added support for dhcp in daemon. On receiving SIGUSR2 daemon checks and updates new address for snat, and nexthop for lb routing

tables. hook needs to be added to dhclient daemon to send SIGUSR2 to wan_lb so notification is generated on address change event. Note
that for this behavior to be active in WLB nexthop needs to be populated with 'dhcp' configuration string.

still requires routing paths availble for target testing, which might require an update to the dhcp client script and possible
configuration knob.

1 files changed, 59 insertions, 2 deletions

diff --git a/src/lbdecision.cc b/src/lbdecision.cc
index e51530a..10a730b 100644
--- a/src/lbdecision.cc
+++ b/src/lbdecision.cc
@@ -138,7 +138,13 @@ if so then this stuff goes here!
     
     //    insert_default(string("ip route replace table ") + buf + " default dev " + iface + " via " + iter->second._nexthop, ct);
     //need to force the entry on restart as the configuration may have changed.
-    execute(string("ip route replace table ") + buf + " default dev " + iface + " via " + iter->second._nexthop, stdout);
+    if (iter->second._nexthop == "dhcp") {
+      string nexthop = fetch_iface_nexthop(iface);
+      execute(string("ip route replace table ") + buf + " default dev " + iface + " via " + nexthop, stdout);
+    }
+    else {
+      execute(string("ip route replace table ") + buf + " default dev " + iface + " via " + iter->second._nexthop, stdout);
+    }
 
     execute(string("ip rule delete table ") + buf, stdout);
 
@@ -147,13 +153,46 @@ if so then this stuff goes here!
     execute(string("ip rule add fwmark ") + hex_buf + " table " + buf, stdout);
 
     if (lbdata._disable_source_nat == false) {
-      execute(string("iptables -t nat -A WANLOADBALANCE -m connmark --mark ") + buf + " -j SNAT --to-source " + fetch_iface_addr(iface), stdout);
+      iter->second._address = fetch_iface_addr(iface);
+      execute(string("iptables -t nat -A WANLOADBALANCE -m connmark --mark ") + buf + " -j SNAT --to-source " + iter->second._address, stdout);
     }
     ++iter;
   }
   execute("ip route flush cache", stdout);
 }
 
+/**
+ * Need to do two things here, check the interfaces for new nexthops and update the routing tables,
+ * and get a new address to update the source nat with.
+ *
+ **/
+void
+LBDecision::update_paths(LBData &lbdata)
+{
+  string stdout;
+  if (lbdata._disable_source_nat == false) {
+    //first let's remove the entry
+    LBData::InterfaceHealthIter iter = lbdata._iface_health_coll.begin();
+    while (iter != lbdata._iface_health_coll.end()) {
+      if (iter->second._nexthop == "dhcp") {
+	string iface = iter->first;
+	string new_addr = fetch_iface_addr(iface);
+	if (new_addr != iter->second._address) {
+	  char buf[20];
+	  sprintf(buf,"%d",iter->second._interface_index);
+	  execute(string("iptables -t nat -D WANLOADBALANCE -m connmark --mark ") + buf + " -j SNAT --to-source " + iter->second._address, stdout);
+	  execute(string("iptables -t nat -A WANLOADBALANCE -m connmark --mark ") + buf + " -j SNAT --to-source " + new_addr, stdout);
+	  iter->second._address = new_addr;
+
+	  //now let's update the nexthop here in the route table
+	  string nexthop = fetch_iface_nexthop(iface);
+	  execute(string("ip route replace table ") + buf + " default dev " + iface + " via " + nexthop, stdout);
+	}
+      }
+      ++iter;
+    }
+  }
+}
 
 /**
  * only responsible for 
@@ -489,6 +528,24 @@ LBDecision::insert_default(string cmd, int table)
   }
 }
 
+/**
+ * currently only reads the nexthop as maintained by the dhcp client
+ **/
+string
+LBDecision::fetch_iface_nexthop(const string &iface)
+{
+  string file("/var/run/vyatta/dhclient/dhclient-script-router-"+iface);
+  FILE *fp = fopen(file.c_str(),"r");
+  if (fp) {
+    char str[1025];
+    int ct = 0;
+    if ((ct = fread(str, 1, 1024, fp)) > 0) {
+      return string(str);
+    }
+    fclose(fp);
+  }
+  return string("");
+}
 
 /**
  * Fetch interface configuration