Re: [PATCH v2 net-next] Enhanced skb_mpls_pop to update ethertype of the packet in all the cases when an ethernet header is present is the packet.

From: Martin Varghese <redacted>

The skb_mpls_pop was not updating ethertype of an ethernet packet if the
packet was originally received from a non ARPHRD_ETHER device.

In the below OVS data path flow, since the device corresponding to port 7
is an l3 device (ARPHRD_NONE) the skb_mpls_pop function does not update
the ethertype of the packet even though the previous push_eth action had
added an ethernet header to the packet.

recirc_id(0),in_port(7),eth_type(0x8847),
mpls(label=12/0xfffff,tc=0/0,ttl=0/0x0,bos=1/1),
actions:push_eth(src=00:00:00:00:00:00,dst=00:00:00:00:00:00),
pop_mpls(eth_type=0x800),4

Signed-off-by: Martin Varghese <redacted>
---
Changes in v2:
    - check for dev type removed while updating ethertype
      in function skb_mpls_pop.
    - key->mac_proto is checked in function pop_mpls to pass
      ethernt flag to skb_mpls_pop.
    - dev type is checked in function tcf_mpls_act to pass
      ethernet flag to skb_mpls_pop.

 include/linux/skbuff.h    | 3 ++-
 net/core/skbuff.c         | 7 ++++---
 net/openvswitch/actions.c | 4 +++-
 net/sched/act_mpls.c      | 4 +++-
 4 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index dfe02b6..70204b9 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h

@@ -3530,7 +3530,8 @@ int skb_zerocopy(struct sk_buff *to, struct sk_buff *from,
 int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
 int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,
                  int mac_len);
-int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len);
+int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len,
+                bool ethernet);
 int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse);
 int skb_mpls_dec_ttl(struct sk_buff *skb);
 struct sk_buff *pskb_extract(struct sk_buff *skb, int off, int to_copy,

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 867e61d..988eefb 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c

@@ -5529,12 +5529,13 @@ int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,
  * @skb: buffer
  * @next_proto: ethertype of header after popped MPLS header
  * @mac_len: length of the MAC header
- *
+ * @ethernet: flag to indicate if ethernet header is present in packet
  * Expects skb->data at mac header.
  *
  * Returns 0 on success, -errno otherwise.
  */
-int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len)
+int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len,
+                bool ethernet)
 {
        int err;

@@ -5553,7 +5554,7 @@ int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len)
        skb_reset_mac_header(skb);
        skb_set_network_header(skb, mac_len);

-       if (skb->dev && skb->dev->type == ARPHRD_ETHER) {
+       if (ethernet) {
                struct ethhdr *hdr;

                /* use mpls_hdr() to get ethertype to account for VLANs. */

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 12936c1..264c3c0 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c

@@ -179,7 +179,9 @@ static int pop_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 {
        int err;

-       err = skb_mpls_pop(skb, ethertype, skb->mac_len);
+       err = skb_mpls_pop(skb, ethertype, skb->mac_len,
+                          (key->mac_proto & ~SW_FLOW_KEY_INVALID)
+                           == MAC_PROTO_ETHERNET);
        if (err)
                return err;

diff --git a/net/sched/act_mpls.c b/net/sched/act_mpls.c
index 4d8c822..f919f95 100644
--- a/net/sched/act_mpls.c
+++ b/net/sched/act_mpls.c

@@ -13,6 +13,7 @@
 #include <net/pkt_sched.h>
 #include <net/pkt_cls.h>
 #include <net/tc_act/tc_mpls.h>
+#include <linux/if_arp.h>

 static unsigned int mpls_net_id;
 static struct tc_action_ops act_mpls_ops;

@@ -76,7 +77,8 @@ static int tcf_mpls_act(struct sk_buff *skb, const struct tc_action *a,

        switch (p->tcfm_action) {
        case TCA_MPLS_ACT_POP:
-               if (skb_mpls_pop(skb, p->tcfm_proto, mac_len))
+               if (skb_mpls_pop(skb, p->tcfm_proto, mac_len,
+                                (skb->dev && skb->dev->type == ARPHRD_ETHER)))
                        goto drop;
                break;
        case TCA_MPLS_ACT_PUSH:
--

1.8.3.1