Don't add null addresses to the address list.

If we don't have an address, don't add a pcap_addr_t with a null addr
pointer to the list of addresses; it conveys no information.

That seems to happen, at least with a venet device on Linux on the
Travis build machine.

1 files changed, 27 insertions, 8 deletions

diff --git a/inet.c b/inet.c
index fad7e25b..e7d2104e 100644
--- a/inet.c
+++ b/inet.c
@@ -572,7 +572,8 @@ get_if_description(const char *name)
  * Try to get a description for a given device, and then look for that
  * device in the specified list of devices.
  *
- * If we find it, add the specified address to it and return 0.
+ * If we find it, then, if the specified address isn't null, add it to
+ * the list of addresses for the device and return 0.
  *
  * If we don't find it, check whether we can open it:
  *
@@ -583,9 +584,17 @@ get_if_description(const char *name)
  *
  *     Otherwise, attempt to add an entry for it, with the specified
  *     ifnet flags and description, and, if that succeeds, add the
- *     specified address to it, set *curdev_ret to point to the new
- *     entry, and return 0, otherwise return PCAP_ERROR and set errbuf
- *     to an error message.
+ *     specified address to its list of addresses if that address is
+ *     non-null, set *curdev_ret to point to the new entry, and
+ *     return 0, otherwise return PCAP_ERROR and set errbuf to an
+ *     error message.
+ *
+ * (We can get called with a null address because we might get a list
+ * of interface name/address combinations from the underlying OS, with
+ * the address being absent in some cases, rather than a list of
+ * interfaces with each interface having a list of addresses, so this
+ * call may be the only call made to add to the list, and we want to
+ * add interfaces even if they have no addresses.)
  */
 int
 add_addr_to_iflist(pcap_if_t **alldevs, const char *name, u_int flags,
@@ -616,14 +625,24 @@ add_addr_to_iflist(pcap_if_t **alldevs, const char *name, u_int flags,
 		return (0);
 	}
 
+	if (addr == NULL) {
+		/*
+		 * There's no address to add; this entry just meant
+		 * "here's a new interface".
+		 */
+		return (0);
+	}
+
 	/*
-	 * "curdev" is an entry for this interface; add an entry for this
-	 * address to its list of addresses.
+	 * "curdev" is an entry for this interface, and we have an
+	 * address for it; add an entry for that address to the
+	 * interface's list of addresses.
 	 *
 	 * Allocate the new entry and fill it in.
 	 */
-	return (add_addr_to_dev(curdev, addr, addr_size, netmask, netmask_size,
-	    broadaddr, broadaddr_size, dstaddr, dstaddr_size, errbuf));
+	return (add_addr_to_dev(curdev, addr, addr_size, netmask,
+	    netmask_size, broadaddr, broadaddr_size, dstaddr,
+	    dstaddr_size, errbuf));
 }
 
 /*