From d67d1f7340b36b5bfebc56f67211501d146fcb91 Mon Sep 17 00:00:00 2001
From: adamdunkels <adamdunkels>
Date: Tue, 9 Feb 2010 12:58:53 +0000
Subject: [PATCH] Major bugfix, found by Raimondas Sasnauskas: the TCP periodic
 timer was not started when a new connection request arrived. If there were no
 other active TCP connections, this means that the SYNACK would never be
 retransmitted, potentially leading to a forever stale TCP connection.

---
 core/net/tcpip.c | 51 ++++++++++++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 19 deletions(-)

diff --git a/core/net/tcpip.c b/core/net/tcpip.c
index 01d98f173..21d6a9f54 100644
--- a/core/net/tcpip.c
+++ b/core/net/tcpip.c
@@ -29,7 +29,7 @@
  * This file is part of the Contiki operating system.
  *
  *
- * $Id: tcpip.c,v 1.23 2010/02/05 12:43:36 nifi Exp $
+ * $Id: tcpip.c,v 1.24 2010/02/09 12:58:53 adamdunkels Exp $
  */
 /**
  * \file
@@ -71,6 +71,7 @@ void uip_log(char *msg);
 
 #define UIP_ICMP_BUF ((struct uip_icmp_hdr *)&uip_buf[UIP_LLIPH_LEN + uip_ext_len])
 #define UIP_IP_BUF ((struct uip_ip_hdr *)&uip_buf[UIP_LLH_LEN])
+#define UIP_TCP_BUF ((struct uip_tcpip_hdr *)&uip_buf[UIP_LLH_LEN])
 
 process_event_t tcpip_event;
 #if UIP_CONF_ICMP6
@@ -156,6 +157,29 @@ unsigned char tcpip_is_forwarding; /* Forwarding right now? */
 
 PROCESS(tcpip_process, "TCP/IP stack");
 
+/*---------------------------------------------------------------------------*/
+static void
+start_periodic_tcp_timer(void)
+{
+  if(etimer_expired(&periodic)) {
+    etimer_restart(&periodic);
+  }
+}
+/*---------------------------------------------------------------------------*/
+static void
+check_for_tcp_syn(void)
+{
+  /* This is a hack that is needed to start the periodic TCP timer if
+     an incoming packet contains a SYN: since uIP does not inform the
+     application if a SYN arrives, we have no other way of starting
+     this timer.  This function is called for every incoming IP packet
+     to check for such SYNs. */
+#define TCP_SYN 0x02
+  if(UIP_IP_BUF->proto == UIP_PROTO_TCP &&
+     (UIP_TCP_BUF->flags & TCP_SYN) == TCP_SYN) {
+    start_periodic_tcp_timer();
+  }
+}
 /*---------------------------------------------------------------------------*/
 static void
 packet_input(void)
@@ -165,6 +189,7 @@ packet_input(void)
     tcpip_is_forwarding = 1;
     if(uip_fw_forward() == UIP_FW_LOCAL) {
       tcpip_is_forwarding = 0;
+      check_for_tcp_syn();
       uip_input();
       if(uip_len > 0) {
 #if UIP_CONF_TCP_SPLIT
@@ -183,6 +208,7 @@ packet_input(void)
   }
 #else /* UIP_CONF_IP_FORWARD */
   if(uip_len > 0) {
+    check_for_tcp_syn();
     uip_input();
     if(uip_len > 0) {
 #if UIP_CONF_TCP_SPLIT
@@ -199,12 +225,8 @@ packet_input(void)
   }
 #endif /* UIP_CONF_IP_FORWARD */
 }
-
 /*---------------------------------------------------------------------------*/
-/*---------------------------------------------------------------------------*/
-
 #if UIP_TCP
-
 #if UIP_ACTIVE_OPEN
 struct uip_conn *
 tcp_connect(uip_ipaddr_t *ripaddr, u16_t port, void *appstate)
@@ -273,10 +295,7 @@ tcp_attach(struct uip_conn *conn,
 }
 
 #endif /* UIP_TCP */
-
 /*---------------------------------------------------------------------------*/
-/*---------------------------------------------------------------------------*/
-
 #if UIP_UDP
 void
 udp_attach(struct uip_udp_conn *conn,
@@ -349,7 +368,6 @@ tcpip_icmp6_call(u8_t type)
 }
 #endif /* UIP_CONF_ICMP6 */
 /*---------------------------------------------------------------------------*/
-
 static void
 eventhandler(process_event_t ev, process_data_t data)
 {
@@ -483,17 +501,14 @@ eventhandler(process_event_t ev, process_data_t data)
         uip_poll_conn(data);
 #if UIP_CONF_IPV6
         tcpip_ipv6_output();
-#else
+#else /* UIP_CONF_IPV6 */
         if(uip_len > 0) {
 	  PRINTF("tcpip_output from tcp poll len %d\n", uip_len);
           tcpip_output();
         }
 #endif /* UIP_CONF_IPV6 */
         /* Start the periodic polling, if it isn't already active. */
-        if(etimer_expired(&periodic)) {
-          etimer_restart(&periodic);
-        }
-        
+        start_periodic_tcp_timer();
       }
       break;
 #endif /* UIP_TCP */
@@ -720,12 +735,10 @@ tcpip_uipcall(void)
      }
      
      /* Start the periodic polling, if it isn't already active. */
-     if(etimer_expired(&periodic)) {
-       etimer_restart(&periodic);
-     }
+     start_periodic_tcp_timer();
    }
  }
-#endif
+#endif /* UIP_TCP */
   
   if(ts->p != NULL) {
     process_post_synch(ts->p, tcpip_event, ts->state);
@@ -751,7 +764,7 @@ PROCESS_THREAD(tcpip_process, ev, data)
 #if UIP_CONF_ICMP6
   tcpip_icmp6_event = process_alloc_event();
 #endif /* UIP_CONF_ICMP6 */
-  etimer_set(&periodic, CLOCK_SECOND/2);
+  etimer_set(&periodic, CLOCK_SECOND / 2);
 
   uip_init();