test for retransmitted segment

mongoose.c

@@ -8085,7 +8085,7 @@ static void read_conn(struct mg_connection *c, struct pkt *pkt) {
     MG_DEBUG(("%lu SEQ %x -> %x", c->id, mg_htonl(pkt->tcp->seq), s->ack));
     // Advance ACK counter
     s->ack = (uint32_t) (mg_htonl(pkt->tcp->seq) + pkt->pay.len);
-#ifdef MIP_TEST
+#if 0
     // Send ACK immediately
     uint32_t rem_ip;
     memcpy(&rem_ip, c->rem.ip, sizeof(uint32_t));

src/tcpip/tcpip.c

@@ -600,7 +600,7 @@ static void read_conn(struct mg_connection *c, struct pkt *pkt) {
     MG_DEBUG(("%lu SEQ %x -> %x", c->id, mg_htonl(pkt->tcp->seq), s->ack));
     // Advance ACK counter
     s->ack = (uint32_t) (mg_htonl(pkt->tcp->seq) + pkt->pay.len);
-#ifdef MIP_TEST
+#if 0
     // Send ACK immediately
     uint32_t rem_ip;
     memcpy(&rem_ip, c->rem.ip, sizeof(uint32_t));

test/mip_test.c

@@ -3,8 +3,6 @@
 #define MG_ENABLE_TCPIP 1
 #define MG_ENABLE_PACKED_FS 0
 
-#define MIP_TEST
-
 #include "mongoose.c"
 #include "driver_mock.c"
 
@@ -55,6 +53,7 @@ static void test_poll(void) {
 struct driver_data {
   char buf[DRIVER_BUF_SIZE];
   size_t len;
+  bool tx_ready; // data can be read from tx
 };
 
 static struct driver_data s_driver_data;
@@ -62,7 +61,9 @@ static struct driver_data s_driver_data;
 static size_t if_tx(const void *buf, size_t len, struct mg_tcpip_if *ifp) {
   struct driver_data *driver_data = (struct driver_data *) ifp->driver_data;
   if (len > DRIVER_BUF_SIZE) len = DRIVER_BUF_SIZE;
+  driver_data->len = len;
   memcpy(driver_data->buf, buf, len);
+  driver_data->tx_ready = true;
   return len;
 }
 
@@ -72,11 +73,19 @@ static bool if_up(struct mg_tcpip_if *ifp) {
 
 static size_t if_rx(void *buf, size_t len, struct mg_tcpip_if *ifp) {
   struct driver_data *driver_data = (struct driver_data *) ifp->driver_data;
+  if (!driver_data->len) return 0;
   if (len > driver_data->len) len = driver_data->len;
   memcpy(buf, driver_data->buf, len);
+  driver_data->len = 0; // cleaning up the buffer
   return len;
 }
 
+static bool received_response(struct driver_data *driver) {
+  bool was_ready = driver->tx_ready;
+  driver->tx_ready = false;
+  return was_ready;
+}
+
 static void create_tcp_pkt(struct eth *e, struct ip *ip, uint32_t seq,
                            uint32_t ack, uint8_t flags, size_t payload_len) {
   struct tcp t;
@@ -88,8 +97,8 @@ static void create_tcp_pkt(struct eth *e, struct ip *ip, uint32_t seq,
   memcpy(s_driver_data.buf, e, sizeof(*e));
   memcpy(s_driver_data.buf + sizeof(*e), ip, sizeof(*ip));
   memcpy(s_driver_data.buf + sizeof(*e) + sizeof(*ip), &t, sizeof(struct tcp));
-  s_driver_data.len =
+  s_driver_data.len = sizeof(*e) + sizeof(*ip) 
-      sizeof(*e) + sizeof(*ip) + sizeof(struct tcp) + payload_len;
+                      + sizeof(struct tcp) + payload_len;
 }
 
 static void test_retransmit(void) {
@@ -97,6 +106,8 @@ static void test_retransmit(void) {
   struct eth e;
   struct ip ip;
   struct tcp *t;
+  uint64_t start, now;
+  bool response_recv = true;
   struct mg_tcpip_driver driver;
   struct mg_tcpip_if mif;
   struct mg_connection *c;
@@ -108,15 +119,17 @@ static void test_retransmit(void) {
   mif.driver = &driver;
   mif.driver_data = &s_driver_data;
   mg_tcpip_init(&mgr, &mif);
-  c = mg_alloc_conn(&mgr);
+  c = mg_alloc_conn(&mgr); // create dummy connection
   LIST_ADD_HEAD(struct mg_connection, &mgr.conns, c);
   c->is_listening = 1;
   mg_mgr_poll(&mgr, 0);
 
+  // setting the Ethernet header
   memset(&e, 0, sizeof(e));
   memcpy(e.dst, mif.mac, 6 * sizeof(uint8_t));
   e.type = mg_htons(0x800);
 
+  // setting the IP header
   memset(&ip, 0, sizeof(ip));
   ip.ver = 4 << 4, ip.proto = 6;
   ip.len = mg_htons(sizeof(ip) + sizeof(struct tcp));
@@ -126,6 +139,7 @@ static void test_retransmit(void) {
   mg_mgr_poll(&mgr, 0);
 
   // SYN-ACK
+  while(!received_response(&s_driver_data)) mg_mgr_poll(&mgr, 0);
   t = (struct tcp *) (s_driver_data.buf + sizeof(struct eth) +
                       sizeof(struct ip));
   ASSERT((t->flags == (TH_SYN | TH_ACK)));
@@ -140,26 +154,50 @@ static void test_retransmit(void) {
       mg_htons(sizeof(struct ip) + sizeof(struct tcp) + /* TCP Payload */ 1);
   create_tcp_pkt(&e, &ip, 1001, 1, TH_PUSH | TH_ACK, 1);
   mg_mgr_poll(&mgr, 0);
+  while(!received_response(&s_driver_data)) mg_mgr_poll(&mgr, 0);
   t = (struct tcp *) (s_driver_data.buf + sizeof(struct eth) +
                       sizeof(struct ip));
   ASSERT((t->flags == TH_ACK));
-  ASSERT((t->ack == mg_htonl(1002)));
+  ASSERT((t->ack == mg_htonl(1002))); // OK
 
-  // packet with seq_no = 1003
+  // resend packet with seq_no = 1001 (e.g.: MIP ACK lost)
+  create_tcp_pkt(&e, &ip, 1001, 1, TH_PUSH | TH_ACK, 1);
+  mg_mgr_poll(&mgr, 0);
+  start = mg_millis();
+  while(!received_response(&s_driver_data)) {
+    mg_mgr_poll(&mgr, 0);
+    now = mg_millis() - start;
+    // we wait enough time for a reply
+    if (now > 2 * MIP_TCP_ACK_MS) {
+      response_recv = false;
+      break;
+    }
+  }
+  ASSERT((!response_recv)); // replies should not be sent for duplicate packets
+
+  // packet with seq_no = 1002 got lost/delayed, send seq_no = 1003
   create_tcp_pkt(&e, &ip, 1003, 1, TH_PUSH | TH_ACK, 1);
   mg_mgr_poll(&mgr, 0);
+  start = mg_millis();
+  while(!received_response(&s_driver_data)) {
+    mg_mgr_poll(&mgr, 0);
+    now = mg_millis() - start;
+    if (now > 2 * MIP_TCP_ACK_MS)
+      ASSERT(0); // response should have been received by now
+  }
   t = (struct tcp *) (s_driver_data.buf + sizeof(struct eth) +
                       sizeof(struct ip));
   ASSERT((t->flags == TH_ACK));
-  ASSERT((t->ack == mg_htonl(1002)));
+  ASSERT((t->ack == mg_htonl(1002))); // dup ACK
 
   // retransmitting packet with seq_no = 1002
   create_tcp_pkt(&e, &ip, 1002, 1, TH_PUSH | TH_ACK, 1);
   mg_mgr_poll(&mgr, 0);
+  while(!received_response(&s_driver_data)) mg_mgr_poll(&mgr, 0);
   t = (struct tcp *) (s_driver_data.buf + sizeof(struct eth) +
                       sizeof(struct ip));
   ASSERT((t->flags == TH_ACK));
-  ASSERT((t->ack == mg_htonl(1003)));
+  ASSERT((t->ack == mg_htonl(1003))); // OK
 
   s_driver_data.len = 0;
   mg_mgr_free(&mgr);