO support will be posted as a patch net-next (Linux mainline)
>   "MPLS: Add limited GSO support"
> * Do not add ETH_TYPE_MIN, it is no longer used
> 
> v2.23
> * As suggested by Jesse Gross:
>   - Verify the current ethernet type when validating sample actions
>     both for the taken and not-taken path if the sample action.
>   - Document that the OVS_KEY_ATTR_MPLS attribute accepts a list of
>     struct ovs_key_mpls but that an implementation may restrict
>     the length it accepts.
>   - Restrict the array length of the OVS_KEY_ATTR_MPLS to one.
>     + Don't add ovs_flow_verify_key_len as it was added to
>       handle attributes whose values are arrays but there are
>       no attributes with values that are arrays (of length greater than one).
> 
> v2.22
> * As suggested by Jesse Gross:
>   - Fix sparse warning in validate_and_copy_actions()
>     I have no idea why sparse doesn't show this up this on my system.
>   - Remove call to skb_cow_head() from push_mpls() as it
>     is already covered by a call to make_writable()
>   - Check (key_type > OVS_KEY_ATTR_MAX) in ovs_flow_verify_key_len()
>   - Disallow set actions on l2.5+ data and MPLS push and pop actions
>     after an MPLS pop action as there is no verification that the packet
>     is actually of the new ethernet type. This may later be supported
>     using recirculation or by other means.
>   - Do not add spurious debuging message to ovs_flow_cmd_new_or_set()
> 
> v2.21
> * As suggested by Jesse Gross:
>   - Verify that l3 and l4 actions always always occur prior to
>     a push_mpls action and use the network header pointer of an skb
>     to track the top of the MPLS stack. This avoids adding an l2_size
>     element to the skb callback.
> 
> v2.20
> * As suggested by Jesse Gross:
>   - Do not add ovs_dp_ioctl_hook
>     + This appears to be garbage from a rebase
>   - Do not add skb_cb_set_l2_size. Instead set OVS_CB(skb)->l2_size
>     in ovs_flow_extract().
>   - Do not free skb on error in push_mpls(), it is freed in the caller
>   - Call skb_reset_mac_len() in pop_mpls() and push_mpls()
>   - Update checksums in pop_mpls(), push_mpls() and set_mpls().
>   - Rename skb_cb_mpls_bos() as skb_cb_mpls_stack().
>     It returns the top not the bottom of the stack.
>   - Track the current eth_type in validate_and_copy_actions
>     which is initially the eth_type of the flow and may be modified
>     by push_mpls and pop_mpls actions. Use this to correctly validate
>     mpls_set actions. This is to allow mpls_set actions to be applied
>     to a non-MPLS frame after an mpls_push action (although ovs-vswitchd
>     doesn't currently do that).
>     Also:
>     + Remove the check of the eth_type in set_mpls() as the new validation
>       scheme should ensure it cannot be incorrect.
>     + Use the current eth_type to validate mpls_pop actions and remove
>       the eth_type check from pop_mpls().
>   - Move OVS_KEY_ATTR_MPLS to non-upstream group in ovs_key_lens
>   - Remove unnecessary memset of mpls_key in ovs_flow_to_nlattrs()
>   - Make a union of the mpls and ip elements of struct sw_flow_key.
>     Currently the code stops parsing after an MPLS header so it is
>     not possible for the ip and mpls elements to be used simultaneously
>     and some space can be saved by using a union.
>   - Allow an array of MPLS key attributes
>     + Currently all but the first element is ignored
>     + User-space needs to be updated to accept more than one element,
>       currently it will treat their presence as an error
>   - Do not update network header in ovs_flow_extract() for after parsing
>     the MPLS stack as it is never used because no l3+ processing
>     occurs on MPLS frames.
>   - Allow multiple MPLS entries in a match by allowing the OVS_KEY_ATTR_MPLS
>     to be an array of struct ovs_key_mpls with at least one entry.
>     Currently only one entry is used which is byte-for-byte compatible with
>     the previous scheme of having OVS_KEY_ATTR_MPLS as a struct
>     ovs_key_mpls.
> * Make skb writable in pop_mpls(), push_mpls() and set_mpls().
> 
> v2.18 - v2.19
> * No change
> 
> v2.17
> * As suggested by Ben Pfaff
>   - Use consistent terminology for MPLS.
>     + Consistently refer to the MPLS component of a packet as the
>       MPLS label stack and entries in the stack as MPLS label stack entries
>       (LSE).  An MPLS label is a component of an MPLS label stack entry.
>       The other components are the traffic class (TC), time to live (TTL)
>       and bottom of stack (BoS) bit.
>   - Rename compose_.*mpls_ functions as execute_.*mpls_
> 
> v2.16
> * No change
> 
> v2.15
> * As suggested by Ben Pfaff
>   - Use OVS_ACTION_SET to set OVS_KEY_ATTR_MPLS instead of
>     OVS_ACTION_ATTR_SET_MPLS
> 
> v2.14
> * Remove include/linux/openvswitch.h portion which added add
>   new key and action attributes. This
>   now present in "User-Space MPLS actions and matches"
>   which is now a dependency of this patch
> 
> v2.13
> * As suggested by Jarno Rajahalme
>   - Rename mpls_bos element of ovs_skb_cb as l2_size as it is set and used
>     regardless of if an MPLS stack is present or not. Update the name of
>     helper functions and documentation accordingly.
>   - Ensure that skb_cb_mpls_bos() never returns NULL
> * Correct endieness in eth_p_mpls()
> 
> v2.12
> * Update skb and network header on MPLS extraction in ovs_flow_extract()
> * Use NULL in skb_cb_mpls_bos()
> * Add eth_p_mpls helper
> 
> v2.10 - v2.11
> * No change
> 
> v2.9
> * datapath: Always update the mpls bos if  vlan_pop is successful
> 
>   Regardless of the details of how a successful
>   vlan_pop is achieved, the mpls bos needs to be updated.
> 
>   Without this fix it has been observed that the following
>   results in malformed packets
> 
> v2.8
> * No change
> 
> v2.7
> * Rebase
> 
> v2.6
> * As suggested by Yamahata-san
>   - Do not guard against label == 0 for
>     OVS_ACTION_ATTR_SET_MPLS in validate_actions().
>     A label of 0 is valid
>   - Remove comment stupulating that if
>     the top_label element of struct sw_flow_key is 0 then
>     there is no MPLS label. An MPLS label of 0 is valid
>     and the correct check if ethertype is
>     ntohs(ETH_TYPE_MPLS) or ntohs(ETH_TYPE_MPLS_MCAST)
> 
> v2.4 - v2.5
> * No change
> 
> v2.3
> * s/mpls_stack/mpls_bos/
>   This is in keeping with the naming used in the OpenFlow 1.3 specification
> 
> v2.2
> * Call skb_reset_mac_header() in skb_cb_set_mpls_stack()
>   eth_hdr(skb) is non-NULL when called in skb_cb_set_mpls_stack().
> * Add a call to skb_cb_set_mpls_stack() in ovs_packet_cmd_execute().
>   I apologise that I have mislaid my notes on this but
>   it avoids a kernel panic. I can investigate again if necessary.
> * Use struct ovs_action_push_mpls instead of
>   __be16 to decode OVS_ACTION_ATTR_PUSH_MPLS in validate_actions(). This is
>   consistent with the data format for the attribute.
> * Indentation fix in skb_cb_mpls_stack(). [cosmetic]
> 
> v2.1
> * Manual rebase
> ---
>  OPENFLOW-1.1+                                   |   4 -
>  datapath/Modules.mk                             |   1 +
>  datapath/actions.c                              | 116 ++++++++++++++++++++-
>  datapath/datapath.c                             |   6 +-
>  datapath/flow.c                                 |  29 ++++++
>  datapath/flow.h                                 |  17 ++--
>  datapath/flow_netlink.c                         | 130 ++++++++++++++++++++----
>  datapath/flow_netlink.h                         |   2 +-
>  datapath/linux/compat/gso.c                     |  78 +++++++++++---
>  datapath/linux/compat/gso.h                     |  41 +++++++-
>  datapath/linux/compat/include/linux/netdevice.h |   6 +-
>  datapath/linux/compat/netdevice.c               |  10 +-
>  datapath/mpls.h                                 |  15 +++
>  include/linux/openvswitch.h                     |   9 +-
>  14 files changed, 409 insertions(+), 55 deletions(-)
>  create mode 100644 datapath/mpls.h
> 
> diff --git a/OPENFLOW-1.1+ b/OPENFLOW-1.1+
> index 927962a..049576c 100644
> --- a/OPENFLOW-1.1+
> +++ b/OPENFLOW-1.1+
> @@ -54,10 +54,6 @@ OpenFlow 1.1
>  The list of remaining work items for OpenFlow 1.1 is below.  It is
>  probably incomplete.
>  
> -    * MPLS.  Simon Horman maintains a patch series that adds this
> -      feature.  This is partially merged.
> -      [optional for OF1.1+]
> -
>      * Match and set double-tagged VLANs (QinQ).  This requires kernel
>        work for reasonable performance.
>        [optional for OF1.1+]
> diff --git a/datapath/Modules.mk b/datapath/Modules.mk
> index b652411..6aa80e5 100644
> --- a/datapath/Modules.mk
> +++ b/datapath/Modules.mk
> @@ -26,6 +26,7 @@ openvswitch_headers = \
>  	flow.h \
>  	flow_netlink.h \
>  	flow_table.h \
> +	mpls.h \
>  	vlan.h \
>  	vport.h \
>  	vport-internal_dev.h \
> diff --git a/datapath/actions.c b/datapath/actions.c
> index 603c7cb..e9cecdf 100644
> --- a/datapath/actions.c
> +++ b/datapath/actions.c
> @@ -35,6 +35,8 @@
>  #include <net/sctp/checksum.h>
>  
>  #include "datapath.h"
> +#include "gso.h"
> +#include "mpls.h"
>  #include "vlan.h"
>  #include "vport.h"
>  
> @@ -49,6 +51,99 @@ static int make_writable(struct sk_buff *skb, int write_len)
>  	return pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
>  }
>  
> +/* The end of the mac header.
> + *
> + * For non-MPLS skbs this will correspond to the network header.
> + * For MPLS skbs it will be before the network_header as the MPLS
> + * label stack lies between the end of the mac header and the network
> + * header. That is, for MPLS skbs the end of the mac header
> + * is the top of the MPLS label stack.
> + */
> +static unsigned char *mac_header_end(const struct sk_buff *skb)
> +{
> +	return skb_mac_header(skb) + skb->mac_len;
> +}
> +
> +static int push_mpls(struct sk_buff *skb,
> +		     const struct ovs_action_push_mpls *mpls)
> +{
> +	__be32 *new_mpls_lse;
> +	struct ethhdr *hdr;
> +
> +	if (skb_cow_head(skb, MPLS_HLEN) < 0) {
> +		return -ENOMEM;
> +	}
> +
> +	skb_push(skb, MPLS_HLEN);
> +	memmove(skb_mac_header(skb) - MPLS_HLEN, skb_mac_header(skb),
> +		skb->mac_len);
> +	skb_reset_mac_header(skb);
> +
> +	new_mpls_lse = (__be32 *)mac_header_end(skb);
> +	*new_mpls_lse = mpls->mpls_lse;
> +
> +	if (skb->ip_summed == CHECKSUM_COMPLETE)
> +		skb->csum = csum_add(skb->csum, csum_partial(new_mpls_lse,
> +							     MPLS_HLEN, 0));
> +
> +	hdr = eth_hdr(skb);
> +	hdr->h_proto = mpls->mpls_ethertype;
> +	if (!ovs_skb_get_inner_protocol(skb))
> +		ovs_skb_set_inner_protocol(skb, skb->protocol);
> +	skb->protocol = mpls->mpls_ethertype;
> +	return 0;
> +}
> +
> +static int pop_mpls(struct sk_buff *skb, const __be16 ethertype)
> +{
> +	struct ethhdr *hdr;
> +	int err;
> +
> +	err = make_writable(skb, skb->mac_len + MPLS_HLEN);
> +	if (unlikely(err))
> +		return err;
> +
> +	if (skb->ip_summed == CHECKSUM_COMPLETE)
> +		skb->csum = csum_sub(skb->csum,
> +				     csum_partial(mac_header_end(skb),
> +						  MPLS_HLEN, 0));
> +
> +	memmove(skb_mac_header(skb) + MPLS_HLEN, skb_mac_header(skb),
> +		skb->mac_len);
> +
> +	__skb_pull(skb, MPLS_HLEN);
> +	skb_reset_mac_header(skb);
> +
> +	/* mac_header_end() is used to locate the ethertype
> +	 * field correctly in the presence of VLAN tags.
> +	 */
> +	hdr = (struct ethhdr *)(mac_header_end(skb) - ETH_HLEN);
> +	hdr->h_proto = ethertype;
> +	if (eth_p_mpls(skb->protocol))
> +		skb->protocol = ethertype;
> +	return 0;
> +}
> +
> +static int set_mpls(struct sk_buff *skb, const __be32 *mpls_lse)
> +{
> +	__be32 *stack = (__be32 *)mac_header_end(skb);
> +	int err;
> +
> +	err = make_writable(skb, skb->mac_len + MPLS_HLEN);
> +	if (unlikely(err))
> +		return err;
> +
> +	if (skb->ip_summed == CHECKSUM_COMPLETE) {
> +		__be32 diff[] = { ~(*stack), *mpls_lse };
> +		skb->csum = ~csum_partial((char *)diff, sizeof(diff),
> +					  ~skb->csum);
> +	}
> +
> +	*stack = *mpls_lse;
> +
> +	return 0;
> +}
> +
>  /* remove VLAN header from packet and update csum accordingly. */
>  static int __pop_vlan_tci(struct sk_buff *skb, __be16 *current_tci)
>  {
> @@ -71,7 +166,8 @@ static int __pop_vlan_tci(struct sk_buff *skb, __be16 *current_tci)
>  
>  	vlan_set_encap_proto(skb, vhdr);
>  	skb->mac_header += VLAN_HLEN;
> -	skb_reset_mac_len(skb);
> +	/* Update mac_len for subsequent MPLS actions */
> +	skb->mac_len -= VLAN_HLEN;
>  
>  	return 0;
>  }
> @@ -116,6 +212,9 @@ static int push_vlan(struct sk_buff *skb, const struct ovs_action_push_vlan *vla
>  		if (!__vlan_put_tag(skb, skb->vlan_proto, current_tag))
>  			return -ENOMEM;
>  
> +		/* Update mac_len for subsequent MPLS actions */
> +		skb->mac_len += VLAN_HLEN;
> +
>  		if (skb->ip_summed == CHECKSUM_COMPLETE)
>  			skb->csum = csum_add(skb->csum, csum_partial(skb->data
>  					+ (2 * ETH_ALEN), VLAN_HLEN, 0));
> @@ -545,6 +644,10 @@ static int execute_set_action(struct sk_buff *skb,
>  	case OVS_KEY_ATTR_SCTP:
>  		err = set_sctp(skb, nla_data(nested_attr));
>  		break;
> +
> +	case OVS_KEY_ATTR_MPLS:
> +		err = set_mpls(skb, nla_data(nested_attr));
> +		break;
>  	}
>  
>  	return err;
> @@ -606,6 +709,14 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
>  			execute_hash(skb, a);
>  			break;
>  
> +		case OVS_ACTION_ATTR_PUSH_MPLS:
> +			err = push_mpls(skb, nla_data(a));
> +			break;
> +
> +		case OVS_ACTION_ATTR_POP_MPLS:
> +			err = pop_mpls(skb, nla_get_be16(a));
> +			break;
> +
>  		case OVS_ACTION_ATTR_PUSH_VLAN:
>  			err = push_vlan(skb, nla_data(a));
>  			if (unlikely(err)) /* skb already freed. */
> @@ -701,6 +812,9 @@ int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb, bool recirc)
>  		goto out_loop;
>  	}
>  
> +	if (!recirc)
> +		ovs_skb_init_inner_protocol(skb);
> +
>  	OVS_CB(skb)->tun_key = NULL;
>  	error = do_execute_actions(dp, skb, acts->actions, acts->actions_len);
>  
> diff --git a/datapath/datapath.c b/datapath/datapath.c
> index 81ecc0f..cd52d92 100644
> --- a/datapath/datapath.c
> +++ b/datapath/datapath.c
> @@ -576,7 +576,7 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
>  		goto err_flow_free;
>  
>  	err = ovs_nla_copy_actions(a[OVS_PACKET_ATTR_ACTIONS],
> -				   &flow->key, 0, &acts);
> +				   &flow->key, &acts);
>  	rcu_assign_pointer(flow->sf_acts, acts);
>  	if (err)
>  		goto err_flow_free;
> @@ -861,7 +861,7 @@ static int ovs_flow_cmd_new(struct sk_buff *skb, struct genl_info *info)
>  		goto err_kfree_flow;
>  
>  	error = ovs_nla_copy_actions(a[OVS_FLOW_ATTR_ACTIONS], &new_flow->key,
> -				     0, &acts);
> +				     &acts);
>  	if (error) {
>  		OVS_NLERR("Flow actions may not be safe on all matching packets.\n");
>  		goto err_kfree_acts;
> @@ -985,7 +985,7 @@ static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
>  
>  		ovs_flow_mask_key(&masked_key, &key, &mask);
>  		error = ovs_nla_copy_actions(a[OVS_FLOW_ATTR_ACTIONS],
> -					     &masked_key, 0, &acts);
> +					     &masked_key, &acts);
>  		if (error) {
>  			OVS_NLERR("Flow actions may not be safe on all matching packets.\n");
>  			goto err_kfree_acts;
> diff --git a/datapath/flow.c b/datapath/flow.c
> index c52081b..cbba1cf 100644
> --- a/datapath/flow.c
> +++ b/datapath/flow.c
> @@ -45,6 +45,7 @@
>  #include <net/ipv6.h>
>  #include <net/ndisc.h>
>  
> +#include "mpls.h"
>  #include "vlan.h"
>  
>  u64 ovs_flow_used_time(unsigned long flow_jiffies)
> @@ -480,6 +481,7 @@ int ovs_flow_extract(struct sk_buff *skb, u16 in_port, struct sw_flow_key *key)
>  		return -ENOMEM;
>  
>  	skb_reset_network_header(skb);
> +	skb_reset_mac_len(skb);
>  	__skb_push(skb, skb->data - skb_mac_header(skb));
>  
>  	/* Network layer. */
> @@ -563,6 +565,33 @@ int ovs_flow_extract(struct sk_buff *skb, u16 in_port, struct sw_flow_key *key)
>  			ether_addr_copy(key->ipv4.arp.sha, arp->ar_sha);
>  			ether_addr_copy(key->ipv4.arp.tha, arp->ar_tha);
>  		}
> +	} else if (eth_p_mpls(key->eth.type)) {
> +		size_t stack_len = MPLS_HLEN;
> +
> +		/* In the presence of an MPLS label stack the end of the L2
> +		 * header and the beginning of the L3 header differ.
> +		 *
> +		 * Advance network_header to the beginning of the L3
> +		 * header. mac_len corresponds to the end of the L2 header.
> +		 */
> +		while (1) {
> +			__be32 lse;
> +
> +			error = check_header(skb, skb->mac_len + stack_len);
> +			if (unlikely(error))
> +				return 0;
> +
> +			memcpy(&lse, skb_network_header(skb), MPLS_HLEN);
> +
> +			if (stack_len == MPLS_HLEN)
> +				memcpy(&key->mpls.top_lse, &lse, MPLS_HLEN);
> +
> +			skb_set_network_header(skb, skb->mac_len + stack_len);
> +			if (lse & htonl(MPLS_BOS_MASK))
> +				break;
> +
> +			stack_len += MPLS_HLEN;
> +		}
>  	} else if (key->eth.type == htons(ETH_P_IPV6)) {
>  		int nh_len;             /* IPv6 Header + Extensions */
>  
> diff --git a/datapath/flow.h b/datapath/flow.h
> index 2018691..ca29d56 100644
> --- a/datapath/flow.h
> +++ b/datapath/flow.h
> @@ -82,12 +82,17 @@ struct sw_flow_key {
>  		__be16 tci;		/* 0 if no VLAN, VLAN_TAG_PRESENT set otherwise. */
>  		__be16 type;		/* Ethernet frame type. */
>  	} eth;
> -	struct {
> -		u8     proto;		/* IP protocol or lower 8 bits of ARP opcode. */
> -		u8     tos;		/* IP ToS. */
> -		u8     ttl;		/* IP TTL/hop limit. */
> -		u8     frag;		/* One of OVS_FRAG_TYPE_*. */
> -	} ip;
> +	union {
> +		struct {
> +			__be32 top_lse;		/* top label stack entry */
> +		} mpls;
> +		struct {
> +			u8     proto;		/* IP protocol or lower 8 bits of ARP opcode. */
> +			u8     tos;		    /* IP ToS. */
> +			u8     ttl;		    /* IP TTL/hop limit. */
> +			u8     frag;		/* One of OVS_FRAG_TYPE_*. */
> +		} ip;
> +	};
>  	struct {
>  		__be16 src;		/* TCP/UDP/SCTP source port. */
>  		__be16 dst;		/* TCP/UDP/SCTP destination port. */
> diff --git a/datapath/flow_netlink.c b/datapath/flow_netlink.c
> index 803a94c..bcd05b3 100644
> --- a/datapath/flow_netlink.c
> +++ b/datapath/flow_netlink.c
> @@ -20,6 +20,7 @@
>  
>  #include "flow.h"
>  #include "datapath.h"
> +#include "mpls.h"
>  #include <linux/uaccess.h>
>  #include <linux/netdevice.h>
>  #include <linux/etherdevice.h>
> @@ -123,7 +124,8 @@ static bool match_validate(const struct sw_flow_match *match,
>  			| (1ULL << OVS_KEY_ATTR_ICMP)
>  			| (1ULL << OVS_KEY_ATTR_ICMPV6)
>  			| (1ULL << OVS_KEY_ATTR_ARP)
> -			| (1ULL << OVS_KEY_ATTR_ND));
> +			| (1ULL << OVS_KEY_ATTR_ND)
> +			| (1ULL << OVS_KEY_ATTR_MPLS));
>  
>  	/* Always allowed mask fields. */
>  	mask_allowed |= ((1ULL << OVS_KEY_ATTR_TUNNEL)
> @@ -138,6 +140,13 @@ static bool match_validate(const struct sw_flow_match *match,
>  			mask_allowed |= 1ULL << OVS_KEY_ATTR_ARP;
>  	}
>  
> +
> +	if (eth_p_mpls(match->key->eth.type)) {
> +		key_expected |= 1ULL << OVS_KEY_ATTR_MPLS;
> +		if (match->mask && (match->mask->key.eth.type == htons(0xffff)))
> +			mask_allowed |= 1ULL << OVS_KEY_ATTR_MPLS;
> +	}
> +
>  	if (match->key->eth.type == htons(ETH_P_IP)) {
>  		key_expected |= 1ULL << OVS_KEY_ATTR_IPV4;
>  		if (match->mask && (match->mask->key.eth.type == htons(0xffff)))
> @@ -255,6 +264,7 @@ static const int ovs_key_lens[OVS_KEY_ATTR_MAX + 1] = {
>  	[OVS_KEY_ATTR_DP_HASH] = sizeof(u32),
>  	[OVS_KEY_ATTR_RECIRC_ID] = sizeof(u32),
>  	[OVS_KEY_ATTR_TUNNEL] = -1,
> +	[OVS_KEY_ATTR_MPLS] = sizeof(struct ovs_key_mpls),
>  };
>  
>  static bool is_all_zero(const u8 *fp, size_t size)
> @@ -643,6 +653,16 @@ static int ovs_key_from_nlattrs(struct sw_flow_match *match, u64 attrs,
>  		attrs &= ~(1ULL << OVS_KEY_ATTR_ARP);
>  	}
>  
> +	if (attrs & (1ULL << OVS_KEY_ATTR_MPLS)) {
> +		const struct ovs_key_mpls *mpls_key;
> +
> +		mpls_key = nla_data(a[OVS_KEY_ATTR_MPLS]);
> +		SW_FLOW_KEY_PUT(match, mpls.top_lse,
> +				mpls_key->mpls_lse, is_mask);
> +
> +		attrs &= ~(1ULL << OVS_KEY_ATTR_MPLS);
> +	 }
> +
>  	if (attrs & (1ULL << OVS_KEY_ATTR_TCP)) {
>  		const struct ovs_key_tcp *tcp_key;
>  
> @@ -1009,6 +1029,14 @@ int ovs_nla_put_flow(const struct sw_flow_key *swkey,
>  		arp_key->arp_op = htons(output->ip.proto);
>  		ether_addr_copy(arp_key->arp_sha, output->ipv4.arp.sha);
>  		ether_addr_copy(arp_key->arp_tha, output->ipv4.arp.tha);
> +	} else if (eth_p_mpls(swkey->eth.type)) {
> +		struct ovs_key_mpls *mpls_key;
> +
> +		nla = nla_reserve(skb, OVS_KEY_ATTR_MPLS, sizeof(*mpls_key));
> +		if (!nla)
> +			goto nla_put_failure;
> +		mpls_key = nla_data(nla);
> +		mpls_key->mpls_lse = output->mpls.top_lse;
>  	}
>  
>  	if ((swkey->eth.type == htons(ETH_P_IP) ||
> @@ -1200,9 +1228,15 @@ static inline void add_nested_action_end(struct sw_flow_actions *sfa,
>  	a->nla_len = sfa->actions_len - st_offset;
>  }
>  
> +static int ovs_nla_copy_actions__(const struct nlattr *attr,
> +				  const struct sw_flow_key *key,
> +				  int depth, struct sw_flow_actions **sfa,
> +				  __be16 eth_type, __be16 vlan_tci);
> +
>  static int validate_and_copy_sample(const struct nlattr *attr,
>  				    const struct sw_flow_key *key, int depth,
> -				    struct sw_flow_actions **sfa)
> +				    struct sw_flow_actions **sfa,
> +				    __be16 eth_type, __be16 vlan_tci)
>  {
>  	const struct nlattr *attrs[OVS_SAMPLE_ATTR_MAX + 1];
>  	const struct nlattr *probability, *actions;
> @@ -1239,7 +1273,8 @@ static int validate_and_copy_sample(const struct nlattr *attr,
>  	if (st_acts < 0)
>  		return st_acts;
>  
> -	err = ovs_nla_copy_actions(actions, key, depth + 1, sfa);
> +	err = ovs_nla_copy_actions__(actions, key, depth + 1, sfa,
> +				     eth_type, vlan_tci);
>  	if (err)
>  		return err;
>  
> @@ -1249,10 +1284,10 @@ static int validate_and_copy_sample(const struct nlattr *attr,
>  	return 0;
>  }
>  
> -static int validate_tp_port(const struct sw_flow_key *flow_key)
> +static int validate_tp_port(const struct sw_flow_key *flow_key,
> +			    __be16 eth_type)
>  {
> -	if ((flow_key->eth.type == htons(ETH_P_IP) ||
> -	     flow_key->eth.type == htons(ETH_P_IPV6)) &&
> +	if ((eth_type == htons(ETH_P_IP) || eth_type == htons(ETH_P_IPV6)) &&
>  	    (flow_key->tp.src || flow_key->tp.dst))
>  		return 0;
>  
> @@ -1301,7 +1336,7 @@ static int validate_and_copy_set_tun(const struct nlattr *attr,
>  static int validate_set(const struct nlattr *a,
>  			const struct sw_flow_key *flow_key,
>  			struct sw_flow_actions **sfa,
> -			bool *set_tun)
> +			bool *set_tun, __be16 eth_type)
>  {
>  	const struct nlattr *ovs_key = nla_data(a);
>  	int key_type = nla_type(ovs_key);
> @@ -1333,7 +1368,7 @@ static int validate_set(const struct nlattr *a,
>  		break;
>  
>  	case OVS_KEY_ATTR_IPV4:
> -		if (flow_key->eth.type != htons(ETH_P_IP))
> +		if (eth_type != htons(ETH_P_IP))
>  			return -EINVAL;
>  
>  		if (!flow_key->ip.proto)
> @@ -1349,7 +1384,7 @@ static int validate_set(const struct nlattr *a,
>  		break;
>  
>  	case OVS_KEY_ATTR_IPV6:
> -		if (flow_key->eth.type != htons(ETH_P_IPV6))
> +		if (eth_type != htons(ETH_P_IPV6))
>  			return -EINVAL;
>  
>  		if (!flow_key->ip.proto)
> @@ -1371,19 +1406,24 @@ static int validate_set(const struct nlattr *a,
>  		if (flow_key->ip.proto != IPPROTO_TCP)
>  			return -EINVAL;
>  
> -		return validate_tp_port(flow_key);
> +		return validate_tp_port(flow_key, eth_type);
>  
>  	case OVS_KEY_ATTR_UDP:
>  		if (flow_key->ip.proto != IPPROTO_UDP)
>  			return -EINVAL;
>  
> -		return validate_tp_port(flow_key);
> +		return validate_tp_port(flow_key, eth_type);
> +
> +	case OVS_KEY_ATTR_MPLS:
> +		if (!eth_p_mpls(eth_type))
> +			return -EINVAL;
> +		break;
>  
>  	case OVS_KEY_ATTR_SCTP:
>  		if (flow_key->ip.proto != IPPROTO_SCTP)
>  			return -EINVAL;
>  
> -		return validate_tp_port(flow_key);
> +		return validate_tp_port(flow_key, eth_type);
>  
>  	default:
>  		return -EINVAL;
> @@ -1427,10 +1467,10 @@ static int copy_action(const struct nlattr *from,
>  	return 0;
>  }
>  
> -int ovs_nla_copy_actions(const struct nlattr *attr,
> -			 const struct sw_flow_key *key,
> -			 int depth,
> -			 struct sw_flow_actions **sfa)
> +static int ovs_nla_copy_actions__(const struct nlattr *attr,
> +				  const struct sw_flow_key *key,
> +				  int depth, struct sw_flow_actions **sfa,
> +				  __be16 eth_type, __be16 vlan_tci)
>  {
>  	const struct nlattr *a;
>  	int rem, err;
> @@ -1444,6 +1484,8 @@ int ovs_nla_copy_actions(const struct nlattr *attr,
>  			[OVS_ACTION_ATTR_OUTPUT] = sizeof(u32),
>  			[OVS_ACTION_ATTR_RECIRC] = sizeof(u32),
>  			[OVS_ACTION_ATTR_USERSPACE] = (u32)-1,
> +			[OVS_ACTION_ATTR_PUSH_MPLS] = sizeof(struct ovs_action_push_mpls),
> +			[OVS_ACTION_ATTR_POP_MPLS] = sizeof(__be16),
>  			[OVS_ACTION_ATTR_PUSH_VLAN] = sizeof(struct ovs_action_push_vlan),
>  			[OVS_ACTION_ATTR_POP_VLAN] = 0,
>  			[OVS_ACTION_ATTR_SET] = (u32)-1,
> @@ -1497,19 +1539,63 @@ int ovs_nla_copy_actions(const struct nlattr *attr,
>  				return -EINVAL;
>  			if (!(vlan->vlan_tci & htons(VLAN_TAG_PRESENT)))
>  				return -EINVAL;
> +			vlan_tci = vlan->vlan_tci;
>  			break;
>  
>  		case OVS_ACTION_ATTR_RECIRC:
>  			break;
>  
> +		case OVS_ACTION_ATTR_PUSH_MPLS: {
> +			const struct ovs_action_push_mpls *mpls = nla_data(a);
> +
> +			if (!eth_p_mpls(mpls->mpls_ethertype))
> +				return -EINVAL;
> +			/* Prohibit push MPLS other than to a white list
> +			 * for packets that have a known tag order.
> +			 *
> +			 * vlan_tci indicates that the packet at one
> +			 * point had a VLAN. It may have been subsequently
> +			 * removed using pop VLAN so this rule is stricter
> +			 * than necessary. This is because it is not
> +			 * possible to know if a VLAN is still present
> +			 * after a pop VLAN action. */
> +			if (vlan_tci & htons(VLAN_TAG_PRESENT) ||
> +			    (eth_type != htons(ETH_P_IP) &&
> +			     eth_type != htons(ETH_P_IPV6) &&
> +			     eth_type != htons(ETH_P_ARP) &&
> +			     eth_type != htons(ETH_P_RARP) &&
> +			     !eth_p_mpls(eth_type)))
> +				return -EINVAL;
> +			eth_type = mpls->mpls_ethertype;
> +			break;
> +		}
> +
> +		case OVS_ACTION_ATTR_POP_MPLS:
> +			if (vlan_tci & htons(VLAN_TAG_PRESENT) ||
> +			    !eth_p_mpls(eth_type))
> +				return -EINVAL;
> +
> +			/* Disallow subsequent L2.5+ set and mpls_pop actions
> +			 * as there is no check here to ensure that the new
> +			 * eth_type is valid and thus set actions could
> +			 * write off the end of the packet or otherwise
> +			 * corrupt it.
> +			 *
> +			 * Support for these actions is planned using packet
> +			 * recirculation.
> +			 */
> +			eth_type = htons(0);
> +			break;
> +
>  		case OVS_ACTION_ATTR_SET:
> -			err = validate_set(a, key, sfa, &skip_copy);
> +			err = validate_set(a, key, sfa, &skip_copy, eth_type);
>  			if (err)
>  				return err;
>  			break;
>  
>  		case OVS_ACTION_ATTR_SAMPLE:
> -			err = validate_and_copy_sample(a, key, depth, sfa);
> +			err = validate_and_copy_sample(a, key, depth, sfa,
> +						       eth_type, vlan_tci);
>  			if (err)
>  				return err;
>  			skip_copy = true;
> @@ -1531,6 +1617,14 @@ int ovs_nla_copy_actions(const struct nlattr *attr,
>  	return 0;
>  }
>  
> +int ovs_nla_copy_actions(const struct nlattr *attr,
> +			 const struct sw_flow_key *key,
> +			 struct sw_flow_actions **sfa)
> +{
> +	return ovs_nla_copy_actions__(attr, key, 0, sfa, key->eth.type,
> +				      key->eth.tci);
> +}
> +
>  static int sample_action_to_attr(const struct nlattr *attr, struct sk_buff *skb)
>  {
>  	const struct nlattr *a;
> diff --git a/datapath/flow_netlink.h b/datapath/flow_netlink.h
> index 4401510..b471ece 100644
> --- a/datapath/flow_netlink.h
> +++ b/datapath/flow_netlink.h
> @@ -49,7 +49,7 @@ int ovs_nla_get_match(struct sw_flow_match *match,
>  		      const struct nlattr *);
>  
>  int ovs_nla_copy_actions(const struct nlattr *attr,
> -			 const struct sw_flow_key *key, int depth,
> +			 const struct sw_flow_key *key,
>  			 struct sw_flow_actions **sfa);
>  int ovs_nla_put_actions(const struct nlattr *attr,
>  			int len, struct sk_buff *skb);
> diff --git a/datapath/linux/compat/gso.c b/datapath/linux/compat/gso.c
> index 9ded17c..dc1e537 100644
> --- a/datapath/linux/compat/gso.c
> +++ b/datapath/linux/compat/gso.c
> @@ -17,11 +17,12 @@
>   */
>  
>  #include <linux/version.h>
> -#if LINUX_VERSION_CODE < KERNEL_VERSION(3,12,0)
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0)
>  
>  #include <linux/module.h>
>  #include <linux/if.h>
>  #include <linux/if_tunnel.h>
> +#include <linux/if_vlan.h>
>  #include <linux/icmp.h>
>  #include <linux/in.h>
>  #include <linux/ip.h>
> @@ -38,6 +39,8 @@
>  #include <net/xfrm.h>
>  
>  #include "gso.h"
> +#include "mpls.h"
> +#include "vlan.h"
>  
>  #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37) && \
>  	!defined(HAVE_VLAN_BUG_WORKAROUND)
> @@ -50,10 +53,11 @@ MODULE_PARM_DESC(vlan_tso, "Enable TSO for VLAN packets");
>  #define vlan_tso true
>  #endif
>  
> -#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
>  static bool dev_supports_vlan_tx(struct net_device *dev)
>  {
> -#if defined(HAVE_VLAN_BUG_WORKAROUND)
> +#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,37)
> +	return true;
> +#elif defined(HAVE_VLAN_BUG_WORKAROUND)
>  	return dev->features & NETIF_F_HW_VLAN_TX;
>  #else
>  	/* Assume that the driver is buggy. */
> @@ -61,24 +65,70 @@ static bool dev_supports_vlan_tx(struct net_device *dev)
>  #endif
>  }
>  
> +/* Strictly this is not needed and will be optimised out
> + * as this code is guarded by if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0).
> + * It is here to make things explicit should the compatibility
> + * code be extended in some way prior extending its life-span
> + * beyond v3.16.
> + */
> +static bool supports_mpls_gso(void)
> +{
> +/* MPLS GSO was introduced in v3.11, however it was not correctly
> + * activated using mpls_features until v3.16. */
> +#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,16,0)
> +	return true;
> +#else
> +	return false;
> +#endif
> +}
> +
>  int rpl_dev_queue_xmit(struct sk_buff *skb)
>  {
>  #undef dev_queue_xmit
>  	int err = -ENOMEM;
> +	bool vlan, mpls;
>  
> -	if (vlan_tx_tag_present(skb) && !dev_supports_vlan_tx(skb->dev)) {
> +	vlan = mpls = false;
> +
> +	/* Avoid traversing any VLAN tags that are present to determine if
> +	 * the ethtype is MPLS. Instead compare the mac_len (end of L2) and
> +	 * skb_network_offset() (beginning of L3) whose inequality will
> +	 * indicate the presence of an MPLS label stack. */
> +	if (skb->mac_len != skb_network_offset(skb) && !supports_mpls_gso())
> +		mpls = true;
> +
> +	if (vlan_tx_tag_present(skb) && !dev_supports_vlan_tx(skb->dev))
> +		vlan = true;
> +
> +	if (vlan || mpls) {
>  		int features;
>  
>  		features = netif_skb_features(skb);
>  
> -		if (!vlan_tso)
> -			features &= ~(NETIF_F_TSO | NETIF_F_TSO6 |
> -				      NETIF_F_UFO | NETIF_F_FSO);
> +		if (vlan) {
> +			if (!vlan_tso)
> +				features &= ~(NETIF_F_TSO | NETIF_F_TSO6 |
> +					      NETIF_F_UFO | NETIF_F_FSO);
>  
> -		skb = __vlan_put_tag(skb, skb->vlan_proto, vlan_tx_tag_get(skb));
> -		if (unlikely(!skb))
> -			return err;
> -		vlan_set_tci(skb, 0);
> +			skb = __vlan_put_tag(skb, skb->vlan_proto,
> +					     vlan_tx_tag_get(skb));
> +			if (unlikely(!skb))
> +				return err;
> +			vlan_set_tci(skb, 0);
> +		}
> +
> +		/* As of v3.11 the kernel provides an mpls_features field in
> +		 * struct net_device which allows devices to advertise which
> +		 * features its supports for MPLS. This value defaults to
> +		 * NETIF_F_SG and as of v3.16.
> +		 *
> +		 * This compatibility code is intended for kernels older
> +		 * than v3.16 that do not support MPLS GSO and do not
> +		 * use mpls_features. Thus this code uses NETIF_F_SG
> +		 * directly in place of mpls_features.
> +		 */
> +		if (mpls)
> +			features &= NETIF_F_SG;
>  
>  		if (netif_needs_gso(skb, features)) {
>  			struct sk_buff *nskb;
> @@ -117,7 +167,6 @@ drop:
>  	kfree_skb(skb);
>  	return err;
>  }
> -#endif /* kernel version < 2.6.37 */
>  
>  static __be16 __skb_network_protocol(struct sk_buff *skb)
>  {
> @@ -135,6 +184,9 @@ static __be16 __skb_network_protocol(struct sk_buff *skb)
>  		vlan_depth += VLAN_HLEN;
>  	}
>  
> +	if (eth_p_mpls(type))
> +		type = ovs_skb_get_inner_protocol(skb);
> +
>  	return type;
>  }
>  
> @@ -232,4 +284,4 @@ int rpl_ip_local_out(struct sk_buff *skb)
>  	}
>  	return ret;
>  }
> -#endif /* 3.12 */
> +#endif /* 3.16 */
> diff --git a/datapath/linux/compat/gso.h b/datapath/linux/compat/gso.h
> index 3041e88..1393173 100644
> --- a/datapath/linux/compat/gso.h
> +++ b/datapath/linux/compat/gso.h
> @@ -4,6 +4,7 @@
>  #include <linux/version.h>
>  #if LINUX_VERSION_CODE < KERNEL_VERSION(3,12,0)
>  
> +#include <linux/netdevice.h>
>  #include <linux/skbuff.h>
>  #include <net/protocol.h>
>  
> @@ -11,9 +12,11 @@
>  
>  struct ovs_gso_cb {
>  	struct ovs_skb_cb dp_cb;
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(3,11,0)
> +	__be16		inner_protocol;
> +#endif
>  	u16		inner_network_header;	/* Offset from
>  						 * inner_mac_header */
> -	/* 16bit hole */
>  	sk_buff_data_t	inner_mac_header;	/* Offset from skb->head */
>  	void (*fix_segment)(struct sk_buff *);
>  };
> @@ -72,4 +75,40 @@ static inline void skb_reset_inner_headers(struct sk_buff *skb)
>  int ip_local_out(struct sk_buff *skb);
>  
>  #endif /* 3.12 */
> +
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(3,11,0)
> +static inline void ovs_skb_init_inner_protocol(struct sk_buff *skb) {
> +	OVS_GSO_CB(skb)->inner_protocol = htons(0);
> +}
> +
> +static inline void ovs_skb_set_inner_protocol(struct sk_buff *skb,
> +					      __be16 ethertype) {
> +	OVS_GSO_CB(skb)->inner_protocol = ethertype;
> +}
> +
> +static inline __be16 ovs_skb_get_inner_protocol(struct sk_buff *skb)
> +{
> +	return OVS_GSO_CB(skb)->inner_protocol;
> +}
> +
> +#else
> +
> +static inline void ovs_skb_init_inner_protocol(struct sk_buff *skb) {
> +	/* Nothing to do. The inner_protocol is either zero or
> +	 * has been set to a value by another user.
> +	 * Either way it may be considered initialised.
> +	 */
> +}
> +
> +static inline void ovs_skb_set_inner_protocol(struct sk_buff *skb,
> +					      __be16 ethertype)
> +{
> +	skb->inner_protocol = ethertype;
> +}
> +
> +static inline __be16 ovs_skb_get_inner_protocol(struct sk_buff *skb)
> +{
> +	return skb->inner_protocol;
> +}
> +#endif /* 3.11 */
>  #endif
> diff --git a/datapath/linux/compat/include/linux/netdevice.h b/datapath/linux/compat/include/linux/netdevice.h
> index d726390..886c2f8 100644
> --- a/datapath/linux/compat/include/linux/netdevice.h
> +++ b/datapath/linux/compat/include/linux/netdevice.h
> @@ -64,11 +64,13 @@ static inline struct net_device *dev_get_by_index_rcu(struct net *net, int ifind
>  typedef u32 netdev_features_t;
>  #endif
>  
> -#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,38)
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0)
>  #define skb_gso_segment rpl_skb_gso_segment
>  struct sk_buff *rpl_skb_gso_segment(struct sk_buff *skb,
>                                      netdev_features_t features);
> +#endif
>  
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,38)
>  #define netif_skb_features rpl_netif_skb_features
>  netdev_features_t rpl_netif_skb_features(struct sk_buff *skb);
>  
> @@ -113,7 +115,7 @@ static inline struct net_device *netdev_master_upper_dev_get(struct net_device *
>  }
>  #endif
>  
> -#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0)
>  #define dev_queue_xmit rpl_dev_queue_xmit
>  int dev_queue_xmit(struct sk_buff *skb);
>  #endif
> diff --git a/datapath/linux/compat/netdevice.c b/datapath/linux/compat/netdevice.c
> index 1dc5abf..72bdec5 100644
> --- a/datapath/linux/compat/netdevice.c
> +++ b/datapath/linux/compat/netdevice.c
> @@ -1,6 +1,9 @@
>  #include <linux/netdevice.h>
>  #include <linux/if_vlan.h>
>  
> +#include "mpls.h"
> +#include "gso.h"
> +
>  #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,38)
>  #ifndef HAVE_CAN_CHECKSUM_PROTOCOL
>  static bool can_checksum_protocol(netdev_features_t features, __be16 protocol)
> @@ -69,7 +72,9 @@ netdev_features_t rpl_netif_skb_features(struct sk_buff *skb)
>  		return harmonize_features(skb, protocol, features);
>  	}
>  }
> +#endif	/* kernel version < 2.6.38 */
>  
> +#if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0)
>  struct sk_buff *rpl_skb_gso_segment(struct sk_buff *skb,
>  				    netdev_features_t features)
>  {
> @@ -89,6 +94,9 @@ struct sk_buff *rpl_skb_gso_segment(struct sk_buff *skb,
>  		vlan_depth += VLAN_HLEN;
>  	}
>  
> +	if (eth_p_mpls(type))
> +		type = ovs_skb_get_inner_protocol(skb);
> +
>  	/* this hack needed to get regular skb_gso_segment() */
>  #undef skb_gso_segment
>  	skb_proto = skb->protocol;
> @@ -98,4 +106,4 @@ struct sk_buff *rpl_skb_gso_segment(struct sk_buff *skb,
>  	skb->protocol = skb_proto;
>  	return skb_gso;
>  }
> -#endif	/* kernel version < 2.6.38 */
> +#endif	/* kernel version < 3.16.0 */
> diff --git a/datapath/mpls.h b/datapath/mpls.h
> new file mode 100644
> index 0000000..7eab104
> --- /dev/null
> +++ b/datapath/mpls.h
> @@ -0,0 +1,15 @@
> +#ifndef MPLS_H
> +#define MPLS_H 1
> +
> +#include <linux/if_ether.h>
> +
> +#define MPLS_BOS_MASK	0x00000100
> +#define MPLS_HLEN 4
> +
> +static inline bool eth_p_mpls(__be16 eth_type)
> +{
> +	return eth_type == htons(ETH_P_MPLS_UC) ||
> +		eth_type == htons(ETH_P_MPLS_MC);
> +}
> +
> +#endif
> diff --git a/include/linux/openvswitch.h b/include/linux/openvswitch.h
> index d7f85ff..1095ece 100644
> --- a/include/linux/openvswitch.h
> +++ b/include/linux/openvswitch.h
> @@ -318,15 +318,14 @@ enum ovs_key_attr {
>  	OVS_KEY_ATTR_DP_HASH,	/* u32 hash value. Value 0 indicates the hash
>  				   is not computed by the datapath. */
>  	OVS_KEY_ATTR_RECIRC_ID, /* u32 recirc id */
> +	OVS_KEY_ATTR_MPLS,      /* array of struct ovs_key_mpls.
> +				 * The implementation may restrict
> +				 * the accepted length of the array. */
> +
>  #ifdef __KERNEL__
>  	/* Only used within kernel data path. */
>  	OVS_KEY_ATTR_IPV4_TUNNEL,  /* struct ovs_key_ipv4_tunnel */
>  #endif
> -	/* Experimental */
> -
> -	OVS_KEY_ATTR_MPLS = 62, /* array of struct ovs_key_mpls.
> -				 * The implementation may restrict
> -				 * the accepted length of the array. */
>  	__OVS_KEY_ATTR_MAX
>  };
>  
> -- 
> 2.0.0.rc2
> 
> --
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