Capture and log STDOUT and STDERR output from dhcp-script.

CHANGELOG

@@ -88,7 +88,12 @@ version 2.77
 
             Add mtu setting facility to --ra-param. Thanks to David
 	    Flamand for the patch.
-	
+
+	    Capture STDOUT and STDERR output from dhcp-script and log
+	    it as part of the dnsmasq log stream. Makes life easier
+	    for diagnosing unexpected problems in scripts.
+	    Thanks to Petr Mensik for the patch.
+
 
 version 2.76
             Include 0.0.0.0/8 in DNS rebind checks. This range 

man/dnsmasq.8

@@ -1577,8 +1577,8 @@ database.
 
 
 All file descriptors are
-closed except stdin, stdout and stderr which are open to /dev/null
+closed except stdin, which is open to /dev/null, and stdout and stderr which capture output for logging by dnsmasq. 
-(except in debug mode).
+(In debug mode, stdio, stdout and stderr file are left as those inherited from the invoker of dnsmasq).
 
 The script is not invoked concurrently: at most one instance
 of the script is ever running (dnsmasq waits for an instance of script to exit

src/dnsmasq.c

@@ -1302,6 +1302,7 @@ static void async_event(int pipe, time_t now)
 		daemon->tcp_pids[i] = 0;
 	break;
 	
+#if defined(HAVE_SCRIPT)	
       case EVENT_KILLED:
 	my_syslog(LOG_WARNING, _("script process killed by signal %d"), ev.data);
 	break;
@@ -1315,12 +1316,19 @@ static void async_event(int pipe, time_t now)
 		  daemon->lease_change_command, strerror(ev.data));
 	break;
 
+      case EVENT_SCRIPT_LOG:
+	my_syslog(MS_SCRIPT | LOG_DEBUG, "%s", msg ? msg : "");
+        free(msg);
+	msg = NULL;
+	break;
+
 	/* necessary for fatal errors in helper */
       case EVENT_USER_ERR:
       case EVENT_DIE:
       case EVENT_LUA_ERR:
 	fatal_event(&ev, msg);
 	break;
+#endif
 
       case EVENT_REOPEN:
 	/* Note: this may leave TCP-handling processes with the old file still open.

src/dnsmasq.h

@@ -145,30 +145,31 @@ struct event_desc {
   int event, data, msg_sz;
 };
 
-#define EVENT_RELOAD    1
+#define EVENT_RELOAD     1
-#define EVENT_DUMP      2
+#define EVENT_DUMP       2
-#define EVENT_ALARM     3
+#define EVENT_ALARM      3
-#define EVENT_TERM      4
+#define EVENT_TERM       4
-#define EVENT_CHILD     5
+#define EVENT_CHILD      5
-#define EVENT_REOPEN    6
+#define EVENT_REOPEN     6
-#define EVENT_EXITED    7
+#define EVENT_EXITED     7
-#define EVENT_KILLED    8
+#define EVENT_KILLED     8
-#define EVENT_EXEC_ERR  9
+#define EVENT_EXEC_ERR   9
-#define EVENT_PIPE_ERR  10
+#define EVENT_PIPE_ERR   10
-#define EVENT_USER_ERR  11
+#define EVENT_USER_ERR   11
-#define EVENT_CAP_ERR   12
+#define EVENT_CAP_ERR    12
-#define EVENT_PIDFILE   13
+#define EVENT_PIDFILE    13
-#define EVENT_HUSER_ERR 14
+#define EVENT_HUSER_ERR  14
-#define EVENT_GROUP_ERR 15
+#define EVENT_GROUP_ERR  15
-#define EVENT_DIE       16
+#define EVENT_DIE        16
-#define EVENT_LOG_ERR   17
+#define EVENT_LOG_ERR    17
-#define EVENT_FORK_ERR  18
+#define EVENT_FORK_ERR   18
-#define EVENT_LUA_ERR   19
+#define EVENT_LUA_ERR    19
-#define EVENT_TFTP_ERR  20
+#define EVENT_TFTP_ERR   20
-#define EVENT_INIT      21
+#define EVENT_INIT       21
-#define EVENT_NEWADDR   22
+#define EVENT_NEWADDR    22
-#define EVENT_NEWROUTE  23
+#define EVENT_NEWROUTE   23
-#define EVENT_TIME_ERR  24
+#define EVENT_TIME_ERR   24
+#define EVENT_SCRIPT_LOG 25
 
 /* Exit codes. */
 #define EC_GOOD        0
@@ -243,8 +244,9 @@ struct event_desc {
 
 /* extra flags for my_syslog, we use a couple of facilities since they are known 
    not to occupy the same bits as priorities, no matter how syslog.h is set up. */
-#define MS_TFTP LOG_USER
+#define MS_TFTP   LOG_USER
-#define MS_DHCP LOG_DAEMON 
+#define MS_DHCP   LOG_DAEMON
+#define MS_SCRIPT LOG_MAIL
 
 struct all_addr {
   union {

src/helper.c

@@ -14,6 +14,7 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <stdio.h>
 #include "dnsmasq.h"
 
 #ifdef HAVE_SCRIPT
@@ -135,7 +136,7 @@ int create_helper(int event_fd, int err_fd, uid_t uid, gid_t gid, long max_fd)
 	max_fd != STDIN_FILENO && max_fd != pipefd[0] && 
 	max_fd != event_fd && max_fd != err_fd)
       close(max_fd);
-  
+
 #ifdef HAVE_LUASCRIPT
   if (daemon->luascript)
     {
@@ -189,6 +190,7 @@ int create_helper(int event_fd, int err_fd, uid_t uid, gid_t gid, long max_fd)
       unsigned char *buf = (unsigned char *)daemon->namebuff;
       unsigned char *end, *extradata, *alloc_buff = NULL;
       int is6, err = 0;
+      int pipeout[2];
 
       free(alloc_buff);
       
@@ -472,16 +474,54 @@ int create_helper(int event_fd, int err_fd, uid_t uid, gid_t gid, long max_fd)
       if (!daemon->lease_change_command)
 	continue;
 
+      /* Pipe to capture stdout and stderr from script */
+      if (!option_bool(OPT_DEBUG) && pipe(pipeout) == -1)
+	continue;
+      
       /* possible fork errors are all temporary resource problems */
       while ((pid = fork()) == -1 && (errno == EAGAIN || errno == ENOMEM))
 	sleep(2);
 
       if (pid == -1)
-	continue;
+        {
+	  if (!option_bool(OPT_DEBUG))
+	    {
+	      close(pipeout[0]);
+	      close(pipeout[1]);
+	    }
+	  continue;
+        }
       
       /* wait for child to complete */
       if (pid != 0)
 	{
+	  if (!option_bool(OPT_DEBUG))
+	    {
+	      FILE *fp;
+	  
+	      close(pipeout[1]);
+	      
+	      /* Read lines sent to stdout/err by the script and pass them back to be logged */
+	      if (!(fp = fdopen(pipeout[0], "r")))
+		close(pipeout[0]);
+	      else
+		{
+		  while (fgets(daemon->packet, daemon->packet_buff_sz, fp))
+		    {
+		      /* do not include new lines, log will append them */
+		      size_t len = strlen(daemon->packet);
+		      if (len > 0)
+			{
+			  --len;
+			  if (daemon->packet[len] == '\n')
+			    daemon->packet[len] = 0;
+			}
+		      send_event(event_fd, EVENT_SCRIPT_LOG, 0, daemon->packet);
+		    }
+		  fclose(fp);
+		}
+	    }
+	  
 	  /* reap our children's children, if necessary */
 	  while (1)
 	    {
@@ -504,6 +544,15 @@ int create_helper(int event_fd, int err_fd, uid_t uid, gid_t gid, long max_fd)
 	  
 	  continue;
 	}
+
+      if (!option_bool(OPT_DEBUG))
+	{
+	  /* map stdout/stderr of script to pipeout */
+	  close(pipeout[0]);
+	  dup2(pipeout[1], STDOUT_FILENO);
+	  dup2(pipeout[1], STDERR_FILENO);
+	  close(pipeout[1]);
+	}
       
       if (data.action != ACTION_TFTP && data.action != ACTION_ARP)
 	{
@@ -580,7 +629,8 @@ int create_helper(int event_fd, int err_fd, uid_t uid, gid_t gid, long max_fd)
 	    hostname = NULL;
 	  
 	  my_setenv("DNSMASQ_LOG_DHCP", option_bool(OPT_LOG_OPTS) ? "1" : NULL, &err);
-    }
+	}
+      
       /* we need to have the event_fd around if exec fails */
       if ((i = fcntl(event_fd, F_GETFD)) != -1)
 	fcntl(event_fd, F_SETFD, i | FD_CLOEXEC);

src/log.c

@@ -288,7 +288,9 @@ void my_syslog(int priority, const char *format, ...)
     func = "-tftp";
   else if ((LOG_FACMASK & priority) == MS_DHCP)
     func = "-dhcp";
-      
+  else if ((LOG_FACMASK & priority) == MS_SCRIPT)
+    func = "-script";
+	    
 #ifdef LOG_PRI
   priority = LOG_PRI(priority);
 #else