inet: rudimentary support for virutal IPs

Author: alfreb

api/net/inet.hpp

@@ -19,6 +19,7 @@
 #define NET_INET_HPP
 
 #include <chrono>
+#include <unordered_set>
 
 #include <net/inet_common.hpp>
 #include <hw/mac_addr.hpp>
@@ -46,6 +47,8 @@ namespace net {
     template <typename IPv>
     using resolve_func = delegate<void(typename IPv::addr)>;
 
+    using Vip_list = std::unordered_set<typename IPV::addr>;
+
 
     ///
     /// NETWORK CONFIGURATION
@@ -80,19 +83,37 @@ namespace net {
     /** Use DHCP to configure this interface */
     virtual void negotiate_dhcp(double timeout = 10.0, dhcp_timeout_func = nullptr) = 0;
 
+    /** Get a list of virtual IP4 addresses assigned to this interface */
+    virtual const Vip_list virtual_ips() const = 0;
+
+    /** Check if an IP is a (possibly virtual) loopback address */
+    virtual bool is_loopback(typename IPV::addr a) const = 0;
+
+    /** Add an IP address as a virtual loopback IP */
+    virtual void add_vip(typename IPV::addr a) = 0;
+
+    /** Remove an IP address from the virtual loopback IP list */
+    virtual void remove_vip(typename IPV::addr a) = 0;
+
+    /** Determine the appropriate source address for a destination. */
+    virtual typename IPV::addr get_source_addr(typename IPV::addr dest) = 0;
+
+    /** Determine if an IP address is a valid source address for this stack */
+    virtual bool is_valid_source(typename IPV::addr) = 0;
+
 
     ///
     /// PROTOCOL OBJECTS
     ///
 
     /** Get the IP protocol object for this interface */
-    virtual IPV&       ip_obj() = 0;
+    virtual IPV& ip_obj() = 0;
 
     /** Get the TCP protocol object for this interface */
-    virtual TCP&       tcp()    = 0;
+    virtual TCP& tcp() = 0;
 
     /** Get the UDP protocol object for this interface */
-    virtual UDP&       udp()    = 0;
+    virtual UDP& udp() = 0;
 
 
     ///
@@ -108,13 +129,13 @@ namespace net {
     ///
 
     /** Get the network interface device */
-    virtual hw::Nic&           nic() = 0;
+    virtual hw::Nic& nic() = 0;
 
     /** Get interface name for this interface **/
-    virtual std::string        ifname() const = 0;
+    virtual std::string ifname() const = 0;
 
     /** Get linklayer address for this interface **/
-    virtual MAC::Addr       link_addr() = 0;
+    virtual MAC::Addr link_addr() = 0;
 
     /** Add cache entry to the link / IP address cache */
     virtual void cache_link_addr(typename IPV::addr, MAC::Addr) = 0;
@@ -123,7 +144,7 @@ namespace net {
     virtual void flush_link_cache() = 0;
 
     /** Set the regular interval for link address cache flushing */
-    virtual void set_link_cache_flush_interval(std::chrono::minutes);
+    virtual void set_link_cache_flush_interval(std::chrono::minutes) = 0;
 
 
     ///

api/net/inet4.hpp

@@ -18,14 +18,16 @@
 #ifndef NET_INET4_HPP
 #define NET_INET4_HPP
 
+#include <vector>
+#include <unordered_set>
+
 #include "inet.hpp"
 #include "ip4/arp.hpp"
 #include "ip4/ip4.hpp"
 #include "ip4/udp.hpp"
 #include "ip4/icmpv4.hpp"
 #include "dns/client.hpp"
 #include "tcp/tcp.hpp"
-#include <vector>
 #include "super_stack.hpp"
 
 namespace net {
@@ -35,6 +37,9 @@ namespace net {
   /** A complete IP4 network stack */
   class Inet4 : public Inet<IP4>{
   public:
+
+    using Vip4_list = std::unordered_set<IP4::addr>;
+
     std::string ifname() const override
     { return nic_.device_name(); }
 
@@ -110,7 +115,6 @@ namespace net {
       return ip_packet;
     }
 
-
     IP_packet_factory ip_packet_factory() override
     { return IP_packet_factory{this, &Inet4::create_ip_packet}; }
 
@@ -231,10 +235,50 @@ namespace net {
       return stack<N>();
     }
 
-  private:
+    /** Add virtual IP4 address as loopback */
+    const Vip4_list virtual_ips() const noexcept override
+    { return vip4s_; }
+
+    /** Check if IP4 address is virtual loopback */
+    bool is_loopback(IP4::addr a) const override
+    {
+      return a.is_loopback()
+        or vip4s_.find(a) != vip4s_.end();
+    }
+
+    /** Add IP4 address as virtual loopback */
+    void add_vip(IP4::addr a) override
+    {
+      if (not is_loopback(a)) {
+        INFO("Inet4", "Adding virtual IP address %s", a.to_string().c_str());
+        vip4s_.emplace(a);
+      }
+    }
+
+    /** Add IP4 address as virtual loopback */
+    void remove_vip(IP4::addr a) override
+    { vip4s_.erase(a); }
+
+    IP4::addr get_source_addr(IP4::addr dest) override
+    {
+
+      if (dest.is_loopback())
+        return {127,0,0,1};
+
+      if (is_loopback(dest))
+        return dest;
+
+      return ip_addr();
+    }
+
+    bool is_valid_source(IP4::addr src) override
+    { return is_loopback(src) or src == ip_addr(); }
+
     /** Initialize with ANY_ADDR */
     Inet4(hw::Nic& nic);
 
+  private:
+
     void process_sendq(size_t);
     // delegates registered to get signalled about free packets
     std::vector<transmit_avail_delg> tqa;
@@ -244,6 +288,8 @@ namespace net {
     IP4::addr gateway_;
     IP4::addr dns_server;
 
+    Vip4_list vip4s_ = {{127,0,0,1}};
+
     // This is the actual stack
     hw::Nic& nic_;
     Arp    arp_;