Subject: Re: [PATCH v2] Change in Openvswitch to support MPLS label depth of 3 in ingress direction

From: Martin Varghese <[email-masked]>
Date: Tue, 22 Oct 2019 18:21:30 +0530

On Tue, Oct 22, 2019 at 12:03:49AM -0700, Pravin Shelar wrote:
> On Sun, Oct 20, 2019 at 7:12 AM Martin Varghese
> <[email-masked]> wrote:
> >
> > From: Martin Varghese <[email-masked]>
> >
> > The openvswitch was supporting a MPLS label depth of 1 in the ingress
> > direction though the userspace OVS supports a max depth of 3 labels.
> > This change enables openvswitch module to support a max depth of
> > 3 labels in the ingress.
> >
> > Signed-off-by: Martin Varghese <[email-masked]>
> > ---
> > Changes in v2
> >    - Moved MPLS count validation from datapath to configuration.
> >    - Fixed set mpls function.
> >
> This patch looks pretty close now.
> 
> >  net/openvswitch/actions.c      |  2 +-
> >  net/openvswitch/flow.c         | 20 ++++++++++-----
> >  net/openvswitch/flow.h         |  9 ++++---
> >  net/openvswitch/flow_netlink.c | 57 +++++++++++++++++++++++++++++++++---------
> >  4 files changed, 66 insertions(+), 22 deletions(-)
> >
> ...
> > diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
> > index d7559c6..21de061 100644
> > --- a/net/openvswitch/flow_netlink.c
> > +++ b/net/openvswitch/flow_netlink.c
> > @@ -424,7 +424,7 @@ size_t ovs_key_attr_size(void)
> >         [OVS_KEY_ATTR_DP_HASH]   = { .len = sizeof(u32) },
> >         [OVS_KEY_ATTR_TUNNEL]    = { .len = OVS_ATTR_NESTED,
> >                                      .next = ovs_tunnel_key_lens, },
> > -       [OVS_KEY_ATTR_MPLS]      = { .len = sizeof(struct ovs_key_mpls) },
> > +       [OVS_KEY_ATTR_MPLS]      = { .len = OVS_ATTR_VARIABLE },
> >         [OVS_KEY_ATTR_CT_STATE]  = { .len = sizeof(u32) },
> >         [OVS_KEY_ATTR_CT_ZONE]   = { .len = sizeof(u16) },
> >         [OVS_KEY_ATTR_CT_MARK]   = { .len = sizeof(u32) },
> > @@ -1628,10 +1628,25 @@ static int ovs_key_from_nlattrs(struct net *net, struct sw_flow_match *match,
> >
> >         if (attrs & (1 << OVS_KEY_ATTR_MPLS)) {
> >                 const struct ovs_key_mpls *mpls_key;
> > +               u32 hdr_len;
> > +               u32 label_count, label_count_mask, i;
> >
> >                 mpls_key = nla_data(a[OVS_KEY_ATTR_MPLS]);
> > -               SW_FLOW_KEY_PUT(match, mpls.top_lse,
> > -                               mpls_key->mpls_lse, is_mask);
> > +               hdr_len = nla_len(a[OVS_KEY_ATTR_MPLS]);
> > +               label_count = hdr_len / sizeof(struct ovs_key_mpls);
> > +
> > +               if (label_count == 0 || label_count > MPLS_LABEL_DEPTH ||
> > +                   hdr_len % sizeof(struct ovs_key_mpls))
> > +                       return -EINVAL;
> > +
> > +               label_count_mask =  GENMASK(label_count - 1, 0);
> > +
> > +               for (i = 0 ; i < label_count; i++)
> > +                       SW_FLOW_KEY_PUT(match, mpls.lse[i],
> > +                                       mpls_key[i].mpls_lse, is_mask);
> > +
> > +               SW_FLOW_KEY_PUT(match, mpls.num_labels_mask,
> > +                               label_count_mask, is_mask);
> >
> >                 attrs &= ~(1 << OVS_KEY_ATTR_MPLS);
> >          }
> > @@ -2114,13 +2129,18 @@ static int __ovs_nla_put_key(const struct sw_flow_key *swkey,
> >                 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)) {
> > +               u8 i, num_labels;
> >                 struct ovs_key_mpls *mpls_key;
> >
> > -               nla = nla_reserve(skb, OVS_KEY_ATTR_MPLS, sizeof(*mpls_key));
> > +               num_labels = hweight_long(output->mpls.num_labels_mask);
> > +               nla = nla_reserve(skb, OVS_KEY_ATTR_MPLS,
> > +                                 num_labels * sizeof(*mpls_key));
> >                 if (!nla)
> >                         goto nla_put_failure;
> > +
> >                 mpls_key = nla_data(nla);
> > -               mpls_key->mpls_lse = output->mpls.top_lse;
> > +               for (i = 0; i < num_labels; i++)
> > +                       mpls_key[i].mpls_lse = output->mpls.lse[i];
> >         }
> >
> >         if ((swkey->eth.type == htons(ETH_P_IP) ||
> > @@ -2957,6 +2977,10 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
> >         u8 mac_proto = ovs_key_mac_proto(key);
> >         const struct nlattr *a;
> >         int rem, err;
> > +       u32 mpls_label_count = 0;
> > +
> > +       if (eth_p_mpls(eth_type))
> > +               mpls_label_count = hweight_long(key->mpls.num_labels_mask);
> >
> The MPLS push and pop action could be part of nested actions in
> sample, so the count needs to be global count across such nested
> actions. have a look at validate_and_copy_sample().
> 

can we embed the mpls_label_count in struct sw_flow_actions? 

> >         nla_for_each_nested(a, attr, rem) {
> >                 /* Expected argument lengths, (u32)-1 for variable length. */
> > @@ -3065,25 +3089,34 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
> >                              !eth_p_mpls(eth_type)))
> >                                 return -EINVAL;
> >                         eth_type = mpls->mpls_ethertype;
> > +                       mpls_label_count++;
> >                         break;
> >                 }
> >
> > -               case OVS_ACTION_ATTR_POP_MPLS:
> > +               case OVS_ACTION_ATTR_POP_MPLS: {
> > +                       __be16  proto;
> >                         if (vlan_tci & htons(VLAN_CFI_MASK) ||
> >                             !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.
> > +                       /* Disallow subsequent L2.5+ set 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.
> >                          */
> This comment needs updated.
> 
> 

Disallow subsequent L2.5+ set and mpls_pop actions
once the last MPLS label in the packet is popped
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);
> > +                       proto = nla_get_be16(a);
> > +                       mpls_label_count--;
> > +
> > +                       if (!eth_p_mpls(proto) || !mpls_label_count)
> > +                               eth_type = htons(0);
> > +                       else
> > +                               eth_type =  proto;
> > +
> >                         break;
> > +               }
> >
> >                 case OVS_ACTION_ATTR_SET:
> >                         err = validate_set(a, key, sfa,
> > --
> > 1.8.3.1
> >