add warning on missing dest IP addr anno; doc updates (inspired by Tim Wilson...

add warning on missing dest IP addr anno; doc updates (inspired by Tim Wilson <timwilson@mediaone.net>

elements/ethernet/arpquerier.cc

@@ -173,16 +173,20 @@ ARPQuerier::expire_hook(Timer *, void *thunk)
 void
 ARPQuerier::send_query_for(const IPAddress &want_ip)
 {
-  click_ether *e;
-  click_ether_arp *ea;
-  WritablePacket *q = Packet::make(sizeof(*e) + sizeof(*ea));
+  static bool zero_warned = false;  
+  if (!want_ip && !zero_warned) {
+    click_chatter("%s: querying for 0.0.0.0; missing dest IP addr annotation?");
+    zero_warned = true;
+  }
+      
+  WritablePacket *q = Packet::make(sizeof(click_ether) + sizeof(click_ether_arp));
   if (q == 0) {
     click_chatter("in arp querier: cannot make packet!");
     assert(0);
   } 
   memset(q->data(), '\0', q->length());
-  e = (click_ether *) q->data();
-  ea = (click_ether_arp *) (e + 1);
+  click_ether *e = (click_ether *) q->data();
+  click_ether_arp *ea = (click_ether_arp *) (e + 1);
   memcpy(e->ether_dhost, "\xff\xff\xff\xff\xff\xff", 6);
   memcpy(e->ether_shost, _my_en.data(), 6);
   e->ether_type = htons(ETHERTYPE_ARP);

elements/ethernet/arpquerier.hh

@@ -2,45 +2,52 @@
 #define ARPQUERIER_HH
 
 /*
- * =c
- * ARPQuerier(I, E)
- * ARPQuerier(NAME)
- * =s Ethernet, encapsulation
- * encapsulates IP packets in Ethernet headers found via ARP
- * =d
- * Handles most of the ARP protocol. Argument I should be
- * this host's IP address, and E should be this host's
- * Ethernet address.
- *
- * Expects ordinary IP packets on input 0, each with a destination
- * address annotation. If an Ethernet address is already known
- * for the destination, the IP packet is wrapped in an Ethernet
- * header and sent to output 0. Otherwise the IP packet is saved and
- * an ARP query is sent instead. If an ARP response arrives
- * on input 1 for an IP address that we need, the mapping is
- * recorded and the saved IP packet is sent.
- *
- * The ARP reply packets on input 1 should include the Ethernet header.
- *
- * If a host has multiple interfaces, it will need multiple
- * instances of ARPQuerier.
- *
- * ARPQuerier may have one or two outputs. If it has two, then ARP queries
- * are sent to the second output.
- *
- * In the one-argument form, NAME should be shorthand for
- * both an IP and an Ethernet address; see AddressInfo(n).
- *
- * =e
- *    c :: Classifier(12/0806 20/0001, 12/0800, ...);
- *    a :: ARPQuerier(18.26.4.24, 00:00:C0:AE:67:EF);
- *    c[0] -> a[1];
- *    c[1] -> ... -> a[0];
- *    a[0] -> ... -> ToDevice(eth0);
- *
- * =a
- * ARPResponder, ARPFaker, AddressInfo
- */
+=c
+
+ARPQuerier(I, E)
+ARPQuerier(NAME)
+
+=s Ethernet, encapsulation
+
+encapsulates IP packets in Ethernet headers found via ARP
+
+=d
+
+Handles most of the ARP protocol. Argument I should be
+this host's IP address, and E should be this host's
+Ethernet address.
+(In the one-argument form, NAME should be shorthand for
+both an IP and an Ethernet address; see AddressInfo(n).)
+
+Packets arriving on input 0 should be IP packets, and must have their
+destination address annotations set.
+If an Ethernet address is already known
+for the destination, the IP packet is wrapped in an Ethernet
+header and sent to output 0. Otherwise the IP packet is saved and
+an ARP query is sent instead. If an ARP response arrives
+on input 1 for an IP address that we need, the mapping is
+recorded and the saved IP packet is sent.
+
+The ARP reply packets on input 1 should include the Ethernet header.
+
+If a host has multiple interfaces, it will need multiple
+instances of ARPQuerier.
+
+ARPQuerier may have one or two outputs. If it has two, then ARP queries
+are sent to the second output.
+
+=e
+
+   c :: Classifier(12/0806 20/0001, 12/0800, ...);
+   a :: ARPQuerier(18.26.4.24, 00:00:C0:AE:67:EF);
+   c[0] -> a[1];
+   c[1] -> ... -> a[0];
+   a[0] -> ... -> ToDevice(eth0);
+
+=a
+
+ARPResponder, ARPFaker, AddressInfo
+*/
 
 #include <click/element.hh>
 #include <click/etheraddress.hh>