IfaceMap add look up index by address, and loopback by index

src/evhelper.cpp

@@ -837,6 +837,21 @@ uint64_t IfaceMap::index_of(const std::string& name)
     return ret;
 }
 
+uint64_t IfaceMap::index_of(const SockAddr &addr)
+{
+    Guard G(lock);
+
+    uint64_t ret = 0u;
+    try_cache(*this, [&ret, this, addr]() {
+        auto it = byAddr.find(addr);
+        bool hit = it!=byAddr.end() && !it->second.second;
+        if(hit)
+            ret = it->second.first->index;
+        return hit;
+    });
+    return ret;
+}
+
 bool IfaceMap::is_iface(const SockAddr& addr)
 {
     Guard G(lock);
@@ -847,6 +862,19 @@ bool IfaceMap::is_iface(const SockAddr& addr)
     });
 }
 
+bool IfaceMap::is_lo(uint64_t index)
+{
+    bool is_lo = false;
+    (void)try_cache(*this, [this, &is_lo, index]() {
+        auto ifit(byIndex.find(index));
+        if(ifit!=byIndex.end()) { // hit
+            is_lo = ifit->second.isLO;
+        }
+        return false;
+    });
+    return is_lo;
+}
+
 bool IfaceMap::is_broadcast(const SockAddr& addr)
 {
     Guard G(lock);

src/evhelper.h

@@ -316,8 +316,12 @@ struct PVXS_API IfaceMap {
     std::string name_of(const SockAddr& addr);
     // returns 0 if not found
     uint64_t index_of(const std::string& name);
+    // lookup interface index by interface address (not broadcast addr)
+    uint64_t index_of(const SockAddr& addr);
     // is this a valid interface or broadcast address?
     bool is_iface(const SockAddr& addr);
+    // is this index the/a loopback interface?
+    bool is_lo(uint64_t index);
     // is this a valid interface or broadcast address?
     bool is_broadcast(const SockAddr& addr);
     // look up interface address.  useful for IPV4.  returns AF_UNSPEC if not found