Re: [PATCH net-next] openvswitch: correctly fragment packet with mpls headers

If mpls headers were pushed to a defragmented packet, the refragmentation no
longer works correctly after 48d2ab609b6b ("net: mpls: Fixups for GSO"). The
network header has to be shifted after the mpls headers for the
fragmentation and restored afterwards.

Fixes: 48d2ab609b6b ("net: mpls: Fixups for GSO")
Signed-off-by: Jiri Benc <redacted>
---
 net/openvswitch/actions.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 4e03f64709bc..370b2ba3df4c 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c

@@ -62,7 +62,8 @@ struct ovs_frag_data {
        struct vport *vport;
        struct ovs_skb_cb cb;
        __be16 inner_protocol;
-       __u16 vlan_tci;
+       u16 network_offset;     /* valid only if inner_protocol is set */
+       u16 vlan_tci;
        __be16 vlan_proto;
        unsigned int l2_len;
        u8 l2_data[MAX_L2_LEN];

@@ -656,7 +657,6 @@ static int ovs_vport_output(struct net *net, struct sock *sk, struct sk_buff *sk

        __skb_dst_copy(skb, data->dst);
        *OVS_CB(skb) = data->cb;
-       skb->inner_protocol = data->inner_protocol;
        skb->vlan_tci = data->vlan_tci;
        skb->vlan_proto = data->vlan_proto;

@@ -666,6 +666,13 @@ static int ovs_vport_output(struct net *net, struct sock *sk, struct sk_buff *sk
        skb_postpush_rcsum(skb, skb->data, data->l2_len);
        skb_reset_mac_header(skb);

+       if (data->inner_protocol) {
+               skb->inner_protocol = data->inner_protocol;
+               skb->inner_network_header = skb->network_header;
+               skb_set_network_header(skb, data->network_offset);
+       }
+       skb_reset_mac_len(skb);
+
        ovs_vport_send(vport, skb);
        return 0;
 }

@@ -684,7 +691,8 @@ static struct dst_ops ovs_dst_ops = {
 /* prepare_frag() is called once per (larger-than-MTU) frame; its inverse is
  * ovs_vport_output(), which is called once per fragmented packet.
  */
-static void prepare_frag(struct vport *vport, struct sk_buff *skb)
+static void prepare_frag(struct vport *vport, struct sk_buff *skb,
+                        u16 orig_network_offset)
 {
        unsigned int hlen = skb_network_offset(skb);
        struct ovs_frag_data *data;

@@ -694,6 +702,7 @@ static void prepare_frag(struct vport *vport, struct sk_buff *skb)
        data->vport = vport;
        data->cb = *OVS_CB(skb);
        data->inner_protocol = skb->inner_protocol;
+       data->network_offset = orig_network_offset;
        data->vlan_tci = skb->vlan_tci;
        data->vlan_proto = skb->vlan_proto;
        data->l2_len = hlen;

@@ -706,6 +715,13 @@ static void prepare_frag(struct vport *vport, struct sk_buff *skb)
 static void ovs_fragment(struct net *net, struct vport *vport,
                         struct sk_buff *skb, u16 mru, __be16 ethertype)
 {
+       u16 orig_network_offset = 0;
+
+       if (skb->inner_protocol) {
+               orig_network_offset = skb_network_offset(skb);
+               skb->network_header = skb->inner_network_header;
+       }
+