UDP backlog and prevent filtering of received messages in uIP

The IP address and port of received UDP message were stored in uIP
record, but if these are set, uIP filters the incoming messages to match
the IP and port.

Author: JAndrassy

README.md

@@ -15,7 +15,7 @@ The modernization includes:
 
 Limitations:
 * UDP.beginMulticast is not supported, because the uIP stack doesn't support multicast
-* UDB broadcasts receiving is turned off on ENC to lower the processing load on the library
+* UDP broadcasts receiving is turned off on ENC to lower the processing load on the library
 
 This library doesn't have examples, because examples of the Arduino Ethernet library apply. You can find them in the Arduino IDE Examples menu Ethernet section. Only change `#include <Ethernet.h>` to `#include <EthernetENC.h>`. Some examples require [a little change](https://github.com/jandrassy/EthernetENC/wiki/Examples). 
 

src/EthernetUdp.cpp

@@ -67,7 +67,7 @@ UIPUDP::stop()
       _uip_udp_conn->appstate = NULL;
       _uip_udp_conn=NULL;
       Enc28J60Network::freeBlock(appdata.packet_in);
-      Enc28J60Network::freeBlock(appdata.packet_next);
+      _flushBlocks(appdata.packet_next);
       Enc28J60Network::freeBlock(appdata.packet_out);
       memset(&appdata,0,sizeof(appdata));
     }
@@ -212,8 +212,10 @@ UIPUDP::parsePacket()
 #endif
   Enc28J60Network::freeBlock(appdata.packet_in);
 
-  appdata.packet_in = appdata.packet_next;
-  appdata.packet_next = NOBLOCK;
+  appdata.packet_in = appdata.packet_next[0].packet;
+  uip_ipaddr_copy(appdata.remote_ip, appdata.packet_next[0].remote_ip);
+  appdata.remote_port = appdata.packet_next[0].remote_port;
+  _moveBlocks(appdata.packet_next);
 
 #ifdef UIPETHERNET_DEBUG_UDP
   if (appdata.packet_in != NOBLOCK)
@@ -301,14 +303,14 @@ UIPUDP::discardReceived()
 IPAddress
 UIPUDP::remoteIP()
 {
-  return _uip_udp_conn ? ip_addr_uip(_uip_udp_conn->ripaddr) : IPAddress();
+  return ip_addr_uip(appdata.remote_ip);
 }
 
 // Return the port of the host who sent the current incoming packet
 uint16_t
 UIPUDP::remotePort()
 {
-  return _uip_udp_conn ? ntohs(_uip_udp_conn->rport) : 0;
+  return ntohs(appdata.remote_port);
 }
 
 // uIP callback function
@@ -319,21 +321,22 @@ uipudp_appcall(void) {
     {
       if (uip_newdata())
         {
-          if (data->packet_next == NOBLOCK)
+          uint8_t p = UIPUDP::_newBlock(data->packet_next);
+          if (data->packet_next[p].packet == NOBLOCK)
             {
-              uip_udp_conn->rport = UDPBUF->srcport;
-              uip_ipaddr_copy(uip_udp_conn->ripaddr,UDPBUF->srcipaddr);
-              data->packet_next = Enc28J60Network::allocBlock(ntohs(UDPBUF->udplen)-UIP_UDPH_LEN);
+              data->packet_next[p].remote_port = UDPBUF->srcport;
+              uip_ipaddr_copy( data->packet_next[p].remote_ip,UDPBUF->srcipaddr);
+              data->packet_next[p].packet = Enc28J60Network::allocBlock(ntohs(UDPBUF->udplen)-UIP_UDPH_LEN);
                   //if we are unable to allocate memory the packet is dropped. udp doesn't guarantee packet delivery
-              if (data->packet_next != NOBLOCK)
+              if (data->packet_next[p].packet != NOBLOCK)
                 {
                   //discard Linklevel and IP and udp-header and any trailing bytes:
-                  Enc28J60Network::copyPacket(data->packet_next,0,UIPEthernetClass::in_packet,UIP_UDP_PHYH_LEN,Enc28J60Network::blockSize(data->packet_next));
+                  Enc28J60Network::copyPacket(data->packet_next[p].packet,0,UIPEthernetClass::in_packet,UIP_UDP_PHYH_LEN,Enc28J60Network::blockSize(data->packet_next[p].packet));
     #ifdef UIPETHERNET_DEBUG_UDP
                   Serial.print(F("udp, uip_newdata received packet: "));
-                  Serial.print(data->packet_next);
+                  Serial.print(data->packet_next[p].packet);
                   Serial.print(F(", size: "));
-                  Serial.println(Enc28J60Network::blockSize(data->packet_next));
+                  Serial.println(Enc28J60Network::blockSize(data->packet_next[p].packet));
     #endif
                 }
             }
@@ -379,4 +382,35 @@ UIPUDP::_send(uip_udp_userdata_t *data) {
 #endif
     }
 }
+
+uint8_t
+UIPUDP::_newBlock(uip_udp_msg_rec_t* block)
+{
+  for (uint8_t i = 0; i < UIP_UDP_BACKLOG; i++)
+    {
+      if (block[i].packet == NOBLOCK)
+        return i;
+    }
+  return UIP_UDP_BACKLOG-1;
+}
+
+void
+UIPUDP::_moveBlocks(uip_udp_msg_rec_t* block)
+{
+  for (uint8_t i = 0; i < UIP_UDP_BACKLOG-1; i++)
+    {
+      block[i] = block[i+1];
+    }
+  block[UIP_UDP_BACKLOG-1].packet = NOBLOCK;
+}
+
+void
+UIPUDP::_flushBlocks(uip_udp_msg_rec_t* block)
+{
+  for (uint8_t i = 0; i < UIP_UDP_BACKLOG; i++)
+    {
+      Enc28J60Network::freeBlock(block[i].packet);
+      block[i].packet = NOBLOCK;
+    }
+}
 #endif

src/EthernetUdp.h

@@ -31,12 +31,20 @@ extern "C" {
 #define UIP_UDP_PHYH_LEN UIP_LLH_LEN+UIP_IPUDPH_LEN
 #define UIP_UDP_MAXPACKETSIZE UIP_UDP_MAXDATALEN+UIP_UDP_PHYH_LEN
 
+typedef struct {
+  memhandle packet = NOBLOCK;
+  uip_ipaddr_t remote_ip;
+  uint16_t remote_port = 0;
+} uip_udp_msg_rec_t;
+
 typedef struct {
   memaddress out_pos;
-  memhandle packet_next;
-  memhandle packet_in;
-  memhandle packet_out;
+  uip_udp_msg_rec_t packet_next[UIP_UDP_BACKLOG];
+  memhandle packet_in = NOBLOCK;
+  memhandle packet_out = NOBLOCK;
   boolean send;
+  uip_ipaddr_t remote_ip;
+  uint16_t remote_port = 0;
 } uip_udp_userdata_t;
 
 class EthernetUDP : public UDP
@@ -123,6 +131,9 @@ class EthernetUDP : public UDP
   friend class UIPEthernetClass;
   static void _send(uip_udp_userdata_t *data);
 
+  static uint8_t _newBlock(uip_udp_msg_rec_t* blocks);
+  static void _moveBlocks(uip_udp_msg_rec_t* blocks);
+  static void _flushBlocks(uip_udp_msg_rec_t* blocks);
 };
 
 #endif

src/utility/mempool_conf.h

@@ -17,7 +17,7 @@ typedef uint8_t memhandle;
 #endif
 
 #if UIP_UDP and UIP_UDP_CONNS
-#define NUM_UDP_MEMBLOCKS 3*UIP_UDP_CONNS
+#define NUM_UDP_MEMBLOCKS ((2+UIP_UDP_BACKLOG)*UIP_UDP_CONNS)
 #else
 #define NUM_UDP_MEMBLOCKS 0
 #endif

src/utility/uipethernet-conf.h

@@ -1,6 +1,8 @@
 #ifndef UIPETHERNET_CONF_H
 #define UIPETHERNET_CONF_H
 
+// https://github.com/jandrassy/EthernetENC/wiki/Settings
+
 /* for TCP */
 #ifndef UIP_SOCKET_NUMPACKETS
 #define UIP_SOCKET_NUMPACKETS    3
@@ -15,7 +17,14 @@
 #define UIP_CONF_UDP             1
 #endif
 #ifndef UIP_CONF_UDP_CONNS
-#define UIP_CONF_UDP_CONNS       4
+#define UIP_CONF_UDP_CONNS       2
+#endif
+
+/**
+ * size of received UDP messages backlog. it must be at least 1
+ */
+#ifndef UIP_UDP_BACKLOG
+#define UIP_UDP_BACKLOG       2
 #endif
 
 /* timeout in ms for attempts to get a free memory block to write