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Date:	Fri, 21 Nov 2014 20:08:35 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	Pravin Shelar <pshelar@...ira.com>
Cc:	Jiri Benc <jbenc@...hat.com>, netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Tom Herbert <therbert@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Daniel Borkmann <dborkman@...hat.com>, mst@...hat.com,
	fw@...len.de, Paul.Durrant@...rix.com, Thomas Graf <tgraf@...g.ch>,
	Cong Wang <cwang@...pensource.com>
Subject: Re: [patch net-next v4 8/9] net: move vlan pop/push functions into
 common code

Fri, Nov 21, 2014 at 07:41:27PM CET, pshelar@...ira.com wrote:
>On Fri, Nov 21, 2014 at 10:05 AM, Jiri Pirko <jiri@...nulli.us> wrote:
>> Fri, Nov 21, 2014 at 05:11:39PM CET, pshelar@...ira.com wrote:
>>>On Wed, Nov 19, 2014 at 5:05 AM, Jiri Pirko <jiri@...nulli.us> wrote:
>>>> So it can be used from out of openvswitch code.
>>>> Did couple of cosmetic changes on the way, namely variable naming and
>>>> adding support for 8021AD proto.
>>>>
>>>> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
>>>> ---
>>>>
>>>> v3->v4:
>>>> - don't try to be smart and copy skb->mac_len manipulation as it is. It can be
>>>>   adjusted later on.
>>>
>>>I am fine with moving this code to generic library, as long as we can
>>>adjust the mac_len as offset for MPLS header, otherwise this breaks
>>>MPLS support.
>>
>> Pravin, I'm just moving the code without changing it in this aspect.
>> Maybe I'm missing something but can you tell me what you see wrong?
>> Thanks.
>>
>
>There is bug in the openvswitch code where vlan-pop does mac-length
>reset rather than subtracting VLAN_HLEN  from mac-len. MPLS code
>depends on this. Now this patch moves the bug to common code. I am
>fine with this patch and I can send fix to change code vlan-pop code
>to adjust mac_len later on.
>But I am worried about the comment made by Jiri Benc on earlier
>version of this patch where is mentioned that subtracting VLAN_HLEN
>can break common case for vlan-pop. In that case we can not change
>this common function. Jiri Benc, Can you point me to the code, so the
>we can work on solution to fix this issue.

Lets move to common code and fix this there with follow-up patches.
This common code should work for all users.

>
>>>
>>>> - fix error path in do_execute_actions as suggested by Pravin
>>>> v2->v3:
>>>> - used previously introduced __vlan_insert_tag helper
>>>> - used skb_push/pull to get skb->data into needed point
>>>> - fixed skb->mac_len computation in skb_vlan_push pointed out by Pravin
>>>> v1->v2:
>>>> - adjusted to fix recent ovs changes
>>>> - included change to use make_writable suggested by Eric
>>>>
>>>>  include/linux/skbuff.h    |  2 +
>>>>  net/core/skbuff.c         | 95 +++++++++++++++++++++++++++++++++++++++++++++++
>>>>  net/openvswitch/actions.c | 86 +++++-------------------------------------
>>>>  3 files changed, 106 insertions(+), 77 deletions(-)
>>>>
>>>> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>>>> index e045516..78c299f 100644
>>>> --- a/include/linux/skbuff.h
>>>> +++ b/include/linux/skbuff.h
>>>> @@ -2679,6 +2679,8 @@ unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
>>>>  struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
>>>>  struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
>>>>  int skb_ensure_writable(struct sk_buff *skb, int write_len);
>>>> +int skb_vlan_pop(struct sk_buff *skb);
>>>> +int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
>>>>
>>>>  struct skb_checksum_ops {
>>>>         __wsum (*update)(const void *mem, int len, __wsum wsum);
>>>> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
>>>> index d11bbe0..c906c5f 100644
>>>> --- a/net/core/skbuff.c
>>>> +++ b/net/core/skbuff.c
>>>> @@ -4163,6 +4163,101 @@ int skb_ensure_writable(struct sk_buff *skb, int write_len)
>>>>  }
>>>>  EXPORT_SYMBOL(skb_ensure_writable);
>>>>
>>>> +/* remove VLAN header from packet and update csum accordingly. */
>>>> +static int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)
>>>> +{
>>>> +       struct vlan_hdr *vhdr;
>>>> +       unsigned int offset = skb->data - skb_mac_header(skb);
>>>> +       int err;
>>>> +
>>>> +       __skb_push(skb, offset);
>>>> +       err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
>>>> +       if (unlikely(err))
>>>> +               goto pull;
>>>> +
>>>> +       skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
>>>> +
>>>> +       vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
>>>> +       *vlan_tci = ntohs(vhdr->h_vlan_TCI);
>>>> +
>>>> +       memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN);
>>>> +       __skb_pull(skb, VLAN_HLEN);
>>>> +
>>>> +       vlan_set_encap_proto(skb, vhdr);
>>>> +       skb->mac_header += VLAN_HLEN;
>>>> +
>>>> +       if (skb_network_offset(skb) < ETH_HLEN)
>>>> +               skb_set_network_header(skb, ETH_HLEN);
>>>> +
>>>> +       skb_reset_mac_len(skb);
>>>> +pull:
>>>> +       __skb_pull(skb, offset);
>>>> +
>>>> +       return err;
>>>> +}
>>>> +
>>>> +int skb_vlan_pop(struct sk_buff *skb)
>>>> +{
>>>> +       u16 vlan_tci;
>>>> +       __be16 vlan_proto;
>>>> +       int err;
>>>> +
>>>> +       if (likely(vlan_tx_tag_present(skb))) {
>>>> +               skb->vlan_tci = 0;
>>>> +       } else {
>>>> +               if (unlikely((skb->protocol != htons(ETH_P_8021Q) &&
>>>> +                             skb->protocol != htons(ETH_P_8021AD)) ||
>>>> +                            skb->len < VLAN_ETH_HLEN))
>>>> +                       return 0;
>>>> +
>>>> +               err = __skb_vlan_pop(skb, &vlan_tci);
>>>> +               if (err)
>>>> +                       return err;
>>>> +       }
>>>> +       /* move next vlan tag to hw accel tag */
>>>> +       if (likely((skb->protocol != htons(ETH_P_8021Q) &&
>>>> +                   skb->protocol != htons(ETH_P_8021AD)) ||
>>>> +                  skb->len < VLAN_ETH_HLEN))
>>>> +               return 0;
>>>> +
>>>> +       vlan_proto = skb->protocol;
>>>> +       err = __skb_vlan_pop(skb, &vlan_tci);
>>>> +       if (unlikely(err))
>>>> +               return err;
>>>> +
>>>> +       __vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
>>>> +       return 0;
>>>> +}
>>>> +EXPORT_SYMBOL(skb_vlan_pop);
>>>> +
>>>> +int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
>>>> +{
>>>> +       if (vlan_tx_tag_present(skb)) {
>>>> +               unsigned int offset = skb->data - skb_mac_header(skb);
>>>> +               int err;
>>>> +
>>>> +               /* __vlan_insert_tag expect skb->data pointing to mac header.
>>>> +                * So change skb->data before calling it and change back to
>>>> +                * original position later
>>>> +                */
>>>> +               __skb_push(skb, offset);
>>>> +               err = __vlan_insert_tag(skb, skb->vlan_proto,
>>>> +                                       vlan_tx_tag_get(skb));
>>>> +               if (err)
>>>> +                       return err;
>>>> +               skb->protocol = skb->vlan_proto;
>>>> +               skb->mac_len += VLAN_HLEN;
>>>> +               __skb_pull(skb, offset);
>>>> +
>>>> +               if (skb->ip_summed == CHECKSUM_COMPLETE)
>>>> +                       skb->csum = csum_add(skb->csum, csum_partial(skb->data
>>>> +                                       + (2 * ETH_ALEN), VLAN_HLEN, 0));
>>>> +       }
>>>> +       __vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
>>>> +       return 0;
>>>> +}
>>>> +EXPORT_SYMBOL(skb_vlan_push);
>>>> +
>>>>  /**
>>>>   * alloc_skb_with_frags - allocate skb with page frags
>>>>   *
>>>> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
>>>> index 7ffa377..4e05ea1 100644
>>>> --- a/net/openvswitch/actions.c
>>>> +++ b/net/openvswitch/actions.c
>>>> @@ -206,93 +206,27 @@ static int set_mpls(struct sk_buff *skb, struct sw_flow_key *key,
>>>>         return 0;
>>>>  }
>>>>
>>>> -/* remove VLAN header from packet and update csum accordingly. */
>>>> -static int __pop_vlan_tci(struct sk_buff *skb, __be16 *current_tci)
>>>> -{
>>>> -       struct vlan_hdr *vhdr;
>>>> -       int err;
>>>> -
>>>> -       err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
>>>> -       if (unlikely(err))
>>>> -               return err;
>>>> -
>>>> -       skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
>>>> -
>>>> -       vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
>>>> -       *current_tci = vhdr->h_vlan_TCI;
>>>> -
>>>> -       memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN);
>>>> -       __skb_pull(skb, VLAN_HLEN);
>>>> -
>>>> -       vlan_set_encap_proto(skb, vhdr);
>>>> -       skb->mac_header += VLAN_HLEN;
>>>> -
>>>> -       if (skb_network_offset(skb) < ETH_HLEN)
>>>> -               skb_set_network_header(skb, ETH_HLEN);
>>>> -
>>>> -       /* Update mac_len for subsequent MPLS actions */
>>>> -       skb_reset_mac_len(skb);
>>>> -       return 0;
>>>> -}
>>>> -
>>>>  static int pop_vlan(struct sk_buff *skb, struct sw_flow_key *key)
>>>>  {
>>>> -       __be16 tci;
>>>>         int err;
>>>>
>>>> -       if (likely(vlan_tx_tag_present(skb))) {
>>>> -               skb->vlan_tci = 0;
>>>> -       } else {
>>>> -               if (unlikely(skb->protocol != htons(ETH_P_8021Q) ||
>>>> -                            skb->len < VLAN_ETH_HLEN))
>>>> -                       return 0;
>>>> -
>>>> -               err = __pop_vlan_tci(skb, &tci);
>>>> -               if (err)
>>>> -                       return err;
>>>> -       }
>>>> -       /* move next vlan tag to hw accel tag */
>>>> -       if (likely(skb->protocol != htons(ETH_P_8021Q) ||
>>>> -                  skb->len < VLAN_ETH_HLEN)) {
>>>> +       err = skb_vlan_pop(skb);
>>>> +       if (vlan_tx_tag_present(skb))
>>>> +               invalidate_flow_key(key);
>>>> +       else
>>>>                 key->eth.tci = 0;
>>>> -               return 0;
>>>> -       }
>>>> -
>>>> -       invalidate_flow_key(key);
>>>> -       err = __pop_vlan_tci(skb, &tci);
>>>> -       if (unlikely(err))
>>>> -               return err;
>>>> -
>>>> -       __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), ntohs(tci));
>>>> -       return 0;
>>>> +       return err;
>>>>  }
>>>>
>>>>  static int push_vlan(struct sk_buff *skb, struct sw_flow_key *key,
>>>>                      const struct ovs_action_push_vlan *vlan)
>>>>  {
>>>> -       if (unlikely(vlan_tx_tag_present(skb))) {
>>>> -               u16 current_tag;
>>>> -
>>>> -               /* push down current VLAN tag */
>>>> -               current_tag = vlan_tx_tag_get(skb);
>>>> -
>>>> -               skb = vlan_insert_tag_set_proto(skb, skb->vlan_proto,
>>>> -                                               current_tag);
>>>> -               if (!skb)
>>>> -                       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));
>>>> -
>>>> +       if (vlan_tx_tag_present(skb))
>>>>                 invalidate_flow_key(key);
>>>> -       } else {
>>>> +       else
>>>>                 key->eth.tci = vlan->vlan_tci;
>>>> -       }
>>>> -       __vlan_hwaccel_put_tag(skb, vlan->vlan_tpid, ntohs(vlan->vlan_tci) & ~VLAN_TAG_PRESENT);
>>>> -       return 0;
>>>> +       return skb_vlan_push(skb, vlan->vlan_tpid,
>>>> +                            ntohs(vlan->vlan_tci) & ~VLAN_TAG_PRESENT);
>>>>  }
>>>>
>>>>  static int set_eth_addr(struct sk_buff *skb, struct sw_flow_key *key,
>>>> @@ -858,8 +792,6 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
>>>>
>>>>                 case OVS_ACTION_ATTR_PUSH_VLAN:
>>>>                         err = push_vlan(skb, key, nla_data(a));
>>>> -                       if (unlikely(err)) /* skb already freed. */
>>>> -                               return err;
>>>>                         break;
>>>>
>>>>                 case OVS_ACTION_ATTR_POP_VLAN:
>>>> --
>>>> 1.9.3
>>>>
--
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