Use label as 24-bit field when encoding/decoding VNI

Change-Id: I60cdae79cf4a8b60ebb9ed271ccafca4193d4a91
Closes-Bug: 1464781

src/bgp/bgp_attr_base.cc

@@ -12,16 +12,32 @@ const size_t BgpProtoPrefix::kLabelSize = 3;
 BgpProtoPrefix::BgpProtoPrefix() : prefixlen(0), type(0) {
 }
 
-uint32_t BgpProtoPrefix::ReadLabel(size_t label_offset) const {
+//
+// Extract the label from the BgpProtorefix.
+// EVPN extensions for VXLAN use the label to convey a 24-bit VNI.
+//
+uint32_t BgpProtoPrefix::ReadLabel(size_t label_offset, bool is_vni) const {
     assert((label_offset + kLabelSize) <= prefix.size());
+    if (is_vni)
+        return get_value(&prefix[label_offset], kLabelSize);
     uint32_t label = (prefix[label_offset] << 16 |
         prefix[label_offset + 1] << 8 |
         prefix[label_offset + 2]) >> 4;
     return label;
 }
 
-void BgpProtoPrefix::WriteLabel(size_t label_offset, uint32_t label) {
+//
+// Write the label to the BgpProtorefix.
+// EVPN extensions for VXLAN use the label to convey a 24-bit VNI.
+//
+void BgpProtoPrefix::WriteLabel(size_t label_offset, uint32_t label,
+    bool is_vni) {
     assert((label_offset + kLabelSize) <= prefix.size());
+    if (is_vni) {
+        assert(label <= 0xFFFFFF);
+        put_value(&prefix[label_offset], kLabelSize, label);
+        return;
+    }
     assert(label <= 0xFFFFF);
     uint32_t tmp = (label << 4 | 0x1);
     for (size_t idx = 0; idx < kLabelSize; ++idx) {

src/bgp/bgp_attr_base.h

@@ -96,8 +96,8 @@ struct BgpProtoPrefix : public ParseObject {
 
     BgpProtoPrefix();
 
-    uint32_t ReadLabel(size_t label_offset) const;
-    void WriteLabel(size_t label_offset, uint32_t label);
+    uint32_t ReadLabel(size_t label_offset, bool is_vni = false) const;
+    void WriteLabel(size_t label_offset, uint32_t label, bool is_vni = false);
 
     std::vector<uint8_t> prefix;
     int prefixlen;

src/bgp/community.cc

@@ -212,6 +212,20 @@ vector<string> ExtCommunity::GetTunnelEncap() const {
     return encap_list;
 }
 
+bool ExtCommunity::ContainsTunnelEncapVxlan() const {
+    for (ExtCommunityList::const_iterator iter = communities_.begin();
+         iter != communities_.end(); ++iter) {
+        if (!ExtCommunity::is_tunnel_encap(*iter))
+            continue;
+        TunnelEncap encap(*iter);
+        if (encap.tunnel_encap() == TunnelEncapType::VXLAN)
+            return true;
+        if (encap.tunnel_encap() == TunnelEncapType::VXLAN_CONTRAIL)
+            return true;
+    }
+    return false;
+}
+
 ExtCommunity::ExtCommunity(ExtCommunityDB *extcomm_db,
         const ExtCommunitySpec spec) : extcomm_db_(extcomm_db) {
     refcount_ = 0;

src/bgp/community.h

@@ -163,6 +163,7 @@ class ExtCommunity {
     }
 
     std::vector<std::string> GetTunnelEncap() const;
+    bool ContainsTunnelEncapVxlan() const;
 
     static bool is_origin_vn(const ExtCommunityValue &val) {
         //

src/bgp/evpn/evpn_route.cc

@@ -34,6 +34,36 @@ const size_t EvpnPrefix::kMinInclusiveMulticastRouteSize =
 const size_t EvpnPrefix::kMinSegmentRouteSize =
     kRdSize + kEsiSize + 1;
 
+//
+// Read label from the BgpProtoPrefix.
+// If the encapsulation is VXLAN and ethernet tag is non-zero use that as
+// the label for backward compatibility with older JUNOS code.
+//
+static uint32_t ReadLabel(const BgpProtoPrefix &proto_prefix,
+    const BgpAttr *attr, size_t offset, uint32_t tag) {
+    if (!attr)
+        return 0;
+    const ExtCommunity *extcomm = attr->ext_community();
+    if (extcomm && extcomm->ContainsTunnelEncapVxlan()) {
+        return (tag ? tag : proto_prefix.ReadLabel(offset, true));
+    } else {
+        return proto_prefix.ReadLabel(offset, false);
+    }
+}
+
+//
+// Write label to the BgpProtoPrefix.
+//
+static void WriteLabel(BgpProtoPrefix *proto_prefix,
+    const BgpAttr *attr, size_t offset, uint32_t label) {
+    const ExtCommunity *extcomm = attr ? attr->ext_community() : NULL;
+    if (extcomm && extcomm->ContainsTunnelEncapVxlan()) {
+        proto_prefix->WriteLabel(offset, label, true);
+    } else {
+        proto_prefix->WriteLabel(offset, label, false);
+    }
+}
+
 EvpnPrefix::EvpnPrefix()
     : type_(Unspecified), tag_(EvpnPrefix::kNullTag), family_(Address::UNSPEC) {
 }
@@ -111,10 +141,8 @@ int EvpnPrefix::FromProtoPrefix(BgpServer *server,
         prefix->esi_ = EthernetSegmentId(&proto_prefix.prefix[esi_offset]);
         size_t tag_offset = esi_offset + kEsiSize;
         prefix->tag_ = get_value(&proto_prefix.prefix[tag_offset], kTagSize);
-        if (attr) {
-            size_t label_offset = tag_offset + kTagSize;
-            *label = proto_prefix.ReadLabel(label_offset);
-        }
+        size_t label_offset = tag_offset + kTagSize;
+        *label = ReadLabel(proto_prefix, attr, label_offset, prefix->tag_);
         break;
     }
     case MacAdvertisementRoute: {
@@ -146,10 +174,8 @@ int EvpnPrefix::FromProtoPrefix(BgpServer *server,
             return -1;
         size_t ip_offset = ip_len_offset + 1;
         prefix->ReadIpAddress(proto_prefix, ip_offset, ip_size);
-        if (attr) {
-            size_t label_offset = ip_offset + ip_size;
-            *label = proto_prefix.ReadLabel(label_offset);
-        }
+        size_t label_offset = ip_offset + ip_size;
+        *label = ReadLabel(proto_prefix, attr, label_offset, prefix->tag_);
         break;
     }
     case InclusiveMulticastRoute: {
@@ -231,7 +257,7 @@ void EvpnPrefix::BuildProtoPrefix(const BgpAttr *attr, uint32_t label,
         size_t tag_offset = esi_offset + kEsiSize;
         put_value(&proto_prefix->prefix[tag_offset], kTagSize, tag_);
         size_t label_offset = tag_offset + kTagSize;
-        proto_prefix->WriteLabel(label_offset, label);
+        WriteLabel(proto_prefix, attr, label_offset, label);
         break;
     }
     case MacAdvertisementRoute: {
@@ -260,7 +286,7 @@ void EvpnPrefix::BuildProtoPrefix(const BgpAttr *attr, uint32_t label,
         size_t ip_offset = ip_len_offset + 1;
         WriteIpAddress(proto_prefix, ip_offset);
         size_t label_offset = ip_offset + ip_size;
-        proto_prefix->WriteLabel(label_offset, label);
+        WriteLabel(proto_prefix, attr, label_offset, label);
         break;
     }
     case InclusiveMulticastRoute: {