fix & enhancement for udp connection handling

1. potential data race in `taosProcessMonitorTimer`:
the issue does not exist at present because there's only one scheduler
thread, which means there's no cocurrent calls to this function for a
same `pMonitor`. but if more scheduler threads are created later,
there's a data race issue in rare case. as threads number can be
easily increased by increase the value of `taosTmrThreads`, it is very
unlikely that the developer could realize this function need to be
revised together. that's why i say it is a 'potential' issue.

this issue happens in below scenario:
a. scheduler thread1: `if (pSet)` is true and new timer is installed by
`taosTmrReset`;
b. scheduler thread1: `if (pMonitor->pSet == NULL)` is true but
`taosTmrStopA` is blocked, either by the mutex of the timer or os thread
scheduler.
c. timer thread: 200ms elapse, new call to `taosProcessMonitorTimer` is
initialized in scheduler thread2;
d. scheduler thread2: `if (pMonitor->pTimer != tmrId)` is false;
e. scheduler thread1: unblocked, stops timer and frees `pMonitor`;
f. scheduler thread2: unexpected behavior because `pMonitor` is not
valid any more.

because the result of this issue is crash or worse, i suggest to fix it
though the possibility of all the conditions are met is very very low.

2. `pthread_attr_t` related issues: per manual, an initialized
`pthread_attr_t` can be reused, should be destroyed, and the behavior of
re-init it is undefined. this issue exist in other modules also.

3. memory leaks;

4. improve failure case handling of `taosInitUdpConnection`;

5. typo

src/rpc/src/tudp.c

@@ -137,9 +137,7 @@ void taosProcessMonitorTimer(void *param, void *tmrId) {
     tTrace("%s monitor timer is expired, update the link status", pSet->label);
     (*pSet->fp)(data, pMonitor->dataLen, pMonitor->ip, 0, pSet->shandle, NULL, NULL);
     taosTmrReset(taosProcessMonitorTimer, 200, pMonitor, pSet->tmrCtrl, &pMonitor->pTimer);
-  }
-
-  if (pMonitor->pSet == NULL) {
+  } else {
     taosTmrStopA(&pMonitor->pTimer);
     free(pMonitor);
   }
@@ -181,6 +179,7 @@ void *taosReadTcpData(void *argv) {
 
     if (retLen != pInfo->msgLen) {
       tError("%s failed to read data from server, msgLen:%d retLen:%d", pSet->label, pInfo->msgLen, retLen);
+      free(buffer);
     } else {
       (*pSet->fp)(buffer, pInfo->msgLen, pMonitor->ip, (int16_t)pInfo->port, pSet->shandle, NULL, pMonitor->pConn);
     }
@@ -214,9 +213,11 @@ int taosReceivePacketViaTcp(uint32_t ip, STaosHeader *pHead, SUdpConn *pConn) {
   pthread_attr_setdetachstate(&thattr, PTHREAD_CREATE_DETACHED);
   code = pthread_create(&(thread), &thattr, taosReadTcpData, (void *)pMonitor);
   if (code < 0) {
-    tTrace("%s faile to create thread to read tcp data, reason:%s", pSet->label, strerror(errno));
+    tTrace("%s failed to create thread to read tcp data, reason:%s", pSet->label, strerror(errno));
+    pMonitor->pSet = NULL;
   }
 
+  pthread_attr_destroy(&thattr);
   return code;
 }
 
@@ -402,6 +403,9 @@ void *taosUdpTcpConnection(void *argv) {
 
   tTrace("%s UDP server is created, ip:%s:%d", pSet->label, pSet->ip, pSet->port);
 
+  pthread_attr_init(&thattr);
+  pthread_attr_setdetachstate(&thattr, PTHREAD_CREATE_DETACHED);
+
   while (1) {
     if (pSet->tcpFd < 0) break;
     socklen_t addrlen = sizeof(clientAddr);
@@ -422,14 +426,14 @@ void *taosUdpTcpConnection(void *argv) {
     pTransfer->port = clientAddr.sin_port;
     pTransfer->pSet = pSet;
 
-    pthread_attr_init(&thattr);
-    pthread_attr_setdetachstate(&thattr, PTHREAD_CREATE_DETACHED);
     if (pthread_create(&(thread), &thattr, taosTransferDataViaTcp, (void *)pTransfer) < 0) {
-      tTrace("%s faile to create thread for UDP server, reason:%s", pSet->label, strerror(errno));
+      tTrace("%s failed to create thread for UDP server, reason:%s", pSet->label, strerror(errno));
+      free(pTransfer);
       taosCloseSocket(connFd);
     }
   }
 
+  pthread_attr_destroy(&thattr);
   return NULL;
 }
 
@@ -448,7 +452,6 @@ void *taosInitUdpConnection(char *ip, short port, char *label, int threads, void
   memset(pSet, 0, (size_t)size);
   strcpy(pSet->ip, ip);
   pSet->port = port;
-  pSet->threads = threads;
   pSet->shandle = shandle;
   pSet->fp = fp;
   pSet->tcpFd = -1;
@@ -458,8 +461,16 @@ void *taosInitUdpConnection(char *ip, short port, char *label, int threads, void
   char udplabel[12];
   sprintf(udplabel, "%s.b", label);
   pSet->tmrCtrl = taosTmrInit(RPC_MAX_UDP_CONNS * threads, 5, 5000, udplabel);
+  if (pSet->tmrCtrl == NULL) {
+    tError("%s failed to initialize tmrCtrl")
+    taosCleanUpUdpConnection(pSet);
+    return NULL;
+  }
   //  }
 
+  pthread_attr_init(&thAttr);
+  pthread_attr_setdetachstate(&thAttr, PTHREAD_CREATE_JOINABLE);
+
   short ownPort;
   for (int i = 0; i < threads; ++i) {
     pConn = pSet->udpConn + i;
@@ -467,6 +478,7 @@ void *taosInitUdpConnection(char *ip, short port, char *label, int threads, void
     pConn->fd = taosOpenUdpSocket(ip, ownPort);
     if (pConn->fd < 0) {
       tError("%s failed to open UDP socket %s:%d", label, ip, port);
+      taosCleanUpUdpConnection(pSet);
       return NULL;
     }
 
@@ -477,11 +489,10 @@ void *taosInitUdpConnection(char *ip, short port, char *label, int threads, void
       pConn->localPort = (int16_t)ntohs(sin.sin_port);
     }
 
-    pthread_attr_init(&thAttr);
-    pthread_attr_setdetachstate(&thAttr, PTHREAD_CREATE_JOINABLE);
     if (pthread_create(&pConn->thread, &thAttr, taosRecvUdpData, pConn) != 0) {
-      close(pConn->fd);
       tError("%s failed to create thread to process UDP data, reason:%s", label, strerror(errno));
+      taosCloseSocket(pConn->fd);
+      taosCleanUpUdpConnection(pSet);
       return NULL;
     }
 
@@ -496,6 +507,7 @@ void *taosInitUdpConnection(char *ip, short port, char *label, int threads, void
       pthread_mutex_init(&pConn->mutex, NULL);
       pConn->tmrCtrl = pSet->tmrCtrl;
     }
+    ++pSet->threads;
   }
 
   pthread_attr_destroy(&thAttr);
@@ -520,6 +532,7 @@ void *taosInitUdpServer(char *ip, short port, char *label, int threads, void *fp
   // pthread_t thread;
   // pSet->tcpThread = pthread_create(&(thread), &thattr, taosUdpTcpConnection, pSet);
   pthread_create(&(pSet->tcpThread), &thattr, taosUdpTcpConnection, pSet);
+  pthread_attr_destroy(&thattr);
 
   return pSet;
 }
@@ -540,13 +553,16 @@ void taosCleanUpUdpConnection(void *handle) {
   for (int i = 0; i < pSet->threads; ++i) {
     pConn = pSet->udpConn + i;
     pConn->signature = NULL;
+    pthread_cancel(pConn->thread);
     taosCloseSocket(pConn->fd);
     if (pConn->hash) {
       taosCloseIpHash(pConn->hash);
       pthread_mutex_destroy(&pConn->mutex);
     }
+  }
 
-    pthread_cancel(pConn->thread);
+  for (int i = 0; i < pSet->threads; ++i) {
+    pConn = pSet->udpConn + i;
     pthread_join(pConn->thread, NULL);
     tTrace("chandle:%p is closed", pConn);
   }