epcap_return: return on failure

If opening the pcap descriptor fails, return and allow the main flow control to exit. Save the pcap error message to the epcap state. Currently the error message is discarded. The plan is to send it to the port process.
msantos · Nov 20, 2017 · 9e81915 · 9e81915
1 parent 9566f04
commit 9e81915
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Showing 2 changed files with 34 additions and 18 deletions.
diff --git a/c_src/epcap.c b/c_src/epcap.c
@@ -170,12 +170,17 @@ main(int argc, char *argv[])
             VERBOSE(2, "env:%s\n", *environ);
     }
 
-    IS_LTZERO(fd = open("/dev/null", O_RDWR));
+    fd = open("/dev/null", O_RDWR);
+
+    if (fd < 0)
+      exit(errno);
 
     if (epcap_priv_runasuser(ep) < 0)
       err(EXIT_FAILURE, "epcap_priv_runasuser");
 
-    IS_LTZERO(epcap_open(ep));
+    if (epcap_open(ep) < 0)
+      exit(errno);
+
     if (epcap_priv_drop(ep) < 0)
         exit (1);
 
@@ -270,21 +275,32 @@ epcap_send(EPCAP_STATE *ep)
     static int
 epcap_open(EPCAP_STATE *ep)
 {
-    char errbuf[PCAP_ERRBUF_SIZE];
-
     if (ep->file) {
-        PCAP_ERRBUF(ep->p = pcap_open_offline(ep->file, errbuf));
+        ep->p = pcap_open_offline(ep->file, ep->errbuf);
+
+        if (ep->p == NULL)
+          return -1;
     } else {
-        if (ep->dev == NULL)
-            PCAP_ERRBUF(ep->dev = pcap_lookupdev(errbuf));
+        if (ep->dev == NULL) {
+            ep->dev = pcap_lookupdev(ep->errbuf);
+
+            if (ep->dev == NULL)
+              return -1;
+        }
 
 #ifdef HAVE_PCAP_CREATE
-        PCAP_ERRBUF(ep->p = pcap_create(ep->dev, errbuf));
+        ep->p = pcap_create(ep->dev, ep->errbuf);
+
+        if (ep->p == NULL)
+          return -1;
+
         (void)pcap_set_snaplen(ep->p, ep->snaplen);
         (void)pcap_set_promisc(ep->p, ep->opt & EPCAP_OPT_PROMISC);
         (void)pcap_set_timeout(ep->p, ep->timeout);
+
         if (ep->bufsz > 0)
             (void)pcap_set_buffer_size(ep->p, ep->bufsz);
+
         switch (pcap_activate(ep->p)) {
             case 0:
                 break;
@@ -293,14 +309,18 @@ epcap_open(EPCAP_STATE *ep)
             case PCAP_WARNING_PROMISC_NOTSUP:
             case PCAP_ERROR_NO_SUCH_DEVICE:
             case PCAP_ERROR_PERM_DENIED:
-                pcap_perror(ep->p, "pcap_activate: ");
-                exit(EXIT_FAILURE);
+                (void)strncpy(ep->errbuf, pcap_geterr(ep->p),
+                    sizeof(ep->errbuf)-1);
+                return -1;
             default:
-                exit(EXIT_FAILURE);
+                return -1;
         }
 #else
-        PCAP_ERRBUF(ep->p = pcap_open_live(ep->dev, ep->snaplen,
-                    ep->opt & EPCAP_OPT_PROMISC, ep->timeout, errbuf));
+        ep->p = pcap_open_live(ep->dev, ep->snaplen,
+            ep->opt & EPCAP_OPT_PROMISC, ep->timeout, ep->errbuf);
+
+        if (ep->p == NULL)
+          return -1;
 #endif
 
         /* monitor mode */

diff --git a/c_src/epcap.h b/c_src/epcap.h
@@ -66,11 +66,6 @@
 #define EPCAP_CHROOT    "/var/empty"
 #define EPCAP_FILTER    ""      /* match any packet */
 
-#define PCAP_ERRBUF(x) do { \
-    if ((x) == NULL) \
-    errx(EXIT_FAILURE, "%s: %s", #x, errbuf); \
-} while (0);
-
 #define IS_FALSE(x) do { \
     if ((x) != 0) \
     errx(EXIT_FAILURE, "%s", #x); \
@@ -110,6 +105,7 @@ typedef struct {
     char *group;        /* run as unprivilted group */
     char *chroot;       /* chroot directory */
     char *file;         /* filename in case we read from pcap file */
+    char errbuf[PCAP_ERRBUF_SIZE];  /* pcap error */
 } EPCAP_STATE;