dns plugin: Resume after receiving a PCAP_ERROR from pcap_loop().

If an interface goes down while capturing, libpcap returns PCAP_ERROR.
Handle this case gracefully.

Github: #308

diff --git a/src/dns.c b/src/dns.c
index fe3b672..aea41c4 100644 (file)
--- a/src/dns.c
+++ b/src/dns.c
@@ -208,7 +208,7 @@ static void dns_child_callback (const rfc1035_header_t *dns)
        pthread_mutex_unlock (&opcode_mutex);
 }
 
-static void *dns_child_loop (__attribute__((unused)) void *dummy)
+static int dns_run_pcap_loop (void)
 {
        pcap_t *pcap_obj;
        char    pcap_error[PCAP_ERRBUF_SIZE];
@@ -236,19 +236,24 @@ static void *dns_child_loop (__attribute__((unused)) void *dummy)
                                "failed: %s",
                                (pcap_device != NULL) ? pcap_device : "any",
                                pcap_error);
-               return (NULL);
+               return (PCAP_ERROR);
        }
 
        memset (&fp, 0, sizeof (fp));
-       if (pcap_compile (pcap_obj, &fp, "udp port 53", 1, 0) < 0)
+       status = pcap_compile (pcap_obj, &fp, "udp port 53", 1, 0);
+       if (status < 0)
        {
-               ERROR ("dns plugin: pcap_compile failed");
-               return (NULL);
+               ERROR ("dns plugin: pcap_compile failed: %s",
+                               pcap_statustostr (status));
+               return (status);
        }
-       if (pcap_setfilter (pcap_obj, &fp) < 0)
+
+       status = pcap_setfilter (pcap_obj, &fp);
+       if (status < 0)
        {
-               ERROR ("dns plugin: pcap_setfilter failed");
-               return (NULL);
+               ERROR ("dns plugin: pcap_setfilter failed: %s",
+                               pcap_statustostr (status));
+               return (status);
        }
 
        DEBUG ("dns plugin: PCAP object created.");
@@ -259,19 +264,30 @@ static void *dns_child_loop (__attribute__((unused)) void *dummy)
        status = pcap_loop (pcap_obj,
                        -1 /* loop forever */,
                        handle_pcap /* callback */,
-                       NULL /* Whatever this means.. */);
-       if (status < 0)
-               ERROR ("dns plugin: Listener thread is exiting "
-                               "abnormally: %s", pcap_geterr (pcap_obj));
-
-       DEBUG ("dns plugin: Child is exiting.");
+                       NULL /* user data */);
+       INFO ("dns plugin: pcap_loop exited with status %i.", status);
+       /* We need to handle "PCAP_ERROR" specially because libpcap currently
+        * doesn't return PCAP_ERROR_IFACE_NOT_UP for compatibility reasons. */
+       if (status == PCAP_ERROR)
+               status = PCAP_ERROR_IFACE_NOT_UP;
 
        pcap_close (pcap_obj);
-       listen_thread_init = 0;
-       pthread_exit (NULL);
+       return (status);
+} /* int dns_run_pcap_loop */
+
+static void *dns_child_loop (__attribute__((unused)) void *dummy) /* {{{ */
+{
+       int status = PCAP_ERROR_IFACE_NOT_UP;
+
+       while (status == PCAP_ERROR_IFACE_NOT_UP)
+               status = dns_run_pcap_loop ();
+       if (status != PCAP_ERROR_BREAK)
+               ERROR ("dns plugin: PCAP returned error %s.",
+                               pcap_statustostr (status));
 
+       listen_thread_init = 0;
        return (NULL);
-} /* static void dns_child_loop (void) */
+} /* }}} void *dns_child_loop */
 
 static int dns_init (void)
 {