- use dig before gethostbyname to resolve host names

ascon.c

@@ -17,75 +17,62 @@
 static double lastClose = 0; /* time of last close operation */
 static AsconProtocol *protocols = NULL;
 
-long parse_dotted_adr(const char *dottedadr) {
-  int ip[4];
-  int i;
-  
-  if (sscanf(dottedadr, "%d.%d.%d.%d", ip, ip+1, ip+2, ip+3) != 4) return 0;
-  for (i=0; i<3; i++) {
-    if (ip[i] < 0 || ip[i] > 255) return 0;
-  }
-  return ip[0] + (ip[1] << 8) + (ip[2] << 16) + (ip[3] << 24);
-}
+static int MakeSocketAdr(
+    struct sockaddr *sockaddrPtr,  /* socket address */
+    char *hostname,       /* name or ip of host. NULL implies INADDR_ANY */
+    int port,             /* port number */
+    char dotted_ip[16]) { /* resolved ip adr */
+  /*
+    Workaround for the following case:
+    switching off and on a LakeShore 336 does acquire a new address,
+    but the value in the cache (for gethostbyname) is not updated.
+    node: dig seems to be recommended over nslookup
+  */
 
-long ns_lookup(char *hostname) {
+  struct hostent *hostent;      /* Host database entry */
+  struct sockaddr_in *sadr = (struct sockaddr_in *)sockaddrPtr;
   FILE *fil;
   char line[256];
-  long ipadr;
+  int l;
 
-  ipadr = parse_dotted_adr(hostname);
-  if (ipadr) return ipadr;
-  snprintf(line, sizeof line, "timeout 1 nslookup %s", hostname);
-  fil = popen(line, "r");
-  if (fil == NULL) {
+  (void) memset(sadr, 0, sizeof(*sadr));
+  if (dotted_ip) { /* default value: failure */
+    dotted_ip[0] = 0;
+  }
+  sadr->sin_family = AF_INET;
+  sadr->sin_port = htons((unsigned short)port);
+  if (hostname == NULL) {
+    /* do not need to copy, as INADDR_ANY is all zero bytes */
+    return 1;
+  }
+  if (inet_pton(AF_INET, hostname, &sadr->sin_addr) == 1) {
+    /* resolved as dotted numbers notation */
+    return 1;
+  }
+  hostent = gethostbyname(hostname);
+  if (hostent == 0) {
+    /* we assume that when gethostname gets no entry, dig will also fail.
+    That way, dig will not be called repeatedly for no reason */
     return 0;
   }
-  while (fgets(line, sizeof(line), fil) != NULL) {
-    if (strncmp(line, "Address: ", 9) == 0) {
-      ipadr = parse_dotted_adr(line+9);
-      if (ipadr) {
-        fclose(fil);
-        return ipadr;
-      }
+  /* copy the address: in case dig fails, we use the cached value */
+  memcpy(&sadr->sin_addr, hostent->h_addr_list[0], 4);
+  /* we use hostent->h_name instead of hostname here, as this has already
+     the proper domain added */
+  snprintf(line, sizeof line, "timeout 1 dig +short %s", hostent->h_name);
+  fil = popen(line, "r");
+  if (fil != NULL) {
+    if (fgets(line, sizeof(line), fil) != NULL) {
+      l = strlen(line);
+      if (line[l-1] <= ' ') line[l-1] = 0; /* strip off newline */
+      /* silently ignore return value, if it fails, we take the cached value */
+      inet_pton(AF_INET, line, &sadr->sin_addr);
     }
+    fclose(fil);
   }
-  fclose(fil);
-  return 0;
-}
-
-/*
-     Based on CreateSocketAdress from John Ousterhout
-     Use ns_lookup instead of gethostbyname, as the latter uses a cache, which
-     is not sufficient in some cases (switching off and on a LakeShore 336 does
-     acquire a new address, but the value in the cache is not updates)
-*/
-
-static int MakeSocketAdress(struct sockaddr_in *sockaddrPtr,  /* Socket address */
-                            char *host,       /* Host.  NULL implies INADDR_ANY */
-                            int port)
-{                               /* Port number */
-  struct hostent *hostent;      /* Host database entry */
-  struct in_addr addr;          /* For 64/32 bit madness */
-
-  (void) memset((char *) sockaddrPtr, '\0', sizeof(struct sockaddr_in));
-  sockaddrPtr->sin_family = AF_INET;
-  sockaddrPtr->sin_port = htons((unsigned short) (port & 0xFFFF));
-  if (host == NULL) {
-    addr.s_addr = INADDR_ANY;
-  } else {
-    addr.s_addr = ns_lookup(host);
-    if (addr.s_addr == 0) { /* try gethostbyname only if ns_lookup failed */
-      hostent = gethostbyname(host);
-      if (hostent == NULL) return 0; /* error */
-      memcpy((char *) &addr,
-             (char *) hostent->h_addr_list[0], (size_t) hostent->h_length);
-    }
+  if (dotted_ip) {
+    inet_ntop(AF_INET, &sadr->sin_addr, dotted_ip, 16);
   }
-  /*
-   * There is a rumor that this assignment may require care on
-   * some 64 bit machines, we do not believe it.
-   */
-  sockaddrPtr->sin_addr.s_addr = addr.s_addr;
   return 1;
 }
 
@@ -140,7 +127,7 @@ static void AsconConnect(Ascon * a)
   /* input state: AsconConnectStart
      output state: AsconFailed or AsconConnecting */
   int ret;
-  struct sockaddr_in adr;
+  struct sockaddr adr;
   char *colon;
   int port;
   int oldopts;
@@ -184,17 +171,15 @@ static void AsconConnect(Ascon * a)
     return;
   }
   *colon = '\0';
-  ret = MakeSocketAdress(&adr, a->hostport, port);
+  ret = MakeSocketAdr(&adr, a->hostport, port, a->ip);
   *colon = ':';
   if (ret == 0) {
-    a->ip = 0;
     AsconError(a, "bad host specification", 0);
     return;
   }
-  a->ip = adr.sin_addr.s_addr;
   oldopts = fcntl(a->fd, F_GETFL, 0);
   fcntl(a->fd, F_SETFL, oldopts | O_NONBLOCK);
-  ret = connect(a->fd, (struct sockaddr *) &adr, sizeof(struct sockaddr_in));
+  ret = connect(a->fd, &adr, sizeof(struct sockaddr_in));
   if (ret < 0) {
     switch (errno) {
     case EINPROGRESS:
@@ -891,10 +876,10 @@ char *AsconHostport(Ascon *a)
   return a->hostport;
 }
 
-unsigned long AsconIP(Ascon *a)
+char *AsconIP(Ascon *a)
 {
   if (a==NULL) {
-    return 0;
+    return NULL;
   }
   return a->ip;
 }

ascon.h

@@ -112,9 +112,9 @@ char *AsconHostport(Ascon *a);
 /**
  * \brief return IP address
  * \param a The Ascon to query
- * \return the IP address 
+ * \return the IP address (dotted numbers)
  */
-unsigned long AsconIP(Ascon *a);
+char *AsconIP(Ascon *a);
 
 /**
  * \brief set or get timeout

ascon.i

@@ -65,7 +65,7 @@ struct Ascon {
   char *sendTerminator;        /**< terminator for sending messages */
   char *replyTerminator;       /**< (std) terminator list for reply. NULL is the special case CR, LF or CR/LF */
   char *hostport;              /**< host:port to connect */
-  in_addr_t ip;                /**< the ip address */
+  char ip[16];                 /**< the ip address (dotted numbers) */
   pDynString errmsg;           /**< error message */
   double start;                /**< unix time when read was started */
   int noResponse;              /**< no response expected */

devser.c

@@ -580,7 +580,7 @@ char *DevHostport(DevSer *devser) {
   return AsconHostport(devser->ascon);
 }
 
-unsigned long DevIP(DevSer *devser) {
+char *DevIP(DevSer *devser) {
   return AsconIP(devser->ascon);
 }
 

devser.h

@@ -206,9 +206,9 @@ char *DevHostport(DevSer *devser);
 /**
  * \brief return IP address
  * \param a The device serializer to query
- * \return the IP address   
+ * \return the IP address (dotted numbers)
  */
-unsigned long DevIP(DevSer *devser);
+char *DevIP(DevSer *devser);
 
 /**
  * \brief return status of device server ("offline", "unconnected", "")

scriptcontext.c

@@ -1742,15 +1742,9 @@ static int SctIpAddress(pSICSOBJ ccmd, SConnection * con,
                         Hdb * cmdNode, Hdb * par[], int nPar)
 {
   SctController *c;
-  uint32_t ip;
 
   c = (SctController *) ccmd->pPrivate;
-  ip = DevIP(c->devser);
-  SCPrintf(con, eValue, "%d.%d.%d.%d",
-     (int)(ip & 0xff),
-     (int)((ip >> 8) & 0xff),
-     (int)((ip >> 16) & 0xff),
-     (int)((ip >> 24)  & 0xff));
+  SCPrintf(con, eValue, "%s", DevIP(c->devser));
   return 1;
 }