dp-core: vr_pexpand_head might return new vr_packet

Changes required to support Contrail on Windows.
- Implementation of vr_pexpand_head on Windows might clone the packet,
  if not enough head space is available. This cloned packet will receive
  the new vr_packet struct, to which pointer will then be returned.
  This change prepares dp-core codebase for this change in semantics.

Initial work:
  https://github.com/codilime/contrail-vrouter/commits/windows

Change-Id: Ie2e7dc3bb00ed7e84189126cd0ab1468ad2d787a
Partial-Bug: #1734699

dp-core/vr_datapath.c

@@ -738,36 +738,36 @@ vr_untag_pkt(struct vr_packet *pkt)
  * modify the data pointer of skb
  */
 int
-vr_tag_pkt(struct vr_packet *pkt, unsigned short vlan_id, bool force_tag)
+vr_tag_pkt(struct vr_packet **pkt, unsigned short vlan_id, bool force_tag)
 {
     uint8_t priority = 0;
     struct vr_packet *tmp_pkt;
     struct vr_eth *new_eth, *eth;
     unsigned short *vlan_tag;
 
-    eth = (struct vr_eth *)pkt_data(pkt);
+    eth = (struct vr_eth *)pkt_data(*pkt);
     if (!force_tag) {
         if (eth->eth_proto == htons(VR_ETH_PROTO_VLAN))
             return 0;
     }
 
-    if (pkt_head_space(pkt) < VR_VLAN_HLEN) {
-        tmp_pkt = vr_pexpand_head(pkt, VR_VLAN_HLEN - pkt_head_space(pkt));
+    if (pkt_head_space(*pkt) < VR_VLAN_HLEN) {
+        tmp_pkt = vr_pexpand_head(*pkt, VR_VLAN_HLEN - pkt_head_space(*pkt));
         if (!tmp_pkt) {
             return -1;
         }
-        pkt = tmp_pkt;
+        *pkt = tmp_pkt;
     }
 
-    new_eth = (struct vr_eth *)pkt_push(pkt, VR_VLAN_HLEN);
+    new_eth = (struct vr_eth *)pkt_push(*pkt, VR_VLAN_HLEN);
     if (!new_eth)
         return -1;
 
     memmove(new_eth, eth, (2 * VR_ETHER_ALEN));
     new_eth->eth_proto = htons(VR_ETH_PROTO_VLAN);
     vlan_tag = (unsigned short *)(new_eth + 1);
-    if (pkt->vp_priority != VP_PRIORITY_INVALID)
-        priority = pkt->vp_priority;
+    if ((*pkt)->vp_priority != VP_PRIORITY_INVALID)
+        priority = (*pkt)->vp_priority;
 
     *vlan_tag = htons((priority << VR_VLAN_PRIORITY_SHIFT) | vlan_id);
 

dp-core/vr_interface.c

@@ -97,22 +97,24 @@ vif_drop_pkt(struct vr_interface *vif, struct vr_packet *pkt, bool input)
  * passing us valid rewrite ptr and len and will not check for those
  */
 static int
-vif_cmn_rewrite(struct vr_interface *vif, struct vr_packet *pkt,
+vif_cmn_rewrite(struct vr_interface *vif, struct vr_packet **pkt,
         struct vr_forwarding_md *fmd, unsigned char *rewrite,
         unsigned short len)
 {
     unsigned char *head;
+    struct vr_packet *expanded_pkt;
 
     if (!len)
         return 0;
 
-    if (pkt_head_space(pkt) < len) {
-        pkt = vr_pexpand_head(pkt, len - pkt_head_space(pkt));
-        if (!pkt)
+    if (pkt_head_space(*pkt) < len) {
+        expanded_pkt = vr_pexpand_head(*pkt, len - pkt_head_space(*pkt));
+        if (!expanded_pkt)
             return -ENOMEM;
+        *pkt = expanded_pkt;
     }
 
-    head = pkt_push(pkt, len);
+    head = pkt_push(*pkt, len);
     if (!head)
         return -ENOMEM;
 
@@ -278,32 +280,34 @@ vif_mirror(struct vr_interface *vif, struct vr_packet *pkt,
 
 /* agent driver */
 static int
-agent_set_rewrite(struct vr_interface *vif, struct vr_packet *pkt,
+agent_set_rewrite(struct vr_interface *vif, struct vr_packet **pkt,
         struct vr_forwarding_md *fmd, unsigned char *rewrite,
         unsigned short len)
 {
     unsigned char *head;
     unsigned int hdr_len;
     struct agent_hdr *hdr;
+    struct vr_packet *expanded_pkt;
 
-    vr_preset(pkt);
+    vr_preset(*pkt);
 
     hdr_len = sizeof(struct agent_hdr) + len;
-    if (pkt_head_space(pkt) < hdr_len) {
-        pkt = vr_pexpand_head(pkt, hdr_len - pkt_head_space(pkt));
-        if (!pkt)
+    if (pkt_head_space(*pkt) < hdr_len) {
+        expanded_pkt = vr_pexpand_head(*pkt, hdr_len - pkt_head_space(*pkt));
+        if (!expanded_pkt)
             return -ENOMEM;
+        *pkt = expanded_pkt;
     }
 
-    head = pkt_push(pkt, hdr_len);
+    head = pkt_push(*pkt, hdr_len);
     if (!head)
         return -ENOMEM;
 
     /* copy the rewrite first */
     memcpy(head, rewrite, len);
 
     hdr = (struct agent_hdr *)(head + len);
-    hdr->hdr_ifindex = htons(pkt->vp_if->vif_idx);
+    hdr->hdr_ifindex = htons((*pkt)->vp_if->vif_idx);
     hdr->hdr_vrf = htons(fmd->fmd_dvrf);
     /* this needs some thought */
     hdr->hdr_cmd = htons(AGENT_TRAP_NEXTHOP);
@@ -866,7 +870,7 @@ vlan_tx(struct vr_interface *vif, struct vr_packet *pkt,
             if (fmd->fmd_vlan != VLAN_ID_INVALID)
                 force_tag = true;
 
-            if (vr_tag_pkt(pkt, vif->vif_ovlan_id, force_tag)) {
+            if (vr_tag_pkt(&pkt, vif->vif_ovlan_id, force_tag)) {
                 goto drop;
             }
             vr_pset_data(pkt, pkt->vp_data);
@@ -1199,7 +1203,7 @@ tun_rx(struct vr_interface *vif, struct vr_packet *pkt,
 }
 
 static int
-eth_set_rewrite(struct vr_interface *vif, struct vr_packet *pkt,
+eth_set_rewrite(struct vr_interface *vif, struct vr_packet **pkt,
         struct vr_forwarding_md *fmd, unsigned char *rewrite,
         unsigned short len)
 {
@@ -1211,10 +1215,10 @@ eth_set_rewrite(struct vr_interface *vif, struct vr_packet *pkt,
      * tunneled packet and not from Agent. Otherwise, apply the new
      * rewrite data
      */
-    if ((pkt->vp_if->vif_type == VIF_TYPE_HOST) &&
-            (!(pkt->vp_flags & VP_FLAG_FROM_DP)) &&
-            ((pkt->vp_type == VP_TYPE_IP) || (pkt->vp_type == VP_TYPE_IP6))) {
-        vr_preset(pkt);
+    if (((*pkt)->vp_if->vif_type == VIF_TYPE_HOST) &&
+            (!((*pkt)->vp_flags & VP_FLAG_FROM_DP)) &&
+            (((*pkt)->vp_type == VP_TYPE_IP) || ((*pkt)->vp_type == VP_TYPE_IP6))) {
+        vr_preset(*pkt);
         return 0;
     }
 
@@ -1345,7 +1349,7 @@ eth_tx(struct vr_interface *vif, struct vr_packet *pkt,
     } else if (vif_is_fabric(vif)) {
         vlan_id = vr_fmd_get_mirror_vlan(fmd);
         if (vlan_id != FMD_MIRROR_INVALID_DATA) {
-            vr_tag_pkt(pkt, vlan_id, force_tag);
+            vr_tag_pkt(&pkt, vlan_id, force_tag);
         }
     }
 

dp-core/vr_mirror.c

@@ -453,7 +453,7 @@ vr_mirror(struct vrouter *router, uint8_t mirror_id, struct vr_packet *pkt,
 
                 clone_len = 0;
 
-                if (pkt_nh->nh_dev->vif_set_rewrite(pkt_nh->nh_dev, pkt, fmd,
+                if (pkt_nh->nh_dev->vif_set_rewrite(pkt_nh->nh_dev, &pkt, fmd,
                                     pkt_nh->nh_data, pkt_nh->nh_encap_len) < 0) {
                     drop_reason = VP_DROP_REWRITE_FAIL;
                     goto fail;